I took my 78 f250 to the local sled pull and took 2nd place but the engine wouldn't make it to the powerbannd. It got close but not all the way there. I have a 2000 stall converter with a stout 460. CR is supposed to be 10:1 (150 psi cranking compression @ 6000' above sealevel) 2.19 intake valves, d3 heads, polished ports, 3310 holley, performer rpm intake, 3/8 pushrods, comp alloy roller rockers, L&L headers uncorked for the race, cam is said to be comp x4270H but I think it behaves and idles more like a x4278h. strait up timing, balanced and so on.

Is there a way to pull the valve cover and verify the cam off of the lift?

I either need lower gears, 4.10s now on 35" boggers, maybe 488s?

A higher stall converter would help, but I would still be tugging that sled at 20+ mph at 6000 rpm after the thing stalled.

This was my first engine build but I think I will redo it for something more impressive. Would a smaller cam work good with that combo, the hi flowing heads or do they just not breathe good until the engine is spinning?

I guess my main goal is give the engine an oppertunity to hit the 3000-6000 rpm powerband or give it a lower powerband and let it tug, but I think I will lose out if I don't have the rpm to keep moving.

I use this for a truck still, 4 wheeling, wood cuttinng, farming, hauling, hunting, so it has to run on pump gas and be reasonably driveable, which it does now, but Something isn't quite right and I was wondering who would help me fix it.

 

with a hyd cam pretty much no. you could remove a rocker then with almost no pressure on the pushrod measure the actual cam lift (no pressure so it doesn't collapse the lifter) then multiply by 1.73 and compare to your cam card to see if it's close.

 

Thanks That was what I was thinking would it be best to measure with a caliper or dial indicator? I have no cam card just what the shop billed me for on the invoice. You know a ton about these big fords, will the big valves and hogged out heads kill my low end? Is it possible to build a 2000-5000 rpm engine with those heads or am stuck in the 3000+ range? I hate to put a cam in that beefs up the low end and have an all out pooch due to the heads flowing too well for a low rpm performer.

 

The bigger valves aren't going to help you below somewhere in the 3500-4000rpm range and may hurt you slightly below 2500.

Here is an online copy of your cam card IF you have the comp X4270H cam

34-239-4 - Xtreme 4 x 4

And if you look it gives you what the lobe lift SHOULD be without doing the math

 

thanks. I found the cam specs online. I need to verify the lift to see if it is the next size bigger. It sure behaves like the next size bigger. I always blamed the pathetic lack of low end and the 3200 rpm eruption of power on my 6000 ft elevation and big intakes and portet out heads. I bet I have the bigger more radical cam and the 2000 rpm stall converter in a 6900# truck just kill everything on the off idle torque. I may pull a valve cover today and see if I can get an idea on the lift of the cam lobes.

 

It does sound like I can either swap in a better low end torque cam or leave it the way it is and buy a torque converter that allows for a 2500 stall and get that thing into it's power.

 

I'd change the gears and get rid of the C6 even if it stays together there is still a given amount of slippage.

 

Im with Mark. I would be thinking gears here. It sounds like the engine is set up for rpm horsepower, so you may as well get the engine there. But if you are driving the truck on the highway, you may not like the rpms the engine will be at.

 

Well, I put a caliper on the push rods and I am pretty sure (not positive) that I have the x4278h. It seemed to have more lobe loft than the 270. I can't be positive but I feel that the cam is too big for a 2000 stall converter. I have a plenty stout c6 as well, It may slip but I have no use for a 4 or 5 spd. I don't like them for off road, I don't like any of the 4 spds I have had. If you guys like them, more power to you. Thanks anyway. I agree 110% on the gears. Atleast 456 and probably 488. That would allow for plenty of RPM. A 18% increase from 410 to 488. I figure that would allow for a 20 mph pull to be at 3600 rpm instead of 3000. I bet at 3600 the extra power would allow a substantial increase in speed as well. What about a torque converter swap, like to a 2500 rpm stall? worth it or not? I bet a 2500 stall would be good and still drive ok for me.