yesterday while driving my car started pinging, under slight to moderate load.
for the life of me I couldnt figure out why.
My block like I stated before is a 350 bored 30 0ver, the heads are a 305 head, casting # 601.
I called my local head machine shop, "action cylinder heads"
and gave them the run down on my setup.
He told me that wiht those heads on a flat top 30 over block I will have a 11:01 comp ratio,
is this true,
I am running 95 octane now, it pings on 92. He reccommended that I yank those heads, but a set of his on, 64 cc 202/160 valves
before I mess with my cam or gearing.
I Just dont know where to start.
any help would be nice.
thanks,
Jer,

 

You will need to know what head gasket you used and what the deck height was on your block.

You can always retard the timing.

 

To repeat what I said in my PM response:

Unless the block has been decked, you probably have somewhere around .030" deck height. If the Felpro was a thick composition type, that would help reduce compression.

Polished chambers can help reduce pinging (I'm using regular unleaded with 9.5:1 CR). Larger valves really help, even on a 305. Unshrouding the chambers around the valves increases chamber volume and helps reduce compression. 305 heads are typically used with dished pistons on a 350, but it can be manageable.

The 64cc, 2.02/1.60 heads would be the easy way out.

 

You would get a 11:1 compression ratio IF the block has been 0decked. if the heads have stock 305 sized 1.84-1.50 valves then are likely 58cc+/- if they have been shaved the compression could be even higher.
Were they shaved?
typicaly a stock block's pistons are between .025" to .045" down in the bore at TDC. if your block was decked the cr will be higher. Makes a difference.
a 55cc head on a 350 that was 0 decked makes 11.5:1
ya that a little too high.
You can remove the heads and install larger 350sized valves (1.94 x1.60") and open up (deshroud) the chambers at the same time to a larger 65cc's. this is typically what you'll end up with.

this would get you 10.36:1 A thicker .051"head gasket would get you down to 10.04:1

I would remove the heads and cc the chambers and measure the deck height of the pistons and valve diameter and go from there.
Do a compression test first . cylinder pressure should not be more than 185psi for pump gas.
A true 11:1 will typically get you over 200PSI .
if its 185psi or less the cr is not too high.

try a cooler spark plug. I like a champion RV8C or a AC R42T with that head on a 350. stock R45TS are just too hot.
What camshaft are u using in this motor?

If your head shop is offering a nice set of late camelbacks with bolt holes (186,492,041,040 casting) or a upgraded L-98 head (083casting) for a good price, could be worth it. get the casting # and a price and compare the $$ cost to fix your heads.
Avoid any 882's 624's etc etc Junk.

if it "suddenly started pinging" yesterday but was running fine before, then you have other issues.
Timeing, fuel, temp, bad gas etc etc.
is this a new/fresh motor or have you been driving it ok for a while and suddenly got a problem?

 

No matter what tricks you try, you will be hard pressed to run iron heads with 11:X compression on pump gas. It will be cheaper in the long run to switch to a larger combustion chamber set of heads.