I'm deciding between the 260XFI and 268XFI cams from Comp Cams. (Of course full porting/AFR 180s will be included).

Both cams have .525ish lift on both sides. The duration of the 260 is 210/218 while the other is 218/224. I have to assume the ramps on the longer duration cam are slightly less steep.

One question is do I need to buy special components to maintain motor longevity with high lift cams? One person suggested I buy LS7 lifters from GM plus whatever pushrods/springs compcams recommends for either cam. Is this all I need to worry about to maintain stock-length motor longevity?

What gains would you estimate with: either cam, fully ported 113 heads, long tube 1 5/8" headers, and a large tube base/runners/plenum? How would it differ if I choose a miniram and/or AFR 180 heads?

I calculate I only need 210cfm for the long tube intake because of the rolloff. Ported 113's should get there easy and the cams shown here will hold that flow damn near the entire intake stroke, right? Even the miniram only needs 230ish...

My thoughts are the long tube intake will be more usefull for my street car that spends most of it's life below 50mph. And, it will pull like it has 50 more hp than the miniram at those low speeds. (IOW, if the change to a miniram got me to 350hp, it would pull on the low-end like it had 400hp).

I get 17 city, 30mpg hwy stock. How will these changes affect mileage?

Any other suggestions before I plunge in?

FYI: I have a 1989 with 3.33 gears and ZF6.

First off, I would expect the MPG to drop. More air = more fuel = more power = less mpg.

If it was mine, I would go with the miniram. Its a nicer fit and less problematic. The only downside is that you lose EGR. However, the right cam can take that and make it moot.

the two cams are very much alike. I suspect the 260 might be a little calmer for the street, but neither are going to break records. I would go with roller rockers, 1.6:1 and hardend push rods. The LS7 lifters won't hurt... but I suspect they are overkill.

The money spent on the AFRs would match the money spent getting the 113s built up. That kinda labour is very expensive and time consuming. And one wrong move on those wussy factory casts and you have coolant mixing with the intake charge.

as for HP estimates. Gee... too damned many variables. The stock L98 is good for 245 hp. The intake alone will rob it of more. same with that junk exhaust. Those alone are worth 50-75hp when done right. Seriously. The LT1 gained 50 from them, and that's not using headers.

I would say 400 is the max on the stock bottom end. it would still be close to 9.5:1, so unless you want to do the bottom end up to change pistons and add a stroker kit, you are not going to see much more than that.

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Please elaborate more on the "right cam can take that and make it moot". What's the right cam?

I will be eliminating the EGR and AIR anyway. My AIR mounting bracket broke and it was noisy. I want to clean things up (in the engine bay) and have feedback that these parts don't perform very well.

I have a local quote to fully port the 113's for $500. Another $250 for valve job, cutting the seats and install new springs.

I'd love to do AFR 180's but I'm not sure they'd give me much in this case. (They'd cost at least $700 more). yeah, if I did the miniram cause they'd flow a little better above 5k rpms and they'd have bigger valves and new everything...

gp

take a look at the specs for the LT4 cam. It did the job without an EGR.

Do you understand what EGR does?

AIR is a pain... it is so much better managed in the later LT1 cars. The electric fan is so much simpler than the stupid engine driven pump.

The company offering $500, what are they offering? Is that for both heads? I doubt they are doing much for that kinda money.

we really need someone like cuisinartvette in here, cause he has a lot of experience with porting those.

I think you would be shocked what 180s would do... and the miniram would flow at better at 6k... The other option is www.corvetteplenum.com. He cleans up the insides. Would help with the big tubes and base. If you don't spend any money on the base, tho, you are wasting money.

One more thought, the LT1 intake is adaptable to the L98. And it breathes...

With the 6 speed and your gears I wouldn't go Miniram. You will want steeper gears if you do. Take a look at the First intake. It cost less, has a new TB included, and keeps some runner length for torque. Match your cam to the intake. With a 6 speed you can use something like a TPiS ZZ-409 cam.
Replace the springs and hardware, I doubt you will need lifters.
If you can get a good porting and valve job for $750 on your 113's by all means do it. The AFR 180's will cost well over twice that when you are done. Remember your current CC is only 58cc's.

I dont know where youre from or what you want this thing to do, but i reckon this cam if you want emission compliance:
http://www.cranecams.com/?show=browse ... =104224&partType=camshaft

And either of these if you want to go further and change the rear end ratio:
http://www.cranecams.com/?show=browse ... =109821&partType=camshaft

Or
http://www.cranecams.com/?show=browse ... =109831&partType=camshaft

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The EGR recirculations exhaust fumes back into the intake to cool the burn during extra hot conditions. And, it reduces Oxides of Nitrous emissions. I will be altering running temp to get it down about 15 degrees. (Water pump, thermostat, and fan settings).

$500 is for both heads and I was shown the work done. His bowl blending and runner polishing look very good. I can "see" how much is removed from inside the runners.

I've talked to Ron... helluva nice guy. He doesn't believe this pricing either! Unless I go miniram, mathematically, I'm not convinced the AFR's would impress me with a large-tube TPI (and yes, base).

I've talked to Mike at CorvettePlenum.com. I like him too. He even WANTs to do the intake for me. And, I do like the looks of what he does. From other posts I've read, it seems probable that he could get SLPs equal to ASMs (since they are smaller). But, I'm not sure he could get them better -- unless I also sent them to ExtrudeHone.

I have a used set (base, ASM runners, ported plenum) lined up if I want it from a CF member. The base has been off a couple of times and he milled his 113s .030. I wonder if that "mushroomed" any of the china rail though. In other words, if it would still seal well on a not milled motor.

AFRs are about $1430ish. I'm not sure about milling. But I would figure about $1600 w 58cc chambers. (My local shop will surface mill for $60. I'm not sure how much it goes up to knock em down from 64cc -- if I used them.

I've got the FIRST in the back of my head -- not out of the running yet. The compcams I listed above are supposed to be better grinds for long-runner intakes. The 2nd CraneCam looks pretty good, but I'm not sure it's better than the other selections. I don't want something where I'd have to change gears.

If you aren't going to do the intake, I would stick with the 113's.

If you do the intake, doing the heads isn't mandatory but it will help quite a bit I would think.

What do you want to do with the car? Does it need to pass emissions? Is it a daily driver?

I think your cam choice is pretty small, but it's probably about all you can put in the 113 heads without the valve spring retainers getting pushed into the valve guides.

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Well in all honesty, if you dont want to swap out that 3.33:1 ratio, youre not going to enjoy the car as much. Its too tall mate, the CompCams may or may not recomend changing the rear gears, but if they dont, they are dreaming if they think youre going to have any kind of low down punch.

For a stock bottom end, those cam choices are not pretty small, the intake will only flow so much. The POWERMAX 2032 would be quite a good choice i reckon. If you wanted to do something serious with the intake (and id have said miniram) then going with the AFR heads and 3rd cam shaft i suggested would be pretty good. Too much cam isnt a good thing, and your intake can only suck down so much air.

Get your heads milled by AFR and shipped complete if you go that route. That way you have one party to hold responsible. As good as the stock plenum/runner porting looks it won't do much. The milling and refreshing of your 113's is a no brainer at that price. As I said, your 3.33's are no good for a Miniram.
If you want a LT1, figure in the price of gears. I would port/refresh your 113's, do a First intake, go with a TPI cam, and call it a day.

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I'd spend the money on 3.73s and then limit the engine mods to the intake.

Of course that's based on your first post. Now if you're drag racing, or concerned more with highway mpg, it needs to be optimized/compromised for that.

Anyhow, welcome to the guru, Gregg. So how's the other side?

I thought of gears first. But here's the deal...

My two big problems are injectors and oil leakage. Though several who've looked at my car think the valve covers were leaking, I see it otherwise.

There is not much evidence on/below the heads. However, the bottom and back of the oil pan, bottom of the ZF6, and left exhaust pipe are being covered in oil. Before beginning disassembly, it was still less than 1qt/2000 miles, but it's leaking. Everytime I run it spiritly, I smelled oil. That has to stop for a re-painted, treasured car. And, it's nearing 20yrs old. Change is probably due.

Though it's only done 55k miles, the seals are getting old and I can't see ignoring them much longer. To do the oil pan, the motor has to be jacked. To do the rear main, the trans has to come off. The intake and valve covers are already off because of the injectors.

After reading about the lame GM TPI, I decided it was time to correct that deficiency. Then, I got hooked on the idea of porting the heads after another (1989 ZF) forum member had done those 2 mods to his -- getting it to 13.2 in the 1/4! After having already done the exhaust (except the manifolds), I knew these changes were likely to make similar improvement on mine.

Then, I was educated on the benefit of adding a cam to this ordeal. One thing led to another and I spent the past nine months learning lots about my vette. I hit 50 years old last year and thought major mods were past me. In fact, I should say "passed by me" -- because I've never modded a car. I've only repaired them. With the need to refresh my old seals, the door creaked open.

Now, a ton of reading later, I see the chance to make a change w/o a ton of expense over what I feel are required repairs. Yeah gears could come first, but the car would still leak. And, I've read some stories where gears didn't create faster times at the track. But, I know these motor mods will.

I've done the reading and the math. I know I don't need a TB. I know the heads don't need to be huge -- even with a mini. And, I know the cam can make good heads come alive. That's what the numbers say.

What I don't know are the pitfalls of this change. For example, I've already bought obsure Tri-Y racing headers from VetteTech in CA. Everything I read says they will be the best for my street application, but after they showed up, I never anticipated they don't allow room for bullet cats. I can cope with that but it was a "gothca".

In this motor upgrade, I'm trying to avoid that.

I know the LARGE TUBE TPI is the path I should go for the street. I also know most people gleen over the mini. I've talked to a couple of people who've tried both and say the mini is superior. But, the numbers say otherwise. They say up to 40lbs can be had below 4.5k rpms using long tubes. The numbers also say the CorvettePlenum's SLP siamesing will raise that peak more than bigger tubes. To me, it looks like shortening runners helps more than increasing size -- to raise the rpm ceiling.

But, I have a hirise hood. Did it when repairing hood damage to add interest to the otherwise wedgy lines of the C4. Now that my AIR is trashed and my EGR took forever to get off, I feel compelled to lose them forever -- especially after I learned how little the AIR helps and saw how dirty the intake is from recirculated exhaust fumes (EGR).

These facts led me to conclude "fate" was leading me toward an HSR. But again, the numbers say go TPI. (Again, LARGE TUBE!) In reality, I'm intrigued by both options. The HSR looks like another path to ease in maintenance for a 20-yr-old car. How much better can it get to access injectors and thermo? And, I know those parts fail -- they always do. I had a Dodge Daytona Turbo Z as my last car. And, it was for 10 yrs. If it was a good car, I would have gone further. That's how I ended up with a vette. I wanted something that was worth performing a 10-yr redo on!

So, the HSR would make maintenance simple, but the TPI would pull the best for me. After studying heads, I'd buy AFRs in a heartbeat but the numbers say I don't NEED them. And, they cost about twice the price of porting/refreshing my 113's.

To finalize the project, I studied cams. I found that most are designed more for short-runner intakes. And, this was as much a design constraint as anything. To ramp a cam higher, it often needs to have more time to get open -- requiring more duration. But that leads to rough idle and is really better for short runner/high-rpms. That's not how I normally get to drive.

The 260 cam is 210/218 with .56 lift on both sides. (.525 w 1.5 rockers). The 268 is 218/224... same lift.

It's my understanding that newer design/thinking has led to steeper cams that still set the valves down softly to retain longevity. That's what articles say. But, I don't know about these cams. And, I dont' know if hardened rods, better lifters, etc... are what I "need".

I know I'd pay $100 for LS7 lifters and that's what I hear they cost. Done deal. I don't know about rods/springs. Should I just buy what CompCams sells with that cam? What parts do I really need? Are these two cams the best choice? To me, it seems so.

I think they get the flow I'd need to pull in low rpms ranges. And, I think more flow than these can provide would be wasted. I think the 268 will help up top and visa versa. I know I like having a 30mpg 6th gear for rare trips on the hwy. It's a selling point. I also know I like a car that pulls like a big-block! OTOH, having a good torque-curve sounds good too. The 268 rounds things out a little better....

So, I'm down to a few combos that all could "work". And, all would create slightly different results. But, I only get one shot. I don't want to redo the redo. (The wife would shit). As it is, I'm lucky she's "good" with me wanting to pump-up-the-volume!

So, fate is pointing me to the HSR. Mike @ CorvettePlenum wants me to choose his option -- to prove to others how well it can perform. But, someone who's tried both SLPs and ASMs proved ASMs are best -- at least w/o Mike's improvement. And yes, even others have said they've tried the rest and the mini's the best. As with heads/cam, there are options. And, I'm not sure if anything is really "right".

After reading lots of negative about TPiS, I think they are out, but the other intakes are still in. So, is the FIRST for that matter.

Heads were easy. I think Kansas City offers good deals for full porting of the 113s and they should handle my need.

Cams are a little harder...

After nine months of thinking/reading/thinking reading, I still have as many questions as what I learned in that time. But my car has been in the garage since last November just waiting for attention.

And, I want to give it.

gp

Geez... everyone always says "I want more info...". I gave it an BAM! Nothing.

So you don't think 3.33's would be O.K. with a mini. I guess that makes my decision for me. LT TPI or FIRST.

The 260 cam would pull best, but the 268 would smooth upper rolloff.

I have one suggestion to pick the 268 lower LSA to 111 (from 113). And, to lower advance the timing 4 degrees. This person didn't explain but I guess it would do this:

-Improve overlap and upper range rolloff
-Keep IVC similar to the 260 for retention of Dynamic Compression Ration. (In other words, it would pull nearly as good as the 260).
-And, it would help mid-range power too.

In other words, it would maximize the TPI setup. And, it would still pull better than most street cars on the road.

gp

Greg -

I'm not a motor junkie like these guys, but I feel your pain. I, too, have an 89 and have been kicking around the same ideas you have. After reading quite a bit, I've been looking for an extra plenum (to port myself) and a used set of TPIS/AS&M runners. I would also like my 113s ported with 1.6 RR and a mild cam for the street. I would eventually add headers to go with my catback. I currently have 2.59 gears (auto) and would like to upgrade to 3.07s.

Keep us posted as to what you decide.

Matthew