[judgeman6970]

I've read many posts about the infamous 8vr cast piston, but rarely do I see any good alternatives listed? Stock rebuild 400 R/A III, looking to hopefully drop the compression slightly(to run well on pump 93). What would guys recommend, that won't break the bank, and possibly lower my compression? Btw, it's a '70 with #12 heads. Thx!!

[65 Lamnas]

Originally Posted by judgeman6970

I've read many posts about the infamous 8vr cast piston, but rarely do I see any good alternatives listed? Stock rebuild 400 R/A III, looking to hopefully drop the compression slightly(to run well on pump 93). What would guys recommend, that won't break the bank, and possibly lower my compression? Btw, it's a '70 with #12 heads. Thx!!

You don't see any alternatives, because most any other piston is a great alternative to those slugs. Speed-Pro L2262 would be a great start. Not sure what you mean by "won't break the bank", as I don't know "what's in YOUR wallet??"

[Formulajones]

I used a forged flat top on my 70 RA III and then machined a small dish in it. It's zero decked as well. 10.13:1 compression and runs nice on 91 octane.

I have no idea what won't break the bank, it's all expensive to do and do it right anymore.

[judgeman6970]

Thanks for the info, guys. It's a stock rebuild, basically a street cruiser. Wasn't looking to spend $700-800 on forged pistons, if I can help it. The L2262F's do seem like a reasonable choice, but compression may be an issue. I assume these 2262's would give me approximately "stock compression", all other things being equal?

[65 Lamnas]

Originally Posted by judgeman6970

Thanks for the info, guys. It's a stock rebuild, basically a street cruiser. Wasn't looking to spend $700-800 on forged pistons, if I can help it. The L2262F's do seem like a reasonable choice, but compression may be an issue. I assume these 2262's would give me approximately "stock compression", all other things being equal?

Use an online CR calculator to figure the compression ratio. Figure 8ccs for the 2262 valve reliefs. If you have access to 92-ish octane fuel, build for a SCR of about 9.7-9.9:1. DON'T leave out zero decking the block and choose a cam wisely or it'll wind up being a pinging turd.

[judgeman6970]

Ok thanks. We have 93 around here. It's been "ok" for my GTO's so far, just don't want to increase the compression above stock. I know there's a lot of factors that go into it. Like previously mentioned, a L2262f "dished out" would be perfect, but at that point, I might as well look into other forged "-cc" options. 🤔

[Tim Corcoran]

There are a few options

What I would do is figure your compression with an online compression calculator using a flat top piston and your planned bore size. Don't forget to include the number of cc's for the valve reliefs as it varies somewhat between piston brand and type. Use a zero deck in the calculator so you know your base point. Then if your compression is still too high then figure what size dish you will need to achieve your compression goal. Then tell your machinist to deck the block to zero deck.

https://butlerperformance.com/i-3164...%3Fq%3Dpistons

https://butlerperformance.com/i-3015...%3Fq%3Dpistons

https://butlerperformance.com/i-2445...%3Fq%3Dpistons

https://www.summitracing.com/search/...ac?keyword=400 piston&ar=1&kr=pontiac 400 piston

https://www.summitracing.com/parts/d...b/make/pontiac

https://www.summitracing.com/parts/d...b/make/pontiac

Among others

[Formulajones]

If you end up machining a dish you'll need those forged units. $7-800 for a set honestly doesn't sound horrible given the prices these days.

[b-man]

Break the bank.

Bust it open.

Order up a set of Ross or Icon custom forged pistons made to the compression height, dish volume and bore size you need.

I wouldn’t order them until the block is decked (to determine compression height) and after your machinist determines the final bore size.

In the end if you buy a heavy press-pin TRW/Sealed Power/Federal Mogul piston and then cut a dish in it you’re pretty much within a hundred or two dollars of a better full-floating pin forged piston that uses a more modern ring pack anyway.

[Jay S]

The best true 8VR economical replacements, which are still a dual purpose 8VR, but a better VR design with the same compression height as an L2262F, would be these:

https://uempistons.com/product/6407/...Set-IC9946.030

[Verdoro 68]

Originally Posted by b-man

Break the bank.

Bust it open.

Order up a set of Ross or Icon custom forged pistons made to the compression height, dish volume and bore size you need.

I wouldn’t order them until the block is decked (to determine compression height) and after your machinist determines the final bore size.

In the end if you buy a heavy press-pin TRW/Sealed Power/Federal Mogul piston and then cut a dish in it you’re pretty much within a hundred or two dollars of a better full-floating pin forged piston that uses a more modern ring pack anyway.

Good advice here.

[judgeman6970]

I appreciate all the info. I kinda had the feeling that I'd probably need to spend more $$$ to get the right set-up. Looks like the Icon (+14cc) forged might work out nicely. 1.720" comp height & probably 10:1 or less compression with my #12 heads. Once the machine shop gets me some numbers, I can do some more accurate calculations. 👍

[judgeman6970]

Originally Posted by Jay S

The best true 8VR economical replacements, which are still a dual purpose 8VR, but a better VR design with the same compression height as an L2262F, would be these:

https://uempistons.com/product/6407/...Set-IC9946.030

Thank you, totally missed these in my searches. 👍

[Formulajones]

Originally Posted by judgeman6970

I appreciate all the info. I kinda had the feeling that I'd probably need to spend more $$$ to get the right set-up. Looks like the Icon (+14cc) forged might work out nicely. 1.720" comp height & probably 10:1 or less compression with my #12 heads. Once the machine shop gets me some numbers, I can do some more accurate calculations. 👍

That should get you close. I forget the cc of my 12's and don't remember how much dish was machined in the piston, that was a couple decades ago, I'd have to find some paperwork. I want to say 13cc on the piston? My heads were milled slightly to true them up as well, then block zero decked and a .039 gasket. Crank was also ground to correct stroke which very slightly affects things as most of these OEM cranks fall a pinch short on advertised stroke. I do remember for sure it's exactly 10.13:1
If you get in that range somewhere it should be fine on pump. I'm using the melling 068 which checks about spot on. A bit small in my opinion but has been happy for years

[steve25]

With a 4.120” to a 4.150” bore and a 3.750” stroke and a 72 Cc head every 4 CCs will change the compression close enough to a 1/4 point in regards to a street motor .

[HWYSTR455]

Agree with you would spend more cutting some pistons' dish.

Another thing you will spend more on is prepping a set of factory rods over replacements. Don't even think twice about using factory rods, you will be sorry in the long run.



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[Formulajones]

Yes, this day and age, if I were to build an engine like that again, I would order a custom made piston to do the job and be done with it, so long as I don't have to wait 6 months for a piston to show up

Back when I did it, that was over 20 years ago and at that time it was just easier and cheaper to order a forged flat top and just machine the dish I needed to get the engine where it needed to be for what I was doing with it.

[HWYSTR455]

I remember the 2262s were like $15 each back in the day!


.

[steve25]

Never, for a L2262F!
Even just the pins where close to 10 bucks each.

[HWYSTR455]

PAW used to sell them cheap, I still have receipts, last set I got from them were like $150 a set and remember complaining about it. That was in the 80s.

I had a Summit flyer on my garage wall for years, they had great prices when they started up. Headman headers were $49 a set.


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