92 L98 SD

My 083 heads are currently at the shop. Had some blowby and 3 leaking exhaust valves so I figured might as well spend lots of money and boost my power. Who needs a good reason to get more horses?

Anyway, I need your opinions. I'm debating between going aftermarket aluminum heads vs. the following head work the shop wants to do.

They'll do:
Hot tank heads
Bronze guides
Guide liners
Mill heads (min. 40.00 mill heads + .020) not sure what these numbers mean
competition valve job + over size in valves (didn't ask what kind of valves but he said the springs would hold fine in the .500+ lift range)
2.02 intake valves (keeping 1.5 exhaust due to "hardness issues")

Port $350
Port match intake $100

Said it would flow 220 to 240 cfm.
Total price $653

Now - pros and cons of spending this money on my 083 heads as opposed to spending more on aluminum heads. I want AFR but the price is kind of on the high side for me considering all the other goodies I want to get.

What do you think of these?
Unless you guys know more than me, which you probably do, I was thinking of going with:

TPIS bigmouth base (as is)
AS&M runners
Stock plenum (sent to mike graycar)
Some sort of cam with a 220-230 duration and .500 lift. Suggestions?

Now I've read that the bigmouth base flows 260 cfm. In this case would it be overkill the get this base as opposed to say, edelbrock, due to my heads only flowing 220-240? Questions like this is what I'm looking to get answered.

1 5/8 hedman longtubes
Remember, i'm looking for 400-500 hp out of my 350 with flattops.


Thought my car was a factory freak when it ran 14.3 at 96mph until I opened it up and found flattops AND my heads had already been worked.

Hit me.

BTW - I was looking at these heads as an option.
http://cgi.ebay.com/ebaymotors/ws/eB...m=260072152965

 

240cfm will not make 500hp at 10:1 compression ratio.
It will make 400+ with the right cam etc. don;t expect more than 440hp. If the cam duration is at or near 220, think 390-410hp range. Why don't you port them yourself? Doesn't pay to have a shop, port stock castings. The flow figures they quoted, are realistic, but you can achieve that, at home and save $350.
You should be able to grind in a new 1.60" exhaust valve job seat for 1.60" valves on the cast heads. If they were aluminum l98 heads you would be limited to 1.56" with stock seat inserts. if in doubt go to a 1.56" valve. Or replace the exhaust seat. Ya want the bigger valve. 1.56 or 1.60". Got to get the exhaust out to make power. Probabily more critical than the size of the intake valve. I would do the porting yourself and get them to do the required machine work to finish them. Or wait and save for new heads that flow the #'s you want/need.

if you want 500hp, think 260+cfm port flow.
And get rid of the long tube intake manifold. Get a short runner one like the LT1, mini ram or Stealth ram.

 

The TPIS big mouth, the Edelbrock, and the newest Accel manifold are all made by Edelbrock now and they're all exactly the same. Get the least expensive one, which is usually the Edelbrock.
Forget the stock 1083 heads. They're not worth the money. Trick Flow 23 degree heads are the best bang for the buck. They flow slightly less than AFR 195's for about $500 less.
90-92 L98 350's came with flat top pistons from the factory.
Remember with a camshaft in the 220-230 intake duration you're going to need a custom chip. I see in your sig you already have that taken care of.
Lastly, 350 TPI automatics in our SoCal club with similar mods are making 300-330 rear wheel horsepower.

 

I will simply say that unless you home port your heads and fix the valve guides, save your money and buy an aftermarket set of heads, www.enginekits.com sells aluminum heads: 64cc, 190cc runner, 2.05-1.60 valves, good for .550 lift all for $789, these would be a nice set of heads for the price, also would be allot more easy to make your desired power, I would use a bout a 224-230 duration cam with a 3000 stall, would run great with a short runner intake as suggested above.

 

vortecs flow 245 cfm and come that way factory. nice ones setup for higher lift are $550 from scoggin dickey parts center

 

Short update.
I ended up biting the bullet and bought the AFR Eliminator's 195cc 65cc angle
My block's now at the shop getting a bath and checked out. Possible bore required. Interesting scoring in cylinder 3. Not sure if it's within ring travel.
The Bigmouth base is on it's way port matched to the Fel-Pro 1205 gasket like the heads.
TPiS runners are still in the works.
1.6 full roller rockers
Am I going to need hardened pushrods?
Still haven't decided on a cam.
Suggestions on a cam that will get me as close as possible to my goals of 4-500fwhp?

 

You wil not make that kind of power from a 350ci motor with a long runner TPI intake. Big mouth or not. The tuning is too low. (RPM) You will need a intake with shorter, more direct runners. No cam will fix this. Easier to work with physics than against it.

 

Then how about as close to as possible?

 

"close" only counts in tiddily winks and atom bombs.

Don't expect more than 360-380hp out of a 350 TPI with a long runner manifold. If you want big power change the manifold.

 

or horseshoes and hand grenades, as my grandfather loves to point out.

 

if you dropped $1600-1800 on those heads, you'll be super disappointed when you drive the car with that TPI based setup on top. Time to sell off all the FI and put on a single plane vic jr and 750 dp holley for HP on the cheap, or go stealth ram, mini ram, etc and keep the FI.

 

360-380 would be satisfying for a while. Suggestions on a cam for that kind of power?
I'm thinking 220-230 lift range 112 lsa and something around .5 duration

 

I would think 220-230 duration, and .5xx" lift, but yea
Go with a computer controlled cam, with the 114 LSA. Remember, 2 points in LSA = 4 points in duration, so that extra 2 LSA is worth it. Comp makes the factory "computer controlled hydraulic roller" cams that would work great there. You'll get more lift than I was first thinking, since it'll be a roller.

 

Would a 114 lsa give me vacuum problems?

 

I would go with a custom cam with the LSK 220 degree lobes on the intake and 1.6 rocker arms to get the max out of your heads for the intake system. Call Thunder Racing they are one of our supporters and are very good with custom cams. Phone 225-754-7223.

You will want 10.5 to 10.75:1 compression. Get your deck on the block milled so that the pistons are .007" in the hole. Then buy the GM .028 head gasket for a .035" quench.

With headers and a good exhaust system you will make good power and get well above 400hp. I have done it with less.

 

Quite the opposite, 114 LSA will give you more vacuum and make the car much easier to tune, and it will idle better. In return, you give up about 10-15 peak horsepower above 5000 RPMs. You wont notice it with a TPI intake.