Hi, I have a 1985 Camaro with a 70s 350 that has a 1991 SD TPI setup. Car is a 5sp manual transmission. Vortec heads modified for higher lift, Edelbrock Vortec TPI lower, ported upper plenum, SLP extrude hone ported runners that are Siamesed 1/3 way down. Currently the engine has a Comp Cams XE274H flat tappet cam (274/286 adv. dur 230/236 @.050" .490"/.490" 110 lobe sep). Top end power is great but I think the cam is to wild for the computer just driving around town and idling.

The car seems to pull high into the RPM range but I can't be certain of how high. Getting the car dyno'd is out of the question as the closest dyno is too far away.

I would say the car pulls to at least 5500 RPM, maybe more, maybe less..The SLP runners have been heavily worked over in regards to inside diameter and the depth of the siamese.

I am looking at 2 different Comp Cam flat tappets:

Extreme Energy Computer controlled hyd flat tappet cam

12-262-4 XE262H - Adv. Dur. 262/270 Dur@.050" 218/224 .464"/.470" 114 lobe sep. 1500-5500rpm

12-268-4 XE268H - Adv. Dur. 268/280 Dur@.050" 224/230 .477"/.480" 114 lobe sep. 1800-5800rpm


*IF* I were to go to a hyd roller...which I don't want to due to cost, I am also considering the 2 following cams:

08-304-8 266HR-14 Advertised Duration 266/276, 210 int./220 exh. Lift .500/.510 114 lobe sep. 1400-5400rpm

08-305-8 276HR-14 Advertised Duration 276/290, 220 int./230 exh. Lift .510/.510 114 lobe sep. 1800-5800rpm

I want a cam that will work well with what I have and be extremely computer friendly so it will idle and run smoothly.

Are there any other suggestions for a cam?

 

http://www.crankshaftcoalition.com/w..._compatibility

 

My engine has 10:1 compression, flat top pistons and with the current flat tappet XE274H cam the cranking PSI is 190.

How much DCR do I want with 64cc iron Vortecs and pump gas? When do you start running into detonation problems?

Using the DCR calculator the 4 cams I listed come out with the following:

XE262H - 7.96:1
XE268H - 7.78:1
266HR-14 - 9.21:1
276HR-14 - 9.02:1

Is a cam that operates in the 1800-5800rpm range outside the top end limits of a modified TPI setup? Will the engine continue to make power up until the RPMs give out due to the LTR design?

Would using a cam that runs to 5400rpm be leaving power on the table if the intake could support 5500-5700?

According to the chart a engine with 10:1 SCR and 221 degrees @.050" would make power 2000-5800. So with the XE268H flat tappet and 276HR-14 hyd roller have similar @.050" duration and RPM operating ranges, how would the big difference in DCR and lifter type change how the engine makes power?

 

Thats not too "wild" of a camshaft by any means. You're spinning your wheels and wasting money worrying about going with a different cam. I actually picked that cam out for one of my friends on a mild 383 thats carb'd and it sounds and performs phenominal. What i would do is focus on the tune, find someone that really knows what they're doing and get it dyno tuned. That cam should pull all the way to 6000 no problem

 

I agree the cam does perform well. Before I put the TPI back on I ran with a Edelbrock RPM Air Gap intake and 600 carb. It made just about 400hp on an engine dyno.

I just wasn't sure if the XE274H would work as well with the modded TPI setup. Even with the ported and siamesed runners the engine isn't going to breathe about 5500-5700. I don't want to give up low end and no be able to take advantage of top end.

 

Well that cam is on a 110 and only .490 lift so you will still have plenty of mid range. That thing needs the duration to breath being a lower lift cam. I had a XR270 Hyd Roller on my old vortec 350 build and it ran a 13.1 at 105 with street tires and a 2200 stall. Never did have the tv cable hooked up right either. But I don't see you making any more power on a smaller cam just more vacuum at idle. Bump the idle up to about 950 to 1000 to make a little more vacuum if you need to and run with it lol. Spend your time on other stuff