Could anybody tell me how to measure for pushrods on GT40p heads and then install them correctly?
Swapped a set (fresh deck and valve job from machine shop) onto my 351w with a new cam and lifters and correct springs. I put the lifters on the base lobe of the cam and tightened to zero lash and then counted how many turns it took to get to 20 ft/lbs. All came out between 1/4 and 1 full turn with some shims here and there. Then tourqed to 25 ft/lbs. Broke the cam in and changed the oil. Started it up and let it idle to set timing and the valve train is making loud ticking/tapping noises. I'm afraid I have my geometry off. I'm lost and have worked countless hours after work for weeks trying to get this running to drive to Lone Star Throw Down here in Texas. Can't help but get down on myself after hearing those noises tonight. Any help would be appreciated.

 

The only way I know how to verify geometry is to remove a rocker, and color the valve tip with dry-erase marker, then crank it over a few times.

The wear pattern should be in the center of the valve.

Are you using roller rockers or a roller cam? Which cam? I have bother rollers and get some of the "sewing machine" sound, which is typical with some cams.

Bottom line, if the wear pattern is good, and your only turning 1/4 to full after zero lash to get to torque spec, you should be good.

-Glaser67

 

If you're getting loud ticking tapping noises, I'd remove the valve covers and measure how much lash you have, if it's excessive, pull those lifters and see what if any wear is exhibited on the bottoms. You could have wiped one or more cam lobes and lifters. When wear on the exhaust sides gets bad enough, you'll have backfiring out of the carb due to the valves not opening enough to let the burned gasses out.

 

After talking to a few machine shops around I concluded that my factory length pushrods should work. So I installed them and tourqed them down to 22 ft/lbs on the heel of the cam. The camshaft I went with was a COMP 280H Magnum and the lifters were also COMP. I coated the cam heavily with COMP's red cam lube as well as the bottom of the lifters. I ran Motorcraft 10w-30 with COMP break-in additive. Started the truck amd everything ran silky smooth and quiet. Truck only idled for 2 minutes max (forgot to turn the box fan on) before I took it up to 2,000 rpm constantly varying the throttle to 2,500. I never let it stay at one constant speed. About halfway through I developed what sounded to be an exhaust leak. After the 30 minutes was up I shut it down and drained the oil while it cooled. Topped it off with new Motorcraft 10w-30, COMP break-in additive, and an FL-A1 Motorcraft filter. Started it back up with the timing light on it and had HORRIBLE valve train noise. I figured the pushrods were indeed wrong so off came the valve covers. Found 1 rocker on passenger side and 3 rockers on driver side tourqe to spec but loose as could be. Pushrods straight as an arrow as well. Off came the intake manifold. Pulled the passenger side lifter, literally had to pull with pliers. Lifter was sloped to one side and chewed to high heaven. I was so mad I stopped right there. I am still mad and it has been 3 days already. I can't believe it honestly.

 

Yep, you wiped a few lobes. The problem was likely poorly machined lifters, not the break-in procedures. Only thing I saw wrong was you used a multiple viscosity oil High detergent oil. Next time use a straight weight ND oil. And inspect the lifter bottoms before using them. Also make sure they spin freely in their bores as you drop them in. You'll need to completely flush the oiling system before you run it again. I'd pull the crank to expose the oiling passage ends and flush the whole system with diesel or kerosene to get any metallic particles out before reassembling it. The rockers if they're pedestal mount just need to be bolted down, there's no need to have the cam on the base lobe to do this, I never have. I only do this with adjustables to set the lash.

 

Oh, and don't get mad, you'll only the latest in a 20 year line of cam/lobe/lifter failures. I've had two myself. Call Comp, tell them what happened and they'll likely send you a replacement cam and lifter at no cost. They did for me. Don't tell them you used a multi-viscosity oil though for break in. If the lifters were not poorly machined, then the cam lobes failed to "get traction" on the lifter bottoms to set them in motion, spinning in their bores. This is why the lobe surfaces are rough(parkerized), not smooth to start with. And carefully inspect the replacement lifters before lubing and installing them next time. The bottoms should be convex (slightly domed), if not they will not spin in the bores, they don't ride the center of the lobes, but are offset slightly to one side to make the lobe spin the lifter as it rides on the lobe, this reduces the wear between the two, the lubrication does the rest.

 

I have already decided on my comeback plan and it absolutely does not include a flat tappet cam. The extra cost of a roller cam and linked roller lifters are far outweighed by the ease of install, turn key, tune, and drive in my mind. The engine will be pulled and sent to a machine shop for cleaning, new bearings, and bore inspection. I'm also going to have the deck zero'd and the heads ported and polished. I'm still on the fence with rocker studs and roller rockers. I'll have to check my budget which is slim from paying off my 2004 F250 that took a dive for the worse (Thank you 6.0).
The engine is in my 1980 F100 with a T5 from a SN95 Mustang and an 8.8 with 4.10s and a Lincoln locker. Its strictly for fun. Any cam recommendations for power from 1,000- 5,500? I was looking at the Howards 221275-10 with their linked lifters.

Specs:
Cam Style:Hydraulic roller tappet
Basic Operating RPM Range:1,400-5,600
Intake Duration at 050 inch Lift:217
Exhaust Duration at 050 inch Lift:225
Duration at 050 inch Lift:217 int./225 exh.
Advertised Intake Duration:270
Advertised Exhaust Duration:278
Advertised Duration:270 int./278 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.528 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.533 in.
Valve Lift with Factory Rocker Arm Ratio:0.528 int./0.533 exh.
Lobe Separation (degrees):110
Camshaft Gear Attachment:1-bolt
Computer-Controlled Compatible:No
Valve Springs Required:Yes
Camshaft Manufacturers Description:Mild rough idle. Good torque and power. 1,800+ stall.

 

You haven't listed any of the intake/carb specs, nor the comp ratio, but you'd be happier on the street with a wider LSA, EFI type roller running a carb. These give you a cleaner idle and quicker response from the carb circuits as they generate more vacuum.

 

Sorry, the compression ratio will come out around 10:1 with the zero deck. Im running an Edlebrock RPM Air-Gap intake, an Edlebrock 600 cfm carb, and Hooker competition longtubes. I will most likely step up a bit larger on the carb after the refresh.

 

Sorry to hear about your cam/lifter wipe out. I am soon assembling a flat tappet 302 with GT40 heads and complete Comp Cams kit, so your pushrod length issues caught my eye and I wanted to follow along.

I'm taking my short block to an engine shop to check/machine, and then I'm getting them to assemble the rest for me. I'm paying extra to have them break-in the engine and test it on a dyno for me.

What is the spec for tightening/shimming the rockers? I assume the shop will have rocker shims if needed....I hope...lol.

 

With that much compression and an EFI wide LSA cam you'd have to run it on 91-93 octane fuel. Might want to stick with what you chose then. With a 351, don't go over 750 cfm on the carb. The smaller carb will give you better driveability, the larger will loose some of that but give it more top end.

 

Make sure they inspect the lifter bottoms and verify they spin freely in their bores. 80ford100's failure wasn't due to pushrod length issues, it was bad lifters or too much lubrication (too slick) to allow the lobes to get traction on the lifters to start with.

 

Has anybody heard of Howards before? Looks like they may be pretty popular in the mustang community. Also, with linked roller lifters I should be able to run any type of roller cam correct? Shouldn't have to be a small base circle retro?

 

They've been around awhile now. And yes, they run on any hydro roller cam. Make sure to get the right length pushrods, they should have a recommendation on this though.

 

Trying to keep to my budget I have turned to the Ford letter cams. These things are only 200 bucks compared to the 350 for others! I know these heads won't breathe too well over 5,500 rpm even with porting. I was looking at the F303. I have to have the lope sound (yea I'm one of those guys) but I also want it to perform well with my setup. Leaving some on the table for future head upgrades would be nice also. I have a Cloyes adjustable timing set so I can play with timing as well. Just remembered I'm going to have to budget in a new gear for my MSD distributor because of the cam material. The list never seems to get shorter.