Need some roller cam advice

[zthis]

I'm considering upgrading to a solid roller cam from a GM solid lifter "40" cam

RPM 4200 - 7200; 257/269 @.050 and the valve lift is .493"/.512 OLD TECHNOLOGY I'M TOLD. Anyway motor specs are

10.75 Comp. Edelbrock Performer RPM Heads 170/64CC. 750 Holley DP.

3.55 Gears BF Drag Radials 26 inches tall 350 Auto Tranny with 3500 Stall

Car is running 11.9 on motor and 10.8 on 180 HP NOS.

the cam i'm considering is a Comp Extreme Energy Solid Roller XR286 248 254 duration and .576 .582 lift

 

Comp Cams recommended i go with the next cam size up which seemed like alot. The Car is used as much at the drag strip as on the road i usually only

cruise maybe twice a week. I'm not worried about adjusting rockers.

 

So the Questions

Is this still to much cam for these heads?.

Should i be concerned with excessive valve train wear with such a high lift Cam ?

How much gain in HP or ET might i expect with this cam

Is the roller cam even worth it should i just get a regular cam

 

Thanks

Curtis

[DaleMX]

Personally I believe the ports are too small for that cam. 200cc or greater would be better.

[Zoldman]

Curtis,

 

Gotta agree with Dale on this. I've got an LT1 motor and was looking at the Edelbrock heads for it, which are about the same config as your performers. With the cam I wanted to use, the heads wouldn't flow enough at higher rpms to do me any good, so I went to AFR LT4 195cc heads w/ 1.6 rockers instead. My cam is much milder than yours (220/224 @ 50), and I still think I needed the bigger ports.

 

You might go to Edlebrock's website, I think they post flow numbers like AFR and some of the others do. With that cam, you would want heads that could flow 250 intake/180 exh at .5" lift at least, or you wont be "using" the whole cam. Check with your cam guy about this also.

 

My recollection is that the Performer RPM heads will be at 225 or 230 intake flow at .5" lift. The exhaust flow is pretty good, I think, but I remember not being happy with the .5" intake flow numbers. A real good engine person should be able to look at what you want to do and help you balance things out.

 

Hope I didn't just make it worse........

 

Bill

[zthis]

thanks guys. I contacted Edelbrock concerning the flow of these heads,

max cam etc. Tech. support from those guys is a joke just as well I had asked

my mother.

[dr_hunt]

Ok, your into the world of cam timing. Small heads are a restriction much like too small a carb or restrictor plate racing. Larger cams will help extract power but you will never see the full potential of the cam. Solid roller in the 250 to 260 duration range at .050 isn't really that big, kind of like a 240 duration in a solid. The attributes of the roller cam are significantly different than solids or flat tappet hydraulics or even hyd rollers. They sound mean but pull from low rpm's. Pay close attention to intake lobe centerline and LSA. For the street 108 to 110 will give you a broader rpm range. Less than that give more mid range torque, but narrows the rpm range and probably won't work that well with your heads. I run two solid rollers on the street, one is 267/276 @.050 .640 lift 104LSA in the 406 and 250/260@.050 .640/.666 108LSA in the little 350. Both have AFR 220 CNC heads, Little one 13:1, big one 14:1. On the engine dyno the little 350 made over 400 lb-ft of torque from 2000 all the way to 7500 with a peak torque of 558 at 5300 rpm.

 

A 250 duration on the intake side will be a stump puller pulling hard from 3000 up. Probably run out of breath with your combination at 6000 or so. Flow numbers in the .3, .4, and .5 range are more important since the valve hits these figures twice during the valve opening event rather than focusing on the peak flow numbers at peak lift. AFR's kick some butt as do the Edelbrock victor jr's. Keep in mind that 20 years ago your heads would have been top of the line.

 

Depends on money, if you don't have any, run what you have, I would! Go with a roller and you'll never look back except to see how far you wasted the other guy!!!

 

David

[zthis]

I realize the heads are too small but i'd like to get a cam that will take them

to the max HP I admit that i don't know Jack Shi.. about cams but i think that

a solid roller has to be better than the cam i'm running now i just got to find the right one. I don't mind spending $1000 + on a cam and matched valve train parts as long as i get 2/10ths (or more) to show for it at the end of the 1/4 mile. Edelbrock Heads are spec. for 1500 to 6500 RPM range and a max lift of .570 so a lower duration cam would be better maybe

Comp Cams XR 274 2200-6200 236/242@50 564/570 lift LSA 110 or

XR 280 2500-6500 242/248@50 570/576 lift LSA 110

 

 

If i go any lower than this i'll be out of the rpm range or should i be more concerned with the duration and less with the stated rpm range of the cams.

 

Any Advice you guys can give would be great.

[dr_hunt]

The stated rpm range by the cam manufacturer is a guideline, not an actual rpm range that your engine will "pull" in and it assumes alot of things, like proper heads, valve size, intake, carburation, compression, header size, timing, elevation, all of which are "optimal". Solid roller is going to make more power and torque end of story due to faster ramp speeds. I run a solid roller in my 9:1 454 in my jet boat on pump gas. I wouldn't worry so much about lift, but getting the duration above 245 IMHO. I mean you have a 3500 converter, which is more of a race converter, so you ideally want peak torque around 4-4500 rpm which should land you somewhere around 250 duration at .050 to achieve that. If you have peak torque about 500 rpm above your stall speed you'll stall the converter better and within feet of launch you'll be in your peak torque. Just a thought, If you have traction issues, then 1000 rpm above stall may even be better, then it doesn't "hit" right away and the launch is "softer". You'll find that valve timing events are far more critical to making torque than just lift and duration numbers and you can tailor them to match the vehicle dynamics and get the power when and where you need it in the rpm range. the critical range is normally at the launch for light weight traction problem prone cars anyway.

 

This is why the computer age is influencing cam design so much. All of the cam manufacturers use computers to model all aspects of camshafts and valve train, from dynamics to engine modeling software. Try the same like DD2000 or something similar. They are not perfect but when you are changing just the camshaft values you can see how that affects TQ and HP, so in a sense you are comparing apples to apples since everything else stays the same. This assumes that you input actual values as you have them for your car, not what you wish they were.

 

EBAY, EBAY, EBAY! If you watch things, you can score a roller cam, springs, lifters and pushrods for under $500 and that is for NIB items. Sell your heads on EBAY, put another $500 with it and buy a set of AFR 210's if you already have stud girdles, buy AFR 220's or 227's if you don't, since they take offset girdles. AFR's with roller springs are good to .670 lift. With a 3500 stall converter, you don't have issues with loss of torque below 2500 rpm so it won't matter. Instead, you'll pick up 2 to 3 tenths with the bigger heads and another 1 or 2 tenths with better cam, switch to Alky and you'll pick up yet another 5 tenths and 5 mph on the top. Spray on top of the alky and your test the limits of the bottom end and balloon your converter. They have a NOS system for alky that is guaranteed to make a 700RWHP gain!!!

[zthis]

thanks dr.