GM Camel Hump Heads (492) & Chevy 355 With TRW L2252A Pistons De-Tuning Queston

Thank you Eddy, as that really helps me with those TRW L2252A piston specs.

My relatives good friend has some 441 heads that need rebuilding, and he's going to give them to me for free. I just need to drive two hours to pick them up. From what I found out on these heads casting numbers, is that they are 76cc open chamber heads that flow good. If the heads are okay then I might just be able to rebuild them and swap out the 462's and drop the CR to a more feasible pump gas friendly number.

That would be a real big win as I wont have to touch the TRW pistons and keep things simple.

 

Sounds like a plan, I have a 355 short block kind of in the same boat, to much (11-1) compression with 64cc heads but to low with 76cc, not many 72cc heads out there.

 

@MoreHPplease
@swade41
Milling top's off pistons was common
Thing ..You see the 2252 numbers based on .025 deck with .021 gasket .. with a Thicker head gasket you can drop the static compression down with .030 .
I did not do the math .
But you can see in second pic
Each 0.030 thoue of bore changes the CC BY 00.9 cc .
Since You going to pull heads to see whats you have for sure ,
You Need to see / check each combustion chamber C.C volume to see if who ever went the extra to build Blue Print spec's.
If factory stamps on pad that already tells you cut , if so ONLY enough to flatten dec...
If heads still on , Next I would be sliding
Feller gauge between Head & block to see what Gasket used .. If gasket more then the 0.021
Then I would of bolted starter on ,
After oil priming engine , No need for intake ,
Me , I would of compression check,
If blow I think the 180 ish # ,
All checks out Oil , cranking #s .
I would bolted intake on & started . On floor .
To me by pics Block not cut , intake not cut , But do not know headgascket thickness , And can not see the combustion chamber as in worked to bigger CC ,
I sill would Run , modern gas you can get away with more with ethanol.

If you still want to lower the compression if you still think it's over
11 plus ,,, I would do the math & Just change head gaskets ,,,,
Or Octane in a can !!
Also do not forget to check push rod to Valve geometry.

The KB piston when they came out
Many where Breaking the top of Pistons
Because tight clearances overcast and forged & also Ring gaps where diffrent
Set wrong broke piston ..

Im my Area One of the pioneers of Mountain motor pro stocks Racer /Engine builder Va was Lee Edwards about 20 mints up the road in the Country,, He would get around One of the Rule weight per Cid was to use a P***enger cast iron block by stacking
.250 plus of head gaskets to get more
Stroke & compression

 

Chevy engine compression help? | The H.A.M.B. (jalopyjournal.com)

some discussion on a similar issue .

the 441 heads will work . may not flow as good as the heads you have but your not looking to make 500 HP either .
I would not spend a lot on rebuilding them if they need much . also be aware that your existing cam likely has big heavy springs and you might want to consider screw in studs or at least cross pinning the original ones.

I have a few sets of 441 heads off 400 SBCs and they will get your compression down but compare the cost of some of the aluminum heads vs a rebuild before you go in to deep. If the 441 valve guides are OK the just check if there flat enough to not need a mill and do a simple valve job on the existing seats and new valves are not that expensive these days .
Id examine those pistons undersides close before having them milled .
If they rise up on the inside were the dome is you better measure close to see how much you can mill .

 

Swade, couldn't you just mill the 76 cc heads down a little in order to decrease the chamber size which would increase the compression ratio?

Nice looking block. Is it a 4 bolt main?

 

Eddy,

All that's highlighted above from your post is very solid advice. I don't have heat in my shed where the engine is at, but if the temps warm up soon then I will pull the intake, timing cover/water pump and likely the heads. But I should be able to get a feeler gauge and check the head gasket compressed size and get a good idea of what I'm currently working with.

 

1biggun,

I just got back this evening from picking up the 441 heads and they are dirty as hell, but they already have screw in studs.

Obviously I don't know what the actual condition is of these heads are, but I was ***ured they are not cracked and were pulled for a set of more performance heads.

I have pics which I will post here.

 

Th

The pistons look like TRW L-2304s

 

My first t-bucket engine had "stock car cut" heads unbeknownst to me, it ****ed a couple sets of intake gaskets before I figured it out. I ended up having to get the intake cut to match the heads, but that made them a bonded pair and no other intake would fit without cutting it too.

 

That would have likely been a angle cut were thye milled the heads to take more off the combustion side of the chamber to get higher compression in cl***es were say in a flat top piston and production heads were required .

You could get well over 11-1 with angle cut heads shim gasket, two eyebrow pistons.

We made 435 HP on a 250 chevy with angle cut heads and two eye brow pistons in a street stock in the early 80's .

you have ot cut the intake at the correct angle to match the heads to make it all work
engine was built by Chris Zootis performance in Healdsburg CA.
that was with a Brezenski reworked iron intake and and a 2 barrel holley reworked by Bolaws ( or how ever it was spelled )

 

Also when you start angle cutting heads, other mods needto be done to head bolt holes & bolt head / stud washer nuts seating ,
And there is a Master FelPro performance only catalog Which is not offered or show @ FelPro website
for correcting port line up , Many of these catalog's are no longer available
For mid 90's & older methods after the Ford Svo Motor sport ,Gm BowTie ect & aftermarket aluminum heads became more common to present

 

Just an update on the 441 heads I acquired for the 335 sbc engine.

Dropped both pairs of the heads (441 and the 492) off to a reputable machine shop, but at a not so near by city. The 441 are going in for a cleaning, crack checking, and refresh.

Today I pulled the intake and heads off the 355 and took some quick measurements. The pistons sitting at top dead center are approximately between 23 and 26 thousandths below the deck. The head gasket looks like a MLS type and when I measured with a micrometer I got roughly a reading around 28 thousandths from the compressed portion of it.

The owner of the shop is going to have his technician evaluate the 441 heads before any actual machining is performed. And if everything checks out on the 441 heads in regards to being crack free, and the valve guides are within specification then he’s going to do a three angle valve job with light cuts at 30, 45, and 60 degrees.

He is also going to cut the spring pockets to accommodate the 492’s springs and swap them over to the 441 heads.

He did recommend going with a 35 thousandths crushed Felpro head gaskets to drop the compression a tad bit more.

When I used an online compression checker I arrived at a 10.5.1 ratio.
Still a little higher compression ratio than I would like, but much better then the 12.5.1 or higher depending on how accurate these on line CR calculators are.

By the way, I did do some research online at websites like Jegs, Speedway, and Summit for new Aluminum heads and the pickings are slim for 73cc heads that are not astronomically over priced.

I’m most likely getting these heads refreshed between $500 and $750 depending on the condition of the valve guides and valve seats.

The cheapest Aluminum heads I could find were between $900 and $1200 a piece fully ***embled. Bare heads were between $400 and $600 a piece not including shipping.

Although these 441 cast iron heads weigh a ton compared to similar aluminum ones, these 441 will serve me very well for what my intended purpose is.

 

Take a photo of the piston at TDC so we all can see what the piston looks like, I'm curious to see the dome.