[John Milner]

Originally Posted by Formulajones

Must be something new because 25 years ago the L2257 TRW 428 piston was a flat top.

I had to machine a dish in them, which ended up being 16cc. Then zero decked the block, or close to it (.004" in the hole) and with a .038 gasket and a 76cc head I had 9.7:1 compression.

Ran that engine for a couple decades on pump gas.

No, nothing new. Strange that yours were flat tops originally as I've had several sets of the L2257's and each set has had the dish. I have a set of L2257's in my '66 421. They had a 13cc dish in them just like my 2282P's which I run in my '65 421.

I did not have a closeup picture of the L2257 number on my pistons in my 421 but found one on the forum that I attached. The 2282P pistons is a set that I have sitting on my shelf for a future build.

[Formulajones]

Yep those are different than mine were.

[racerboy]

Originally Posted by John Milner

L2257 and 2282P forged Speed Pro pistons have roughly a 13cc dish. I run several 428's with these pistons and 72cc heads on pump gas.

Thanks John. Those pistons look just like mine. I ran my 670s on this engine for something like 5000 miles and I don’t recall any pinging, but that was more than 7 yr ago. The cc kit I bought from Jegs came today so I am still going to cc the heads, if for no other reason than to do something I’ve never done before, but it sounds like I should be able to just put these heads back on and run them until my 400 is done. Hopefully. Saves me the $ of buying another set of heads. I guess I still will have to decide which cam is best.


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[racerboy]

Originally Posted by Formulajones

Yep those are different than mine were.

FJ
I found a set for sale and you can see that they came with the small dish and 4-valve reliefs. I don’t recall the machine shop adding any dish to my pistons, but is has been almost 20 yr.

https://egge.com/part/egg-1000-l2257-8/

[racerboy]

https://egge.com/part/egg-1000-l2257-8/

[tom s]

For a little more you can get a custom piston with the correct dish for what ever head you want to run.I just did 2 428s with Autotec pistons.Tom

[Formulajones]

Yep those are different for sure.

I haven't seen the combustion champers on a 670 head in a long time, but the 13's I used for that combo don't have much quench area. In fact most of the quench is around the parameter of the chamber as you can see in this picture. So I didn't need a fancy "D" shaped dish to take advantage of a big flat area, these heads didn't have enough of that to worry about. In fact the ring I created with the bowl style dish was wide enough to take advantage of most all of it. Plus I could create the CC needed with the added area instead of making a smaller D shape deeper to gain CC and possibly making the piston weaker, there is only so much meat to work with.

[racerboy]

FJ
I am about to cc my first combustion chamber. Do I need to put anything down to seal the plexiglas to the head, or just let it lay flat?

[b-man]

A little Vaseline will seal it up.

[racerboy]

Thanks b-man. I used a little film of grease. The smallest chamber came out around 73.5. The others were between 74-75.




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[MarkS57]

Originally Posted by Formulajones

Must be something new because 25 years ago the L2257 TRW 428 piston was a flat top.

I had to machine a dish in them, which ended up being 16cc. Then zero decked the block, or close to it (.004" in the hole) and with a .038 gasket and a 76cc head I had 9.7:1 compression.

Ran that engine for a couple decades on pump gas.

There could be a flat top version, TRW had flexibility years ago with compression ratios. My stock 69 428 had the smaller dish in the factory pistons.

[lust4speed]

Both valves look to be about even with the floor. Any problem with the measuring fluid seeping past the valve seats?

[77 TRASHCAN]

Originally Posted by John Milner

No, nothing new. Strange that yours were flat tops originally as I've had several sets of the L2257's and each set has had the dish. I have a set of L2257's in my '66 421. They had a 13cc dish in them just like my 2282P's which I run in my '65 421.

I did not have a closeup picture of the L2257 number on my pistons in my 421 but found one on the forum that I attached. The 2282P pistons is a set that I have sitting on my shelf for a future build.

LOL, your garage looks a lot like mine

[John Milner]

Originally Posted by 77 TRASHCAN

LOL, your garage looks a lot like mine

There are a few small trails to walk through. They fill up quickly as I’m sure you know.

[racerboy]

Originally Posted by lust4speed

Both valves look to be about even with the floor. Any problem with the measuring fluid seeping past the valve seats?

I didn’t notice any seepage. This is the first time I ever cc’d anything.


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[racerboy]

Do you think I can run these heads as is or should I look for a set of 6X-4 heads with bigger chambers.

If you think I’m ok compression wise, would you re-install the XE274 cam or switch to the Crower. If I don’t use the Crower I am going to sell it. Several forum members have contacted me about it.


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[Jay S]

If your panning on running 93 octane just put it back together as it was. For 91 octane I would swap in the Crower and run the 670s. 87 I would look for the 6x-4s and keep the XE. Sell the Crower and lifters. 670s aren’t bad property either, appear to be a good set of 670s.

[racerboy]

Thanks Jay. Is there any specific head gasket thickness I should run, or should I just get a regular old Fuel-Pro engine gasket kit?

[Jay S]

My preference would be to use the standard 8518 perma-tech felpro.

[racerboy]

Another question. When I built this motor back in 2001 or so, I went with the aftermarket SFI damper. If I chose to, could I just substitute this with a stock balancer? I could never seem to get the belts to be perfectly aligned, even when I used the adapters.



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