Cam selection help

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Badart

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First of all this is not for drag racing!!!!! This car will be setup for SCCA Solo racing so I need a flat low rpm torque curve. This is for a 3,000lb early A body (class I will be running in). For the time being I will be running a fresh 904 with a TF2 shift kit. Why an automatic? 90% of the courses out there you never shift out of second gear once you trip the timer. Many guys run automatics in autox and do well. I may upgrade to a 833 down the road, but I have to get this car together for the spring. I will be running a 3.55 gear in the rear and stock converter to have engine braking. The stock convertor will be the tricky part with cam selection. Talking to an experienced early A autocrosser he suggested a 3.23 gear for a 833 and I figure a 3.55 for the 904 with the 1.45 second gear ratio.

Here is what I have come up with so far, I have not figured in slip with a little slip even with a stock convertor.

Rpm 2000 Rear gear ratio 3.55 trans ratio 1.45 Tire height 25.3 MPH 28.8
RPM 6000 Rear gear ratio 3.55 trans ratio 1.45 Tire height 25.3 MPH 86.6

Remember that the timing lights is a rolling start and most are followed by a turn shortly after so 60' times won't matter LOL. The reason why I am setting this up to run one one gear basicly is because you really don't have time to shift through the course. Seriously.

Here is what I have for the car so far, Fresh assembled .030" over externally balanced LA 360, KB107's zero deck, stock rods, 2.02" J heads with a bowl blend and runner clean up and gasket match by my engine builder (not sure what they flow). With the head gaskets that he provided it comes in at 10:1 cr. Stainless PRW 1.6 roller rockers and most likely and LD340 or Eddy RPM and a 750 holley. Windage tray and double roller. I also plan on running TTI's.

I have a comp XE284H that I was going to use for another project, but it's a street/strip which requires more stall and convertor, so it won't work. I would like to use a hydraulic flat tappet, but would consider a solid flat tappet or even a roller as long as I don't have to do any machining to the block.

What cam would you recommend and why? Remember stock convertor and one that will pull from 2000-6000.
 

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Oh and please don't say build a 408 or 390 :angry4:

This will give you and idea of what it is all about. [ame="http://www.youtube.com/watch?v=fPde0SNEQ_c"]Fox Mustang Autocross SCCA C Prepared CP - YouTube[/ame]
 
How about an old Mopar 268/272 450/455 or a comp 260 or 268h ? Thoose cams seem to work well with stock converter. Im sure there is better cams just a thought ?
 
Being how it's a rolling start, i'm not sure how the converter will make much difference. I would think tight is good. As far as cam, a custom grind would be the best way to go. Most off the shelf circuit/circle cams seem to be in the 3500/6500 range and solid. I would think a 106/108 lsa would give you the mid range torque you'll need.....I'll throw out this Comp hyd, but i still think some phone calls with your combo will get you better results.
http://www.summitracing.com/parts/cca-20-601-4/overview/make/plymouth

Should mention that with the 1.6 rocker ratio the Int. lift is .530 and Ext. is .514.
 
If that's the case I may just run what I have. What do you think? I know it will be a pig off the line.
 

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A couple of suggestions.Crane makes some 110 lobe center,single pattern cams.The 2 I like,are 216@ .050.454 lift.Next one,222@ .050,.480 lift.I thought,Scummitt was selling them,under their brand name cheaper.1st one,stock converter no problem.2 nd one,some tuning,should work with 10 to 1.
 
Below is 4 Comp Cams-1st graph show horsepower curves biggest cam makes most power and smallest makes least 2nd graph shows torque curves and the opposite is true smallest cam has most torque and largest the least, I wouldn't focus on the number so much as the curves once you pick what range of cam I can try different cam of similar spec's from same and different company's to see whats best.

20-222-3 262/270 367hp@5000 472lb-ft@3500
http://www.summitracing.com/parts/cca-20-222-3/overview/make/plymouth

20-223-3 268/280 394hp@5000 472lb-ft@3500
http://www.summitracing.com/parts/cca-20-223-3/overview/make/plymouth

20-224-4 274/286 405hp@5000 467@3500
http://www.summitracing.com/parts/cca-20-224-4/overview/make/plymouth

20-225-4 284/296 420hp@5500 457@4000
http://www.summitracing.com/parts/cca-20-225-4/overview/make/plymouth
 

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looking at those graph a 268 cam seems best doesn't give up too much torque to the 262 and too much horsepower to 274 and will work with stock converter and the 286 makes best power but I can't see you spending to much time up top to make it worth while.
 
Abodybomber said:
A couple of suggestions.Crane makes some 110 lobe center,single pattern cams.The 2 I like,are 216@ .050.454 lift.Next one,222@ .050,.480 lift.I thought,Scummitt was selling them,under their brand name cheaper.1st one,stock converter no problem.2 nd one,some tuning,should work with 10 to 1.
Click to expand...

Thanks bomber. I will look at them also.



273 said:
looking at those graph a 268 cam seems best doesn't give up too much torque to the 262 and too much horsepower to 274 and will work with stock converter and the 286 makes best power but I can't see you spending to much time up top to make it worth while.
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Thanks 273. I already have the last cam installed, but never ran. It's the XE284H. I guess I have some thinking to do.
 
That's the best way nothing tells you better than track time plus you could always run a little more gear to make up for the torque and get you in your extended powerband.
 
273 said:
That's the best way nothing tells you better than track time plus you could always run a little more gear to make up for the torque and get you in your extended powerband.
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Since it's already installed and degreed I may just run it and see. I think that will have a couple different gear sets just in case.
 
I see the similarities in the one i posted in #4 and the XE284. The reason i looked at that Thumper was for the 107lsa. Since yours is in i'd agree, give it a shot. I've used some narrow lsa cams before and they really do pump up torque, although in a more narrow range. You always have the option of advancing/retarding the cam to better match your needed rpm range.

I have a question?.......With that automatic valve body and the required throttle pressure linkage hooked up, how are you gonna keep the trans from downshifting all the time out of the tighter turns? Don't you really need a Manual VB?
 
OldmanRick said:
I see the similarities in the one i posted in #4 and the XE284. The reason i looked at that Thumper was for the 107lsa. Since yours is in i'd agree, give it a shot. I've used some narrow lsa cams before and they really do pump up torque, although in a more narrow range. You always have the option of advancing/retarding the cam to better match your needed rpm range.

I have a question?.......With that automatic valve body and the required throttle pressure linkage hooked up, how are you gonna keep the trans from downshifting all the time out of the tighter turns? Don't you really need a Manual VB?
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Thanks rick. So would you just run the cam strait up 106 degrees? The manual valve body was going to be my next question and I was going to get with Tony aka 70aarcuda. He has done a few. Thanks again, John
 
Badart said:
Thanks rick. So would you just run the cam strait up 106 degrees? The manual valve body was going to be my next question and I was going to get with Tony aka 70aarcuda. He has done a few. Thanks again, John
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Yes, i would go with it as is for now. I realize the 1st turn comes quick, but you may carry a little more rpm in there that you think? After some runs thru the course, and getting familiar with the car, it will probably become apparent whether you need any help at the low or high end. I've never raced anthing like this before, but it sure sounds like fun. And you get to show off some suspension pieces :thumrigh:. You've peaked my interest for sure, and i'll be keeping tabs on everthing, Rick
 
OldmanRick said:
Yes, i would go with it as is for now. I realize the 1st turn comes quick, but you may carry a little more rpm in there that you think? After some runs thru the course, and getting familiar with the car, it will probably become apparent whether you need any help at the low or high end. I've never raced anthing like this before, but it sure sounds like fun. And you get to show off some suspension pieces :thumrigh:. You've peaked my interest for sure, and i'll be keeping tabs on everthing, Rick
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Thanks Rick. I have raced autocross and rallycross in the past, but they were in imports :wack: ,but still a ton of fun. Much like drag racing, you finish a run and get out the car shaking. I miss that feeling.
 
1wild&crazyguy said:
Comp FL272 cam, I think with a lil advance would work good. Jmo
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That's the type of cam i spoke of earlier regarding circle/circuit grinds. I still think it may be a little steep for what John is doing. Lift with the 1.6 rockers would be, on paper, in the 575/595 range and may require some additional guide work, maybe? The other thing is the 47* int. close will bring the dynamic compression in around 8.90 to 1. Might be pushing it for pump premium if that's what he chooses to run. Just a few thought:D.
 
IMHO, that Comp XE284 cam would be a real dog with the stock converter.

- 240/[email protected] is a pretty big cam for any 360, and asking a 360 to run well with a big cam, 3.55 gears, high elevation, mild heads and no converter is setting yourself up for very underwhelming overall performance.

I would call Bullet cams and have Tim Goolsby spec you a custom cam based around the converter, weight, usage, and elevation.

As a baseline, I would be looking for something no bigger than [email protected] on the intake and ground on a 108° or tighter LSA. You need to generate explosive torque to accelerate out of the slow corners, and a small cam with a tight LSA would certainly help in this regard.
The small cam with a tighter LSA will help with dynamic/cranking compression also which is helpful at our high elevation.

Stock inexpensive auto parts store replacement Dacco converters can run pretty good if you don't overcam the engine.
Here is a cool example of a small cam/stock converter getting it done!
This awesome 4 door Valiant was on Moparts years ago and I saved the info.

70 Valiant 4 door that weighs 3,320 with Driver.
The best run was 11.96/113 but it typically went 12.0's in decent air.
Typical 60'was low 1.70's

- 40 over 360 short block. decked, 10.51comp
- reversed cast dished pistons, good rod bolts.
- J heads pocket ported with 2.02 int. valves and 273 adjustable rockers.
- Old Manley cam. .443" lift [email protected]. lobe separation was around 108.???
- LD340, 1" 4 hole spacer and a Vac. 750.
- Hedman 1 5/8" headers, 3" exhaust with ultra flows dumped at the axle.
- 904 trans with a (cheap)Dacco 2,400 stall replacement converter
- 8 3/4, 3.91's 8"x 26" slicks.
- 6 cyl. torsion bars and Competition Engineering Adjustable front shocks
- 002/003 SS springs with MP 50/50 xtra long rear shocks

5969007-ValiantAtco.jpg
 
Though not often spoke of here on FABO, Howards cams are inexpensive ($129.95) and there are some nice shelf cams that you might look at.
Howard cams has been affiliated with some of the best cam designers in the business throughout their history, so I would be confident in their products also. They are availabe in custom grinds, also.

This one would probably run quite well in your application.

Howards 710461-10
- 2200-6000 range,
- 273/277 advertised duration
- 226/230 [email protected]
- .525"/.531" Lift
- 110° LSA / 106° intake centerline (or have it custom ground on a 108lsa+4 for more mid punch)

http://www.summitracing.com/parts/hrs-710461-10/

http://www.howardscams.com/chrysler/chrysler-v8-273-360-1965-1995-318-1967-1995
 
OldmanRick said:
That's the type of cam i spoke of earlier regarding circle/circuit grinds. I still think it may be a little steep for what John is doing. Lift with the 1.6 rockers would be, on paper, in the 575/595 range and may require some additional guide work, maybe? The other thing is the 47* int. close will bring the dynamic compression in around 8.90 to 1. Might be pushing it for pump premium if that's what he chooses to run. Just a few thought:D.
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its true the dynamic would be edgy, but i do believe it would have gobs of torque for every corner.
 
1wild&crazyguy said:
its true the dynamic would be edgy, but i do believe it would have gobs of torque for every corner.
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Your right Justin, if a solid was used, with some of your heads:D, and that cam was in it's zone, it would be more stout then the one i was talking about. I'm just making the assumption that these courses are fairly short with slow corners. When John gets some runs in and we get some feedback, i may change my mind.

P.S. We may be splitting hairs here on the power. The Dillinger chassis parts may make the real difference.:thumbrig:
 
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