Rebuilding a Californian 1756. Change Pistons?

[dickykitch]

I've started taking a look at the motor on my long-term '78 rebuild. It last ran about 25 years ago, but the indicated 36k miles looks genuine and it has been stored properly during this time. Removing the head shows the bores are in good shape and a fairly straightforward overhaul is all that's really needed.

However, this is a Californian spec engine (132 A1 031.6) so although I will be removing all the smog stuff and changing the exhaust manifold to a 4-2-1, and probably swapping out the carb, the compression ratio is only 8:1 I think and that will ultimately limit performance.

So, should I change the pistons and up the CR? If so, what spec pistons should I be looking for? As a re-bore is not required, they would be standard 84.0mm.

I'm not looking for ultimate performance, but just something usable and fun.

I've never done a full engine build before so appreciate any advice / experience.
Rich

[narfire]

My .25 cents..... take the head in, do the valves, seals and guides. Take perhaps 15 thou off the head. Get a 32/36 or 34 adf carb and as you mentioned a 4-2-1 exhaust and 2 inch diameter pipe back.
If more $$ are available then perhaps consider swapping out the cams for after market ones but get the adjustable cam wheels to do the cams justice, and degree the cams in .
Lighten the flywheel if you can, or purchase one from a vendor here.
I really don't know what to suggest regarding the bottom end...leave it or take apart and swap out the bearings, rings ect.
Perhaps another will chime in there.
Chris

[So Cal Mark]

with that low compression, you could always turbo charge it. Or, put some 10:1 pistons in it. Your options will always be limited with the low compression

[vandor]

Here are some standard size 8.8:1 pistons:

https://www.autoricambi.us/product/EN7- ... m---88-CR/

You could deck the block some for a little more compression, as these pistons usually end up slightly under the deck.
If yo shave the block 0.020" (0.5mm) the CR should be ~9.2:1. Of course the best way to do it is to measure everything
on assembly and then you will know your exact CR.
One could even deck the block so the pistons stick out ~0.020" (0.5mm), as the head gasket is ~0.060" thick. That would get you in the high 9s for compression (again, you'd have to measure the volumes and do the math to be sure).

[dickykitch]

Thanks for the input guys, much appreciated.

If I were to go with a set like the ones from Auto Ricambi, how do I cope with bore / piston class? My block is marked with C2, B, D, B, though there is also a +0.10 stamped near the C2 bore, but I’m not sure what this means - unless it means I need to add 0.1mm to the C class, in which case I'm screwed and will probably need to keep the original pistons or rebore oversize.

I can understand that if a block is rebored, it can be done to suit individually measured oversize pistons. But how can I cope with replacement pistons without a rebore? Measure and hone as best I can or something more?

Thanks
Rich

[vandor]

I suppose first step would be to measure the bores with an ACCURATE (ie. not $10 made in china) calipers to see where you are. Possibly ask the vendor for the actual pistons size. Then you will have an idea what the clearances are.
Of course to be totally exact you will have to insert the pistons in the bore and measure the clearance with a feeler gauge.

[dickykitch]

OK, thanks again. I think I'll do some measuring and take it from there......

Rich