400 ci small block build?s

Fathead Racing

Fathead Racing

Well Known Member
Supporting Member 7
I am helping build a 400 small block. The block is a stock deck height, never been decked. The pistons are forged stock replacement dished pistons. I do not know the cc. I slipped a .025" feeler gauge under a straight edge layed across the bore and there was still plenty of room between the piston and the straight edge measured at the edge of the piston not from the dish. I assume this small area would be were you measure for quench? Based on this measurement we ordered 58 cc aluminum heads. Does anyone know anything about how far down in the bore a stock piston is? What quench distance should I be shooting for? My thoughts are around .040" This may be hard to acheive with the piston being .025+ from the deck without finding a very thin head gasket, somewhere in the .020" range. Thoughts anyone.
 
G

gearhead409

Well Known Member
Ray, the 400 ome style dish piston is down the hole somewhat. i like the TRW flat top piston and cut my own Dee shape in it or a std. Dee shape TRW. they are closer to the deck and gives you a nice quench area to play with. make sure your new heads have the 400 style steam holes in them. this engine will surprise you to how much power it will make. good luck.
 
J

jr.W

Well Known Member
Fatride stock small block should be .025 deck height, but with after market
pistons? Some of the 350 cast replacement pistons are an additional .020 down
so you end up with .045 with out a gasket not good. Ideal would be the
.038 to .040 you refereed to. FElpro has a .015 gasket, MrGasket has
a .020 Steel gasket, and gm has a .028 comp. gasket for 350s not
sure on the 400 stuff. If It is a street engine I would figure out the comp.
because with a 58cc head it could be real high on a 400.

jr.W
 
bubbletop1961

bubbletop1961

Well Known Member
Just so happens my engine is out. I went out and measured the same way. Above the valve reliefs is about .010. and below is about .020. My block has been decked. Im using kb pistons # kb126. They have a 30cc dish. head gasket with about a .039 and a 64cc chamber I am right at 9:1. I dont remember why but Ive been using a marine head gasket #17031. Dont remeber what made me start using it?:dunno but Its been working good. I belive the 1014 is also a good felpro gasket with the same .039.

Good to hear of more 400 builds. Ive been thru alot of them. They are great street motors. Tell us more about the build.
 
bubbletop1961

bubbletop1961

Well Known Member
http://store.summitracing.com/partdetail.asp?part=LUN-30114&autoview=sku

This is a hyd flat tappet I used and had great luck with. It was in a 72 monte. 406 sbc. trw flat top pistons with 487 heads 2.02/1.60 valves 350 trans with a 10 convertor. 12 bolt rear with 4.10 gears. It would run consitant 12.60's I drove that thing every where. I would drive it 2 hours on the highway. Or to work. That car was abused to death. One of the most fun cars and set ups I ever had.
 
Fathead Racing

Fathead Racing

Well Known Member
Supporting Member 7
Building the engine for a friend so I'm stuck with the TRW dish piston. I can't change how far down the piston is in the hole. Owner does not want to pull the engine. This is a head swap only. I ordered a 58cc head because the piston was so far in the hole. I figured that I wanted to be around 10.1 compression with an aluminum head. I couldn't find a picture of the piston anywhere but Ebay. this is the piston we have. What gasket should I use? Remember these are aluminum heads. This is a street engine some strip action.

http://cgi.ebay.com/ebaymotors/400-...190655656QQcmdZViewItem?hash=item170190655656
 
Fathead Racing

Fathead Racing

Well Known Member
Supporting Member 7
The deck height to piston is .034". If I use a .040" Fel Pro head gasket I will end up with .074" quench. If it was my engine I would find this unacceptable. What I am worried about is having too high compression with too much quench. This would end up with a detonation problem that I could not fix with timing. How can I without cc'ing the bore calculate the comp ratio. I would feel better knowing this. Anyway, where is the quench area on these pistons?
 
bubbletop1961

bubbletop1961

Well Known Member
I work at the parts store tomorow night. Ill try to look thru the felpro performance book and see what I can find as far as a thin head gasket.
 
bubbletop1961

bubbletop1961

Well Known Member
I looked thru the felpro performance and mr gasket. The thinest head gasket listed was .039 The 1014 was ok with alluminum heads. You may try cometics. Ive heard good things about them.
 
fourspeed409

fourspeed409

Well Known Member
Ray
What about running the cheapy steel shim gaskets. The Victor gaskets in my alum head 350 are only .015". The guy that did my machine work builds race engines and he said they where ok to use with aluminum heads. Felpro actually sells a rubber coated steel shim gasket for use with alum. heads. http://store.summitracing.com/partdetail.asp?part=FPP%2D1094&autoview=sku Only thing about those gaskets is the bore may be too small. You could check and see if they make them in a bigger bore.

Shane
 
Fathead Racing

Fathead Racing

Well Known Member
Supporting Member 7
Well, I'm freaking out a little with my choice of 58cc heads. I chose the 58 cc head because the piston was .034" in the hole. I was figuring that I would come out of this with around 10:1 comp. If I start squeezing the quench I will end up with comp to high for a street engine. I may just have to use the .039" Fel Pro. The dish piston may not be prone to detonation,,,I hope!
 
32witha409

32witha409

Well Known Member
Supporting Member 3
Your Setup is Fine!

Fatride,
Similar pistons have a dish volume around 20cc. In your engine as setup@ .034 in the hole , .025 shim head gasket and your 58cc heads you end up with at 10.0-1. or 91cc/910.5cc=10.005-1 compression. I would say your head choice is perfect. Yea a bit big on quench but run the .015 thick gaskets and 88cc/908.5cc will yeild 10.35-1 compression and .049 quench. Perfect!!!!!!:clap

Robert
 
Fathead Racing

Fathead Racing

Well Known Member
Supporting Member 7
32witha409 said:
Fatride,
Similar pistons have a dish volume around 20cc. In your engine as setup@ .034 in the hole , .025 shim head gasket and your 58cc heads you end up with at 10.0-1. or 91cc/910.5cc=10.005-1 compression. I would say your head choice is perfect. Yea a bit big on quench but run the .015 thick gaskets and 88cc/908.5cc will yeild 10.35-1 compression and .049 quench. Perfect!!!!!!:clap

Robert
Click to expand...

Robert, are we talking copper gaskets? I have heard that you cannot run a steel gasket with an aluminum head. What gaskets are you referring to? Thanks for the info.
 
32witha409

32witha409

Well Known Member
Supporting Member 3
Fatride,
Sorry, I did not see that the heads you ordered were aluminum.:doh :takethat

I was in fact talking about the steel shim but. I like it when I put my foot in the ole pie hole. Copper would work with the aluminum for racing.

Are these GM L 98 fast burn heads? I have a set on my boat/350.
I found these guy's and they may have a gasket for the SBC @ .030 thick http://www.cometic.com/catalogs/AutoDomestic.pdf

I think the name rings a bell. Sounds like they have a multitude ov different thickness and bore size combo's.

Robert
 
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