ross flat top piston compression on my 1970 455

I just finished my .030 455 with ross flat top pistons with only two valve notches. Engine set at initial timing of 15. Cam Is a ta 290-94h and stage 1 heads. My problem is it pings to much. Have to retard timing to use.

 

Read Larrys "Power Timing Thread"

 

what compression ratio did you end up with?

 

I dont know. If it helps I know cylinder psi is 205 to 210 .

 

run your details through this calculator to get close.

Hopefully you know the details to complete it. That can get close. Too high a CR with iron heads can also lead to pinging.....


http://www.csgnetwork.com/compcalc.html

 

Sorry for the lack of information but everything leads to to much compression. Will thicker head gaskets help with my situation.

 

what head gaskets are you running now?

do you have all the info for the CR calculator?

 

They will certainly lower compression, and maybe whil heads are off polish the chambers up with some 80grit, open the chambers up a little too

 

Just cc the area at the top of cylinder at true tdc then you can easily do the math to see where your chamber cc's need to be, good thing is you may very pick up some head flow with a revised chamber shape

 

Felpro head gasket 0.30 compressed I do not have all spec.for calculator.

 

from here it looks like those heads have been worked some...post some pics of the business sides of them...

 

Heads are 1973 machined for stage 1 valves.

 

maybe its the angle of theb pic but the chamber does not look to be unshrouded for the big valves, and they look like they have been surfaced some. Definately had work in there.... Again, pic and I am pretty far away....:Smarty:

 

Yes heads have been surfaced . On first pic valve unshrouding were not done yet you can notice them on second pic.

 

Under what conditions are you experiencing the ping? I'm going to be running a set of .030 Ross pistons in my current build. They are job #62418. If you have the same pistons then the net dome cc is 10. That is with a .045 dish and 2.200 X .220 deep valve pockets. If your pistons are a true flat top then my numbers will be off. A cam with more overlap, tighter lobe center would help until rpm builds, but thats money and time. If this is a street car....a lot can be said for a proper distributor curve. Gearing also plays a roll.

 

Engine starts to ping when I attempt to launch hard. When not in gear I rev it up and can hardly hear it pinging. I have not driven it to much not even enough to feel cruising conditions im afraid to ruin my engine. My pistons are Ross job 35316. Bore 4.342 stroke 3.900 rod length 6.600 they are full floating. My initial timing is 15 and is 34 deg. all in at 2200 and stays there.Rear gears are 3.90.

 

Cometic makes steel layered head gaskets from .027" to over .100" in thickness, you can kill a lot of compression here when you know your other particulars.For every .020" thickness, you'll change compression by .5 point. Bringing total advance back to 30deg total will also help.
gary

 

Wont ping in neutral, no load on engine.
If in fact your compression (excessive) is causing your pinging, you MAY need more cam, in other words your cam may be too small for your static compression ratio.
Also, what convertor are you using? A stock (tight) convertor loads the engine more.

 

Converter is 2600/2800 boss hog.