Previous Thread
Next Thread
Print Thread
Page 3 of 3 1 2 3
Re: camshaft lobe sep [Re: BradH] #2702910
10/02/19 09:21 AM
10/02/19 09:21 AM
Joined: Jan 2007
Posts: 8,027
Mt Morris Michigan
mopar dave Offline OP
master
mopar dave  Offline OP
master

Joined: Jan 2007
Posts: 8,027
Mt Morris Michigan
I have his book and yes that's pretty much what I remember reading. Your number 4about excessive overlap came into play when Dwayne spec'd my cam. He asked if the combo would have exhaust and said it would need 110lsa with exhaust and a 108 would work better without exhaust. So, I agree to the best of my understanding.

Re: camshaft lobe sep [Re: mopar dave] #2702937
10/02/19 10:03 AM
10/02/19 10:03 AM
Joined: Aug 2003
Posts: 750
Zumbrota,MN
A
als499 Offline
super stock
als499  Offline
super stock
A

Joined: Aug 2003
Posts: 750
Zumbrota,MN
I was under the impression that bigger motors like a wider lobe seperation . So a 600" motor may respond better to a 114-116, a 500" may run better with a 110-112, a 400" motor may like a 106-108' , etc....

Re: camshaft lobe sep [Re: fast68plymouth] #2702948
10/02/19 10:21 AM
10/02/19 10:21 AM
Joined: Oct 2007
Posts: 4,205
New York
polyspheric Offline
master
polyspheric  Offline
master

Joined: Oct 2007
Posts: 4,205
New York
Exhaust far more sensitive to opening point than to lift. Once the valve cracks open, there is easily 70 psi escaping. Compare this to perhaps 1 psi at the intake seat...

Comparing LSA between cams is meaningless unless that's the only change.


Boffin Emeritus
Re: camshaft lobe sep [Re: Skeptic] #2702950
10/02/19 10:23 AM
10/02/19 10:23 AM
Joined: Jan 2003
Posts: 4,394
The Pale Blue Dot
Skeptic Offline
master
Skeptic  Offline
master

Joined: Jan 2003
Posts: 4,394
The Pale Blue Dot
Originally Posted by Skeptic
Originally Posted by fast68plymouth
I’d love to see a dyno test, for any make of motor, that saw any kind of real power gain, where the only change was the exhaust rocker ratio....... in a combo where the exhaust port wasn’t just horrible(relative to the intake port), or way too good for the application......... and the cam wasn’t just flat out wrong for the combo.

In other words....... nothing appears out of place or way off for the combo...... you do nothing but swap the ex rocker ratio...... and see a worthwhile improvement.
I thought Hod Rod did something like that. I don't recall the results. Off to the Googles!
Here it is No surprises here SBC with a small HR cam.

Re: camshaft lobe sep [Re: als499] #2702958
10/02/19 10:35 AM
10/02/19 10:35 AM
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
B
BradH Offline
Taking time off to work on my car
BradH  Offline
Taking time off to work on my car
B

Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
Originally Posted by als499
I was under the impression that bigger motors like a wider lobe seperation . So a 600" motor may respond better to a 114-116, a 500" may run better with a 110-112, a 400" motor may like a 106-108' , etc....

Like about 90% of the questions asked here, the only valid answer without knowing more of the details is: "It depends..."

Re: camshaft lobe sep [Re: BradH] #2702970
10/02/19 11:04 AM
10/02/19 11:04 AM
Joined: Jan 2007
Posts: 8,027
Mt Morris Michigan
mopar dave Offline OP
master
mopar dave  Offline OP
master

Joined: Jan 2007
Posts: 8,027
Mt Morris Michigan
Yeah, almost like shooting at a moving target. Every combo is different. It would be nice if all the convertor guys, cam guys, cylinder head guys and what ever guys got together and wrote a book on a bunch of different combos to show what works and what don't.

Re: camshaft lobe sep [Re: BradH] #2702973
10/02/19 11:06 AM
10/02/19 11:06 AM
Joined: Jan 2003
Posts: 19,304
Las Vegas
Al_Alguire Offline
I Live Here
Al_Alguire  Offline
I Live Here

Joined: Jan 2003
Posts: 19,304
Las Vegas
I have played rocker ratio roulette before myself. On my current predator deal in fact. I have even played with lash as well. Usually if you find something with ratio or lash for a given cam all you are learning is that you likely didn't get the correct cam the first time.

FWIW my current predator had a few cams and different ratios in it. The current one picked up 25 peak HP and 22 average from opening up the intake lash .010 and closing the exhaust .015, so what's that tell you? It made the best average and peak and is still in the engine but when we freshen it will likely have a new cam in it once again. And let me tell you those 60MM stocks dont come cheaply but I am trying to dqueeze all I can from this limited bore engine, while still maintain some semblance of reliability, so far so good on both fronts.


"I am not ashamed to confess I am ignorant of what I do not know."

"It's never wrong to do the right thing"
Re: camshaft lobe sep [Re: Skeptic] #2702974
10/02/19 11:07 AM
10/02/19 11:07 AM
Joined: Jan 2003
Posts: 14,479
So. Burlington, Vt.
F
fast68plymouth Offline
I Live Here
fast68plymouth  Offline
I Live Here
F

Joined: Jan 2003
Posts: 14,479
So. Burlington, Vt.
Originally Posted by Skeptic
Originally Posted by Skeptic
Originally Posted by fast68plymouth
I’d love to see a dyno test, for any make of motor, that saw any kind of real power gain, where the only change was the exhaust rocker ratio....... in a combo where the exhaust port wasn’t just horrible(relative to the intake port), or way too good for the application......... and the cam wasn’t just flat out wrong for the combo.

In other words....... nothing appears out of place or way off for the combo...... you do nothing but swap the ex rocker ratio...... and see a worthwhile improvement.
I thought Hod Rod did something like that. I don't recall the results. Off to the Googles!
Here it is No surprises here SBC with a small HR cam.


Actually, that’s a camshaft LSA test in the link, not an exhaust rocker ratio test.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: camshaft lobe sep [Re: BSB67] #2702990
10/02/19 11:35 AM
10/02/19 11:35 AM
Joined: Apr 2003
Posts: 3,496
Tulsa, Oklahoma
340Cuda Offline
master
340Cuda  Offline
master

Joined: Apr 2003
Posts: 3,496
Tulsa, Oklahoma
Originally Posted by BSB67
Originally Posted by 340Cuda


On the dyno with the reground cam the engine made about the same peak HP but made more power and torque at all RPM levels below peak.

Your mileage my vary...



How did the HP look after peak? Curve after matters as well. I think as a general rule, if you compare hp only up to peak hp, the narrower lsa, and move advanced ICL will be the winner. But I don't think best ets come from shifting at peak, at least for me.
I would have to dig out the dyno sheets but my recollection is that the power was flat after peak. However we did not run it very far past peek. On the track both cams quit pulling at peak.

Re: camshaft lobe sep [Re: 340Cuda] #2703049
10/02/19 01:49 PM
10/02/19 01:49 PM
Joined: Jan 2003
Posts: 14,479
So. Burlington, Vt.
F
fast68plymouth Offline
I Live Here
fast68plymouth  Offline
I Live Here
F

Joined: Jan 2003
Posts: 14,479
So. Burlington, Vt.
Originally Posted by 340Cuda
Originally Posted by BSB67
Originally Posted by 340Cuda


On the dyno with the reground cam the engine made about the same peak HP but made more power and torque at all RPM levels below peak.

Your mileage my vary...



How did the HP look after peak? Curve after matters as well. I think as a general rule, if you compare hp only up to peak hp, the narrower lsa, and move advanced ICL will be the winner. But I don't think best ets come from shifting at peak, at least for me.
I would have to dig out the dyno sheets but my recollection is that the power was flat after peak. However we did not run it very far past peek. On the track both cams quit pulling at peak.


Sounds like you dyno and track tested both cams.
115lsa in at 113 vs 110lsa in at 109.

Which went quicker, and just how much difference in ET between the two?


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: camshaft lobe sep [Re: fast68plymouth] #2703085
10/02/19 03:28 PM
10/02/19 03:28 PM
Joined: Aug 2003
Posts: 43,007
Bend,OR USA
C
Cab_Burge Offline
I Win
Cab_Burge  Offline
I Win
C

Joined: Aug 2003
Posts: 43,007
Bend,OR USA
I tested several (3) different camshafts years ago on a NHRA legal 1971 340 stocker rmotor , two Isky cams with the same lobes with one on a 107 LSA and the other on a 105 LSA. I moved both of these cams from 2 degrees retarded in two degree increments to 6 degrees advanced in the same motor on the same day wrench The 105 cam advanced 4 degrees on the ILC made the most peak HP and torque. Both of those cams made peak HP right at 5900 RPM and had a very steep gain and drop off after peak HP reaching 430 HP. those cams would make under 390 HP at 5000 RPM and droop off to less than 400 HP at 6400 RPM work Both of these cams had rounded tops on both lobes like most roller cams have, not a V shape nose shruggy
The last cam was a Lunati brand with V nose lobes ground on a 106 LSA , I move the ILC around just like I did on both of the Isky cams, this camshaft made 10 HP less at peak RPM(5800 RPM making 420 HP from 5600 to 6200 RPM and it made 400 HP at 5000 RPM all the way to 7000 RPM with no drop off shock shruggy
My message is the total package on the cam designs need to be look at very closely to help you decide on what to use for your deal work shruggy


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: camshaft lobe sep [Re: fast68plymouth] #2703360
10/03/19 10:56 AM
10/03/19 10:56 AM
Joined: Apr 2003
Posts: 3,496
Tulsa, Oklahoma
340Cuda Offline
master
340Cuda  Offline
master

Joined: Apr 2003
Posts: 3,496
Tulsa, Oklahoma
Originally Posted by fast68plymouth

Sounds like you dyno and track tested both cams.
115lsa in at 113 vs 110lsa in at 109.

Which went quicker, and just how much difference in ET between the two?

Unfortunately I don't have a definitive answer on track times. The new cam seemed to have more horsepower, enough to introduce some chassis problems. All the car wanted to do was turn right at the start. I found some things wrong with the chassis but that did not solve the problem. Turns out it was a bad slick. I got new tires and it went straight.

However tighter LSA means less valve to piston clearance. I knew that and checked it. It was tight but not as tight as some folks said they got away with on this thing called the Internet.

Turns out the exhaust valves were touching the entire time I ran this cam. At 6,450 RPM in low gear a head came off an exhaust valve and destroyed the block. I am in therapy, the head is being repaired and a replacement R3 block I had is in Maryland being machined.

Maybe I can give you a better answer next spring.

Re: camshaft lobe sep [Re: 340Cuda] #2703372
10/03/19 11:39 AM
10/03/19 11:39 AM
Joined: Jan 2003
Posts: 14,479
So. Burlington, Vt.
F
fast68plymouth Offline
I Live Here
fast68plymouth  Offline
I Live Here
F

Joined: Jan 2003
Posts: 14,479
So. Burlington, Vt.
Quote
The new cam seemed to have more horsepower, enough to introduce some chassis problems.


The “new cam” being the 110lsa?


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: camshaft lobe sep [Re: 340Cuda] #2703398
10/03/19 01:10 PM
10/03/19 01:10 PM
Joined: Jan 2007
Posts: 8,027
Mt Morris Michigan
mopar dave Offline OP
master
mopar dave  Offline OP
master

Joined: Jan 2007
Posts: 8,027
Mt Morris Michigan
Not sure how much on average narrowing the lda would also narrow piston the valve clearance on a 4.25 stroke, But I currently have 110*lda and .160" clearance on intake valve and .230" on exhaust. I would be sure to measure if I went 108lda, but looks like I have a ton of room as is.

Re: camshaft lobe sep [Re: fast68plymouth] #2703740
10/04/19 10:03 AM
10/04/19 10:03 AM
Joined: Apr 2003
Posts: 3,496
Tulsa, Oklahoma
340Cuda Offline
master
340Cuda  Offline
master

Joined: Apr 2003
Posts: 3,496
Tulsa, Oklahoma
Originally Posted by fast68plymouth
Quote
The new cam seemed to have more horsepower, enough to introduce some chassis problems.


The “new cam” being the 110lsa?
Yes sir...

Page 3 of 3 1 2 3






Powered by UBB.threads™ PHP Forum Software 7.7.1