I have a 1992 6 speed car with a Procharger 600B running 8 psi. Today I did a compression check and found that my number 8 cylinder only has 60 psi! It is a stock LT1 with cast pistons and 50k on it. I am guessing I have a cracked piston or some bad ring lands on that cylinder.

I am going to pull the engine and rebuild it before summer gets here in northern Wisconsin But since I just recently bought the car, my savings is a bit depleted. I have no choice but to pinch pennies and make this happen. I could always leave the car sit and wait until I save enough cash to do the awesome 383 build I want to do but that means I wont be driving the car all summer and that will drive me nuts.

So my question is, Should I pull the engine, bore the block .030 and put scat H-beam forged rods, Probe forged pistons, and a scat 9000 series crank, use my stock heads, a mild cam, 1.6 rockers and leave it as a 355 or should I build a 383 using the same parts with the 3.75 crank. The delema is I dont have the funds to buy new heads like I want right now considering they are anywhere form 1500 used to 2400 new for the AFR 210 comps. I am leaning towards building a forged 355, using my heads and intake, keeping the tuning issues to a minimum, having fun with the car for the summer and next winter I can pull the stock heads and intake and replace them with the AFRs like I want. .

I am going to have to have a local shop dyno tune the car anyway which is going to be expensive so I am wondering how a 383 would stand up with the stock heads and 8 pounds of boost...

Any opinions/advice would be much appreciated!

 

Heads make the power, and a 383 is not much more money than a 355

Glad I went 383, helps fill in the bottom end until the blower starts making boost.

 

Yes I know I need a good set of heads But the funding isnt there right now and I dont want to leave the car sit. I would like to rebuild the bottom end with all forged stuff and drive it for the summer. Next winter I plan on putting heads on it. Im just wondering if a 383 is a bad idea considering I will be using the stock heads for the summer.

 

Hers a good build, http://www.gmhightechperformance.com...l/viewall.html

 

Go ahead and build the 383. replace the heads later, just work out the compression later given the stock volume chamber and what you plan on doing later.

 

Thanks. I think I might have a local shop build and tune a 383 for it and just get it done and over with. I am going to Put a full forged, balanced and printed rotating assembly in it. They are also going to open up my stock heads and intake for me and port match everything. The shop is really reputable and they do great work but the 5500.00 price tag is what I dont like. They are telling me it should make a easy 550 rwhp. What do you guys think? I am sticking with the p600b ati blower also.

 

Well I have been researching this a long time. my set up now is providing plenty of power (Vortech V2T Trim) and the stock motor I used runs Fantastic so, Until something breaks loose ( pry will be in the trans or differential ) I am leaving well enough alone.
The pistons on the above build are economy minded and do snap landings with anything over moderate boost. At 550 rwhp you will be at that level and beyond.
My pocket says Diamond pistons and very stout rods and A good forged crank. Worry about the heads later. ( Have them checked out) Enjoy

<< Doing a weiand blowie 8-71 on my 74 now.

 

Ok so I decided to go all out, I am building the engine right the first time.

BrianCunningham, what is the compression ratio on your 383? Also what cam and blower are you running ?

 

I'm running an S trim
I'm thinking of running a T trim when it wears out
So I lowered the compression down to 9 to 1

the cam is a custom grind by my tuner SloRvette

 

Thanks, The car goes in monday. Any good advice is appreciated.

 

I bought 195 afr's and had them flat milled at the factory from a forum member on here. TPI421Vette. Shipped to my door i don't think I cleared 1600 brand new.

 

Good choice ........

KW

 

Same heads I have on my car
BTW you can have your stock intake ported to match those heads

 

Hey Smooth,

I'm probably a bit late with my advice, but I've been in your situation and let me tell you, if you don't have the funds for a motor build then don't do it! The last thing you need is to burden yourself with something you can't handle financially.

My advice would be to pull the head and see what is going on with the cylinder. It could be something as easy to fix as a blown head gasket. If it is a cracked piston it may not have damaged the cylinder walls and you can probably get away with just a ball hone and picking up a used stock piston from someone that has rebuilt their engine. That could get you back up and running with a very minimal cost. piston, rings, head gasket, oil pan gasket, and some coolant and oil.

If you are going to build the engine I would go with the 383. The low end torque will make the car much more fun to drive. The downside is that you may run out of air at the top end with the smaller heads. I'm not sure how much air the blower can push, but that might limit your upper rpm as well. You would need a dyno to really tell you.

9.0-9.5 would be good for the compression ratio, but make sure they gap the top ring extra wide. I had a boosted engine that didn't make it off the engine dyno before it destroyed the pistons because the ring gaps were done for an NA engine.

The other problem you may run into is that you will want to spin the blower faster to up the boost with the new engine. That means more of a chance of belt slip. But you can start changing that once the engine is up and running and back in the car.

 

Thanks for the advice MN_Vette and all you other gentleman. I am having a pretty reputable shop build this thing and tune it for me. As of right now I am shooting for some AFR 210 comp port heads, Port matched Lt4 intake, and a solid forged lower end. We are using a forged scat crank and rods along with SRP forged pistons. I wanted to go with Diamond blower pistons but the extra funding isnt there right now. I am trying to keep the build and tune under 7 grand. The car has a P600B blower on it along with the FMU from ATI. We are ditching the Fmu and going with a bigger pump, bigger injectors and ofcourse some custom mapping on the dyno. I plan on documenting the whole build with pictures and some videos of the car on the dyno. The only thing I have alot of questions about is the valvetrain but the gentleman that is building/tuning the car for me is going to handle that. As far as belt slipping goes, Greg at blowerworks makes a awesome bracket and balancer to limit that. I am going to go with that as well. Maybe not right away but for sure not long after the car is together. I will keep this thread updated as the car comes along. Lets hope She is as fun as I plan on it being!