Rixter

Hello,

So let's say I have some GT-40p heads, now lets say, for some reason, I wanted a .565 lift cam. What exactly has to be done to make that work?
Most of what I see say GT-40 heads are good up to .500 lift, but I've seen some higher. On ebay somebody was selling a set of worked GT-40's that he said were good up to .600 lift.

If I were to put a 565 cam and 1.7 rr, would I be pushing valves out the block?!

Thanks

Joel5.0

GT40p heads and .550"+ lifts shouldn't be a problem, provided the basic clearances + correct spring/retainers/valves are used....FYI...I'm running .576" lift (X303 cam w/1.7RR) on '66 289 HiPo heads with no problems (15 yrs. now)......suggest to check http://www.cranecams.com/?show=faq&id=5 for all the critical areas that need to be checked, and corrected if required.

AdderMk2

.565 with 1.7's will bring you close to .600 lift, gotta get some deep fly-cuts, and all you need to run high lift on gt-40 heads is a new set of springs

jrxs_racer

most of your worries may also be within duration of the cam also, look into that

Rixter

So, if I were to get a short enough duration cam, would I not have to notch the pistons or anything like that?

jrxs_racer

i dont wanna answer that because i dont know, but duration has more to with hitting the pistons than lift does, to some degree

Joel5.0

It's the overlap period you have to worry about PtV problems..... http://www.fordmuscle.com/fundamenta...ve/index.shtml

r.barn

the problem is that the GT40P head will not flow any more past about .500-.550 lift,
anything beyond that is just waste since you're at max flow for the head anyway.

even AFR 165's level off past .550 lift and flow the same at .600

you will definately want to upgrade the springs if you go beyond .500 lift.

Rixter

The reason I'm looking at such a high lift is I'm planning on doing a little junkyard turbo to it (yeah, I still have a lot to learn). Any thoughts on that? Is it still unreasonble to go that high?

Thanks for the info guys.

r.barn

again, you're just not going to see any gain from lifting the valves open that far
on those little heads.

The duration and lobe seperation will play as big a part in the turbo as the lift.

bigger duration will open the valves sooner, so you have more time to shove more air in there.
but too big a duration will hurt your streetability.

something like a TFS stage 1 cam with 1.7 rockers would be good in my opinion.