Cam Centerline questions

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metallidart

metallidart

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Seems like I have a new question every day!

I sent Bullet a rec form for my stroker recently. They sent back a recommendation similar to what comp told me, and I guess I am a little baffled.

I know already I will be on the ragged edge of pump gas. My comp with my 422 sb will be 10.7-11:1. Open chamber W2 heads. Gonna polish the chambers. Pistons are ft at zero deck.

I know its just a number, but I have read most people agree that for pump gas--we have 93 everywhere--that the dynamic compression should be close to 8. I am trying to get it as low as possible on paper, to HELP me choose a cam. I have settled at an 8.2-8.3 goal.

I told them pump gas is a priority, 3.73 gears, 3400lb, 11:1, auto w/appropriate stall for cam, W2 heads with 2.08 valves, ported, 422cid 4" stroke 4.1 bore. Street/strip, idle/vacuum not important.

They said 278/282 adv, 251/255@.050, .570/582 lift, 108lsa, and a 104 centerline. I thought this was a little small for what I want, but, they make cams, not me lol.

I noticed playing around with the dynamic compression calculator on Wallaceracing.com that moving the centerline is what changes the dynamic compression the most.

What would happen if the cl was changed from 104 to 106? It brought my dynamic compression down to something that might work.

I am still leaning towards a few Lunati cams recommended by a well-respected builder on here, but I do have a used solid that I may be able to regrind or something. Guess I am just trying to learn.

Also, what would the aproximate rpm range be on that cam? Stall?

Thanks!
 
Sounds a bit small tome too. I am wondering if what you want to do is even possible on pump gas. Even 93. But WTF do I know? lol

I do know this. You want to pay closer attention to the intake valve closing point than the centerline, I believe.
 
RustyRatRod said:
Sounds a bit small tome too. I am wondering if what you want to do is even possible on pump gas. Even 93. But WTF do I know? lol

I do know this. You want to pay closer attention to the intake valve closing point than the centerline, I believe.
Click to expand...

wish we could get 93 in tulsa,all we get is 91 cowpiss.
 
If pump gas is a priority then why not get the static compression down to a realistic number for iron heads? You're tying the cam builders hands & I'm betting the trade off power wise would be minimal.
 
RustyRatRod said:
Sounds a bit small tome too. I am wondering if what you want to do is even possible on pump gas. Even 93. But WTF do I know? lol

I do know this. You want to pay closer attention to the intake valve closing point than the centerline, I believe.
Click to expand...

Lol, you know enough that I don't take your advice or opinions lightly! The guy that had the shortblock before me ran pump gas, but that was with aluminum Indy heads and 65cc, he had quench to help him, and a huge roller cam. I am hoping to get it to be pump gasable (I made that word.), but I will mix if I gotta. If there was more than one E85 pump in a 25 mile radius I think I would go that route!
For the intake valve closing point, what do I need to pay attention to, exactly? Would closing later help ward off detonation?

I always gotta do stuff the hard way.


80fbody said:
If pump gas is a priority then why not get the static compression down to a realistic number for iron heads? You're tying the cam builders hands & I'm betting the trade off power wise would be minimal.
Click to expand...

I bought the shortblock assembled, I don't have the cash for new pistons, rings, bearings, balancing, etc. Just trying to work with what I got. Had I built it, I would have probably gone with dished pistons. Besides, this is a challenge and I am learning alot about what you can do in different areas to affect power and streetability. I am just making the cam builders think harder and work for their money :) I could probably open the chambers by unshrouding the valves more, etc, and get the compression down lower, but I don't know enough about flame travel or air flow in the combustion chambers to deviate too far from stock.
 
Trust your gut, that cam is too small. This combination will not run on pump gas. Sorry to say, but this only goes to prove what I have said all along, the cam people do not know how to grind a cam for pump gas. The lobe separation is to narrow, the duration is to short and the cam is ground with to much advance. The combination of those three will kill any chance with pump gas.

I went to two cam grinders when I had to set the 515 Ford up for pump gas and asked them their opinions for a grind. Hung up shaking my head. Called the third and just told them what grind I wanted without telling them what it was for. Single 4bbl, 10.5:1, 785 HP on 91 octane.
 
Your setup sounds similar to mine. Building a 417 SB with closed chamber W2's. My priority was pump gas as well as power for the rebuild. So I left all that up to the guys that do this for a living. Ended up with 11:1 static and somewhere around 8:1 (I think) dynamic. Cam is a comp roller with around 268 duration @.050 and .650" lift with 106 or 107 LSA. But anyhow, we only get 91 around here and the engine builder gave no doubt that it will run pump gas. BUT, that means I'll be pulling back some timing and losing some power on 91. Throw some race fuel in and advance the timing, it will pick up a few more ponies. So it's a trade off. I think it's a good one IMO since this will be both a street and track car and I won't have to run straight race fuel around town like I used to.
 
Here is the cam I was thinking about. Its a Lunati Voodoo solid flat tappet, pn 30200743, 288/296 adv, 259/267@.050, .586/.606 lift w/1.5 rockers, 110lsa and 106cl. Its not alot bigger, but it seems alot closer to what I want. How well would this one work?
 
[ame]http://www.hughesengines.com/Upload/TechArticles/Fading_Color_Article.pdf[/ame]

here is an cam comparison with a 421 cu in motor....just something to look at.
 
metallidart said:
Here is the cam I was thinking about. Its a Lunati Voodoo solid flat tappet, pn 30200743, 288/296 adv, 259/267@.050, .586/.606 lift w/1.5 rockers, 110lsa and 106cl. Its not alot bigger, but it seems alot closer to what I want. How well would this one work?
Click to expand...

I think you're more on the right track with that cam.
 
Mettliadart,no comment on converter. Cam sounds close,the converter is the decideing point here.This is HUGE,guy. Before you buy that cam,call a few torque converter companies,before you pull the trigger ,on that grind. One's to avoid: New TCI,off the shelf ,anything B&M off the shelf. Yes to ,CRT,Coan ,Munsinger,Turbo Action(maybe,call em) and Edge. A lot of work,why stop now....?
 
my slant with no quench, 91 octane, and a 8.1 DCR dosn't ping with a locked dizzy at 30*.

you have more compression but more cam as well... i think 8.3 would be fine
 
IQ52 said:
Trust your gut, that cam is too small. This combination will not run on pump gas. Sorry to say, but this only goes to prove what I have said all along, the cam people do not know how to grind a cam for pump gas. The lobe separation is to narrow, the duration is to short and the cam is ground with to much advance. The combination of those three will kill any chance with pump gas.

I went to two cam grinders when I had to set the 515 Ford up for pump gas and asked them their opinions for a grind. Hung up shaking my head. Called the third and just told them what grind I wanted without telling them what it was for. Single 4bbl, 10.5:1, 785 HP on 91 octane.
Click to expand...

I agree. Bullet is usually pretty good on this stuff.

The cam recs sure seems small to get by with pump gas. You got two unfriendly pump gas strikes already with 10.7+ compression and open chamber heads.

I'd figure an intake lobe in the low-mid 260's at .050 and 290+ advertised, cut on a 110-112 and installed in the 108-112 range. Lift in the high 500-low 600's range. It's gonna make good low end torque anyways, no real need to advance the cam.

You can definitely get a custom cam cut that would meet you needs. I'd call someone that builds engines and see what they might say.
 
Abodybomber said:
Mettliadart,no comment on converter. Cam sounds close,the converter is the decideing point here.This is HUGE,guy. Before you buy that cam,call a few torque converter companies,before you pull the trigger ,on that grind. One's to avoid: New TCI,off the shelf ,anything B&M off the shelf. Yes to ,CRT,Coan ,Munsinger,Turbo Action(maybe,call em) and Edge. A lot of work,why stop now....?
Click to expand...

+1 for Edge.

converter people are gonna want you to pick a cam first though!
 
metallidart said:
Here is the cam I was thinking about. Its a Lunati Voodoo solid flat tappet, pn 30200743, 288/296 adv, 259/267@.050, .586/.606 lift w/1.5 rockers, 110lsa and 106cl. Its not alot bigger, but it seems alot closer to what I want. How well would this one work?
Click to expand...

Using a generic calc.....the intake close on that cam is 74* give or take. What altitude are you using? I came up with a 8.07 dynamic at 400'. From what i'm seeing, i think you're good with this one. If you think you're close, you could always install it a few degrees retarded, but I don't see the need at this point.
 
metallidart said:
Here is the cam I was thinking about. Its a Lunati Voodoo solid flat tappet, pn 30200743, 288/296 adv, 259/267@.050, .586/.606 lift w/1.5 rockers, 110lsa and 106cl. Its not alot bigger, but it seems alot closer to what I want. How well would this one work?
Click to expand...

No.
 
R.R.R,please offer a alternative. I know ,you know "converters & camshafts,combinations". What's yours,in response to "no"?...
 
Just like Rob said. Mid 260s for the intake lobe. "I" would look for something in the low to mid 270s on the ex lobe payin close attention to the intake closing event.
 
IQ52 said:
Trust your gut, that cam is too small. This combination will not run on pump gas. Sorry to say, but this only goes to prove what I have said all along, the cam people do not know how to grind a cam for pump gas. The lobe separation is to narrow, the duration is to short and the cam is ground with to much advance. The combination of those three will kill any chance with pump gas.

I went to two cam grinders when I had to set the 515 Ford up for pump gas and asked them their opinions for a grind. Hung up shaking my head. Called the third and just told them what grind I wanted without telling them what it was for. Single 4bbl, 10.5:1, 785 HP on 91 octane.
Click to expand...

I am noticing that too about the cam grinders. If the accuracy of the recommendation affected their salary, I'm sure there would be higher hp and happier people!

I have talked to bullet before, except on the phone it was with Tim and he seemed to know his stuff. It wasn't him that sent me the email recommendation, tho.

Just from what you said about the combination of three things helped me learn a little more about cams. I wish I felt comfortable doing what you did! And btw, thats alot of friggin power on 91!
 
OldmanRick said:
Using a generic calc.....the intake close on that cam is 74* give or take. What altitude are you using? I came up with a 8.07 dynamic at 400'. From what i'm seeing, i think you're good with this one. If you think you're close, you could always install it a few degrees retarded, but I don't see the need at this point.
Click to expand...

I used 1800, just because I couldn't remember, and I figured I would rather err to the high side. I just checked, the elevation where I live is 1000', and the local track, Quaker, is 1300'. That's what led me to that cam, I plugged all kinds of cams into there. It is about the lift that I have read the w2's like (I know I would lose some with the lash, geometry, etc), the duration/rpm range I would like, etc. It's not out of the picture yet!
 
clinteg said:
Your setup sounds similar to mine. Building a 417 SB with closed chamber W2's. My priority was pump gas as well as power for the rebuild. So I left all that up to the guys that do this for a living. Ended up with 11:1 static and somewhere around 8:1 (I think) dynamic. Cam is a comp roller with around 268 duration @.050 and .650" lift with 106 or 107 LSA. But anyhow, we only get 91 around here and the engine builder gave no doubt that it will run pump gas. BUT, that means I'll be pulling back some timing and losing some power on 91. Throw some race fuel in and advance the timing, it will pick up a few more ponies. So it's a trade off. I think it's a good one IMO since this will be both a street and track car and I won't have to run straight race fuel around town like I used to.
Click to expand...

Didn't you used to have a solid flat tappet in yours? From what I can tell, it seems like the solid rollers are more streetable than the flat tappets. Hmmm...
 
crackedback said:
I agree. Bullet is usually pretty good on this stuff.

The cam recs sure seems small to get by with pump gas. You got two unfriendly pump gas strikes already with 10.7+ compression and open chamber heads.

I'd figure an intake lobe in the low-mid 260's at .050 and 290+ advertised, cut on a 110-112 and installed in the 108-112 range. Lift in the high 500-low 600's range. It's gonna make good low end torque anyways, no real need to advance the cam.

You can definitely get a custom cam cut that would meet you needs. I'd call someone that builds engines and see what they might say.
Click to expand...

That is on the agenda for today I think. The Lunati cam is close with 259@.050 and .596 lift. Do they custom grind cams, say, the one I picked out but with a different centerline?
 
Abodybomber said:
Mettliadart,no comment on converter. Cam sounds close,the converter is the decideing point here.This is HUGE,guy. Before you buy that cam,call a few torque converter companies,before you pull the trigger ,on that grind. One's to avoid: New TCI,off the shelf ,anything B&M off the shelf. Yes to ,CRT,Coan ,Munsinger,Turbo Action(maybe,call em) and Edge. A lot of work,why stop now....?
Click to expand...

I have never heard of Edge, I was thinking about going with dynamic. I'm not too worried about the stall, but I would like to keep it as low as possible. This time around, I will pay the money for a good, efficient converter. I was thinking about waiting to make the calls until after I am done building the engine, I hope to get it dynoed and I figured that may help with the converter selection.
 
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