swemdog

Hey guys. I have a set of Mr Gasket #5716 head gaskets (4.100 in. Bore, .026 in. Compressed Thickness) laying around. Would these be ok for my LT4 383 build? I'm mostly concerned with the small thickness of the gasket and a high compression motor. I will be at 12.5:1 static and around 8.8:1 dynamic with these gaskets and my pistons/rod/cam combo in my block. Thanks

Trevor

STRYKER

If you have done all the math correctly and those are the correct numbers, you should have nothing to worry about. I have seen guys on here run their DCR's up around 9.2 and have no problems. Just make sure your cooling system is up to par. The only thing I would be concerned with would be your p to v (piston to valve) clearance. I dont know the specifics on your engine but typicaly the quench heigth should be at least .030 and if your piston tops come up flush with the block deck then that would leave your quench heigth at .026. you are probably ok but I would still check it anyway.

L8R

swemdog

How do you figure the quench height of the piston? In summit catalogue, they list the "compression distance", is that the same number? I'm going with a 3.75" stroke and a 6" rod. My deck height was measured at 9.023.

swemdog

Bore (in): 4.030
Piston Material: Hypereutectic aluminum
Piston Style: Flat
Compression Distance (in): 1.130
Dish Volume (cc): 7.00
Valve Reliefs: Two
Wrist Pin Style: Floating
Pin Diameter (in): 0.9272
Top Ring Thickness: 1/16 in.
Second Ring Thickness: 1/16 in.
Oil Ring Thickness: 3/16 in.

ok, 6" rod+1.875" stroke= 7.875" +1.13" piston = 9.005"
And 9.023" deck -9.005" = 0.018" plus a .026 head gasket= .044 clearance?

is this right?

SStrokerAce

What's the chamber volume on your heads?

Personally I would worry about a 9.0DCR motor, and I've built them, just wouldn't do it with a Hyper piston.

Bret

swemdog

Yeah I'm getting mixed feelings about the hypers. I will likely end up going with a forged piston. My heads are LT4 castings, 54 cc chambers.

SStrokerAce

54cc Chamber
-7cc Dish
.026 x 4.100 Gasket Volume
.018 x 4.030 Deck Volume
=12.14:1 SCR

I would have the chambers opened up with porting... to about 58cc, and run a forged flat top piston (-5cc dish) which will give you 11.83:1 SCR

Bret

swemdog

I guess it would be better not to design my engine around a head gasket, lol. I want to get my LT4's ported by lloyd and get one of his cams to get the most out of this motor. I used the GM847 cam specs and got a 72* IVC value, and along with this http://www.smokemup.com/auto_math/dy...sion_ratio.php

i got my dynamic and static. Can anyone tell me how Lloyd's LE3 cam compares to the gm847's IVC of 75*?

SStrokerAce

58cc Chamber
-5cc Dish
.026 x 4.100 Gasket Volume
.018 x 4.030 Deck Volume
=11.83:1 SCR

The GM 847 and LE3-383 Cam have the same DCR, it's worth about 10-15hp over the GM847.

Bret

swemdog

thanks for the info and replies Bret! I really appreciate it