A couple piston questions for the group

[BTF/PTM]

Hi guys,

I'd like to do a mild but fun L28 street build which would entail a combination of a flat-top-piston L28 block and a milled P90 head to get an even 10:1 compression ratio. There will be a cam upgrade as well, but that's not relevant to my questions. Here goes:

1) Aiming for a streetable 10:1 engine means that spending $800 on a set of forged pistons is kinda nuts. Are there suppliers out there for new OEM cast pistons or maybe an aftermarket supplier that someone has tried? Z Car Source, for example, has a reasonably priced piston/pin/ring set that's listed as "new aftermarket" and can even offer a few different oversizes. Anyone have experience in this area?

2) Is swapping a used set of pistons into either block a feasible option, or would the wear pattern difference potentially be enough of an upset to make it not worthwhile?

3) Would finding an F54 flat-top-piston short block and giving it new rings be my best option?

My '72 is currently equipped with an N42/N42 L28 which I've read has dished pistons. The car also came with an F54/P90 turbo long block (equipped with SU's) that should also have dished pistons being a turbo engine. I can't look into the cylinders, so I don't know for sure, but according to what I've read, that's the case.

Thanks, everyone.

[Diseazd]

An F54 short block with flat-top pistons will work fine........If you install the pistons in your block install new rings, hone the cylinders, new bearings and you should be good to go. The P90 head shaved .080 with .080 shims on the towers and valve springs should give you slightly under 10 to 1 compression. Here's a similar build........

http://www.classiczcars.com/forums/showthread.php?t=34448

Edited March 15, 2011 by Diseazd

[BTF/PTM]

If I find a short block I'll use the whole assembly rather than transfer pistons from one block to another - assuming all is undamaged, of course. Maybe I can trade my F54 turbo block for an F54 n/a block. Any takers?

I really wish I could find new factory slugs to go .020 oversize and eliminate all risk of excessive wear, but I'm a few years too late. To add on to my initial questions, anyone have advice on the best way to diagnose whether a block and pistons are usable after all its years? I know the rule that no scratch should be big enough to catch a fingernail, but are there other pointers?

Edited March 15, 2011 by BTF/PTM

[Travel'n Man]

Call Dave Rebello and have a conversation with a racing professional! He can guide you in the right direction -mild to wild - ship you what parts you want to buy from him - I, much like you, have a N42-N42 combo with a little Rebello tweeking.........I am still in the break in period from last fall - (damn snow and salt). I would have to think honing would be your very first step with either block of your pick. Start clean and fresh and follow up with a re-build. I did go to flat tops, 240 rods, with a Dave doing all the head work with a mild cam.

Dave and his team are great and they know their stuff and will share information with you. He can help a little or a lot - depending on your budget.........he has the goods....check this link out below.

http://www.rebelloracing.com/

[BTF/PTM]

I talked for a while with the folks at Rebello today, thanks for the tip! We covered too much info to dump it all here, but definitely suffice it to say that they'll play a part in the build I go with