602 GM Crate vs. Built Engine

[CamKing]

Any agreement on what flat tappet cam to run? 1/4 mile asphalt oval track... would like around 6500 rpm...

Part # M72352-106
244/244@.050"
.352"/.352" Lobe Lift
106 LSA

[MidgetMotorsports07]

Camking is right on the money in my opinion. I have never ran his camshafts but I hear very good things abuot his work.

[rick7343]

Curious as to the benefits/drawbacks of cams with bigger and smaller differences in the advertised duration vs. the .050 numbers...

I know it affects ramp speed, but what about power characteristics?

[dirtracr5]

camking probably has a better answer but from what i've seen and what my cam guy has told me, cams with tight .020 to .050 numbers are more aggressive and are a benefit in restricted applications. the down side is they can be harder on valvetrain parts if not designed right. we've been using cams with 24 degrees of difference and higher ratio rockers. my grinder has some with 22 degrees of intensity but he recommends only 1.5 rockers and the lobes are built for a .450 lift rule. also top quality valvetrain parts are a must. no z/28 springs here...lol.

[CamKing]

Curious as to the benefits/drawbacks of cams with bigger and smaller differences in the advertised duration vs. the .050 numbers...

I know it affects ramp speed, but what about power characteristics?

Read this.

viewtopic.php?f=15&t=22828

[swatson454]

Nice! I was looking for that thread awhile back and couldn't find it. Got 'er captured now

[rick7343]

Curious as to the benefits/drawbacks of cams with bigger and smaller differences in the advertised duration vs. the .050 numbers...

I know it affects ramp speed, but what about power characteristics?

Read this.

viewtopic.php?f=15&t=22828

That is a lot of reading.... and a bit of bashing...what's up with that?

Looks like it mainly looks at how cams are measured not the differences in performance...

[CamKing]

Looks like it mainly looks at how cams are measured not the differences in performance...

Then you didn't read it.

It shows how the performance can not be predicted by the differences between advertized duration and .050" duration, or .050" duration and .200" duration.

[rick7343]

well... it was a lot of reading and I started to lose interest with the bashing posts...

So do faster ramps not give more area under the curve and better torque as most claim?

[Brian W]

Just ordered a cam from Camking today. I will be pulling the PRC105 cam out of the engine I posted the dyno results for, and installing the new one. New cam specs are 244/244 @.050 on a 105 lobe sep. Should be interesting when I get it back on the dyno!! This engine has ran three races so far with the PRC105 cam installed. The first race, the car had chassis issues and only finished 7th but placed 2nd and 1st in the other two... going for all wins with the new cam!!

[rick7343]

Any agreement on what flat tappet cam to run? 1/4 mile asphalt oval track... would like around 6500 rpm...

Part # M72352-106
244/244@.050"
.352"/.352" Lobe Lift
106 LSA

Is that hydraulic? I should have mentioned we have to run hydraulic lifters......

[dirtracr5]

keep us posted on the results. i think you should see big gains going from the ancient shelf cam to a nice modern grind!

[CamKing]

Any agreement on what flat tappet cam to run? 1/4 mile asphalt oval track... would like around 6500 rpm...

Part # M72352-106
244/244@.050"
.352"/.352" Lobe Lift
106 LSA

Is that hydraulic? I should have mentioned we have to run hydraulic lifters......

No. That's a solid grind.
Our Hydraulic is part#H76333-106
243/243@.050"
.333"/.333" Lobe Lift
106 LSA

[Brian W]

keep us posted on the results. i think you should see big gains going from the ancient shelf cam to a nice modern grind!

I think I will start a new thread when I get the engine back on the dyno and have the results. But in the meantime, anybody care to take a stab at what difference I will see on the dyno with the cam change?

Old JR PRC105 cam specs are 251/248 @ .050 on a 106 lobe sep installed @ 102 ICL

With Stock spec heads, modified log manifolds and 2.5" pipes, the engine made:
Peak Tq was 355 @ 3500, Peak HP was 285 @ 4900. @ 6200 Hp was 260.

Same setup with 1 3/4" headers made:
Peak TQ was 366 @ 3500 and peak HP was 324 @ 4900. Hp@ 6200 was 298

New Jones cam specs are, 244/244 @ .050 on a 105 lobe sep.

Remember this is a 9 to 1 IMCA Hobby stock engine running a Rochester 2bbl carb...

[raceman14]

If you change nothing but the camshaft I would guess +15-25ft# increase on TQ and +10-15HP.

Proper selection of the right fuel for you engine along with matching your carb and ignition to the rate of burn that your engine wants and the acceleration rate of the engine will yield about the same results as above.