Alright, I need to mod a 85 L98 to be as stock sounding as possible and retain most of the stock looks.

Thought process

1) Ditch Cast iron heads, go to stock 86-91 alum heads with some porting work
2) Upgrade cam to roller, need recs on something to increase power band but can not have any lump to it.
3) port stock TPI, which is a waste, or find a LT1 intake to convert or buy one that is already converted.


I can not do headers, and exhaust is extremely picky as well.

What are your suggestions?

Is this for your racing class?

I think the retrofit kit for the roller cam would be cost prohibitive. How about a motor swap with a factory roller motor block?

I think the 88 challenge cars cheater cam might be a good choice that isn't too lumpy.

If this is for the race class, does it matter what year the intake is from? Do they check that?

I've seen pictures where people have ported the exhaust manifolds and cleaned up the casting flaws. Looked better than stock.

Matthew

Jeff... think in this manner... I know it's a bit apples/oranges, but still.

The C5R and C6.r used those monster 7l motors... the powerband, thanks to the restrictors, was between 2900 and 5400.

So it can be done.

I would exude hone the hell out of the factory crap. I would also clean up the inside of the plenum.

I don't see how your rules would allow for an LT1 intake.

Hell, if it allows that, why not convert over to a 4bbl throttle body and use a dual plain intake!

Roller rockers are a must, if the rules allow.

For the camshaft. You need to talk to my cam grinder Mike Jones. A lot of his work is "spec engine camshafts". Just let him know about the rules, stock exhaust exct and he can hook you right up with something that sounds stock and makes good power.

http://www.jonescams.com/2006catalog_001.htm

I would pay attention to the very small things. A couple of good friends in NC race a TPI car in NHRA Stock Eliminator. The little things make a world of difference in those cars. The machine work is perfect in those engines, everything from the ring end gap to the deck height to the brg clearance is dead on the same.

For your 85. I think alum heads are a good idea mainly to get weight off the front end. I would recommend you port them as much as you can afford to. The runners are small and you really can't get them too big for a 5.7L motor without getting into water first. Pay somebody to do a good Serdi or Newen 3-5 angle valve job on them. 30* Back cut on the intake valves.

Port the intake. Port it as much as you can.

If your going run the stock 85 short block. Meaure the deck clearance. Pistons will probally be .020-.030 in the hole. Run a super thin head gasket. I'd recommend one of the OE steel shim head gaskets that are .015. YES it will brinnel a fire ring dent in the deck surface of the alum cyl heads but it's free HP and the only way your going to get the quench anywhere near .040 or less.

Also what you can't make power wise in the motor you have to make up for in the chassis or driveline. Lots of easy (but expensive) power in REM polishing gear sets. Engine accy drive, think about what you don't need. Light weight FW, light weight wheels ect.
Will

When it comes to the exhaust, here's a link of possible interest:

http://www.gesslerheadporting.com/mem ... p.nsf/sub-menu/Services03

Double check on using a thin head gasket when switching the heads to the 113 aluminum heads. I am going to do that same on my 85 and everyone has been telling me my compression will increase from 9:1 to around 11:1, so a really think gasket may not be a good thing depending on piston to valve clearance. Also, I didn't see mentioned, adding 1.6 roller rockers is good too. If you can afford, there as been articles about people running 1.6 intake and 1.5 exhaust making better numbers than 1.6 on all.

My stock block '91 has 113 heads and the Fel-pro 1094 steel shim coated head gasket.
Stock deck hgt. +-.025" + .015 gasket =.040" quench and 11:1 compression. With my hot cam the comp. is in the 210 lb. range and hasn't changed in 2500 mi. which included 20+ drag strip runs and two dyno sessions.
Plenty of valve piston clearance with the .525" lift.

@Flyboy:

What have you changed to get 11:1 compression? Stock L98 had 9.5:1 with stock 113 heads. The 85 cars had iron heads with flattop pistons and chamber size of i think 73cc. The 113 heads are 58cc chambers, with the current flattop pistons. I do not know much about engine building. I have asked the question several times before I bought 113 heads for my 85, so I was just saying to make she the OP checks it out as well. Making sure there would be enough clearance with flattop pistons with the 113 heads, and possibly 1.6RR

We're veering off course here but basically by changing from stock gasket thickness of .055" to .015" with the stock 58cc chambers and .025" deck.
There's a formula out there.

To bad you couldn't put this in.

Quote:


Really we're not veering off course. The OP has an 85 car, I also have an 85 car. the 85's came with cast iron heads with a 73cc chamber @ 9:1 compression. The Op is asking about putting the 113 heads with a 58cc chamber. The cars with the 113 head I believe had dished pistons to keep compression at 9.5:1 where as our 85's have forged flattop pistons with big chamber @ 9:1 compression. All I was saying was to make sure that you have enough vavle clearence with the smaller chamber and flattop pistons if you're going to run 1.6RR, but also to make sure you have clearence between piston and valve either way the OP goes. The OP may need, as well as myself, to use a thicker head gasket, even the quench might be bigger, he(we) are also increasing compression ratio by quite a bit with changing to the 113 casting heads from the later L98 cars.

No if there is not enough clearence between piston and valve and the touch, the OP my not be happy with the information he got here in the forum saying that it will be okay, I'm just saying to make sure the OP looks into that aspect of it. The information I have been given was that it should be no problem. Since I really dont KNOW FOR SURE, I am slightly hesitant to just throw the 113 heads on my car, as I do not have cash laying around to start from scratch.

Forgot about this thread.

Been poking around, and I knew about the compression issue. I was worried a bit about the clearance as well. One thing I was wondering about, the 86/87 128 casting heads maybe a better substitution.

Still up in the air on a cam though. Might think stock LT4 cam. I think I have one laying around on the shelf.

TPIS torque secrets cam (does it have to be a GM cam)
porting, heavy angle milling (changing valve angle) all of that stuff helps.

Hey Jeff is your phone broken?