cam for 2 barrel short oval??

[goldmember63]

I have a freshen up on a short(1/4 ish mile) dirt oval track. Its a 408 SB mopar 4"x 4.03" ,stock w-2 heads,12 to 1 comp,1.6 rockers, headers and a 2 barrel carb on race gas. The carb is cheated a bit but not sure the cfm. It runs typically 2800-6300 rpm and runs a solid flat tappet cam. Any suggestions would be great. The old cam is 283@.02 256@.05 169@.2 .346 lobe lift on a 106 lsa in at 104 and missing a lobe LOL. Let me know if you need more info. Thanks

[Walter R. Malik]

I have a freshen up on a short(1/4 ish mile) dirt oval track. Its a 408 SB mopar 4"x 4.03" ,stock w-2 heads,12 to 1 comp,1.6 rockers, headers and a 2 barrel carb on race gas. The carb is cheated a bit but not sure the cfm. It runs typically 2800-6300 rpm and runs a solid flat tappet cam. Any suggestions would be great. The old cam is 283@.02 256@.05 169@.2 .346 lobe lift on a 106 lsa in at 104 and missing a lobe LOL. Let me know if you need more info. Thanks

With a Mopar lifter diameter you can surely use a more aggressive design than a normal Chevrolet would run.

Personally, I would stick to the .875" diameter families of lobes as usually those lobes have been run a lot more and a whole lot is known about how they actually perform in an older NASCAR short track piece.

There are going to be many preferences here.

Without getting really into it ... I would say about 284/276@.020"- 254/248 @.050", (with the more aggressive lobe on the exhaust), having somewhere around .365" or more lobe lift, ground at around 106 separation installed about 99 to 100 degree intake.

[Charliesauto]

I have a freshen up on a short(1/4 ish mile) dirt oval track. Its a 408 SB mopar 4"x 4.03" ,stock w-2 heads,12 to 1 comp,1.6 rockers, headers and a 2 barrel carb on race gas. The carb is cheated a bit but not sure the cfm. It runs typically 2800-6300 rpm and runs a solid flat tappet cam. Any suggestions would be great. The old cam is 283@.02 256@.05 169@.2 .346 lobe lift on a 106 lsa in at 104 and missing a lobe LOL. Let me know if you need more info. Thanks

Are you confident in that 2800 rpm as your minimum, that's awful low?

I assume some kind of aftermarket intake?

If so, I am thinking 244 @ .050" on the intake and about 4 degrees more on the exhaust. Like Walter said, at least a .875 lobe. Control should not be an issue at 6300 rpm so get as aggressive as possible with the lobe lift. I would be 105-106 separation and 101-102 ICL.

If you can work on your combo to achieve more RPM, that would help you a ton. If so, you would need to adjust the cam(larger) accordingly.

Good luck with your build.

[In-Tech]

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[In-Tech]

Code: Select all

Erson .875" lobe, F296/.408-A	296	258	0.408	0.012	0.875 MECH	172		
Ground on a 6 and in at a 100
258 @ .050"  Multiply lash ramp(.012) times RR to get actual setting lash, 172 @ .200

Agree on more rpm 108 + 4 and 7400 rpm but that's just me

[goldmember63]

I'm guessing the low rpm is to make the cast crank last? I dunno but he wins often against much better builds so I'm just trying to not get to far from what works for the customer and if there is a bunch of room to gain I'm all ears. I've run a quite few of the older Ultradyne .875 and .904 lobes in my own stuff so I may run to Bullet Cams and see if we can find something usable. Thanks for the feedback

[MadBill]

Is that 2800 the lowest observed RPM, or lowest WOT?

[goldmember63]

I will call him but my guess is he meant on a slow restart ,doubt it spends much time that low RPM.

[Krooser]

You'll never break a cast Mopar crank at 7300...

Cam King spec'd a cam for my sbm (dirt late model) that's really not far off from what you have now... His stuff often specs pretty low compared to what you might expect.

My deal is a 4.030 x 3.79 with a ported set of W2's expected to run about 7200...

[ZIGGY]

2800 rpm sounds low to me to me too. IMO lugging is the biggest crank killer
in CT racing. (Hitting the wall also can do the job .)

[goldmember63]

You'll never break a cast Mopar crank at 7300...

Cam King spec'd a cam for my sbm (dirt late model) that's really not far off from what you have now... His stuff often specs pretty low compared to what you might expect.

My deal is a 4.030 x 3.79 with a ported set of W2's expected to run about 7200...

How many laps do you get from a cast 4" crank? I've seen a few break in mild bracket cars that never saw 7300 rpm , but if you have on track experience that would be cool. I'm sure Mike could come up with a good cam for this combo.

[goldmember63]

2800 rpm sounds low to me to me too. IMO lugging is the biggest crank killer
in CT racing. (Hitting the wall also can do the job .)

He might take out the flagstand again after getting hit by a chevy and not break a crank but stuff happens/

[ZIGGY]

[Geoff2]

I would think more intake duration would be a good idea as Walter Malik suggested because of the restricted 2bbl breathing.

[mag2555]

What do the heads in ported form flow now Intake and Exh wise, as you really need that info for a Cam pick!
These iron heads do like 245 intake cfm @ 28" out of the box .