PLease eval this cam!

[Ironmike]

OK guys this cam ain't goin back in my stroker this year. It just felt very weak on the bottom end.

The reason I'm posting this is I saw someone's thread saying he never saw a stroker with a weak bottom end. Well here's one!

Gave all the specs to Bullit and he's gonna grind me a .668/.668 with 272/278 degrees @.050 on a 106 LSA. Guy told me it'll feel like a whole different animal. Said the tighter LSA will be better down low. "A world of difference", says Bullit.

So the old one (attatchment) never made more than 513 ft/lbs. It just really felt lame under 5000RPM. I will say it made pretty decent HP, but just wasn't that FUN torquey drive. The cam before it was a solid flat tappet (.100 less lift) and FELT like a monster down low.

I guess I should say it's a stroker 10.6 to 1, ported Super Victor. Iron heads were just flowed, 294@.600 BUT down 292@ .650.

Do you all think the new Bullit will really make a difference? I'm sure as hell not a cam doctor and I know some of you are!

 

[twayne24365]

With 10.6:1 the new cam should keep the cylinder pressure a little higher and help the low end,

 

[Coronet 500]

I would like to compare Intake opening/Exhaust closing (overlap) as the Bullit has more duration at .050" than the Comp.

272/278 vs 258/268 at .050".

 

[RustyRatRod]

Generally, strokers prefer a wider LSA. That's something "I would think" Bullit would know.

 

[nm9stheham]

Weird... I don't think of myself as a cam expert at all.... but I normally expect a smaller LSA and higher duration to lower low RPM performance and boost high RPM performance. Maybe Bullitt will be putting a lot of advance ground into the cam?? Did they give you an installed intake centerline number?

 

[Ironmike]

nm9, that's what I was thinkin', too. They didn't give me an installed number, yet. I was wondering if maybe the old cam just had too much lift for my heads to support.....and not much duration. I mean I do understand cam basics, but as it gets deeper it becomes voodoo to me.

Why throw a ton of lift in there, if there ain't much duration? I always was under the assumption that DURATION was the big key to power.

Guess I gotta do some more reading....

Oh. I'm not locked into any cam just yet. Bullet just seemed to tell me more of what I wanted. I will say I was shocked that Lunati did not impress me at all. Maybe I got the wrong guy.

 

[AJ/FormS]

I'm no cam guy
but I did a little math and see that the change is mostly during the overlap period. The ICA may only change 3 or 4 degrees, so it won't change the cylinder pressure much. Extraction is similarly 3*more.But, I see the overlap drops from 63* to 45*, so it(the 258* cam) will build more idle vacuum and will idle a little smoother. Also the vacuum will come up a bit quicker, so if the current cam is giving you a problem below 2200rpm or so, the new one will be an improvement. This would only be a problem with a manual trans.
I think the real issue is the 10.5 Scr, but you may not want to change it much. With the swap to the smaller cam,the Dcrs, might change from about 8.77 to 8.96, and the cylinder pressure might change from about 179 to 184 psi. These are worked out from your provided numbers, and a little guess-work on my part. With more exact numbers there could be minor changes.
If it was mine to do,IDK.I think the low-rpm torque difference might be barely measurable, until you get out of reversion. With a loose TC tho, the overlap event of 63* on the 272* cam, is pretty attractive, and would pump up the midrange noticeably, and extend the operating range, meaning MoPower.
So if you find a 500plus ftlbs stroker; weak on the bottom......................IDK

 

[justinp61]

I'm one of the guys that has never seen a stroker with a soft bottom, but anything is possible if you mismatch the parts enough. IMO, if it's soft on the bottom with 258/268 @ .050 you'll be sick with the 272/278. My 408 was 10.9-1 with a flat solid 260/264 @ .050 and it pulled hard everywhere. BTW it was in at 102.

Initial and total timing? Gears? Where was it installed at? The card says 107, IMO 103 or 104 would be better. Do you have W-2 heads? If not that 290 number is suspect, the best I've ever seen is in the 260s for iron heads other than W-2s. The Super Victor is probably not helping any either.

 

[fishy68]

I don't claim to be a cam specialist but I do know a fair amount about what works and I can't see how reducing the LCA to 106 and adding 14 degrees at .050 will make for a torquier engine. I think the biggest problem down low is the ported super victor. That intake don't even start to work till 4500 so it isn't going to make great low end torque. I bet if you keep the same cam you have and stick a Eddy Air-gap on it it'll really surprise you down low and pull just as strong to 5500-6000

As for your question about lift. It does affect making power. And duration does too but it also alters the rpm starting and stopping points. You have to remember that when a cam rotates it's only at max lift for a very very short amount of time so even if ithe cam maxes out at .050" above the max head flow lift the heads would have to go into reversion pretty hard to hurt performance

 

[nm9stheham]

nm9, that's what I was thinkin', too. They didn't give me an installed number, yet. I was wondering if maybe the old cam just had too much lift for my heads to support.....and not much duration. I mean I do understand cam basics, but as it gets deeper it becomes voodoo to me.

Why throw a ton of lift in there, if there ain't much duration? I always was under the assumption that DURATION was the big key to power.

Guess I gotta do some more reading....

Oh. I'm not locked into any cam just yet. Bullet just seemed to tell me more of what I wanted. I will say I was shocked that Lunati did not impress me at all. Maybe I got the wrong guy.

Torque cams are classically high lift, lower duration. Flow is a combination of the 2; at low RPM's, you need to avoid exhaust reversion with a long duration, so that limits duration if you want torque, and you have to go with higher lift. But limited duration eventually limits lift due to the ramp and lifter shape limitations.... hence roller cams. This Bullitt combo would seemingly go in the opposite direction.

With where you want to go, a roller cam makes the best sense IMO.

One thing about not being impressed with the Lunati guy: technical types can sometimes easily get frustrated with customer asking for the impossible.....did Lunati actually make a recommendation? I have been wondering what is with the Bullitt guy and his recommendations since it seems backwards.....I suggest you call Crane and a couple of other companies.

And BTW, I have only done one high lift, long duration 4 cylinder engine so have limtied experience in this neighborhood of cams.... it was a 3800 to 8000 RPM engine only. It had absolutely NOTHING below 3800 LOL

 

[rumblefish360]

Just try it. Worst case, you throw it up for sale and get some money back.

 

[FredS]

Any dyno numbers on that motor setup? Was the peak torque at what RPM?

Whats the rest of the info, converter/stall, rear ratio, tire size.

What heads, what rocker ratio, headers, exhaust, carb?

Mine's a beast at idle all the way to 7K. 3K stall, and dyno numbers showing over 400lbft starting at 3K.

 

[Marcohotrod]

compression ratio is low. sounds like bullit is trying to sell a cam. throw the comp cam back in and advance it. try it with less lash, try it with more lash. and if u buy a new cam and are not happy with it, I would never buy a used flat lifter cam. maybe too much intake manifold, I am happy with the old ld340

 

[modracerx]

need to talk to tim at bullit if he is still there ....he would not sell you that cam if you are looking for more bottom !!!...also look at the voodoo lunati line best off the shelf cam line there is ...match it to your rpm range you are looking for ...i agree on the intake ...killing you if you not looking for 6000 and above ....rpm airgap ...great all around intake for those heads ...you need to tell us what you using the motor for ?......street ...strip ...or both ...

 

[Ironmike]

The cams I've posted about ARE solid rollers. Guess I shoulda mentioned that...

Car is 3190 with me in it. 4 spd. 4.10 axle, 28 inch tire. I'm running 1.6 rockers and my heads are RHS/Indy X, CNC ported. Had them flowed here, by an "independant" head guy.
They didn't flow quite up to the claims, but real close. Exhaust ports untouched. My head guy thought that was weird....

The car is a street car that gets raced a lot, but to the strip maybe only 4 times a year. TNT days only. Last year only once, due to the issues it had.

Lunati recommended a 616/626 lift with 243/249@ .050 110 LSA........seemed kind weak on duration to me, but....what the hell do I know.

So I will not run the cam I have. It was kinda "pushed" on me, used. All that says is someone else didn't like it either. My machinist thinks "somethin' ain't right" with it. Me too.

I did have an AirGap with a 1 inch spacer...in it's first incarnation and you're right. Torque was monstrous, but it didn't have a whole lot after 6 grand. Still pulling, but not hard,
If I thought, with the head and cam upgrade it would pull HARD to 6500, I'd put another AirGap right back on.

Maybe I want to have my cake and eat it too......

There's gotta be a good compromise:coffee2:

 

[justinp61]

Where was the Comp installed at?

 

[modracerx]

40200734 lunati voodoo solid roller .....255/263...600/600....lsa 110 / ica 106 ...install at a 102 ....its there pro-street /mild bracket racing ...3200-7200 rpm range...tight lash 16/16....harold birkshire designed the voodoo line of cams for lunati ....IMO the smartest cam designer hands down in the country ...he owned ultra-dyne cams ....his cams have won races in every thing that has motor ......two nascar championships for me ...he has passed about a year ago ...but tim at bullit worked for him for 17 years and is a very smart man ...also has a lot of harolds lobes at bullit ....also mike hughes at howard cams has some of his latest computer designed lobes off of the diameter of the roller ...these were all cnc ground cams ...howards bought it all ...we back to back dynoed the same cam ...old school grind vs new cnc to the lifter grind ....harold said it would be 10 to 20 hp. better every were ....it was 16 better from one end to the other !!! ....he designed the voodoo line the same way for lunati ....mike at MRL engines on here uses the voodoo line and makes some killer numbers ...look up his posts ...

 

[Ironmike]

Comp was installed at 107. That Lunati looks kinda small to me. I guess with my 1.6 rockers it would behave a bit "bigger". Short duration, no?

The Voodoo looks like it has 4 degrees advance ground in. You're saying advance it 4 MORE?

 

[modracerx]

if anything imo that cam is on the big side for your heads ....it is all about torque and its curve ....h.p. will take care of itself ....mike at mrl has made 577 ft. of torque...just a tic off 600 h.p. with a smaller voodoo roller in a build close to yours ....pm him on here MRL is his handle ask him about the 734 voodoo....he has told others on here about it ...

 

[Ironmike]

Yeah I know about the 734 Voodoo. I agree with ya on the fact that my heads probably couldn't take advantage of the cam I ran.

You think install the Voodoo at 102? And....I know this is a silly issue, but I heard the entire Voodoo line idles pretty smooth. For me, the rougher the better. It's an intimidation thing here where I live.

 

[modracerx]

the 734 idles like a funny car ...lol....JMO on the 102 that still is a big cam for a car you will drive on the street also ....it will just move the bottom down a few rpm and build a more cylinder pressure ...i did it on the 703 in my duster glad i did ....

 

[Ironmike]

Man. Now I'm leaning toward the Voodoo 734. I have about 4 days to nail down my cam. It's really not an easy choice.

 

[nm9stheham]

Rougher usually means longer duration and more overlap and thus less low end....so that tends to work against the goal of better bottom end torque. Mod the exhaust system to make it sound meaner as a separate exercise, and set the cam where you need it to be...IMHO.

I had not ever looked at the Lunati solid rollers..... looks pretty interesting. In my way of thinking, the 110 LSA will be decent for torque. And the lift is good on all of them.... it does not go down much with shorter durations (very different than flat tappets), so you can tune the duration a bit to match your SCR for the low end, and not lose much lift. IMO, these look pretty good for high lift and limited duration to get decent breathing but not totally sacrifice the low end.

BTW, the 734's duration is not all that different from what you had, so you might want to look down a step or so. But I also notice that the cam card's ICL for the Comp Cam was 107, only 2 degrees cam advance. If you put the Lunati's at 104 or 102 ICL, then you are at 6 and 8 degrees cam advance; that is a significant low end aid by itself. The high valve lift of the Comp Cam (over .680") may have excluded much cam advance to avoid hitting the piston so that may been working against you, and doubly so if the extra lift did not buy more flow.