Comp cut my cam wrong???

2339 Views 16 Replies 7 Participants Last post by Jackson72ss, Jun 10, 2009

Jackson72ss

Discussion Starter · Jun 9, 2009

Ok guys, I'm sitting at school now so I dont have my cam card or anything handy but I'll do the best I can here. I'm running a Comp Solid Flat 4/7 Firing Swap Cam in my 377. Its supposed to be .520/.540 lift and 244/252 duration at .050. I am also using comp gold 1.6 rockers. When checking P/V clearance we noticed that the exhaust lift was approx .545 and intake lift was .576. Duration was 252 on the intake side, but 258 on exhaust. What happened with this thing? Did Comp screw up my grind???

I have several options here and I was wanting some opinions on what would be the best route:

#1. Call Comp and yell until they replace my cam.
#2. Call my guy at Nickols and send my 1.6 rockers back and get 1.6s for intake and 1.7 for exhaust.
#3. Go with 1.5/1.6
#4. Finish putting the motor together and see what happens. Worst case I break a lot of really expensive parts.

I've had the worst luck with this motor, but according to 2 different dynosims the screwed up version on the cam makes more power than the right one... So who knows...
Here are the specs on the motor... Some things have changed since the last time I posted about it.

2 bolt main 400sbc, .030 over. 4.155 bore
Eagle 3.48 Forged Crank
Eagle 6'' I beam rods
220cc RHS heads, 64 CC chambers 2.02/1.6 valves, comp springs matched to cam.
Victor Jr Intake, Polished and mildly ported
KB forged flat top pistons, 4.5cc valve reliefs
Mighty Demon 850 Carb
Hooker 1 3/4 headers, need collectors...still undecided
MSD ignition (Probillit Distribution, Digital 6 Box, Coil, etc...)
Comp hardened pushrods
Comp Lifters matched to cam w/ the little hole in the center

11:1 compression, 3500 Stall Converter, 4.10 gears, approx 3400lb car. This is about a 50/50 split between track and a street bruiser. I just need a little help deciding on what my best option is here. Thanks in advance.

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Frisco

· #2 · Jun 9, 2009

Jackson72ss said:
Ok guys, I'm sitting at school now so I dont have my cam card or anything handy but I'll do the best I can here. I'm running a Comp Solid Flat 4/7 Firing Swap Cam in my 377. Its supposed to be .520/.540 lift and 244/252 duration at .050. I am also using comp gold 1.6 rockers. When checking P/V clearance we noticed that the exhaust lift was approx .545 and intake lift was .576. Duration was 252 on the intake side, but 258 on exhaust. What happened with this thing? Did Comp screw up my grind???

The difference in the advertised lift and the "approximate" lift you are seeing is because the advertised lift is when using 1.5 rockers. Since you stated that you are using 1.6 rockers the lift will be increased.

Whenever swapping out the cam (especially when swapping out the rockers with a greater ratio); you need to check the valve to piston clearances before ever running the engine.

SIDE NOTE:

That 850cfm Demon carb is way too big for your motor for street use.

ap72

· #3 · Jun 9, 2009

To be sure of what the cam is you need to check it off the cam, not off the valve as the geometry can play hell on precise readings of the cam. Even the pushrod length can affect the readings you're getting. If it looks close I'd just save the headache and run what you have- then tune from there.

Frisco

· #4 · Jun 9, 2009

Jackson72ss said:
I'm running a Comp Solid Flat 4/7 Firing Swap Cam in my 377.

2 bolt main 400sbc, .030 over.

How are you taking a 400cu.in. motor bored .030 over and making it a 377cu.in.?

cobalt327

· #5 · Jun 9, 2009

Frisco said:
How are you taking a 400cu.in. motor bored .030 over and making it a 377cu.in.?

3.48" stroke crank.

What happened with this thing? Did Comp screw up my grind???

As has been said, the lift needs to be figured w/the correct ratio- the cam was likely spec'ed for 1.5:1 ratio rocker arms, in any event, it will be stated on the card.

The cam card figures don't always take the lash into account, either.

Check all the cylinders- not just one. If the deviations are the same for all the cylinders' valves, you might chalk it up to manufacturing tolerances. If the cylinders show different cam timings and/or lifts- send the p o s back.

GXR11

· #6 · Jun 9, 2009

as far as lift goes, id say you got what you asked for.. if you do the math your lift is what its supposed to be. as others have said, the factory rocker ratio on a small block is 1.5... your using 1.6's. .520/1.5= .34666 lobe lift. .34666 x 1.6= .55466. 0.540/1.5=0.36, 0.36x 1.6=0.576... you rocker ration is whats giving you your diff. numbers then expected. going up to 1.7's will just make the diff. greater. if you want the numbers you think you ordered go down to a set of 1.5 ratio roclers.
hope this helps ya..if im wrong, please, some one correct me
dan

Chris Kemp

· #7 · Jun 9, 2009

As far as the cam goes 1.5 vs 1.6 is were the problem is and if you drop back in carb size to around 700cfm then you will see an increase in torque. As long as the valves clear the pistons I would see how it runs and what kind of power it makes before I changed the rockers.

cobalt327

· #8 · Jun 9, 2009 (Edited)

Jackson72ss said:
Its supposed to be .520/.540 lift and 244/252 duration at .050. I am also using comp gold 1.6 rockers. *snip* exhaust lift was approx .545 and intake lift was .576. Duration was 252 on the intake side, but 258 on exhaust.

Supposed to be (w/1.5 ratio):
.520 IN/.540 EX lift (LOBE .347/.360)
244 IN/252 EX duration at .050

Is seeing (w/1.6 ratio):
.576 IN/.545 EX (LOBE .360/.341)
252IN/258EX (+8 IN/+6 EX degrees)

Are your measurements taken at the end of the valve stem? If so, are you directly above the stem w/the plunger of the dial indicator?

Are the valves set w/the correct lash when your measurements are taken?

There's no way- if you've measured correctly- that this cam can be said to be within spec.

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ap72

· #9 · Jun 9, 2009

Incorrect lash settings can easily account for that difference, If you're that concerned about it you need to check it off the cam itself, not the other end of the valve train.

cobalt327

· #10 · Jun 9, 2009

ap72 said:
Incorrect lash settings can easily account for that difference, If you're that concerned about it you need to check it off the cam itself, not the other end of the valve train.

What part of this statement do you not understand:

"There's no way- if you've measured correctly- that this cam can be said to be within spec."?

And, how's about offering up something useful? Going behind me sniffing deeply of the aroma emanating from my *** does the OP no good, you know.

ericnova72

· #11 · Jun 9, 2009

Easy Cobalt, AP72 has a point. If the OP is measuring at the valve and using math to backfigure the readings to the cam card the rocker ratio and his measurement method can pretty much account for the discrepancy.

Jackson72ss, are you degreeing the cam from the lifter side of the valvetrain?

Hydraulic or solid lifters?

cobalt327

· #12 · Jun 9, 2009

ericnova72 said:
If the OP is measuring...

Click to expand...

If the OP has gotten a measurement that goes from what he said it was suppost to be (larger exhaust lift than intake, by 0.020", to where the intake is now larger)- SOMETHING'S not right- be it the OP, the cam or the cam card- or the OP's memory.

Jackson72ss, are you degreeing the cam from the lifter side of the valvetrain?

Click to expand...

Did I not just ask this?

Hydraulic or solid lifters?

Click to expand...

See post #1.

ericnova72

· #13 · Jun 9, 2009

Cobalt, my bad. I had to re-read post #1, guess I just missed the word solid, and didn't catch the flop from exhaust to intake being bigger, must have been looking at just the #'s

you are right something is wrong here, either the OP checked the wrong lobes and confused intake and exhaust lifter bores( I've seen people mistakenly think the first lifter bore is the intake lobe

), measured wrong on the correct lifter bores, or something is bad wrong with the cam.

The whole thing needs to be re-degreed to be sure now, as nothing matches up.

ap72

· #14 · Jun 10, 2009

If you're just concerned with the lift value being right, pull the cam out and mic it. Measure the lobes to check the lobes. a lot can be wrong in the pathway between the valve and the lobe.

Jackson72ss

Discussion Starter · #15 · Jun 10, 2009

Everything with the cam is right. With a set of 1.5s it measures correct, just the intake and exhaust lobes are backwards. We noticed this little issue when checking piston to valve clearance. I'm going to call comp tomorrow and see what they think the issue is, it just kinda worries me. I have approx 6-7k in this motor and I paid $350 for the cam alone. I know that everything has been measured correctly...end of valve stem with dial gauge. And every cylinder is within .002'' lift. I'm going with the idea that somewhere someone screwed up and it made it past quality control.

And as far as the Demon 850 being too big for street... I know this, but i believe I read on here that someone would drive a promod car on the street if it didn't eat plugs and overheat. Well, same concept. No street manners, a pain to drive, but rev on me at a stoplight. The car wasn't built for a daily driver. I just want to be able to drive to and from the track and play a little on the street.

Thanks for all the help guys.

Edit:
Double checked the cam card and memory was right. Cam was degreed from lifter side and valve lash was set correctly. I just think I have some bad luck...

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ap72

· #16 · Jun 10, 2009

Or it was just miscommunication somewhere a long the line- could have been on the shop floor. At least they'll fix it for you.

Jackson72ss

Discussion Starter · #17 · Jun 10, 2009

Hopefully they will. Getting ready to call them in about 20 min. I would think they would though, considering I have bought every thing possible from them. I'll post again in a couple hours and let everyone know how the situation played out.

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