Sounds like someone needs to know, do some measuring, for piston depth at tdc.
If it's detonating he'll be doing this again!
Sounds like someone needs to know, do some measuring, for piston depth at tdc.
With -17.5cc dish pistons, zero deck, 62cc chambers, and typical .040 gasket his compression is 10.5:1 which is more than enough to detonate with ANY camshaft if he got a bad batch of pump gas or old gas...
And that's if his timing was perfect. Guys don't realize with iron heads once you go over 10:1 even with good quench you have the potential for detonation using PUMP gas. And where the cam was installed has an impact on that as well.
You say his machinist told him it's zero decked...CHECK it yourself!!
I'm just sayin.....
With -17.5cc dish pistons, zero deck, 62cc chambers, and typical .040 gasket his compression is 10.5:1 which is more than enough to detonate with ANY camshaft if he got a bad batch of pump gas or old gas...
And that's if his timing was perfect. Guys don't realize with iron heads once you go over 10:1 even with good quench you have the potential for detonation using PUMP gas. And where the cam was installed has an impact on that as well.
You say his machinist told him it's zero decked...CHECK it yourself!!
I'm just sayin.....
Run a tap in all holes put a very small amount of oil on bolt threads this helps the torque read right. also the torque sequence is critical.
Use a good torque wrench that is calibrated.
Measure and measure again if you are getting your heads resurfaced witch I suggest you do that will change the clearance.
Head bolts do stretch good bolts are very important.
If you lock it out, it will want to detonate easier! I'd make sure you end up with as close to .040 piston to head clearance as possible, leave the advance curve in it, don't up the compression just clean the heads with as light of a cut as possible.
Anywhere from 32-34 total advance is fine, just make sure you rev it up high enough...I've seen MSD dist. and MP dist. need as much as 3800rpm before they quit advancing!!
Make sure you chamfer the chamber where it meets the deck all the way around the chamber...lightly.
What plug are you running?
Run a tap in all holes put a very small amount of oil on bolt threads this helps the torque read right. also the torque sequence is critical.
Use a good torque wrench that is calibrated.
Measure and measure again if you are getting your heads resurfaced witch I suggest you do that will change the clearance.
Head bolts do stretch good bolts are very important.
If you drive it hard, I'd run a bcp6es plug. I'd run a .039 felpro if it's true zero. Yes leave the timing curve in the dist. I like to use the light silver and light blue together in place of the heavy silver springs.
And yes check that the bolts don't bottom out in the block.
those 8553pt gaskets are .045 compressed and run.
I ran 165-170psi cranking ' 9.9 static' with those head gaskets and had no issues.
I used 91 octane, quench domes w/open chamber heads around .037 q/d and 24* initial & 32* total timing.
140psi is weak, but the cam is bleedin it too..., so doesnt mean it cant detonate up top...but just maybe the tune was crap.
If you drive it hard, I'd run a bcp6es plug. I'd run a .039 felpro if it's true zero. Yes leave the timing curve in the dist. I like to use the light silver and light blue together in place of the heavy silver springs.
And yes check that the bolts don't bottom out in the block.
Also Brian I'm using the bolts you sent me with the heads so they shouldn't bottom out right??
Hey so I measured my deck and it is at 0 , also got my heads back from shop yesterday,he took off.004 and checked all valves to make sure they were sealing up all the way, now is that .039 a compressed thickness ? Also what bore diameter would I need if my cylinder bore is 4.040? Would you recommend a different camshaft? Cause the one I have is bleeding out pressure?? Want to make sure this is the last time I have to do this for a long time thanks
Also Brian I'm using the bolts you sent me with the heads so they shouldn't bottom out right??
Hey so I measured my deck and it is at 0 , also got my heads back from shop yesterday,he took off.004 and checked all valves to make sure they were sealing up all the way, now is that .039 a compressed thickness ? Also what bore diameter would I need if my cylinder bore is 4.040? Would you recommend a different camshaft? Cause the one I have is bleeding out pressure?? Want to make sure this is the last time I have to do this for a long time thanks
Also Brian I'm using the bolts you sent me with the heads so they shouldn't bottom out right??
Why not just use ARP studs....they are stronger AND you don't have to worry about them bottoming out causing false torque issues.
Personally I think it was detonating. Now if you go with the 1008 felpro gasket, you'll have proper quench and that should take care of that. Leave the advance curve in the dist., set total timing at 33°, use the bcp6es plug (stock #4930), and set lash hot at .018 and see what she does.
closing to .18 will give more cranking compression and lift