Author Topic: 1975 Esprit build  (Read 534 times)

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Offline LostHighway

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1975 Esprit build
« on: December 15, 2019, 05:10:06 PM »
Hello Folks!
 I recently purchased a 1975 Firebird Esprit and I must say it's VERY clean. (Pic provided). White with a black vinyl top and black interior. Before the car has even been delivered I also purchased a very expensive but complete Formula hood that wont take too much work to be flawless. Ive got some 17x9" Rally II's and a rear spoiler also soon to come (just waiting on the car to get here). The plans for the car are simple, 400hp, cold A/C, great driver, nice exhaust, tight chassis and suspension that rides well and smooth. Did I mention killer stereo?

As a GM tech for 20 years and p/t automotive restoration Technician for a company that does very meticulous work, I am all in on this car and starting off ahead since I will be doing a lot of this work myself with the help of my aid (wife) who likes to help out on these deals. This isnt her first rodeo either, so lets begin.

So as I understand Pontiac, the company did not do much compression changes by way of pistons which is different than my SBC, SBF traditional builds. What I'm trying to do is find a good replacement cylinder head that will raise compression and not break the bank. Ive been looking at a company up north called Nightmare Performance which has a decently priced 6x head that has some bowl work that are also set up with better springs. Has anyone had experience with this company?

I am aiming for 9.0-9.5:1 cr. I could run more with an aluminum head of course and thats not out of the question. The problem is I cannot find any machinists measurements on the P350 from the low to mid 70's.
How far is the piston below deck @ TDC?
What reliefs are typically found on stock and replacement pistons?
Whats the typical compressed head gasket thickness for these engines? I found a set of Cometics with .027" compressed thickness but I am not sure if they will work with a block that has scalloped valve reliefs?
Also... Stock combustion chamber volume differs from site to site. I see a 94cc and I see bigger. What's the real deal?

I am guessing a 70cc chamber would be optimal but I really need to know as I do not want my quench area to be too large. Especially since these are open chamber heads and closed chamber show better fuel atomization due to squish areas directing the mixture and allowing better/lower timing. This is where I REALLY like the KRE 65cc aluminum D ports with a fast burn style modern chamber.

If I cannot get quench where I want, I may be looking at decking the block and buying another rotator. If thats the case, I see no point in staying with the 350 since this will be better money spent on doing a 400.

Now before you write back saying, DO THE 400, I have found more than a few 350 builds which are well north of what I am wanting and I seriously do not think 400hp out of a 350 is too much to ask for, even with a cast bottom end. I think it should be easily do-able.

I'd like to hear some responses while I watch the Cowboys hopefully win a game for a change. lol Thanks