I recently installed a single turbo on my lg4. It now has three bad cylinders (broken rings or cracked piston) and one is definately a broken piston, so basically I need another engine. I haven't really done too much research, just because I was hoping this engine would've lasted until the summer and when I'm out of school. But, since I have to deal with this now, I need some advice on what to replace the 305 with.



I want something that will mount up to to everything that I have done turbo-wise. I'm going to be keeping the carb, intake, turbo manifolds, and if possible the mech. fuel pump. I definately don't want to put another 305 in it. Is there any kind (l98, lt1, ls1) or size (327, 350, 377) that would help to optimize the turbo set-up while keeping with the system I have now?

Thanks

 

Any Gen I Small block will be a direct bolt up. I'd say go with a 350 built for boost to keep your budget down. Any motor can be built to be "optimised" for a turbo, it's just a matter of $$$. Depending on how much boost you run(and it sounds liek it's a bit givin what you broke) count of having the whole bottom end forged.

 

I decided on building a generation I 350 engine. How should I build the motor for it to be able to handle boost around 14-16psi? It will be street car that might see the track a few times a year. I talked to Summit and a local engine builder and they didn't really get into any detail about it. I was told a four-bolt main would be stronger than the 2-bolt. You mentioned the whole bottom end being forged. What all does that include (piston, crank, rods)? I want this engine to be able to last more than a couple years. What else do I need to consider when building the engine for boost?

 

Try to find a 4 bolt main block and install ARP main studs. The crank should be a Eagle or Scat Forged steel crank. Since you are rebuilding the entire engine I would build a 383. Use the 3.75 stroke crank. Rods should be an H-beam design from eagle or scat with good rod bolts. The pistons should be a good low compression design. They should be a good brand like SRP, Ross, Diamond, or CP this will depend on your budget. This will set you up with a killer bottom end that can handle alot of boost. With the 383 it should make alot of extra torque. What type of intercooler do you have on the car? What size turbo do you have? Are you wanting different cylinder heads or are you going to run a stock cylinder head?

 

The turbo is a T6 Garrett with 1.05 A/R turbine. It was oversized for the 305, but I knew that I would be replacing the engine with a bigger one so it should work well with a 350 or larger. The intercooler is a Spearco race intercooler with 2.5" inlet/outlet and a core of 3"x10"x24". I don't know what cylinder heads I will want. I was advised to use aluminum heads though.

 

I would run a good set of aluminum heads. You need something with a good intake side. The exhaust is not as important on a turbo car like it is on a blower, nitrous or NA car. You will have the turbo pulling the exhaust out of the port. Try to run a 9.0 compression ratio with the turbo.

 

9:1 compression seems a bit high for a motor that will repeatedly see 15 PSI of boost on pump gas. I disagree with what 92camaro said on heads. Under load(boost), the turbo will NOT suck the exhaust out. Just the oposite. In a turbo motor, you want as much pre-turbo exhaust flow as you can get. the better you can get the exhaust out to the turbo, the quicker you'll start making boost. The intake isn't as important because you are forcing air in. I would also look for a turbo specific cam. Generally, a turbo cam has more exhaust duration than a standard cam has, again increasing exhaust flow. It would also be to your benifit to have your exhaust manifolds ceramic coated. The more heat you can keep in the system before the turbo, the better. Hotter gas has more volume, and more kenetic energy, both of which help spin the turbine.

If your up for some reading, Corky Bell's book "Maximum Boost" is an excellent book on designing turbo systems. It's more for designing turbo systems than the motors to put under them, but it's still a great resource.Book

 

I appreciate all the info, especially what to look for in an intake and cam. I've read 'Maximum Boost' and 'Turbochargers' and both were very good resources for the turbo build. I might have to go back and see what they say about the engine. Also, 8.5:1 would be the highest compression that I would want to run. But, after going through an engine, I guess the main thing I'm worried about is strength and longevity of the motor rather than its performance potential.

Will this be enough to be able to handle some abuse every now and then? Also, I'll probably stick with a 350.