Combo suggestions


Apr 25, 2005
McKinney, TX
Current combo:

.040 289
Forged TRW's
Isky 262 cam (.445/.445 262/262adv 108*)
Ported E7's w/ adj. 1.6rr's
RPM Air-Gap
600 Edelbrock carb

This combo puts the car in a 13.9 1/4 with 2.80's and a C4. I am in the process of putting a T-5 in it and will eventually put decent gears in it.

The question is that I have a Comp Cams xe-266-hr (.544/.555 216/224 112*) roller cam sitting in my garage that I planned to put into my 5.0. Plans changed. How well would this cam work in my combo? Would I have to worry about valve clearance? I dont know where my compression ratio is with these heads. 64cc vs. 54cc. Any advice. Thanks
  • Sponsors (?)

Well, you should always check P-V clearences because timing events (ramp rates) are what will cause problems. That being said I have an F303 with 1.7 RR .544/.544 lift 226/226 @.05 and GT-40p heads with a zero deck and I have over .150 clearence.
You should call Comp and see what they say. You may need a retrofit-type cam with a different base circle, or maybe just using linked roller tappets is okay - I'm not sure as my block is a roller block and I didn't have to look into that. As far as cam specs go, I would think that that cam would be fine. You don't want to use too big of a cam (duration-wise) with 64cc heads or you will loose too much dynamic compression. It would be a good idea to have the heads shaved.

Your springs are likey not optimum for that cam and you must use screw-in studs. P-V clearance should always be checked, but it should be okay if you are using valves that match (or are smaller than) the valve reliefs on your pistons.
The t-5 and a gear will definetly keep a smile on your face for the next couple of months or so.

But I think, as in any project, you really need to decide your plans. If you don't want to spend too much more and decide you are close to the end of your project, I would get a custom ground cam and mill the heads some (probably end up spending for some new pushrods) and call it a day. You can get a hyd flat tappet from Jay Allen for $140. Would be much better than any OTS cam.

But that XE cam won't work in the block you have unless you get different roller lifters (expensive).
I'd guess your comp ratio is way low at around 8 to 1. Less if the pistons have anything less than a zero deck clearance. Increasing the compressed volume by 10cc's is at least good for a 1 full point reduction in the ratio. I don't have my calculator here, but I'll bet I'm not far off on this. Now if those TRW's are the popup's, then disregard this estimate. As for the P/V clearance, I don't think you'd have a problem with the roller.