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| 89Vette | 383/DMF considerations | ||
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Senior Guru
 
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Please let me know the considerations for building a 383 while using a (new) stock DMF. Here are some things I'm concerned about:
1) Holding power of the DMF. Consider that I won't be "racing". This is strickly for a street motor where the absence of rattle over-rides the NEED for a 383. Would it be better to stick with a 350 -- if I'm set on using a DMF? 2) Balancing issues...To get the 383 rotating assembly balanced, do I buy an external balanced 1-pc 383 crank? Would everything bolt-up and work w/o alterations? Would you expect add'l wgt to be necessary as lug/tab weight? *** 3) Are 5.7" rods the best for street? That's what I've heard. 4) What crank/rods/pistons do you guys like of this type of build. (Street w/o FI/NOS) 5) With angle-milled, intake-face corrected AFR heads (cut from 65cc to 56cc), will I have any fitment issues if I run with a .050" to zero-decked short block? 6) Best I can figure, I should use 20-22cc dished pistons to keep compression around 10:1 -- which would prevent issues using pump gas. Comments/feedback appreciated ***Note: Believe it or not, local shops in K.C. are unfamiliar with the DMF and also question the correct 383 crank to mate with a DMF...specifically how it will balance. |
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Posted on: 2009/9/27 0:37
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383 stroker -- Semi-Siamesed SLP long-runner intake, AFR 195's, 4-2-1 headers, and a SR cam. ZF6 short-throw shifter. Custom body/interior. |
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| BeachBum | Re: 383/DMF considerations | ||
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Master Guru
 
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I'll help with my opinion, but may I ask what a DMF is ? This is new to me.
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Posted on: 2009/9/27 0:42
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| pianoguy | Re: 383/DMF considerations | ||
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Dual-Mass Flywheel - it's typically externally balanced. |
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Posted on: 2009/9/27 1:58
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1996 LT4 �Before you criticize someone, you should walk a mile in their shoes. That way when you criticize them, you are a mile away from them and you have their shoes.�- Jack Handey |
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| 89Vette | Re: 383/DMF considerations | ||
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Senior Guru
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DMF does mean dual-mass flywheel. It's the 2-piece dampener/FW used with ZF6's from 89-96. Bill @ ZFDoc tells me it contains a 30g offset weight. He wasn't certain -- though he believed automatic flexplates of the same era would also contain a 30g offset. That would allow motor interchangability. I haven't determined if 30g is really what a 350 externally balanced (@ the rear) crank "expects" to see for a counterbalance. Moreover, how that would differ from a 383 (or even 400 crank). When talking to local machine shops, they were unaware of the considerations for using that FW with a 383 crank. To me, it sounds like an externally balanced 383 crank would balance just like a 350 ext (rear)/ int (front) crank. However, the use of extra weight might be required. (CNC-Motorsports thought it would depend on the weight of the pistons.) Can I also be certain that FW/clutch clearance/geometry would be unchanged with a 383 using a DMF? |
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Posted on: 2009/9/27 2:56
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383 stroker -- Semi-Siamesed SLP long-runner intake, AFR 195's, 4-2-1 headers, and a SR cam. ZF6 short-throw shifter. Custom body/interior. |
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| rklessdriver | Re: 383/DMF considerations | ||
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Senior Guru
 
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1. The more power and traction you have (and abuse/use it) - the quicker you will wear the springs out in the DMFW. That said, IMO a new DMFW will last fine in all but the most radical street car. Don't be concerned. A guy in my club has a 440RWHP Grand Sport running on the stock DMFW and it's doing great.
2. Your machinest should be able to put a DMFW in a lathe and cut the external weight off it if you buy an internal balance crank. If your crank is external balance you should leave it as it is. There is no right or wrong here, everything depends on the crankshaft you buy. I prefer internal balance cranks because I don't like weights hung off the end of the crank on the FW or balancer - but in a street car there is an advantage to keeping it external blance... when you need a new FW, you can just go buy a new one and put it on.... 3. 5.7 rods do have some advantages for a 3.75 stroke street car IMO. They have a taller compression height and a)that keeps the wrist pin from intersecting the oil ring and b) spaces the rings apart futher so they are better able to with stand pre-ignition. An engine with 5.7 rods will have a TQ band that comes on slightly sooner and ends slightly sooner than an engine with 6" rods. It has higher piston speed and can take advantage of slightly bigger cyl head because it has higher "signal" when the intake valve opens. Becasue of the faster piston speed on and off of TDC the engine is capable of standing more compression and timing advance before pre-ignition sets in. 4. A street car with NO blower or NO2... You can save some $$$ with a good cast crank (Eagle or Scat 9000) and Eagle SIR or Scat I beam 3/8 cap screw type rods. I would recommend forged Pistons in any hi performance engine. Probe and KB have forged pistons that are the same $$$ as hyper's and they have a huge selection. No reason to buy a piston that is not as strong. 5. Every engine/cyl heads/intake manifold combo is different, there is no way to answer that until you have everything done and mock it up. 6. Depending on deck clearance and head gasket... 20cc pistons will get you there no problem. Depending on camshaft, quench cyl head combustion chamber desgin - 10.1 to 12.5 SCR will run on pump gas (your DCR needs to be 8.0-9.0). The new AFR's have a very nice chamber, that coupled with tight quench (.040-.036) will stand more SCR than you think. Give me some cam specs and I can target your SCR and DCR better. Will |
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Posted on: 2009/9/27 3:04
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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| bogus | Re: 383/DMF considerations | ||
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Grand Imperial Pooh-Bah
 
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As an aside, the NAPA clutch hydraulic slave is a REAL nice piece. It's cast, so the unit won't leak like my old AC part did...
As for a clutch solution, I would look at the RAM with a hydraulic throw-out bearing. http://www.ramclutches.com/Specialty%20products/C4_Conversion.htm |
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Posted on: 2009/9/27 3:15
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| RedGut86 | Re: 383/DMF considerations | ||
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I'm confused, are your heads already cut? Why not just run a flatop or lesser dish piston and not cut the heads.
Or is this because you are fitting up SBC heads on an LT1 or something? |
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Posted on: 2009/9/27 3:25
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| vetteoz | Re: 383/DMF considerations | ||
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Beaware; the external balance on a 1 pce seal crank is different to the external balance as used on the 400's which requires a weighted balancer and weighted flywheel. Some of the stroker kits notably the cheaper ones use this configuration ;essentially a 400 crank with 350 journals The 1 pce seal crank is ext balance AT rear only ; the front is neutral using any regular ( non 400ci ) balancer |
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Posted on: 2009/9/27 3:53
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| 89Vette | Re: 383/DMF considerations | ||
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Are there any forged pistons that will minimize/prevent noise during warm-up. One shop said hyper's were better because they weren't noisy. They added, forged isn't necessary for a street car. Quote:
To be honest, I bought a cam (and cut my heads) based on a 350 motor. It's a custom Bullet 214/214 with .544"/.544" lift using 1.6 rr. In reality, .050" duration would increase to ~ 216/216 duration with those rockers. (Unless I could get damn near what I paid for it, that's the cam I'm using btw.) The good news is I bought AFR 195's. So, they'll flow a LOT even with a mild cam. A 383 simulation that was sent to me showed peak at 5800 rpms -- which is fine by me. The heads have been angle-milled down to 56cc chambers (because I was originally planning on reusing my 350). FWIW: I have 1.75" headers and the choice of two intakes. |
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Posted on: 2009/9/27 4:18
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383 stroker -- Semi-Siamesed SLP long-runner intake, AFR 195's, 4-2-1 headers, and a SR cam. ZF6 short-throw shifter. Custom body/interior. |
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| 89Vette | Re: 383/DMF considerations | ||
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Senior Guru
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Quote:
Oh yeah...CNC-Motorsports did recommend an Eagle or Scat 9000 crank. With the Eagle, they said it was ext balanced front and rear -- which would require an aftermarket balancer IIRC. The Scat 9000 was "better" if I liked the option to re-use my stock balancer. They said it was due to it's ext/rear, int/front balancing config. I haven't heard any recommendation from anyone on rods aside from using SIR or I-beam rods with ARP bolts. Quote:
I really don't think cutting a DMF to neutral balance is what I want to do -- especialy if an external balanced setup isn't that difficult. |
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Posted on: 2009/9/27 4:25
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383 stroker -- Semi-Siamesed SLP long-runner intake, AFR 195's, 4-2-1 headers, and a SR cam. ZF6 short-throw shifter. Custom body/interior. |
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| dan0617 | Re: 383/DMF considerations | ||
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Senior Guru
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If you are SURE you are never going to spray nitrous or anything, go with a cast or SIR crank, and hyper pistons. I'd used a forged I-beam rod in that engine, but that's me. 5.7" would be a good choice.
Don't get the static compression very high with that cam in a 383, or your dynamic compression will be too high and you will have problems on pump gas. That cam isn't going to "bleed off" much compression. You said you have the choice of 2 intakes. Figure out which intake you are going to use first. If you are considering a miniram or LT1 intake, that cam is too small. If a TPI, ok, but you will have a serious torque monster. If you are looking at using a superram or HSR, consider selling that cam and getting a 219 or 224 intake duration. The one you have will work but you are leaving a good deal on the table with anything other than a reworked TPI intake. |
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Posted on: 2009/9/27 14:30
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´89 Vert, 383, 230/236 cam, AFR 195's, LT Headers, HSR intake, 2800 stall, Zex 200 shot, ET Street Radials, tune by me. Runs were with D36 3.07's. On spray, 10.55 @ 132.78, 1.55 60 ft. On motor, 12.08 @ 113.15, 1.66 60 ft. |
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| anesthes | Re: 383/DMF considerations | ||
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If you are buying a 383 rotating assembly for a 1pc rear main seal block, I'm not all that sure I'd expect it to be balanced as a 400.. Double check with what you are buying, and tell them you want to use your stock flywheel and harmonic balancer.
-- Joe |
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Posted on: 2009/9/27 14:34
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'79 Z28. 412 CID, NP 833 transmission, 3.73 10.5" rear end. |
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| rklessdriver | Re: 383/DMF considerations | ||
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To be honest, I bought a cam (and cut my heads) based on a 350 motor. It's a custom Bullet 214/214 with .544"/.544" Ok you have the Bullet HR269/340 lobe. That is a symetrical lobe desgin with a very smooth ramp desgin. IMO it is a very good choice for a long runner TPI intake but not much else in a 380 inch engine. What did you have the intake centerline and lobe seperation cut on? I need that info as well. Quote: Are there any forged pistons that will minimize/prevent noise during warm-up. One shop said hyper's were better because they weren't noisy. They added, forged isn't necessary for a street car. Ideally you want something forged from 4032 alloy - but 2618 alloy is also acceptable. Either material will run with .004 of piston to wall clearance in a 4" bore and be safe in your application. I have .005 in my engine with ultra light Manley pistons (2618 alloy) and it dosen't have any piston slap at start up. Some people get by or have gotten by with Hyper pistons. I'm in the latter. I've used the KB hypers before... even in some lower powered bracket engines without problems. I think they are a trade off. You have to open up the ring end gap to run them and I don't like to do that any more than nessescary. Ring end gap in a hyper piston motor is CRITICAL. If you run it too tight it will butt and break the top off a piston. Hyper pistons are not strong at all. They are also very brittle and if you get any detonation at all they will come apart. IMO they are stock replacement parts that can be used in hi performance engines if the owner/builder understands their VAST limitations. I stand by my recommendation of KB or Probe forged pistons and add in SRP and Mahle depending on how much you are willing to spend. Hypers are a possibility but we are talking that KB hypers cost $275.00 and KB FHR Forged cost 285.00 for the same application (4.030/3.75/5.7/18cc dish)... The better Forged pistons cost between $350 to $550+. It is not that much money IMO but there is that much difference in strength. Quote: I haven't heard any recommendation from anyone on rods aside from using SIR or I-beam rods with ARP bolts. NOT BOLTS. I stated CAP SCREWS. Scat offers a rod with thru bolts (like stock) and one with 3/8" capscrews. Buy the latter. Eagle switched their SIR rods to 3/8" capscrews about 3yrs ago. For all intense purposes the cap screw rods are equall and I would by the lowest price one. The Scat 9000 is a good crank for what your doing. But I'm with Joe, be sure of what your buying. I know for a fact Eagle offers a 3.75 cast crank that is external (rear) and internal (front) just like the Scat and factory cranks. Like I said about the DMFW balance deal.... Keeping it in the stock configuration is your choice and does have it's advantages. If I were in your position I would probally try to do the same. Will |
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Posted on: 2009/9/27 18:48
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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| rklessdriver | Re: 383/DMF considerations | ||
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Senior Guru
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Just to add some prelim calaculations.
The KB 18cc dish piston (KB 9926) block decked to piston .010 in the hole, .025 X 4.100 head gasket (Victor Reinz PN 5746), 56cc combustion chamber. This combo gives you a SCR or 10.61 with a quench distance of .035 If you degreed your camshaft in on 108 Intake centerline, it would give you a DCR or 8.66 10.6 SCR and 8.66 DCR would be perfectly fine on 92 octane provided your EFI tune is good. It is actually what I would shoot for were I building your engine. Will |
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Posted on: 2009/9/27 19:02
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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| anesthes | Re: 383/DMF considerations | ||
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I screwed that up with the 412, and had to go with a small base circle cam for clearance. Long strokes need cap screws to be safe (with 5.7" rods). -- Joe |
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Posted on: 2009/9/27 19:45
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| 89Vette | Re: 383/DMF considerations | ||
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108 ICL and 112LSA is what I picked. You guessed well. What if it's decked .005"-.010" and I use a thicker head gasket? In KC, 91 Octane is more prevalent (though 92 might still be available at BP). I think planning on 91 octane is a better plan. I'm thinking 10.2(ish):1 compression might be safer? Thanks for the info on the pistons. I've had enough people tell me to go forged that I'll do that. If I use my 214 cam with my HSR, what do you really think I'll be missing out on for a street car? Like I said, a sim showed it doing pretty well up to 5800rpms. (FYI: My exhaust is semi-constrictive in that it MAY only flow about 700cfm [sidepipes].) My other intake is a 4" mega-ported/siamesed SLP/TPI setup. I went ALL the way thru the tubes and got them >= 1.65" gp |
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Posted on: 2009/9/28 0:59
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383 stroker -- Semi-Siamesed SLP long-runner intake, AFR 195's, 4-2-1 headers, and a SR cam. ZF6 short-throw shifter. Custom body/interior. |
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| rklessdriver | Re: 383/DMF considerations | ||
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It is not nessescary to change anything. I wouldn't be afraid to run it on 91 oct with 10.6 SCR and 8.66 DCR. I run LTX's on 89oct with this compression. With your new AFR heads and that high swirl combustion chamber... your L98 will run on 91oct no problem.
If you wanted to drop some compression just for the heck of it... Do NOT do by increasing quench distance (either not decking the block or using a thicker head gasket). That is one of the worst things you could do. Quench plays a big part in how the mixture is forced into a certain area of the combustion chamber during the power stroke. IME .035 to .040 is the magic number... Just put a 20cc dish piston in it. Probe PN 12344-030 ($455.00) has a 20cc dish and gets you 10.3 SCR using everything else I told you. This piston has floated wrist pins like the KB, but uses 1/16 compression rings - so be sure to get the correct rings. Probe PN P3832F-030 ($372.00) has a 22cc dish and gets you 10.14 SCR using everthing else I told you. This piston uses the same 5/64 compresion rings as the KB piston but has pressed wrist pins - so be sure to get the correct connecting rods. You can lower it if you want with either of these alternate pistons - but I don't think you should bother. I would buy the KB 9926 pistons... deck the block till it is .010-.015 in the hole and run the Victor 5746 gasket. Will |
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Posted on: 2009/9/28 1:46
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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| 89Vette | Re: 383/DMF considerations | ||
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Quote:
Thanks for all your answers Will! How do the Probe 3832's fit in your recommendation to use 4032/2618 alloy? (They are made of "Forged VMS-75 High Silicon Aluminum".) Mostly I ask with regard to slap, though explanation of other diffs are welcomed. What's the pros/cons of 1/16 vs 5/64 ring sizes? |
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Posted on: 2009/9/28 6:49
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383 stroker -- Semi-Siamesed SLP long-runner intake, AFR 195's, 4-2-1 headers, and a SR cam. ZF6 short-throw shifter. Custom body/interior. |
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| rklessdriver | Re: 383/DMF considerations | ||
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VMS-75 alloy is very similar to 4032 alloy. Both contain 11% silicon which makes them very low expansion. VMS-75 is a newer version of 4032 that Federal Mongral brought out when they consolidated TRW's piston mfgring capabilities back about 6-7 yrs ago. Those Probe pistons fit in perfectly with what your looking for in reguard to tight piston to wall running clearance and no start up noise. 5/64 rings are what GM desgined into the SBC. They are cheap and fool proof. Actually most all domestically prouduced engines used 5/64 rings until the early/mid 90's (GM changed the SBC in 1992 with the LTX) when the Govt/EPA push for more fuel efficient engines forced the OEM's to look for ways to reduce friction inside the engines..... Part of what they changed was the ring pack - something us racing engine builders had been doing for 30+ years. 1/16 rings are the "old standby" of the racing engine world. They are thinner and have less radial tension on the cyl walls compared to 5/64 rings. They create less drag and free up some HP. They cost more. Most sets are "file fit" and must have the end gap precisley fitted to the cyl wall. Unknowlegeable engine builders cause all kinds of oil consumption problems by running the wrong ones (the "low tension" oil ring set) in street cars. I like to run 1/16 rings. There are "trick" ring sets out there in this size with a "Napier 2nd ring" that make HP and reduce oil consumption in street cars. This kind of stuff is just not availiable in 5/64 rings. In all honestly many street cars will probally never know the difference. It's not like it's the kind of HP difference you can feel in the seat of your pants with a low HP engine and the extra $100 those 1/16 rings cost (and the added $83 more for pistons), could be better spent else where in your case. Will |
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Posted on: 2009/9/28 13:04
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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| 89Vette | Re: 383/DMF considerations | ||
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Today was funny... After calling shop after shop after shop, I found everyone afraid of what a DMF is! LOL Finally, in the oddest place, I found a winner. I was referred to a machinist at a CarQuest of all places.
He went thru everything I wanted and provided the exact Eagle crank to use. He was the only (local) shop that was confident clearancing wouldn't "hit water -- requiring hard-blocking", he was confident in his blocking machine, and with the crank selection. Better still, he'd done a 92 ZF6 vette last year! Downside...He can't complete a block for me until mid-November. :-( I followed up his Eagle crank afterwards. It was a 10352375057E. (They have two other versions of this crank as well. Drop the 57E to get the ext/ext version and change the 57I to get the int/int version.) Scat said their crank will work too. I can't find the model# this minute, but it had 383-5700-L at the end IIRC. One other thing he added was to refuse any bearings containing aluminum and to use 3/4 groove mains. Oh yeah... CNC-Motorsports shows the Eagle "57E" crank as an LT1 crank. Is the crank interchangable between L98's and LT1's? gp |
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Posted on: 2009/9/29 4:40
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383 stroker -- Semi-Siamesed SLP long-runner intake, AFR 195's, 4-2-1 headers, and a SR cam. ZF6 short-throw shifter. Custom body/interior. |
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| rklessdriver | Re: 383/DMF considerations | ||
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Quote:
Oh yeah... CNC-Motorsports shows the Eagle "57E" crank as an LT1 crank. Is the crank interchangable between L98's and LT1's? Yes, it will work fine. Quote: One other thing he added was to refuse any bearings containing aluminum and to use 3/4 groove mains. The only brgs that have a high content of Alum that I'm aware of (currently) are Federal Mongrals. They have a reputation for being very hard on crankshafts but I have not had any problems with them in limited application (ie. I only use them for one type of engine). I'm guessing he likes Clevite 77 or maybe King brgs. Both are top notch products. The 3/4 groove main brg is the engine builders choice. What it does is open up the oiling window on the mains a few more degrees of crank rotation. Becasue both oiling holes in the main journal of the crank are uncovered at the same time for those few degeees, it will bleed off a little more oil pressure than a 1/2 groove brg. This can be a good thing if you have a HV/HP oil pump. Since the Melling M55 series pump breaking fiasco of a few yrs ago I've been running Milodon oil pumps. Until this year Milodon did not offer a std volume pump, so I had to run a HV pump.... I used 3/4 groove main brgs in those engines - one of which is the engine in my 92. With .0028 Main clearance and .0025 rod clearance it holds right at 50-60psi (hot) oil pressure at idle with 15W40 Shell Rotella T. I like to see good oil pressure but I don't like to see the gauge pegged @80psi all the time. The fact that the guy has a good amount of work is usually a good sign. I would ask if he would give you the ZF6 Corvette owners name and contact info for a reference. Corvette owners are usually willing to talk to one another about their engine builders. Good luck with your build. Will |
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Posted on: 2009/9/29 12:59
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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| 89Vette | Re: 383/DMF considerations | ||
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Quote:
I decided to follow-up on this post. From what's said above and what I learned when reading up on quench, I wonder if this advice should/could be revised. Quench, by definition, is the piston face area that would contact the cylinder head if deck height was reduced to zero. With the KB piston that would include the area behind the valve reliefs and the rim. With the two Probe pistons listed as alternatives, there appears to be more of a dish present. So, nothing but the rim would contact the fact on a zero deck. From my understanding, the alternative pistons would violate the premise that quench should NOT be increased -- if I wanted to lower compression. Look how the piston faces look recessed for the two alternative pistons.... Probe P3832 Probe 12344 See how they're both recessed inside the rim! After reading more about quench and talking to a couple of builders, I've decided that quench really is important. And, to satisy the requirements of staying within good quench, I'm down to only two pistons as a valid option for my particular build (with 56cc chambers). The KB FHR piston is like a flat-top behind the reliefs and a dish in the middle. This works. The SRP Inverted Dome pistons probably have the best quench shape of all my piston choices. (The KB is fairly similar but the only pic I could find is a line-drawing in their online catalog. So, the point of this thread is to show what I believe to be the best piston face when a dished piston can be used. And, though I'd bet other dished pistons have been used successfully, this is the shape I'd put money on to handle the highest compression. Note: Please click on the BOLDED links above to see piston images! |
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Posted on: 2009/11/17 5:28
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383 stroker -- Semi-Siamesed SLP long-runner intake, AFR 195's, 4-2-1 headers, and a SR cam. ZF6 short-throw shifter. Custom body/interior. |
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| rklessdriver | Re: 383/DMF considerations | ||
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Gregg
I just went and looked in my Probe Book and the web site links you have are just generic pics for both... PN 12344 is a "D" shaped reverse dome. (Pic Wrong) PN P3832 is a full circular dish. (Pic Correct) Yes, the "D" shaped reverse dome pistons are where I put my faith when building hi compression pump gas engines when you must have a dished piston. The PN 12344 is still a viable piston option for you. Here is an actual pic of it. You can even zoom in on the PN and see it's correct. http://www.probeindustries.com/Chevy_ ... e_SRS_Pistons_p/12344.htm Will |
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Posted on: 2009/11/20 22:54
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1984 Corvette. 434 SBC with a Powerglide. Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials. 1972 Corvette. LS5 454 BBC with M20 4 speed. Best Pass - Doing good to just pass a gas station. |
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