Sorry no cold clearance or seat preasure.

Thanks!! very close cam to mine, it doesnt by chance say what the cold clearance is does it? also the seat pressure?

I took motor apart today, nothing major just some contamination damage on NO:4 due to pathetic air filters (next on the list)

What I did find is they didnt use the supplier GX spring washers/seat, they used regular flat round washers like the A-15 had stock... will put a post in the forsale/wanted section, inner spring must have had near no tension.

my cam is 280 inlet 276 exhaust .295'' lift . inlet opens 30 closes 70 exhaust opens 65 closes 31. clearance hot is .012'' on inlet and exhaust (all on my cam card). The cam grinder told me I can go down to .010''. curently running .011''. the timing is set 14deg about 1200rpm and is fully advanced at 3500rpm at 34 deg. no vacume advance.
I am not running as high a comp as you.

good luck.

Quote:
I tried this once. Connect a spare dizzy vacuum advance to it and take the top off while the engines running. You'll see it fluttering at idle leading to strange advance characteristics. I'd disconnect it, check the timing without it and see if you still have the problem. I've never seen anyone run sidedrafts with vacuum advance even on roadcars. Initial advance somewhere around 10*~12* is a good place to start.

I had the same problem with mine when i first assembled it, it wouldn't go over 7000 rpm. I was running dual mikuni 40's changed out to 44's and it solved the problem.

That is exactly why i free rev'd it, ignition problems tend to be more load based/show up more under load,,, one free rev is a quick way to work out probability of ignition causing it

For now ill have to build up another motor with mazda pistons, this time ill try find a set that had drilled holes for the oiling not slots, I knew those slots would cause drama but honestly this motor was a "trial and error" setup and cost me next to nothing, wanted to find out what would work for me and my power goals, now its time to do it right, pity no one seems to have stock of the A15 high comp's so ill build a 3rd forged motor when i have time!

i think your on the money with valve spring
control, suprising how often that is over
looked. The end result is usually valves and
pistons crashing-which makes a big mess!!

Edit: The point about free revving is that it
does not correctly simulate problems which occur
under load. I have had ignition
problems undetectable in the pits but cronic
and undriveable on the track. If an engine is
going to fly apart, especially with standard
parts, it will be with big revs & no load.

i was thinking that, try another dizzy and coil, but u have already.

because I have ran from 28deg to 36 deg total advance and it did the EXACT same thing at EXACTLY the same RPM,

I have also tried using my old points dissy, same thing, same RPM, and I have also changed coil same thing same RPM.

Fair to say its not likely to be ignition?

How can you say its valve related if your ignition is not doing its job?

If you are using vacuum for the distributor, then it needs to be 'ported' vacuum from the carb, not from the manifold. The only sidies I have seen with vacuum port are solexes.

I would take off the vacuum can, up the base timing to 12-15