I have an L03 engine in good condition, but with awful 58cc. Swirl port heads. I don't have the cash right now to get some aftermarket heads (porting mine would be a waste of money), so I'm thinking of getting some 350 heads (most are 64cc's), and I would have to change the manifold also, since the TBI manifold won't fit.

The problem, is that my 9.0:1 compression would be even lower with the bigger chambers, so I'm thinking of changing the pistons to some that give me higher compression (flat top or domed) but I don't know if I will run into any valve clearance problems, since I don't know what are my stock pistons like.

Has anyone done this, or knows what pistons could I use? I want to get the parts and put the car in the shop only when I'm ready to make the head swap, since I don't have a second car right now that I could use.

305 TPI heads are very scarce around here, so I can't go for that either in case someone will suggest that...

Thanks for your help,

 

You'll find that 64cc 350 heads are even scarcer than 305 TPI heads. There are none except for certain 70 and older ones, 350 TPI motors, and 96-up Vortec heads.

Your TBI manifold will bolt right up to a set of 081 castings (87 up 305 TPI, LG4 & L69 heads), with no modifications whatsoever.

Watch the classifieds on this site; they show up there all the time, seems like somebody has some on there right now. I have no idea what the customs implications are, but it can't be too bad. That would have to cost less, be less trouble, and create less down-time than changing pistons.

Your L03 has flat-tops.

You won't have any piston-to-valve clearance problems with those pistons, as long as you exercise a little restraint and keep your cam to less than .650" or so of lift.

 

I wouldn't even think about it, especially with flat tops. To keep the CR up around 9.5 or 10 to 1, you would need some massive dome top pistons, unless you find some LT-1 heads ('70-72) or Vortecs.

 

Why not use 350 heads that have been milled down. Seems like that would be less expensive than putting in new pistons...

 

Most any 350 (64cc) head can be milled down to 58cc's. .050"to .060" should do it.

Use a thin .015" shim type gasket. (like the factory origional).

If you can't find 305TPI heads, look for 305 HO (carbed) heads
casting number ends in 416. Much more common.

For the cost and trouble of rebuilding with high compression 305 pistons you might as well build a 350 for your planned 350 heads.