[462ta]

Thks Cliff, any idea where to start looking for the lost power, i tried adv cam with just putting it on the 4 deg keyway and put it on the same dyno and it was down to 240 rwhp so i put it back straight up, tried deg cam with a buddy but we kept getting some scewed up numbers so eventually we gave up, i need to do it again with someone who knows more about it. with the cam straight up it cranks 150 and when i put it on the 4 deg it cranked 165 on compression check.
built a pretty good bottom end with 5140 rods and KB forged pistons 14cc dish, 13 heads at 78cc ported using Jims book but did not go crazy, gasket match, ran the cutters down the bowl and blended, smoothed out runners and pushrod bulges,unshrouded valves.Built quadrajet using your book on stock 69 intake with tri y headers and 2 1/2 mandrel bent full exhaust.
Do you think deg cam properly will make a difference in finding some of the lost power im down 60-80 hp from what others are seeing.

[Cliff R]

78cc plus 13cc is 91cc. I don't know how you get up to 9 to 1 compression, should be closer to 8.2 to 8.4? Nothing mentioned about zero deck height and gasket thickness?

In any case, with that much area above the piston, a smaller cam would be a much better choice, something down around 214/224/112.....Cliff

[chiphead]

According to the CP website, 91CC on a zero deck shortblock is 9.3 compression. That's about what I have, with 70CC heads and 20CC dished pistons.

If you don't degree the cam with a degree kit, you don't really know where you are. +4 on the timing chain gear isn't always really +4. You can still be way off in the weeds with cam timing.

What are your ignition timing settings? What carb, intake, etc?

[Cliff R]

Might be 9 to 1 depending on deck height and gasket used. In any case, not enough compression for that camshaft, IMHO. I've never even tried one below 10 to 1 compression, most were 10.2 to 10.4 to 1 or so, and we prefer the 60243 for manual transmission and any more compression than that.

+1 on the 4 keyway set, could have moved the cam just about anyplace, at least from what I've seen here with those set-ups.....Cliff

[462ta]

zero deck with 038 gasket
36 deg all in by about 3000 near as i remember
quadrajet on 69 intake
i guess where im at is do i remove the heads and bump comp keeping the 60916 cam or just leave that alone and go with a smaller cam, best bang for the buck in other words

[71 Ventura II]

Originally Posted by 71 Ventura II

Automatic transmission I'd expect to see in the neighborhood of 286 HP to 296 HP at the rear wheels. If your at a fairly high altitude then 275 RWHP is all you can expect. JD

Originally Posted by Cliff R

With unported heads on a zero deck shortblock we've made 419hp/453tq at the flywheel.

We've got customers running mid to high 12's in street driven FB's and GTO's with that combo, so the track numbers support what we saw on the dyno.

Something fundamentally wrong someplace? Even at 9 to 1 compression it should make more HP than what you are seeing. Torque may be down some do to the lower compression, but I'd still expect 380-400hp/420-430tq at the flywheel with that cam in a 400 engine with 9 to 1 compression.

One negative I've seen with that cam, without exception every single one has needed to be advanced at least 4 degrees, some more than that, to get them down to 108-109ICL......Cliff

Originally Posted by chiphead

According to the CP website, 91CC on a zero deck shortblock is 9.3 compression. That's about what I have, with 70CC heads and 20CC dished pistons.

If you don't degree the cam with a degree kit, you don't really know where you are. +4 on the timing chain gear isn't always really +4. You can still be way off in the weeds with cam timing.

What are your ignition timing settings? What carb, intake, etc?

Hello guys, remember "He's" reporting +- 275 RWHP not crankshaft! 275 RWHP is equal to +- 357 HP at the crank when running a traditional 3 speed automatic. A full point of compression equals +- 8% difference in HP. So, for you guys who found +- 405-419HP at the crank running @10.0-1 compression in a similar combo try the math. Drop the power by the 8% accounting for the drop to 9.0-1 compression you get, 372-385 HP at the crank or expected +- 286.44-296.45 RWHP .

Accounting for the 8% loss due to compression drop the 372-385 will yield a RWHP of 286.44-296.45 as stated. That's only 3-7% below expected return, Not a fundamental issue, more like a fine tuning reward.

Factors in play effecting results: Lower compression and driveline parasitic loss. He's not far from expectation for the combination of parts in the environment. He lives only 627' above sea level which is cool! JD

[Cliff R]

The power loss for compression formula doesn't hold water, never did. We choose the camshaft based on the compression and CID. A cam that works well for 400cid at 10 to 1 compression is NOT as good of a choice at 9 to 1. For every full point of compression the cam needs to be about 10 degrees smaller, to keep idle quality, off idle power, and torque production in the lower rpm range on par with the larger camshaft in the higher CR engine.

What we are seeing here is typical of choosing a camshaft that is too big for the application. It would be a LOT happier with something closer to an 068 grind...IMHO.....Cliff

[71 Ventura II]

Originally Posted by Cliff R

The power loss for compression formula doesn't hold water, never did. We choose the camshaft based on the compression and CID. A cam that works well for 400cid at 10 to 1 compression is NOT as good of a choice at 9 to 1. For every full point of compression the cam needs to be about 10 degrees smaller, to keep idle quality, off idle power, and torque production in the lower rpm range on par with the larger camshaft in the higher CR engine.

What we are seeing here is typical choosing a camshaft that is too big for the application. It would be a LOT happier with something closer to an 068 grind...IMHO.....Cliff

Here's an example of over camming an engine for return. Above I posted all the major details of building a 400 w/#60916 cam running 12.50's @107 mph. I tried changing the #16 cam to a Crower #60311 w/1.65's, Torker II intake w/1" spacer, and 3800 converter in an effort to go fast. WELL RESULTS: The damn car ran the same ET! I mean there wasn't more than .01 difference between them. But with the larger solid cam combo I had to raise my shift rpm from 5600-5800 to 6500 rpm's to get it to respond!!! Now that was a diminished return on investment by grossly over camming. LOL

[chiphead]

Ventura, those are some stout numbers with the 60916 cam. You sure your compression wasn't more than 9.7? My 400 will just break the 12s on motor with the XE274. 3750 race weight. Cranking compression is 165 PSI with the cam adv 2*. 38* total timing. Don't get me wrong, it's fast and fun. But I'm trying to maximize the combo, so I'm wondering if a Crower would work with 9.3 compression.

It seems like the OP has a similar setup, so I'm curious why it's so down on power. I'd love 15" of vacuum at idle. Sounds like this cam really needs to be degreed, to eliminate that as a problem.

Are they checking AFR on the chassis dyno?

Should a 60916 cam be making 15" of idle vacuum at 9:1 compression? I'm at 8-10". Yes, I've got idle fuel.