High compression blues.

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hosehead

hosehead

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Hey guys, I've been getting into drag racing the last year or so and had a 440 built for my 65 belvedere. I've basically been chasing a light ping at high rpm and it's been a bit challenging to tune. So I did a compression test today and was amazed at my cylinder pressure. 195-205 per cylinder! Anyhow, I know I need a bigger duration cam to deal with some of this cylinder pressure and was looking to go faster anyway. So here is what I'm working with currently:
Stock stroke 440 with .030 over icon pistons
Bullet hydraulic cam(yes, I know this is my problem area). 490/492 235/240@50
Trick flow 240 heads
Street dominator
Holley 850
Rev nator
Stock distributor 15 initial 31 total. (Pings with any more timing)
100 octane helps but want a pump gas motor.
727 with 9.5" ultimate converter flashes to 3800-ish
3.54 Dana.

When choosing a cam, I called bullet and told them what I was doing. DRIVING a car to the track. This has to be a street/strip car. No room for a trailer at present.
So far, I've only run 1/8th mile passes. Runs 7.70-7.80 @ 90 mph.
Icon's website says with my pistons and the 78cc trick flow combustion chamber I should be around 10.9 to 1. I thought I could get away with this combo with the aluminum heads buuuuuuut, maybe not. Lol.
And finally, I was (admittedly) building a mild-ish motor to get my feet wet at the track. After a bunch of passes, I feel good about upping the performance level now.
My budget has me looking at solid, flat tappet cams in the 250-ish duration area. I know I need to release some cylinder pressure to run pump gas. Any help/suggestions are greatly appreciated but go easy on me. Lol. Thanks guys, flame away.....
 
Some preliminary info, what plugs are You running, how does it run on less timing, what is the piston to deck height, what head gaskets...?
 
Autolite 3924, runs best where timing is now. Not sure about the gasket. Im pretty sure they were out of the fel pro kit. I'm calling the builder on Monday. The block was previously uncut. Only surfaced when engine was rebuilt. Hope to have some more info on Monday after a talk with the builder.
 
Retarding the cam timing will drop the cyl pressure a little.
 
I guess this is a cam suggestion thread. Lol. Should said that I guess. Thanks for the replies guys. Keep em coming!
 
All options for this issue basically suck with the exception of a bigger cam.
I think the best possible route is a thicker head gasket to reduce some compression.

Staying tuned!
 
The current cam is 292/296 adv duration @ .006

IMO, retarding the cam isn't an option as it would have to be backed up at least 10*
 
It certainly could use a good bit "more" cam with those heads. I am sure that would solve both the spark knock as well as make more power.
 
crackedback said:
The cam is 292/296 adv duration @ .006

IMO, retarding the cam isn't an option as it would have to be backed up at least 10*
Click to expand...

I agree 100%. More camshaft will solve it and make more giddiyup.
 
Looks like the internets say that the compressed thickness of the head gasket is .040". Shopping around for higher duration solid cam. Recommendations welcome!
 
:wtf:

IMG_1217.JPG
 
Do you have the fund for a solid roller? That's what I would recommend.
 
What head gaskets are you running?

Maybe 10 deg duration bigger cam with thicker gaskets.

Seems like many people push higher compression setups. It's easy HP, but not realistic with 91 octane pump gas.

And people think/say they are running higher compression than they really are. Some like to brag and bench race inflating their compression numbers.

I'm 9.7-9.6:1 measured with 242 @0.050 and on edge with pinging.
 
autoxcuda said:
What head gaskets are you running?

Maybe 10 deg duration bigger cam with thicker gaskets.

Seems like many people push higher compression setups. It's easy HP, but not realistic with 91 octane pump gas.

And people think/say they are running higher compression than they really are. Some like to brag and bench race inflating their compression numbers.

I'm 9.7-9.6:1 measured with 242 @0.050 and on edge with pinging.
Click to expand...

I'm guessing the ones out of the fel pro ks2110 gasket set. The builder wasn't super communicative about some of this stuff. He thought I'd be able to get away with pump gas with aluminum heads. Live and learn, I suppose.
 
I was re reading your first port and that ratio is high for Cali. 91 & the cam is on the small side. I’m not sure I’d run that no mater who said I could. It’s just to close for me.

To suggest a cam without getting into the science of it all, another 10*’s duration would be about right. As also asked/suggested, a solid roller would also help due to the way there ground and act. I know it is expensive.

Perhaps a stout solid cam would be the best middle ground. Also might as well get it with an amount of lift generous enough to take advantage of the heads cfm flow ability.

Solids tend to need a little more duration and will out rpm a Hyd. cam quite well.
 
rumblefish360 said:
I was re reading your first port and that ratio is high for Cali. 91 & the cam is on the small side. I’m not sure I’d run that no mater who said I could. It’s just to close for me.

To suggest a cam without getting into the science of it all, another 10*’s duration would be about right. As also asked/suggested, a solid roller would also help due to the way there ground and act. I know it is expensive.

Perhaps a stout solid cam would be the best middle ground. Also might as well get it with an amount of lift generous enough to take advantage of the heads cfm flow ability.
Click to expand...

Yep, that's what I'm thinking. The heads are awesome. Getting a big solid cam would solve my problems and get me a lot more power. Gonna call bullet on Monday.
 
Be careful here. Keep this in mind. When comparing a hydraulic to a solid, to get "about" the same duration in a solid, you need to add about 10* duration. So, that means if you want 10* duration BIGGER than the comparable hydraulic when going to a solid, you need to choose one about 20* bigger than the hydraulic. That's why I gave the recommendation I did.
 
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