I'd like to choose a new cam for my 350... The final engine will have 64cc aftermarket heads. (probably AFR) But for the time being, I will use my 76cc 487X heads, which are unported, but have 2.02/1.60 stainless valves. I don't know how horrible the cam for the aftermarket heads will be with my current stock heads, but I'll live with it for a year till I can afford better heads.

Engine combo:
.040 350
3.48 stroke Eagle cast crank
KB hyper pistons, 6cc valve reliefs (about 9.0-1 w/76cc, 10.2 w/64cc)
6" Eagle I-beam rods
Performer RPM air-gap
650 dp Holley
MSD dist and 6AL
1.6 Crane full roller rockers
1 5/8" hooker competition headers
2 1/2" flowmaster system

Car:
Close ratio muncie
255/60R15 BFG's (will try approx 28-29" drag radials soon)
4.66 olds rear
3750 lbs w/me in it
SSM's and KYB shocks (kyb's gotta go...too stiff)

My current engine is very similar, but with less compression, and still using the 487X heads. I've been using an XE284 (284/296adv 240/246 @.050, .540/.544 lift using 1.6 rockers) I know this cam is too big, but it does run really good once it's given some RPM. I currently run a best of 13.54@104mph, and cross the line above 6100 rpm. This is with street tires, and 2.1x 60 foot times. Seems to be fastest when I shift arounf 5500 rpm. I don't want to use a new cam that's too small and lose too much top end, but I feel that there is some torque to be gained in the lower end. The XE284 is a bit of a pooch below 3000. However, the close ratio trans, and the 4.66 gears are really good once the car is moving, and I think that a sort of a narrow powerband is kind of acceptable....given the gearing.

Any suggestions on a cam that will give me a little more off the line, without sacrificing too much up top? I'm also thinking about trying a solid. I was looking at the XS282S, and the XS274S. Any opinions? Thanks! smile.gif

Chris

oops.. smile.gif

The 274 looks like a good match with the 64cc heads. The DCR is 8.24 which will be fine. However, I suggest having the cam ground on a 108 LSA and install it with 4º advance. The DCR is 8.34 which will be better with aluminum heads (alum draws a lot of heat out of the chambers). I think, however, that this may not be enough cam for the gears. You can go up in size, with a bit lower DCR, and run the rpm the gears would like. In that case the 284 or a 292 would work. DCR for the 284 (on a 108 LSA, 102 ICL) is 8.17 still very good. DCR for a 292 (same LSA and ICL) is 7.9 which is very usable.

A 108 LSA will work well with a close ratio box. It will narrow the power band and make more mid-range peak torque. You could use the 284/110 cam as well with the 64cc heads. None of these cams, however, are a very good match for the 76cc heads.

I think if it were me, I'd go with the 274 on a 108 LSA and install it at 102º for the 76cc heads. It will be much better than what you have. When you put the 64cc heads on install it at 104º. I think that is your best bet. However, as I said above, the gears at a bit of a problem. The 274 might run out of steam before you reach the finish line.

Thanks Pat! I have been using your calculator a lot recently... How did you calculate DCR with the solid cams? I haven't figured out how to get the seat timing from the advertised specs.

I agree, the gears are what makes this a tough choice for me. New heads are first, and after financial recovery, I'd like to replace the axle. Ultimately, I think 4.10 would be pretty good with the 2.20 first gear. But the axle I have isn't broken, so I'll live with it for a while.

That's one reason I thought about using a taller drag radial. My street tires are a little short, and slippery. I need better tires, so I thought I'd get as tall a tire as I can. How much do you think that would help reduce the gearing? Enough to keep from over shooting the 274 power curve?

What does changing the ICL do? You suggested 102deg for the 76cc heads, and 104 for the 64cc heads. Does that just help the DCR for the big chamber heads? Does it move the curves around at all?

Ok, one more question smile.gif I was planning on re-using the 1.6 rockers I have. Do you think they are ok? Or should I invest in some 1.5's?

Thanks again!


Chris

I just used the adv duration (put it in on the middle page). There's not much choice, really, unless you know the rise rate of the cam. I think the DCR is far enough from the danger zone that it should be safe. If the top ring crevice space is included the DCR is about .06 lower.

The taller tire should make about a 25% difference. Very noticable. At 105 mph (which you could exceed handly with the new setup) with a 28" tire you should cross around 5900. That should be close to the max with the 274.

In Comp's catalog, in the drag racing cams, there is a 280º solid that looks good (PN 12-221-5). It's a 280/285 on a 108 LSA. RPM range is 3000-6000 with .026" lash. This cam can be lashed at .022" (or so the Comp rep told me) which will make it longer and raise the top end rpm. A buddy is using this cam in his mid 11 second 383 powered car.

Increasing the advance raises the DCR. That the reason for more with the 76cc heads. it's just a fudge until you get the smaller chambers. Advancing lowers the torque peak about 100 rpm per degree.

Use the 1.6 on the intakes only. The engine will make more power that way. Using 1.6's on the exhaust, in most cases, cost power. You are using a roller rocker, right?

I looked at the 280 deg solid you mentioned. It looks pretty nice, kinda in between the 2 I listed. But better suited for what I'd use it for? Do you think it would be better in the low end than what I have now? And still have better power in the range I need at the dragstrip? I could live with the same low end, if I get a better pull up top.... ;)

I drive on the street too, the drag race cam won't prematurely wear or anything would it?

Yes, I have 1.6 Crane Gold rollers. I should get a set of 1.5's for the exhaust. I've been meaning to try that anyway...

Chris

I was looking at the AFR 195's. The street head was $1300 and 8-10 weeks for delivery.

I choose Canfields 195 from Competition Products out of Oshkosw, WI. They were $1055 delivered to my door, set up for 650 lift hyd or solid cam, they come with a 2.05 int valve too. In the CHP head flow chart they actually out flow the AFR's on the intake and are just a touch behind on the ex.

OH, i got them in 4 days too. They are nice and i'm happy with them.

just another thought.

Chris,

Off your main subject, but I used to have a '77 Camaro (pretty similar weight to your car) with an M22 trans and 4.10 gears--IMHO you'll be happier with the 4.66 gears that are in the car now rather than changing to 4.10s; I always felt that the 2.20 first gear really hurt my acceleration off the line. A smaller cam may help you with that, but for the cost involved you'll be ahead by sticking with the gearing you have now, especially once you have some nice free breathing AFR heads.

Matt

What I'd expect is the mid range will get much stronger. This should help a bunch with both ET and MPH. I'm sure the bottom will be stronger. The intake closes 4º earlier with the 280/108. This increases the DCR, which help the bottom end a lot with either head.

Those cams are just Magnum lobes mixed and matched on tighter lobe centers. It will be no harder on parts than a Magnum cam and probably easier on them than an Extreme Energy cam.

The 280/285 has a bit less overlap than the 284/296 you now have. You might notice slightly less lope. It might be a smidge easier to live with on the street.

Anyway, that the cam I think I'd go with from Comp. If UD Harold pops in, he may have a Lunati cam to recommend.

See if you can find someone to split a set of 1.5's with. That's what I did for my 1.6's. Half the cost that way.

Thanks guys! I appreciate the tips on the gearing and heads. I haven't made my move yet with either of them, and will think about it more before I spend any money there.

I like the looks of that 280/285 cam. I'm gonna look around a little more, but I'm definately leaning in the direction of that one. I'm very excited now about the possibility of my engine and cam being better suited for each other... I'm anxious to see the results! smile.gif

One last question..... with proper tires, do you think this combo has a 12.99 in it? It'd be :cool: if it did...

Thanks again....

Chris

On Pat's recommendation, I installed/ran that Comp 280/285 solid cam in my AFR headed 383 last year.
Awesome results...the car ran mid 12s with a 3.73 gear and a TH350 w/3500 stall... best 60' was a 1.67 on Nitto 555R. Used 1.6 rockers on the intake to balance out the lifts.
Very streetable, too. :cool:

I think you will be well into the 12's provided the chassis is right. Even 11's are possible but you, more or less, have to dedicate the car to racing. Just a wild guess, I'd say with the 280/285 and the 64cc chambers you'll get about 450-475 HP.

:eek: hehe, now I want the new heads even more than I did before....

I'm awfully curious to see if the new engine and cam will get a 12 something before I put on some new heads.... I've got a few more bolts to tighten before I can find out smile.gif

Pat, I think I'm gonna try the 280/285. Do you still recommend installing it at 102 ICL for the 76cc heads and 104 for the 64cc heads?

Thanks again

Chris

With the low CR of the 76cc heads, advancing the extra 2º willl help trap more of the mixture and reduce reversion. With the 64cc heads 4º of advance will be fine. That's a nice cam.

Be aware that none of Comps' racing cams have any advance built into them so where you set the timing set is what you have. You'll need a 2º bushing for the 76cc heads and a zero degree for the 64cc heads. I highly recommend degreeing the cam. You could run it at 4º with the 76cc heads. The engine would run well but it would be down a bit on the power it could have.

I love my 280 mag, ...go with it... I had a slightly larger XE and I swear it didnt pull as hard..

just a little advice i had to find out the hard the way...buy bare castings when you purchase your heads, then have a good machine shop install some quality parts in them. there's usually a reason why certain heads are cheaper than others, it's the quality of parts and the competantcy of who puts them together. good luck!