Cam theory/decision time...

BigPurp · Post by **BigPurp** » Tue Jul 19, 2005 10:43 am

Well i've been reading as much as possible on cam theory and practical application in hopes of getting something that will work well for my truck. Seems the more I read the more I realise how little I actually know

If you guys with far greater knowledge than myself wouldn't mind throwing your .02 in here I would really appreciate it.

Motor:
SB Mopar, 408ci stroker (360 based)
Iron Magnum r/t heads (2.02/1.625 valve)
Static comp 9.8:1 (.040 quench)
dynamic comp to be right around 8.0 (ivc 63* abdc)
Single plane 4bbl m1 intake manifold
FAST standalone EFI
Hyd roller cam, but lifters have been shimmed so only provide .010 movement. Run with .006-010 lash (similar to a solid roller)

this is going in a 4400lb truck. 4.10 gear, 28" tire, 3400 stall converter, through a 4spd auto. Pump gas street/strip. Will get nitrous later down the road.

What I came up with was: these #'s are @ .050
IVO- 9btdc
IVC- 41abdc
EVO- 48bbdc
EVC- 8atdc

Gives a 230/236 dur .540/.560 lift, on a 108lsa (106cl)

I'm shooting for good power from 2800-6200 and not a super wild idle.

One question I did have was, is there any advantage to going with a bigger duration, say 236/242 and opening up the LSA to 110.. seems this would give similar idle characteristics (overlap is only 2* more) yet let it breath better on the top end.

Also, if you guys can point me in the direction of some good literature on cam theory I would greatly appreciate it.

I'm open to hear anything you guys have to share.

SStrokerAce · Post by **SStrokerAce** » Tue Jul 19, 2005 11:31 am

I think your first choice is a good one. I might add a little more lift in there but I think you are in the right area for a tame cam in that stroker.

Bret

airflowdevelop · Post by **airflowdevelop** » Tue Jul 19, 2005 1:00 pm

what is condition of the cylinder heads? in stock trim the r/t heads start becoming shakers at .450" on the intake. specifically for a 400+ inch motor, I would hope you have added a good deal of volume, and fixed the short turn. If not, keep the overall lift about where you have it, and blow a few more degrees of duration in the intake. Pulling the centerline back on the intake a few degrees would not hurt either.

We are currently working on a project for another board member for a late 90's truck, with a set of commando's...pretty neat project but a little tough to get the heads to come around.

We currently have the master port done, and digitizing. I don't know how many of these things I will ever do, but non the less a cool project (we have relocated the approach of the port, relocated the pushrod location, sleeved and buttoned the head bolt pinch, moved the intake valve and did a complete redesign of the chamber)

Dennis

BigPurp · Post by **BigPurp** » Tue Jul 19, 2005 1:23 pm

airflowdevelop wrote:what is condition of the cylinder heads? in stock trim the r/t heads start becoming shakers at .450" on the intake. specifically for a 400+ inch motor, I would hope you have added a good deal of volume, and fixed the short turn. If not, keep the overall lift about where you have it, and blow a few more degrees of duration in the intake. Pulling the centerline back on the intake a few degrees would not hurt either.

We are currently working on a project for another board member for a late 90's truck, with a set of commando's...pretty neat project but a little tough to get the heads to come around.

We currently have the master port done, and digitizing. I don't know how many of these things I will ever do, but non the less a cool project (we have relocated the approach of the port, relocated the pushrod location, sleeved and buttoned the head bolt pinch, moved the intake valve and did a complete redesign of the chamber)

Dennis

They have had quite an extensive port job done. Flow just over 300 on the intake @.600, don't recall the exhaust. I lost the printout from the flow bench

I thought about pushing the lift higher but need to check the P:V and see what kind of room I have. Using diamond dished pistons so it shouldn't be too tight, but i'm gonna check it none the less.

If I bump the duration up a bit is it still going to pull good vac? I'm hoping to keep at least 10" @ idle (800rpm ish) It's still running power brakes etc.

Sounds like you are going full tilt on those commandos. Is he using a mag or LA block? There are quite a few of these trucks being built to run the #'s... if you guys had a CNC program for the R/T heads selling them wouldn't be hard at all. Tho I would really like to run a nice aluminum head, W5 or maybe an indy 360-2 if they fix the casting flaws.

My ultimate goal is to run in the 12.5x area on the motor, and deep into the 11's on nitrous.

Thanks for the insight

airflowdevelop · Post by **airflowdevelop** » Tue Jul 19, 2005 2:14 pm

10" of vacuum should be no problem, if the induction system is working correctly.

How big of a strap did you have to use to keep the flowbench on the floor?

Seriously, start probing the port and you will see what I mean. If you shorten the SSR and widen the walls at the bottom of the port, it will hurt your flow a fair amount, but the head will start making power. The sound that you start hearing around .400" (the one that makes the dogs bark 4 states away) is a bad thing.

Also, it may not be a bad idea to pick some of Don's tapes up on head development, much valuable information. When you figure the induction system out, and what it is trying to do, picking a camshaft becomes allot easier.

Thanks
Dennis

BigPurp · Post by **BigPurp** » Tue Jul 19, 2005 2:18 pm

haha, i'll have to talk with my head guy and see what kind of info I can get.

Whos Don? I'm always looking for books, vids, etc. on stuff like this.

Do you have a website for your shop? Or any contact info?

airflowdevelop · Post by **airflowdevelop** » Tue Jul 19, 2005 2:48 pm

Don Terrill (sorry if I murdered your last name)
he is the moderator of this site, if you look around you can find his bio.

http://www.speedtalk.com/calendar_racing.html

here is a list of interviews.

website is currently down (too many phone calls, not enough work getting done!)

my contact info though
717-887-4666
airflowdevelop@netscape.net

Thanks
Dennis