First thing is first...this website is awesome! About 6 months ago, I won a POS F-250 in a poker game. The truth was, the joke was on my because it didn't run and got delivered to my driveway! Out of spite, I decided to get it driving to rub it in my buddies face. That is when I stumbled across this site. I barely knew how to change oil, and now...thanks to reading through this site, Mr. Chilton and a lot of coffee...I've restored a 1987 F-250. I did everything myself from the paint, interior, and with a little help from my local machine shop, ground up rebuild on a 351w motor.

It has been fairly easy until now...I could sure use some advice.

Here are the basics. 87 F-250, 351W, Holley 4180c, Duraspark II, Calif. Emmission vacuum setup. Ive upgraded to Edelbrock intake, High Energy Comp cam (252H), K&N filter, new plugs, wires, etc.

I set the timing to TDC, got her fired up (no problem) and then turned the distributor to about 10* BTDC. Then, I went back, turned the flywheel to 10* BTDC and reset the distributor position so that it fired exactly on #1 (no offset on the magnetic pickup). The truck idles very rough.

I hooked up a vacuum guage to find 17-18 inches but the needle was rapidly fluttering between 17 and 19. So fast that you can barely see it.

I tried adjusting the curb idle rpm, but it doesn't seem to make sense to adjust the idle on a truck that is running rough anyways.

My real problem is that I can't find the idle mixture screws on my stock 4180c Holley carb.

Could this rebuilt carb be way off because of the new cam and cylinder heads? I suspect that with a different cam, the timing might not be what the stock manual calls for? As far as the carb goes, how do you adjust the damn thing?

Im in the music business, and Ill send a few CD's to anyone who helps me get this thing running right.

Thanks!

 

I think you should use a timing light to set your ignition advance. It's so easy for it to be off, using the mark one eye ball, to set the rotor position. This is probably why it's running so rough. With the vacuum hose to the distributor disconnected, use a timing light, and rotate the distributor untill you have 10-12* BTDC indicated at the damper marker, at idle. Re-set the idle speed at the carb to 750 RPM with the egine warm(the vacuum hose should be connected for this, but not for intial timing), and then go back and re-check the timing. Re-set it if it's changed.

This model Holley is an emissions carb so the idle mixture isn't adjustable. You can set the idle speeds though. The jets in the front can be changed based on reading the plugs. You have to take the carb apart to change jets though, so you may need to get some help.

These emissions Holleys have a special two stage power valve that opens early(about 10-11 inches of vacuum) but only a small amount, and then it opens up all the way at a lower vacuum, usually 6.5 inches of vacuum. I dislike this power valve myself, because it complicates tuning(it never consistant), but it does make it possible for smoother throttle response, and extra lean main jets. I just installed a regular 65 power valve for better tuning, when I used to use this model Holley. The main jets will probably need to be about two sizes larger in that case, though.

BTW, I'm a guitarist.

 

I actually did use a timing light to set the initial timing. Right now, it is at 11* BTDC. One thing that I didn't do was to reconnect the vacuum hose to the distributor before setting curb idle. Would that matter that much? I found a website that instructed me to file off the "tamper proof" plugs to set the idle mixture. Ill try that next. One more question, should I be turning the distributor or not? The engine runs better when I advance the timing, but it seems to me that because of the duraspark module, I shouldn't be turning the rotor off the magnetic pickup? If I installed a non stock cam, would that affect where initial timing should be set? The truth is, my new comp cam isn't exactly a beast. It is probably only slightly more aggressive than the stock cam. I appreciate your help with this.

 

Rotating the distributor enough to adjust the timing shouldn't hurt anything.

Re-connecting the vacuum hose to set the idle is required, because with it connected, the timing is more advanced, speeding up and smoothing the idle.

I'm with you, IMO, that cam isn't really radical enough to cause a real rough idle. It's actually fairly close(but slightly more conservative) in lift and duration to a stock 5.0 Mustang cam. It might a have a slight lope, but should be nothing too lumpy.

FWIW, 5.0 Mustangs with a carb and the duraspark II were factory set to 12* BTDC initial. Most people just go ahead and crank it up to 14*, so don't worry about advancing it a bit. What applies to a 5.0, generally applies to 351W's.

 

I really appreciate your help with this. I ended up making a special tool so that I could adjust the hidden mixture idle screws while the engine was running. Ill go ahead and set the idle to 14* and see if I can get her humming.

BTW, do you play for a living?

 

Not anymore, not that it was ever much of a living. I have played semi-profesionally on and off for many years, and I actually have a minor in music performance, but if it aint no fun, I don't worry about. I don't care to deal with the bussiness aspects of it, and the head aches of keeping bands together. I just go to blues jams now when I play out.

 

The music business sure isn't what it used to be.

I ended up taking two allen wrenches, cutting the 90's off them and super-gluing them into the mixture idle screws. It worked great! I can now adjust the mixture while the motor is turning without having to fish for the hidden mixture screw ports.

I have her running better, but frankly not perfect. Timing is at 14 BTDC, mixture about 1.5 turns out and idling steady at 800 rpm. It just doesn't seem smooth enough to me yet. Im going to finish adjusting the mixture tonight with a vacuum guage to get closer. If that doesn't work, I think I have vacuum trouble.

Hey, I really appreciate your help. Send me an email to jmorey@moreymanagement.com with your address so that I can send you some music.

 

Sorry - Im too new to this site to send you a private email. Send me your address - I have something cool to send you.

 

You will need to change the settings in your profile or somthing because it say's that you don't wish to recieve E-mails.

 

If you notice any spark knock or pinging, you will need to back it back down to 12*BTDC or lower, although you will probably be fine. Check the cam card, that came with the cam, and check the lobe speration angles. If it's less than a 112* average, then that would explain a rougher idle despite rather mild lift and duration figures.

 

You aren't going to believe this one. After troubleshooting for two days straight, I realized that I put the cylinder heads on backwards (the left on is on the right side, etc.). I had no idea that there was a difference. So, Ill be starting again this weekend. Any suggestions for an almost beaten down new mechanic would be highly appreciated.

Now that I have to do this again, Ill go ahead and rebuild the whole engine.

 

Whoa! Before you go too far, that doesn't matter. To make sure, I took my E5 heads and laid them out on the garage floor. No matter if I put either to the right or left, as long as the intakes were inboard, and the exausts were outboard everything was the same. The holes (as are all the holes) for the air injection system, usually out back, are located the same either way, but for the holes forward,they have threaded inserts.

One thing I thought about-You may double check the plug wires, and make sure they are correct to the firing order. Please don't take offense at this suggestion, but it's simple things that can problems, and most of us have done this at one point or another.

 

Don't worry - you're not going to offend me! My mechanic mentioned the same thing to me on the phone (his first assumption). I quadruple checked the wires.

I took a long look at trying to find a way to get those inserts out the back without pulling the heads again. I just dont think I can do it. I can't see back there, and well, in a sick sort of way, Im looking forward to doing this again to re-inforce all the stuff Ive learned.

One concern I had was that when I pulled the heads, the cylinder walls looked excellent (shiny, smooth and no sign of wear) a few of the pistons should slight signs of rust on the lowest point where obviously coolant had entered the pistons and was puddling. Other than that, everything was clean, and nice. My instinct is to pull the pistons, clean them up and re-intall them if possible. I guess Im getting nervous that I'm in over my head.

 

Yeah, I think your correct to pull the heads. It's just about impossible to get those inserts out with the heads on the engine, and the engine in the truck. In fact it can be a pain with the heads on a work bench. It would be easier to just reverse the heads and not mess with the inserts.

As long as your conifident that the bottom end is properly assembled, it would be a waste to take it apart again. Think about the following things to determine if it's worth it, just for peace of mind.

Bearing clearances- Are all the clearances within spec? Did you plasti-guage all of them as you went?

Bolt tourqe values_ Are allbolts properly tourqed? I usually mark them with a paint marker as I go.

Ring end gap- Are all ring end gaps within spec for the particular cylinder they go in? Are any rings that may be marked up-positioned up? Were the gaps rotated to the correct positions before the pistons were installed?

Timing chain-Is the timing chain and gear positioned properly relative to number one piston at exact TDC?

Cam gear assembly- Are the cam gear, the retaining plate(with the oiler passage), any spacers, the fuel pump eccentric, and the bolt and washer installed properly. I like to put some thread locker on the cam bolt, just in case.

Assembly lube- Were all the cylinders, bearings and rings, and any moving parts properly lubed for first startup.

 

Thanks for all your help. Rebuild complete, heads on correctly and a purring motor. No problem.

I learned so much on this one...after this, everything else seems easy.