Thread: new top end and no more power???

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what was the duration of the old cam? I'm willing to bet it's quite less than 224*... that's where your cranking compression went. What vehicle is this in? Transmission? Torque converter? Gear ratio? Where does it not "seem" to have enough power? Out of the hole or up top? Does it pull at high revs? What is your redline? What fuel are you using (octane)? Retarding the cam also is killing your cylinder pressure... all this explains why you can run so much timing lead... try running some crap regular gas in it and you might find more power

-Chris

In your calculations for static compression ratio, I suspect you forgot the piston deck height. I further suspect that on that year motor, the piston is down in the bore by about 0.030".
cylinder 727
chamber 62
piston crown 22
piston deck 6
gasket 3
820/93 equals 8.81:1
That cam would work well with 9.75 to 10.0, but it ain't gonna work too well with 8.81, particularly being retarded by 2 degrees. You might try advancing it 4 degrees from straight up and see how it works.

seat of the pants and also my friend has this "G TECH" dohicky that is also very accurate...we have used it on dyno'd cars and it and awesome tuning tool.

the old cam was stock, along with the heads and intake etc. i have a 4 speed in a 1960 chevy truck (3700 lbs w/me in it and a full tank of gas) 3.73 rear gears. 28 in tall tire. it pulls fine until about 3500ish rpm. i dyno'd the truck and it made a whopping 206 whp @ 5200rpm up here at 4500 ft. which equates to about 230hp at sea level. it power just levels off for the most part after 3500. but i'm shifting at around 5500 where i should be. right now i'm using shell regular 89 octane for gas.

and in my compression i did not forget the deck height or the piston dish.
stock piston dish is 20cc for my 74 truck 350. it is also bored .060 over.
stock deck height is .025
gasket is .015 inch compressed....etc.
and with all that info put into the compression ratio equation, comes out to exactly 9.17:1

and the cam has 5 degrees of advance built into the lobes. isn't 9 degrees of cam advance a little excessive???? and i honestly don't think that i need that much compression for this cam, yeah a little more because of the elevation, but even edelbrocks performer rpm crate engine only has 9.5 to 1 compression and that cam is quite a bit bigger than mine.

also my friend has the performer rpm cam in his pontiac 428 with just under 9:1 compression and he is even getting a minimum of 120 psi cranking. that cam has 4 degrees of advance built in it.
so theoretically my cam installed exactly how it is in the truck (retarded 2 degrees) is only retarded 1 degree more than his with about the same compression ratio and he has a lot more duration/overlap than mine too. AND he has .5* less LSA!

Swell. Have it your way.

hey i'm not saying i don't appreciate your advice, i do. but what's the reason for what you're suggesting? i just replied with what i know from experience and what i've read elsewhere. and i've never heard of advancing a cam a total of 9 degrees. i'm just frustrated and confused. sorry if i sound rude, i really don't mean to. thanks

What exhaust are you running?

Kitz

Cranking pressure has everything to do with the cam.Unless rings are shot or the valves are not seating correctly {from bad machine work or being held open}.