Thread: New 409 Sbc Chassis Dyno

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So I have a 68 camaro 409 sbc w/ M21 Four speed, hooker side pipe headers w/ high flow inserts.


400 sbc bored 40 W/ splayed main caps
scat crank
h-beam 6" rods
SRP flat top piston
rev kit
comp roller lifters vertical looking bar
comp 1.5 roller rockers
AFR 210 comp heads
super victor manifold
Quick fuel p-950 carb
501C2LUN Solid roller cam Deg *7 adv
6al Msd


So I went to the chassis dyno the other day and made three dyno pulls changing full advance each time.

1) 403 RWHP at 5300 and 424 RWTQ @ 35* full timing by 2800
2) 399 RWHP at 5300 and 428 RWTQ @ 31* full timing by 2800
3) 405 RWHP at 5300 and 434 RWTQ @ 36* full timing by 2800

The Air fuel ratio is between 12 and 13 threw the pulls. I also have a 1 inch spacer and 1/2 NOS plate. (The bottle is not in the car but its set for it). Compression is 11.4- 1 i run 92 octange.


The cam the heads and the intake are all suppose to make power between 3500 - 7500 so why is my max power 5200-5400 and it falls off prety good by 7000. So what im asking I guess ….. what is it that moves the peak HP up the rpm scale?

advancing the cam moves peak hp down in rpm range retarding cam moves peak hp up in rpm range.

was timing the only thing you changed?

Yea timing is the only thing that i changed at the dyno started 35 then 31 ended at 36.

The only thing i have changed sence the dyno was the valve lash i had it at .16 cold i changed it to .22 hot.

If you want to move the numbers up---retard the cam setting to straight up and see where it goes--might want to check for ex valve clearance at 10* btdc

Originally Posted by jerry clayton

If you want to move the numbers up---retard the cam setting to straight up and see where it goes--might want to check for ex valve clearance at 10* btdc

NOW im confused.....For years i always advance as much as possible for max top end hp even my three dyno pulls shows the same when i retanded from 35 to 31 i lost 4 hp then up to 36 i gained 6,the hole time peak hp was around 5300 rpm's.

You are confused between ignition timing and camshaft timing----advancing the cam (7*) will bring the power band lower---retard the cam to straight up and the numbers will be at a higher number--however you need to check that you have exhaust valve clearance as the piston is chasing the valve as it closes and the closet is area from arond 10*btdc to about tdc

Oh i see...ya..

cam deg is nothing i have ever done..... I had some one help me with that well good thing i put in a timing cover has an easy acsess to ajust cam timing... I have to pull the hole top down to check vaule clearance.

you can put checker springs on 1 in.and 1 ex and check valve clearance that way. if its a street car just live with it the way it is .prolly still do a smoke show.

If you are retarding the cam you will only need to check exhaust because intake clearance will increase as the cam is retarded---of course knowing what the clearance is makes it nice to know when playing with the cam timing--

Thanks alot im going to set to straight up and go from there.