UltRoadWarrior9

So, it's understood that optimal quench is .040".

Is it more desirable to have a piston 'in the hole' say .010" and a head gasket close to .030", or a zero deck and a head gasket close to .040"?

sofakingdom

iTrader: (1)

The latter.

Some modern engines (N* for example) actually put the piston ABOVE the deck, stock.

86LG4Bird

iTrader: (1)

I'd say the former, especially if it's a high end build with a lot of work to the block that you may want to take advantage of again on a subsequent rebuild. Plus, even on your present build, mistakes do happen, and it's nice to have a second shot at it. No sense in cutting more off the decks than necessary to equalize their height and square them to the bore. There's no performance or durability benefit to having them out of the hole.
If it's just a cheap build and you're certain you'll never go back into it for a rebuild, then it's not a big deal either way.

And BTW, optimum quench is actually less than .040"; however, .040" is a common target that keeps everyone out of trouble even for crooked blocks with varying deck clearance cylinder to cylinder. I'm targeting .032" on my current LT1 build.

UltRoadWarrior9

Guys thanks for responding. All my parts are brand new. I've paid to have the block machined so that the pistons are .010" below the deck.
So....050" quench a 'no go' for a 500HP 11:1 compression engine build?

86LG4Bird

iTrader: (1)

That big .050" quench clearance isn't a good idea for high compression.
Go with something like this:
https://www.summitracing.com/parts/f...make/chevrolet
Even with the slight increase in compression, your detonation resistance and tuning window will improve. It will require less timing for best power.

11:1 is pushing it for a pump gas Gen1 SBC. What heads and cam are you going to use?
Have you purchased the pistons and heads already?

UltRoadWarrior9

I'm well into the build...
I have a Scat forged and balanced rotating assembly, including 6" H-beam rods, crank, pistons and flexplate.
The heads I just got in are competition ported AFR210's.
The cam I'm planning first installing is a CompCams 292XFI.
Exhaust will be 1 3/4" longtube headers by OBX racers.

UltRoadWarrior9

I didn't see that FelPro gasket, you mentioned, originally when I was searching on Summit. I only saw their .041" thick gasket. But I like your choice. I was also looking at Cometic head gaskets. A friend (Honda builder) swears by Cometic. But since I have an iron block and aluminum heads, I wonder...

86LG4Bird

iTrader: (1)

I don't see an issue with the Cometics on iron block / al heads. I've seen lots of successful builds with them.
With a big cam like the 292, you shouldn't have any problem with pump fuel, even if your SCR ends up a couple of tenths above 11:1. I hope you have plans for a stout valvetrain. Those XFI lobes are hell on springs! With the ported 210's, I assume you'll be revving above 6500, in which case I'd advise about 160 lbs on the seat.
If it were mine, I'd be calling Lloyd Elliott and getting a custom cam in lieu of the XFI. Proabably about the same cost. and he'll guide you better than I can regarding valvetrain requirements. www.elliottsportworks.com

UltRoadWarrior9

With the head gasket you mentioned, my SCR will be close to 11.11/1 compression...
Yes, I've read alot about the XFI lobes also. The AFR210's I got online came with custom PAC Racing valve springs which have 220lbs on the seat. The were meant for a solid roller cam. Some here say that pushes the upper tolerance limit on the LS7 lifters, which I am using. Someone recommended, in a different thread, Morel lifters for that seat pressure, but I had already purchased new LS7 lifters and Morel lifters are very expensive.

So I chose a new valve spring instead, a PAC Racing spring, Part #1934. 160lb on the seat. It's a dual spring design with damper. OD and ID spring measurements are the same measurements as the 220lb springs that came with the AFR heads. Only the install height is .070" less. So today I should receive .060" shims to place under the spring locators and next week me and my machinist are gonna check these AFR heads out and install the new springs.

86LG4Bird

iTrader: (1)

I do believe you have it covered
Wise to back away from that 220 lb seat load on HR lifters!

Orr89RocZ

iTrader: (20)

220 is fine with morels but i agree is alot on ls7's. Proper valvetrain geometry and stiff pushrods, 175-180 seat 400-430 open is about all you'd need

UltRoadWarrior9

If the 292XFI doesn't perform, I'd be willing to make the call. Even if it does perform, I might make the call... This is my first build so patience is required...

I've made a setup that makes it easy to switch out a cam, without removing the oil pan and front timing cover.

UltRoadWarrior9

Can you rec pushrods Orr? This is the last part of my build: 1.6:1 rocker arms, pushrods and valve covers.

Orr89RocZ

iTrader: (20)

No thats something you have to measure. They'll usually be between 7.2-7.45" on oem hyd roller setups

Widest diam rod you can fit. 3/8 is more stable than 5/16 but a .080 wall 5/16 should be ok

86LG4Bird

iTrader: (1)

Ult, I'll be running .105" wall 5/16" pushrods on my upcoming LT1 SR build, just so I can use my existing valvetrain setup minus the cam. Lloyd advised those, based on ~190 lbs on the seat with the tight lash SR setup.
Not a hard requirement for 160 lb seat, but as Orr said, more valvetrain stability is always a good thing.

UltRoadWarrior9

Manley seems to have all the bases covered when it comes to pushrods. I'm liking their 5/16 .120" thick pushrods.
Also like Scorpion roller rockers. They make a set for the left AFR head and the right AFR head? I understand the offset of .1", but what differentiates the left and right heads?
A pushrod length checker and 1 of each of those L &R roller rockers is in my budget @$70 from Summit.
EDIT: I have a set of used ls7 lifters so I can disassemble 1 at work and convert it to solid roller, for pushrod measuring purposes only.