HotRod777
Well-Known Member
I have 2 questions to see if advancing my cam is doable and worth while.
Here is all the dirty details of the combo that I put together in the middle of last summer. It’s in a 1966 Coronet, just a cruise car, never will see the strip or above 75mph. I think I picked pretty well as far as the whole combo... but I have to admit I was expecting a bit more from it.
383, 40 over. Sealed Power forged flattops, .018 in the hole. 1967 915 heads with new 2.14, 1.74 valves, bronze guides and hardened seats. Single street springs good to .520. .020 steel shim head gaskets giving .038 quench and roughly 10:1 calculated compression. I run 93 octane Sunoco pump gas. DP4B intake, new AVS2 650, HP manifolds and 2.5” TTI system. Refurbed factory 10.75” Hi-Stahl, 3.73 sure grip and 27” tire.
Timing set at 16 initial, 34 all in by 2200 with light springs and fbo plate.
Cam is the Comp 270H (.224 @50, .470” lift) installed straight up.
The car runs good but regrettably it idles smooth like a tow truck unless I slow the initial down to 5°. I wish it lumped more at idle. It seems to start to pull better after 2000rpm. Maybe this wasn’t the best cam choice...
I just checked cranking compression, plugs out and carb open... 150# in all cylinders give or take 2 or 3 pounds. Ideally I think I’d like to have 10-20# more...
Do you think advancing the cam 4° will provide a noticeable gain down low and how much more cylinder pressure could I expect? (And I know advancing “might” add a bit more exhaust note being the pressure is higher)
And, I know the big intake valve might be getting close the to flat-top... but with only 224° and .470” will I be ok? Has any one used a bore scope to see how much clearance they have?
Thanks for any ideas/insight
Here is all the dirty details of the combo that I put together in the middle of last summer. It’s in a 1966 Coronet, just a cruise car, never will see the strip or above 75mph. I think I picked pretty well as far as the whole combo... but I have to admit I was expecting a bit more from it.
383, 40 over. Sealed Power forged flattops, .018 in the hole. 1967 915 heads with new 2.14, 1.74 valves, bronze guides and hardened seats. Single street springs good to .520. .020 steel shim head gaskets giving .038 quench and roughly 10:1 calculated compression. I run 93 octane Sunoco pump gas. DP4B intake, new AVS2 650, HP manifolds and 2.5” TTI system. Refurbed factory 10.75” Hi-Stahl, 3.73 sure grip and 27” tire.
Timing set at 16 initial, 34 all in by 2200 with light springs and fbo plate.
Cam is the Comp 270H (.224 @50, .470” lift) installed straight up.
The car runs good but regrettably it idles smooth like a tow truck unless I slow the initial down to 5°. I wish it lumped more at idle. It seems to start to pull better after 2000rpm. Maybe this wasn’t the best cam choice...
I just checked cranking compression, plugs out and carb open... 150# in all cylinders give or take 2 or 3 pounds. Ideally I think I’d like to have 10-20# more...
Do you think advancing the cam 4° will provide a noticeable gain down low and how much more cylinder pressure could I expect? (And I know advancing “might” add a bit more exhaust note being the pressure is higher)
And, I know the big intake valve might be getting close the to flat-top... but with only 224° and .470” will I be ok? Has any one used a bore scope to see how much clearance they have?
Thanks for any ideas/insight