460 lifter problem???????

[rickpilgrim]

Early this winter we found an 1986 460 van engine for our 87 F-350 4x4. This motor had rebuild paperwork from 3853.2 ago complete rebuild and ran perfect with great(warm 43psi@650rpm w 10w-30@192 degrees) oil psi. I was never satisfied with the stock 460's power so I added a Stealth intake, 750 Edelbrock carb, an HEI style distrbutor and a Howards Cam with [email protected], .494 lift with 106 lobe seperation, cheap sealed power lifters and some exhaust port work and some Headman headers with the factory dual exhaust system. It idles fairly rough and acts weak below 2500 rpm, from there to 5000 rpm it seams good. We have 15" vacumn @650rpm timing is set at 10 btdc, any more than that and forget hot restart, less than that and vacumn drops radically. The spark plugs are light tan. here's whats strange-cranking compression is 194 psi to 189 psi but doing a running compression test says 135-138psi at idle.
Is it possible that the cam is to aggressive and causing the lifter to "pump up" and open the valves a bit? It starts easy and vacumn is 17 untill oil psi comes up.
We have a similiar setup with the same cam(performer intake and 650 carb) in our 86 F250 4x4 and smokes the 265/75/16's with ease, this 460 is weak comparatively.
Idea's anyone???

 

[5.0Flareside]

to me thats to little lobe seperation on a fairly stock 460.. thats a pretty rowdy rumpity rump cam. not a ton of lift though.... thats whats pulling the lower " of vacuum.. and also making the low end power go bye bye..

how can you not set the timing any further ahead though?? just 12* shouldnt affect hot restart that much...

 

[primetime]

Do you know if the block or heads were milled? I would check your lifter preload? I think you want .040-.060 if I remember right. Does the vacuum gauge hold steady? Any missing or popping through the intake or exhaust?

 

[rickpilgrim]

I would say yes to the block/deck milling and no we did not check preload on the net lash. Vacumn is rock steady 15 in and yes it does sound very uneven on the exhaust side. Also if you shut it off and restart it before oil psi goes down it does pop back though the carb once or twice before it starts again.
As far as the Howards cam goes its # CL241021-11
duration .050 lift with 1.74 rocker lobe seperation intake centerline
267 267 213 213 .502 .502 111 106 Hyd.

1000-4400 Smooth idle. Great for Off-Road & Towing. Good fuel economy

We have that same cam in our 86 F-250 ex cab 4x4's 460 and it does very well in that one, IE floor from dead stop and lay 35' of black stripes and with our landscape trailer the 6.0 diesel guys ask wtf as we pass them on hills and on ramp merge lanes. Not to mention 8 mpg towing heavy with a 4.10 geared C6 is not bad.
When the snow slows down here back in the shop and check lifter preload and get the matched lifters and try it that way.