stealtht/a

iTrader: (1)

Hello all, looking for some advice on mild 305 building. Ill start off with the usual disclaimer: I am building the 305 NOT a 350, please dont waste any bandwith trying to convince me to go 350 instead. Im using an 87 305 roller block that seems to be all stock except someone put roller tip rockers on it. I was told the engine has around 50k on it and it looks like thats probably true. It ran well when i drove the car home. I have a few disassembled 305s around and I was thinking of swapping the flat top pistons from an 85 TPI LB9 into this 87 to up the compression a little. the 87 engine will be mildly ported, headers, and Ill put a mild cam in it, not sure which yet. Ill probably use the roller rockers too. Its a 5 speed car, with a regular T-5. Anyone know what the resulting compression would be and If it would be within the abilities of the stock computer? is it too little difference to bother? Any other small mods to take advantage of it? (different cam choice?)

Apeiron

No point unless you're already rebuilding it.

88gta3508

you need to know what pistons 2 or 4 valve relief??? or are they still dished
2 or 4 relief will give you 9:5-10ish... what is your real goal...
if your swapping out pistons... your better off going through the complete motor

stealtht/a

iTrader: (1)

I wasnt planning on completely rebuilding, but the engine is out and on a stand, heads are already off and the flat top pistons are already removed, so its not impossible, but sounds like you are saying its not even worth the trouble of disassembling the crank, yes?

Apeiron

You can't replace pistons without a complete rebuild.

stealtht/a

iTrader: (1)

by "complete rebuild" you mean honing the cylinders and replacing bearings and rings, yes? I figured it would take at least that. I am assuming the cylinders dont need sleeving or boring. Still something i can do if its worth it.

Apeiron

That at the very least, but even a minimal bore would be preferred for new pistons. You're also changing the weight of the reciprocating assembly, so balancing is a good idea.

stealtht/a

iTrader: (1)

ah, the balance, i knew I was forgetting something. that alone plus boring almost certainly doesnt make it worth it. Ill save them for the next total rebuild.
thanks
Peter

darbysan

For your cam, consider an Lt1 cam. The heads can accept the lift without any machining, and they work pretty good. An LT4 cam ( not the LT4 hot cam) is even better, but harder to find.