Cam question

[Chaplin]

Don't know if anyone can answer this but here goes:
How much difference in idle quality and low rpm torque could you expect between the following 2 cams (both in a solid lifter 428)

Cam 1- duration I/E @.50 236/236, lift .571
Cam 2- duration I/E @.50 238/246, lift .540

Obvioulsy the shorter duration is milder, but does the decreased lift of the second cam help to improve the poor idle qualities associated with increased duration? I'd like a motor that make the bulk of its torque/hp b/t 2500-5000. Any thoughts/ insight appreciated.

Thanks in advance,
Mike

[Jack21]

I'm not an FE guru, and it depends on more parameters than just the cam, (heads, intake, carb) but neither cam is going to give you what you want.

Go with a flat tappet hydraulic, or retrofit hydraulic roller. Intake duration should be in the 222 - 224 (@.050) range, and exhaust up to 232 - 234 range if you use a dual pattern cam. This should put your torque peak at 3500 - 3800 RPM, and HP peak at 5500 - 5800 RPM. Motor should idle at 750 - 850 RPM with a nice rumpeta-rumpeta lope, and pull like a diesel from off-idle - up.

[Tom Kirkham]

The most important parameter in idle quality is how much overlap the cam has. The more overlap a cam has (everything else being equal) the rougher the engine will idle. Overlap is determined by a large part by the lobe center angle of the cam shaft. Two cams with identical cam lobes but on different lobe centers will run very differently. Tighter lobe centers (like 105 degrees) will have more overlap than a wider lobe centers (like 114 degrees).

[decooney]

I ran cam #1 (.236@.050) in my last car with a 428, solid lifter, running 9.8:1 compression. It was actually mild on the idle side (to me) in a Cobra. I would have like to tried the next cam up. It had incredible power from 2500 to 5000 though. I found it would pull on other comparable Cobras with bigger cams, up to about 5500 rpms. I have two friends that run this same (236@.050) cam in a hydraulic version, and it sounds a tad bit more radical at idle than the solid lifter version. I preferred the solid version, winding up so smooth and clean - effortlessly. Either solid/hydraulic seemed to idle fairly smooth at 850 rpms or so, and really smooth at 950 - in my setup. Good luck.

[Mr.Fixit]

Idle quality is based on two biggies:

valve overlap as pointed out by Tom Kirkham, 108=choppy, 112=smooth

The other big determinator is when the intake valve closes. Both cams you listed have near identical duration on the intake side, so if they are installed at the same cam timing, idle quality would be very comparable. You might be happier with less duration if you like street driving, most motors spend more time at 2500 than 7000 rpm.

[decooney]

ie.. my response was in thinking je was considering the infamous 236 Comp Cam that a lot of people use in FEs. Just a guess on my part. Mine had 110 degree lobe center, and was pretty tame at idle, but had great power from 2500 to 5000 rpms...

[ERA 626]

just watching...
Mike

[Chaplin]

Duane-
You are correct- that is the Compcam.

Tom/Mr. Fixit-
I believe the lode separation angle of the second cam is also 110.

Forget to ask the first time around, how much of a difference does the dual pattern make??

Thanks for the replies.
Mike

[ERA 626]

After reading this thread I was wondering about the cam that I purchaced.
I don't know much about cams and I desire the;

"Motor should idle at 750 - 850 RPM with a nice rumpeta-rumpeta lope, and pull like a diesel from off-idle - up".


Here is the info on my cam;
Ultradyne Cam

intake/exhaust

Duration @.050 221 / 221
lobe lift .3027/.3027
lobe seperation 110 degrees
seat duration @ .020 276/276
gross valve lift .533/.533


This is the cam I have but I could easily return it, does this cam profile look good??
I have a 428 FE with a factory FOMOCO 2X4 intake, Holly 570cfm bj/bk carbs, with edelbrock aluminum heads & roller rockers.
Thanks,
Mike

[Mr.Fixit]

Mr Mike,

That is a good street cam that will make power down low in the rpm's. What are your gears and compression? You'll need good amounts of both to make a big duration cam work. I would go for a few more degrees on the intake side, and 10 more than the intake on the exhaust side. Dual pattern cams are great.

[Chaplin]

So Mr. Fixit-
Based on your last response, I have the following question. I want my motor to do the same as Mr. Mike described. Comp. will be apx. 9.8:1, edel heads, blue thunder intake, holley 750 vac. secondary, rear end gears will be 3.31 with Tremec TKO II. Do you think 238/246 is too much duration on both I and E to accomplish the stated goal. If so, what specs would you recommend?

Thanks for your help,
Mike

[Jeff Frigo]

Mike:

That is a very mild cam, it should idle almost dead smooth. I would go for some more duration and lift, keep the lobe seperation at 110 degrees or above. Cams in brand new Corvettes and Camaros are only about 10 degrees less than the one you are looking at. FE's like duration more than many other engines. I have a stroked 427 with ported Edelbrock heads. 258 / 260 degrees at .050 and .620 / .625 lift. Idles at 850 rpm all day. Made 585 hp on pump gas @ only 6,000 rpm. Now you don't need anything that big (I've got more inches, and heads are ported), but you can go another 20 degrees with great idle and off the line acceleration.

[ERA 626]

Mr Fix it and Jeff
Can you make a recomondation for me?? I have a richmond 5 speed with 288 gear.
I thought that cam was mild and I want somthing more aggressive.

[decooney]

Chaplin,

keep in mind, a Cobra is light car. You can easily go up a notch or two on the cam, and you'll still have PLENTY of grunt down low too. I had the exact 236 Comp cam you mentioned, and it was a tad bit mild for me after driving it a few thousand miles. I ended up going with a custom ground Crower cam on my next car, with the .262 dur @.050, .640 lift, and wow its much more agressive side. SouthernAutomotiveengines sells a 247/252 duration cam at .050, with a .570 lift, if I recall, and its a nice comprimise between what you were considering and what I have.

Good luck.

[Chaplin]

Duane-
I actually spoke to Bill Parham about his standard cam- he said it has "A Nasty idle" - which made me think it might be more than I want. I definetely want a noticeable lope and rumble, but Nasty might be too much- that's why I was thinking about the smaller cam. Plus, I'm trying to keep my peak hp/torque below 5500 rpm. I think I'll talk to Bill again and see what his other cam suggestions are.

thanks,
Mike

[Tom Kirkham]

On the street you need to run with wider lobe seperation angles due to the restrictive exhaust system on many cars. On an open header we typically run 108 degree cams. One of the best running street engine we have ever run was a 427 with a 4.0 inch stroke crank with ported E-brock (6008 w/big valves) heads single Holley 830 DP. The cam was a Crower 16357 Duration 278 I, 284 E at .050 240 I, 243 E LCA at 114 duration Lift .530 I, and .535 E. You can read how the engine ran for Car and Driver at www.kirkhammotorsports.com under the section of In the Press. The car has 3.31 rear gear with a CR top loader. The car would have been quicker with a WR. Our orginal car had a Holman and Moody tunnel port 427. The strocker engine would pull away from the orginal car on all but the top end. On the street the strocker engine was much more fun to drive. Hopes this helps.

[Jack21]

Think your 221/221 for what you want would be plenty. Remember, you have sidepipes, and even a mild cam will give you a great sounding exhaust. But, that's just my $.02 worth. I tend to start conservative, then work up to dial it in.

[Jeff Frigo]

Mike:

I'm guessing you are using hydraulic lifters. I now understand why you chose the cam you did from Ultradyne. I went to their web site tonight, their reccomendations seam very conservative. I would reccomend Crane grind number H-296-2. It is number 6 on the link below. It has a 112 degree lobe seperation, which will give you a nice idle, 234 / 238 duration @ .050 and .554 / .563 lift.

Crane Cams

[decooney]

Chaplin,

I think you are at a point, where its all "relative" to what is rough or what is calm is to you. Bill told me the same thing, and I ended going a step up from his 247/252 cam, and I love it. I would suggest you hook up with a few people with FEs, to see, hear, and feel the engines run through a full exhaust. What you might think is rough, others might consider tame... For me, a tame or flat sounding motor/cam in a Cobra gets a bit boring after a while, but you may be planning on driving your car a lot more than I do, etc. I've ran in to a few gents with FEs in their Cobras, that have stepped up vs. stepped down on cams with the 2nd or 3rd+ FE, by going too conservative the first time. Whatever you do, take the time to find and select the cam (and valvetrain components, rockers/etc) thats right for you and the application that makes sense for you. Here is another place to check for a 5th opinion..., try: Tom Lucas at FE Specialties 916-339-0427. Tell him I sent you. Good Luck.

[Mr.Fixit]

Big duration cams need compression to work right. At lower rpm's they don't build as much cyl pressure. I have gone through 4 cams on my 396 in the last 10 years. Started small, then went big, then backed it down a bit, now I have the smallest duration cam the motor has seen yet. It is more fun to drive, but it idles really smooth. Quarter mile times never changed as much as I thought they would, but the "seat of the pants" impressions sure changed. Everything in a motor has to work as part of a combination, so blanket recommendations for what cam you might be happiest with gets tough. I like tons of torque for passing without downshifting, it's more fun than peaky high rpm HP.