Cam Talk

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Ironmike

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Ok so we have 2 solid roller cams with .640/.640 lift, 255/263@ .050. Both identical these specs, but..

Cam A has a 110 LSA and 104 ICL

Cam B has a 106 LSA and 100 ICL

Assuming we run them both in the same 11 to 1 stroker with great heads..

How will they compare?
 
Hmmmm. With great heads? What's your definition of a great head? What's the rod/stroke ratio? Single 4 or a manram with 2 fours?????

If the rod/stroke ratio isn't whack, and the heads are great, you could run the 110 but I would never run it 4 ahead.

If the R/S ratio is whack (less than about 1.65:1) and the heads are Pcar heads, the 106 would be better, but never 6 ahead.
 
Not enough info to make any informed decisions. Given what you gave us, I'd say run them both in the chassis and tell us what it likes more.
 
Cam b should have narrower powerband with more peak hp and torque.

Doing a cam shoot out is the only way to know. If you just want to pick one if you go with optimal stall and gears for your combo I'd go with cam b if not I'd go cam a
 
I'm running cam A right now. Lunati wanted it installed at 104, it came out to104.5, so I left it right there. 5.5 degrees advanced. Makes good power, idles nice at 1150 with 12 inches vacuum. 185 cranking psi.

Heads are cnc Indy/RHS, flowed 296 at .600, but down to 292 at .650. My combo made 562 on a real, calibrated, local dyno that ain't customer friendly. My guy says it's accurate and I believe him. It made 488 on a chassis dyno (tuner shop)4 months later and 45 miles away. So please let's not do the dyno dance....numbers are numbers.

Just researching to pick a cam for my combo I'm building this winter. Only difference is I will be using Edelbrocks with Hughes full CNC deal. Really trying to get closer to 600. I think the heads will really help, but more cam can't hurt. I run a 4 speed with 4.10 gear.

I've read LSA wider than 108 is a power killer. My machinist feels the same. Seems like back in the good Ole days i never even heard of anything wider than 106. Just hoping to get a better understanding of LSA.
 
Ironmike said:
I'm running cam A right now. Lunati wanted it installed at 104, it came out to104.5, so I left it right there. 5.5 degrees advanced. Makes good power, idles nice at 1150 with 12 inches vacuum. 185 cranking psi.

Heads are cnc Indy/RHS, flowed 296 at .600, but down to 292 at .650. My combo made 562 on a real, calibrated, local dyno that ain't customer friendly. My guy says it's accurate and I believe him. It made 488 on a chassis dyno (tuner shop)4 months later and 45 miles away. So please let's not do the dyno dance....numbers are numbers.

Just researching to pick a cam for my combo I'm building this winter. Only difference is I will be using Edelbrocks with Hughes full CNC deal. Really trying to get closer to 600. I think the heads will really help, but more cam can't hurt. I run a 4 speed with 4.10 gear.

I've read LSA wider than 108 is a power killer. My machinist feels the same. Seems like back in the good Ole days i never even heard of anything wider than 106. Just hoping to get a better understanding of LSA.
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How about asking Hughes,themselves? They owe you that customer service,for the product paid for.... Find the specs from them,ask all cam companies you like... Personally ,Moper nailed it.... Intake car weight ,gears ,hell..even driving style affects these choices... Add the whole combination,you get a couple of dead on answers..(a simple example: You stated stroker,...witch one?????).
 
Ironmike said:
I'm running cam A right now. Lunati wanted it installed at 104, it came out to104.5, so I left it right there. 5.5 degrees advanced. Makes good power, idles nice at 1150 with 12 inches vacuum. 185 cranking psi.

Heads are cnc Indy/RHS, flowed 296 at .600, but down to 292 at .650. My combo made 562 on a real, calibrated, local dyno that ain't customer friendly. My guy says it's accurate and I believe him. It made 488 on a chassis dyno (tuner shop)4 months later and 45 miles away. So please let's not do the dyno dance....numbers are numbers.

Just researching to pick a cam for my combo I'm building this winter. Only difference is I will be using Edelbrocks with Hughes full CNC deal. Really trying to get closer to 600. I think the heads will really help, but more cam can't hurt. I run a 4 speed with 4.10 gear.

I've read LSA wider than 108 is a power killer. My machinist feels the same. Seems like back in the good Ole days i never even heard of anything wider than 106. Just hoping to get a better understanding of LSA.
Click to expand...



I would call Jim at Racer Brown. He will explain it better. But LSA and ICL are a function of other parameters.

It also follows the line of thinking that a 6.123 rod is a "long" rod. It is if the stroke is 3.313 then it's a long rod, relatively. But if you have a 4 inch stroke, the rod isn't so long. So really, what is a narrow LSA and what is a wide LSA? It's relative.

As to intake centerline, I am way old school. This bullshit marketing ploy that Comp devised decades ago to install everything 4* ahead is just that. Bullshit marketing. The reason for using 1 or 2 degrees of advance was to compensate for timing chain stretch. The cam will retard under load and chain wear. Then Comp pulled a marketing scam.

The intake centerline is just that. Where the intake is at max lift, after TDC. If you have to advance a cam more than 1-2 degrees to compensate for timing chain stretch, you have the wrong events to start with, and you are leaving power on the table.

All that said, heads with crappy exhaust ports and great low lift flow, will get hurt with a narrower LSA, and then the cam guy will advance the ICL to fix it. You should fix the head. Set your valve job to stop reversion. Reversion causes rough idle and makes the fuel curve rich. Think about it. The air goes through the booster 3 times!!!!!! That gives you 200% more fuel than you want. That really isn't an LSA or ICL issue, it's a port/valve job/chamber issue. So the cam guys, instead of educating the customer on air flow and such, they make the LSA wider and set the ICL earlier. Power right down the toilet (or port as it may be).
 
yellow rose said:
I would call Jim at Racer Brown. He will explain it better. But LSA and ICL are a function of other parameters.

It also follows the line of thinking that a 6.123 rod is a "long" rod. It is if the stroke is 3.313 then it's a long rod, relatively. But if you have a 4 inch stroke, the rod isn't so long. So really, what is a narrow LSA and what is a wide LSA? It's relative.

As to intake centerline, I am way old school. This bullshit marketing ploy that Comp devised decades ago to install everything 4* ahead is just that. Bullshit marketing. The reason for using 1 or 2 degrees of advance was to compensate for timing chain stretch. The cam will retard under load and chain wear. Then Comp pulled a marketing scam.

The intake centerline is just that. Where the intake is at max lift, after TDC. If you have to advance a cam more than 1-2 degrees to compensate for timing chain stretch, you have the wrong events to start with, and you are leaving power on the table.

All that said, heads with crappy exhaust ports and great low lift flow, will get hurt with a narrower LSA, and then the cam guy will advance the ICL to fix it. You should fix the head. Set your valve job to stop reversion. Reversion causes rough idle and makes the fuel curve rich. Think about it. The air goes through the booster 3 times!!!!!! That gives you 200% more fuel than you want. That really isn't an LSA or ICL issue, it's a port/valve job/chamber issue. So the cam guys, instead of educating the customer on air flow and such, they make the LSA wider and set the ICL earlier. Power right down the toilet (or port as it may be).
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That is beautiful...(explanation wise..) The guy I like,prefers wide lobe center cams,degrees as necessary.. He prefers 78-80 percent intake to exhaust,with a minimum valve size,'(maximum velocities) ,for the job.(FWIW ,he was bitching about turblence noise on the exhaust port,since the early 90's....)
 
What Yellow Rose just said was pretty much spot on. I'm a believer that if you have to move the cam to make it "right", you have the wrong cam and if you have big gains with a spacer, you have the wrong intake. I deal in street engines first, race engines second. So they need to perform at all different levels. WOT is only run for bursts and represent a small percentage of total running time. If you are street driving this car, you might want to worry less about a specific HP number. With no other changes switching to RPMs will drop you 50+lbs over the front axle anyway... helping acceleration, weight transfer, and braking...lol. Just a thought there.
In terms of your dyno tests - I'm not questioning them - IMO they are where they should be.
12" at 1150rpm is not an idle - not sure of the carb choice but you're probably not on the idle circuit of it anyway.
I don't see a cam that similar making a 40+hp gain with a head like what you currently have. Because what you have is too close to maxing the heads' potential at this point. So a lot will depend on the Hughes program. If it were me, I would take their work, have it flowed by a shop I trust ('cause I don't trust Hughes), then have a cam designed to get me where I want to be. Stage III RPMs will exceed 600hp with cams a little bigger than you list, but it all comes back to what your exact heads can do.
 
Thank you guys! Exactly the kinda stuff I was looking for. Absolutely will get the heads to my local guy AFTER I get them from Hughes.

My machinist gave me a couple cam guys.......one was Jim at Racer Brown, the other was Tim at Bullitt.

Appreciate the help, as always!
 
Oh yeah. Running a 950 HP. I AM still on the idle circuit....1/8 holes in all 4 butterflies.
Am certainly open to change in the carb. 1000HP, maybe. Maybe even a 2 circuit Dominator. Still has to be a street car, although I am very tolerant of what a street car is. Some guys would never want what I'm running now on the street.

Also.....finally figured how to empty my inbox.
 
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Cam a will probably make more hp at a higher rpm but less torque than b .A should have a wider flatter torque curve than B.B should be more agressive but in a narrower rpm range and also need a looser converter.Anyone who knew Harold at ultradyne knew he designed these cams to be advanced 6 degrees thats why he built it in.Lunati,Bullet,and Howards all use his lobe designs now.Nothing wrong with Racer Brown but to say he is the best, ask the top mopar engine builders in the country who their using and I bet it aint RB . These cams you have work great and I think MRL uses them,Hell they just might even work great with your new heads.
 
moper said:
Nice looking rig Mike!
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Thank ya, sir. I'm gonna feel kind of bad yanking it out, just for 40 horsepower, maybe..........
Took a little blast before work tonite, just turned 2200 miles for the season. It's so mannerly(to me). Until you mash it then its like an explosion. What still shocks me is how quick the shift light comes on in 3rd gear. Seems like I used to have time to take a breath between 3rd and 4th. No more.
 
Strokers generally respond better to the wider LSA. If there was a third choice with a 112 LSA, I would say use that.
 
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