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| djxib | A couple of engine rebuild questions | ||
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I'm just about to start the reassembly of my motor. New rings and rod bearings, cam bearings, cam, lifters, rocker arms etc etc. I've done head gaskets before so I'm cool with all the valvetrain assembly and new bolt / heat cycle re-torque etc.
Rod bolt question. If I put my new rod bearings in, torque the rods (for a plastigage measurement), undo, then re-torque, will I stretch the rod bolts? How many times can I do this before I'm looking at a new set of rods? Piston Ring question. I managed to snap a couple of rings when removing them from the pistons - and I'm worried that I may snap the new ones putting them on. Any guru techniques for new rings? However it is possible that the old ones were brittle through detonation, maybe I'm unnecessarily concerned. Thanks! |
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Posted on: 2011/1/25 20:37
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Andy 1996 Greenwood Collectors Edition LT4 Previously 1992 Convertible Polo Green. 383 LT1/LT4 forged/balanced. V7-YSi, Alky. 608RWHP... Now sitting at a dismantler with a salvage title. Still runs... |
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| bogus | Re: A couple of engine rebuild questions | ||
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Grand Imperial Pooh-Bah
 
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Practice... that is how one installs rings! I also find oiling them will allow them to slip onto the piston a little easier. There is a piston ring tool that will gently and evenly open them up to slip them over. The other advantage to oiling them rings is that they will stay where you put them.
As for the bolts, you will safely get a couple of torquings out of them. They are designed for the test and final torque. I would use ARP, at the very least. |
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Posted on: 2011/1/25 20:42
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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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| rklessdriver | Re: A couple of engine rebuild questions | ||
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Senior Guru
 
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On the rod bolts. We measure the free length in our racing engine's rod bolts. Then every tear down - we check them against that orginal measurement. Easy to spot one that's ready to go off the reservation. Of course that's not possible with used rods.
Luckily stock SBC thru rod bolts last a very long time. As long as you do not over TQ the bolt and permantly stretch/damage it or pull the threads off - they are capable of being TQ'd and un-TQ's and re-used within their capability many times. You can usually spot an over stretched thru bolt type rod bolt by the threads first - The nut won't spin on freely. If thats the case it could just be a burr or dent on the threads - but if you come across one like that - inspect it with a magnifying glass to find the problem. If you have ANY doubt - replace them. It's not worth it. I've broken rods before and it's usually 100% destruction at any RPM. On the rings. I use the "spiral" tech to install rings on the piston. Start by placing one end of the ring into the desired ring land. Then you slide the rest of the ring around in a circle across the top and crown of the piston pulling at the inside of the ring so it drops over the crown of the piston (it will get tighter/harder to do as you go along). Then you take the other end of the ring and pull it back a little flexing the ring so the edge will clear the crown and drop down into the desired ring land (be careful not to drag the edge of the ring across the side of the ring lands). They do make pliar type tools that expand the rings so you can install them - but you can still break rings using them. When installing the compression rings it takes practice to know when have stretched them "just enough" to clear the crown of the piston. I personally don't use oil until after all rings are installed on the piston. It makes them too slipperly to handle. Will |
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Posted on: 2011/1/25 21:25
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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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| BillH | Re: A couple of engine rebuild questions | ||
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The Stig Moderator
 
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My piston ring spreader (plyers) was a huge "bang for the bucks" tool. Like $6.00. I lightly clamp the rod in a vice (wooden jaws) where the piston is sitting on the jaws so that it can't rock. Yea, on the comp ring, opened with the spreader just far enough to slip over the piston. Me too on no oil when installing. |
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Posted on: 2011/1/25 21:46
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Every man dies but not every man lives. |
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| rayquayle | Re: A couple of engine rebuild questions | ||
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Hey Will, quick probably dumb question. What about new rods that come with cap screws? The caps come torqued, so is there any way to know what the original length was? I suppose ARP has the nominal length posted somewhere? |
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Posted on: 2011/1/25 21:55
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Ray Quayle in England '86 Indy PaceCar, 4+3 NCM Founder #2896 NCM Lifetime #672 Graduate of Gordon's School |
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| BillH | Re: A couple of engine rebuild questions | ||
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The Stig Moderator
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Mine' s the Comp Cam design. Never broke a ring with it and IMO, much easier than spirling. $20
Attach file:  249-POW105060.jpg (0.00 KB) |
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Posted on: 2011/1/25 21:59
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Every man dies but not every man lives. |
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| BillH | Re: A couple of engine rebuild questions | ||
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The Stig Moderator
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Measure them before you remove them for the first time. I'd have to look in my ARP book but IIRC I don't think they would give more than a nominal measurement. Will may know. I can dig my book out if you want. |
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Posted on: 2011/1/25 22:05
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| rayquayle | Re: A couple of engine rebuild questions | ||
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No worries, Bill. I'll do as you suggest and measure before I remove them for the first time. Ray |
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Posted on: 2011/1/25 22:40
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Ray Quayle in England '86 Indy PaceCar, 4+3 NCM Founder #2896 NCM Lifetime #672 Graduate of Gordon's School |
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| rklessdriver | Re: A couple of engine rebuild questions | ||
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Senior Guru
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Ray
Now there are common nominal lengths - However the rod bolts/cap screws will all vary in length a few tenths of a thou.... You need to know which bolts your rods have. ARP mfgr's a number of different length rod bolts and list them in their book. SPS CARR and MSA also mfgr different length bolts. The rod mfgr should also include info as to which bolts are installed in the rods yo have. The most common lengths are 1.50" and 1.60" but there are 1.550 and 1.80 long bolts as well as others.... You measure the bolts out of the rod (free length) and then again once the bolt is tightened or TQ'd properly in the rod. The spec for stretch varied by bolt material, under head length, thread pitch and dia. For example an 3/8"X 1.5" ARP 8740 should stretch .0046-.0050 (in addition to it's nominal free length). So a 1.5" bolt would measure 1.5046 to 1.5050.... If you were real anal - You could zero the gauge on the bolt as they are deliverd out of the box (TQ'd by the mfgr) and then check that measurement against the free length and again against your TQ'd bolt length - but I honestly don't know of anyone who does that. Reason is - It's unlikely that the mfgr would have damaged the bolt during the rod mfgring process. I can't speak for all mfgrs but on a well know engine site a rep for one rod mfgr (SCAT) actually stated that they burnish (roll) the rod bolt threads by TQing them 2 times and then they honing the rod to size (which is how it's delivered to the customer)... so like I said, it's very unlikely they used up all of the bolts elasticisticy during manufacturing. Will |
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Posted on: 2011/1/26 15:31
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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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| rayquayle | Re: A couple of engine rebuild questions | ||
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Senior Guru
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Apologies to Andy, never intended to hijack his thread. Thanks for the reply, Will. Much appreciated. The rods I'm waiting for are the SCAT Ultra Q-Lite Stroker rods. They say they come with 1.4 special ARP 8740 7/16 Cap Screws. Nice to know they apparently roll them in before shipment. I guess I won't bother measuring stretch and just torque them to spec during pre and final assembly.
Thanks again for the help. Ray |
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Posted on: 2011/1/26 19:52
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Ray Quayle in England '86 Indy PaceCar, 4+3 NCM Founder #2896 NCM Lifetime #672 Graduate of Gordon's School |
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| rklessdriver | Re: A couple of engine rebuild questions | ||
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Senior Guru
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Ray
I would HIGHLY suggest you measure the bolt stretch. The tool from ARP or BHJ is only $150.00-$200.00 and is $$$ well spent. I can guarentee that short 7/16 ARP 8740 bolt will not stretch the proper amount using a TQ wrench.... There is a good reason Scat changed those rods 2 years ago from 3/8th ARP 2000 bolts to the 7/16 bolt - because people were building oval track engine right on the 550HP power rating and using TQ wrenches.... Those rod bolts were breaking and scattering motors everywhere. The ARP 2000 bolt is VERY sensitive to proper stretch for proper clamp load..... The 7/16 ARP 8740 bolt is more forgiving but I can tell you as short as it is.... I'd bet the TQ rating is 70-75 lbs.... I would like you to read this. It pretty well covers the peril of using TQ wrenches on a critical fastner like a high performance rod bolt. http://www.campbellenterprises.com/co ... tretch-assembly-specs.php I'll also offer my apologies for the thread drift and subsequent Hijack. Will |
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Posted on: 2011/1/26 20:12
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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: A couple of engine rebuild questions | ||
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Grand Imperial Pooh-Bah
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I don't consider this to be hijacking to drift. It is very good discussion on advanced engine build techniques, which to be honest, I am, not that well versed in.
I fully understand the issues discussed; I was rather ignorant to the issue in the first place. This is good stuff! Keep it coming! |
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Posted on: 2011/1/26 20:32
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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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| BillH | Re: A couple of engine rebuild questions | ||
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The Stig Moderator
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Yea, I learned that the hard way. Different motor,Ford 4cyl that runs no lower than 5,000 and shifts at 7 for an entire race. Even using ARP lube and the lubed torque spec. Sliced right thru my brand new Scat crank, took out the block, drysump pan, cam, 4 rods. And the Scat crank alone costs $850. Very expensive learning experience. |
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Posted on: 2011/1/26 21:57
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Every man dies but not every man lives. |
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| rayquayle | Re: A couple of engine rebuild questions | ||
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Senior Guru
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OK Will, very good info. I actually have an ARP stretch gauge and intended to use it, but in the past I'd always had new bolts that I'd measure relaxed, right out of the box then torque to the specified stretch. I was unsure what to do with pre torqued bolts that come with new rods. I guess I didn't get what you were saying in the last post. Must've gotten distracted when you said anal!  So what I want to do is measure the length as they come from Scat torqued in the rod and then torque to the same length when I reassemble. Sound right? Thanks again for all the help. |
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Posted on: 2011/1/27 1:42
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Ray Quayle in England '86 Indy PaceCar, 4+3 NCM Founder #2896 NCM Lifetime #672 Graduate of Gordon's School |
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| rklessdriver | Re: A couple of engine rebuild questions | ||
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Senior Guru
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Ray
What it sounds like your doing is double checking Scat to ensure they stretched the bolts the proper amount when they mfgr'd the rods. If Scat stretched the bolts incorrectly when they honed the rods to size it could distort the rod bore out of round when they are stretched correctly during engine assembly. That is why I said it's an overly anal step.... Your going to find out when you check the rod bore. I think what I have below (consider it my connecting rod check list) would have made this much easier to explain.  I first take the rods apart, clean them up, inspect them for physical defects, measure and record the rod bolt free length, re-assemble the rods with the rod bolts stretched correcly and measure the big ends (and the pin bore/little end)... If something is wrong you can then take the rod to the machine and fix it. At that point I record all the connecting rod measurements in the spec sheet. After that I weigh them and correct any variance greater than a gram. At that point I record all the weights in the spec sheet. After that, clean them up once more and they are ready to assemble on to the pistons. Will |
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Posted on: 2011/1/27 14:35
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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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| rayquayle | Re: A couple of engine rebuild questions | ||
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Will, I see what you're saying now. I was assuming that once Scat had stretched the bolts and I removed them, it's too late to get the original length as a certain amount of stretch remains. I guess that as it has only been done a couple of time during manufacturing this is nothing to be concerned with.
Thanks again for all your help. Ray |
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Posted on: 2011/1/27 17:40
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Ray Quayle in England '86 Indy PaceCar, 4+3 NCM Founder #2896 NCM Lifetime #672 Graduate of Gordon's School |
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