cam?

[Anonymous]

I need advice on cam selection. Dirt late model on alky weighing 2300 lbs. 410 c.i. Brodix -12 head 290 cc runner 2.9 sq.in.w/2.18 ti. intake. 15.5 compression ratio. 1/4 to 3/8 mile traction tracks and keep rpm to 8200 range. I have two ported intakes to choose from, one with larger runner and plenum than the other. thanks for advice.

[Anonymous]

I forgot to mention 1.65 intake and 1.55 exhaust rockers.

[Jay Allen]

I need advice on cam selection. Dirt late model on alky weighing 2300 lbs. 410 c.i. Brodix -12 head 290 cc runner 2.9 sq.in.w/2.18 ti. intake. 15.5 compression ratio. 1/4 to 3/8 mile traction tracks and keep rpm to 8200 range. I have two ported intakes to choose from, one with larger runner and plenum than the other. 1.65/1.55. thanks for advice.
What is the bottom or low side of the RPM range?
Carb CFM?
Head flow (approx)?
Header primary? Length? Open or Schofield type muffler?
Roller or SFT?
Intake I/H and spring pocket?

[lashing out]

5700 low rpm on average, lower on restarts and in criticle traffic jams. 900 cfm alky, intake flow is .3 228 .4 278 .5 321 .6 345 .7 349 at 28 in. Ex. is about 65% tho the valve job needs blending. Headers are 30"x1.875x3.5 into a small spintech baffled muffler 95db. @ 100'. Roller cam with standard cam tunnel. I/H 2.00 and about 1.570 pocket. Thanks again ( P.S. Am I a minority on this subject of alky on dirt with no restrictions?) Oh yeah the stroke is 3.75 x 4.155 bore.

[Chris Uratchko]

You might be a minority but there is another fellow in here by the name of ROB that has a lot of experience building late model engines...

[Jay Allen]

As I told Tom, if I spend the NORMAL amount of time on each inquiry here at Yellow Bullet, it'll be JUST a full time gig doing this. So running some basic numbers here is what I have. I did a cam for a 408cid Chevy with the same Brodix heads. Alcohol with down nozzles. That camshaft was:

254/263 at .050. 457/461 lobe lift. He had 1.6/1.5 rockers so you are close. 108 LSA with an IC of 107. The cam was designed for lash to be set at .022/.022 HOT. But I ran the lash at .016/.018 to make it do what we needed. Initially he thought the cam was *too small*. What is that? He said that the cams he had were 265'ish but only .425-.430 lobe lift. I told him this cam would make WAY more tq, which it does. And it would pull HIGHER upstairs. Which it does. And looking at the lobe area, my cam was considerably larger.

His lap times on 1/2 mile dirt improved dramatically and he says the car is far more driveable. As I told Tom (and others), there is not much effort here based on what I really do. All of my cams are CNC ground. I design the lobe for each customer based on what I think they need.

If you want some basic, real basic, numbers, there you go. If you want a *cam* for *your* combination, the please PM me.

Thanks.

[lashing out]

Thanks for the quick reply and your time. I will PM you.