My Cam doesn't fit. :(

[DarkMesa8]

I measured P/V clearance using the drop valve method and a "solidified" lifter.

Exhaust .069
Intake .089

Head Gasket installed.

1978 351W Block
Brand New DSS Flat top Forged pistons .034 in the hole.
Brand New AFR 185cc Heads
Ed Curtis Cam

Very dissapointing, but glad I checked. I had to advance the cam 4 degrees in order to get it within spec on the cam card, could that have made a difference?

What now? I'd rather buy thicker head gaskets than flycut these rather expensive pistons.

 

[Paul Perreca]

is that a custom cam??

 

[5spd GT]

Yes, the Ed Curtis cam (flowtech induction) or FTI Cam is a custom cam.

That is pretty close tolerances...you might be alright...but why chance it...

Good Luck!

 

[04sleeper]

You could always buy some Cometic head gaskets. They come in a variety of thicknesses.

 

[txstang84]

the piston is 0.034" in the hole? damn...

the only problem with putting on a thicker head gasket is expanding your quench area, if the piston is too far away from the head surface at TDC, it kills combustion turbulence which can lend to increased potential for detonation...even in non-boosted applications, or non-nitrous

how big is that cam that you only had such a small amount of clearance, and pistons so far in the hole?

 

[wildfiveo88]

must be a pretty big cam to get numbers like that

 

[DarkMesa8]

the piston is 0.034" in the hole? damn...

the only problem with putting on a thicker head gasket is expanding your quench area, if the piston is too far away from the head surface at TDC, it kills combustion turbulence which can lend to increased potential for detonation...even in non-boosted applications, or non-nitrous

how big is that cam that you only had such a small amount of clearance, and pistons so far in the hole?

Do you think just keeping a standard head gasket (say .040) and having a total area of .074 will cause detonation problems?

Ed Curtis communicated me on corral, wants me to double check everything. DSS pistons, according to Ed, should give me plenty of clearance.

 

[5spd GT]

Ed Curtis told me that my .560 lift cam (that is all I give out) would clear my stock pistons with the AFR 165's. Many people doubted it would be sufficent and it works and has been for 15,000 daily driven miles

 

[txstang84]

I'd call upon some of the more seasoned engine builders in here, the only reason I mention it is because I saw it on the KB (Keith Black, not Kenne Bell) website, there's alot of good information on there about combustion theory, compression ratio (static vs dynamic), alloys, etc.

but it's all theory, I don't know for a fact, but in a way it makes sense when you read through it...basically it says that flame propogation is the best way to avoid detonation, and one of the best ways to do that is by "quench" or the "close collision" between the piston @ tdc and the cylinder head deck...in a nutshell, the closer you can come without actually touching, the less chance there is for detonation. They recommend 0.035"-0.040" on street/strip engines that run less than 6500rpm. the more radical the engine, the more quench space you need to keep from actually having the piston collide with the cylinder head...it's pretty good reading.

 

[coming4you]

hmmm

Seems like you may want to recheck the p/v clearance again... I have dss flattop pistons in my 306 and with a 580 610 solid roller with 1.6 rockers... i have 112 in 102 ex....

You may be doing something wrong..
But then again you may have gotten a bad batch of there pistons...
Mean not flycut correctly

 

[DarkMesa8]

I'm going to address this quench problem first, pulling the rotating assembly and getting a zero deck.

Here's the cam specs for the EC cam:

Gross lift- int .6001 exh .5797
Duration at .050- 228* 234*
Separation 111*

 

[5spd GT]

There is a lot of factors in piston to valve clearance. If Ed says it then it is most likely true...but your block height and all could be that factor

 

[DarkMesa8]

Yeah, maybe I did measure it wrong. Will worry about that after I deal with quench.