I was hoping to get some input from the cam guru's on the site. After recently suffering through crate motor hell I thought i might ask for some advice on a cam that has been suggested for my " new and improved" locally built crate! One of the cams being suggested based on builders prior expierience is a Comp grind # CS270B-6.

These Specs Are For The Cam Installed At 106 Intake CL
Intake Exhaust
Duration At 0.05 235 242
Lobe Lift 0.33 0.338
Lobe Separation 106
Any comments on estimated performance or lack of? Thanks for your help.

There is nothing time and money can't fix !
-Dave

Way too small for a 11-1 383, but would be a sweet cam for a low compression 350 or 383. With a 11-1 383, that is just asking for detonation on pump gas. Now for the next problem I see...overdrive, 3.42's, and 11-1 compression. To get enough cam in there to bleed off some cylinder pressure to allow for pump gas, you will run into a engine that struggles in overdrive...ie, bucking, snorting, lugging, etc when cruising in overdrive. You will want something with a wider lsa...like 112-114 for smoother operation at lower rpm's. But, IMO, the best thing to do would be drop the compression down to about 9.5-10.0 or so...that would greatly open up your options on camshafts. 220cc heads also seem rather large for an engine with a low cruise rpm.

cam isn't too small if running 1.6 rockers will be alright
would most definitely swap gears, 3.73s at least, I love my 4.10s w/ the 200-4R

Well i am stuck with the pistons for now and the heads so i guess that a different grind is my only option. I just had some Jesels ordrered(by builder) so i will see if they are 1.6's or 1.5's and and will ask about the grind again. Keep the suggestions coming. with the 25" tires i think i'm spinning 2000 at 65 mph which is only 500 below the 2500-6400 range for the cam. Is this also a concern?

[ 05-10-2003, 06:57 PM: Message edited by: dceresa ]

I tend to go with Travis on this one. Something around .520 total lift with the intake duration around 245 and a LSA around 112 should make a nicer driver with pin you to the seat performance and a better idle. Not to mention decent cruise manners. Just my opinion. Talk to Harold at Ultradyne Cams.

Thanks Toby i printed up one of Harolds spec sheets for solid grinds and gave him a call but no answer. I understand he is a a hands on guy(which makes his opinion all that much more valuable) i will keep at it. Is he in on saturdays :D

With 11:1 and aluminum heads you'll need a cam with about 290-295* advertised duration to run on pump premium. The tighter the lobe separation is and the more you advance the cam, the more advertised duration you'll need.

For example:

290* advertised duration, 110* LSA, 106 ICL = 8.36 DCR (acceptable)

290* advertised duration, 106* LSA, 102 ICL = 8.65 DCR (too high IMO)

290* advertised duration, 106* LSA, 106 ICL = 8.36 DCR (acceptable, but you might want to install the cam on the manufacturer's recommended ICL for best results - usually 4* advanced)

296* advertised duration, 106* LSA, 102 ICL = 8.36 DCR (acceptable but, will have a narrow power band that is too high for your overdrive trans)

286* advertised duration, 112* LSA, 108 ICL = 8.36 DCR (best compromise IMO)

See how LSA and ICL affect dynamic compression ratio? Also, you want to consider that the lobe separation angle affects the width of your power band. A cam with a narrow LSA (like 106*) will make the most PEAK torque and HP but the usuable RPM band will be pretty narrow. A cam with a wider LSA will do two things for you - 1) it will make a wider power band which will help when in overdrive A LOT and 2) bleed off cylinder pressure at lower RPM without needing a lot of extra duration to do it.

Now the advertised duration affects DCR the most but don't forget about the .050 duration because it can significantly affect the engine's power band too. So if you go too big on the duration you wind up with a cantankerous engine that only makes power in a narrow RPM band. You want a cam that has the right advertised duration numbers but you really don't need a cam with super agressive ramps (short advertised duration and long .050 duration numbers)

With your gears and tranny I would guess you want a power band of 2500 - 6000 RPM (depends on converter too). I would look for a cam with about 286* advertised duration and a 112* LSA. Definately go with a dual plane intake like the Performer Air Gap.

As for cam lift, just get as much lift as you can, but IMO lift is a secondary consideration. If the cam with the RIGHT duration numbers is low on lift you can always go with 1.6 rockers to compensate.

Hope this helps.

Eric thanks for taking the time to school me that is probabbly the best explanation I have read. graemlins/thumbsup.gif I'll have to print it out and read it a couple of times to let it all sink in. graemlins/clonk.gif Do you know of any grinds off the shelf that are in the ball park?

Thanks,Dave

Comp 294s is what I run. 294* advertised, 248* @ .050 lift, 110* LSA, 106* ICL. Power band is 3000 - 6500. Not exactly what you are looking for though IMO, but it might work well if you have a 300 or taller stall.

Here's a hydraulic FT -

Crower 284 HDP #00243. Advertised duration 284/290, duration @ 050 226/232, lift 459/479, LSA 112*, ICL 105*. Not ideal but not bad.

I'll think about it and edit if I think of any others.

Eric, I had the tranny built by Art Carr it is his extreme duty with a 10" lock up converter from them as well. Should stall at 2850 + or - if i'm making 480 ft.#'s. I gave my cam card for the XE284H that came with my mail order boat anchor :mad: . They based the stall on that info. I would now like to go with a solid just because i get a chance to do it all over again and with the jesel rockers i should have a stout top end. I guess I will be able to wind up this motor 6500 but it sounds like i need to be more concerned about what it is doing at 2000 and base the cam on that. Realistically this motor will only see overdrive 10-20% of the time. Most of my driving is canyon carving here in the santa cruz mountains. I still want to have the carr function well on the freeway when neccesary.

Thanks,Dave

I think I said pretty much what Eric said, just with less typing and math ;) In any case, talk to any of the better cam companies tech support...any of them can custom grind a cam to the specs that will work best for you for just a few $$$ more than what an off the shelf grind costs. Crower, Isky, Ultradyne, and others have some very good, professional tech people that are great to work with. I ordered a custom ground Isky solid flat tappet cam on a small base circle for my 388 and it was the same price as their off the shelf grinds, and I got it in about 2 weeks.

I talked to Harold at Ultradyne today. I wanted to let everyone know that he took at least fifteen minutes to talk me through some of my options and explained the performance pro's and con's of each. It is rare to find someone who will take the time to talk to a customer like that without talking down to them. My builder is going to give him a call in the morning a go over my choices. Hopefully he can become familiar with some of Harolds grinds and send some business his way. Thanks for the tip Toby.