Hi all,

Newbie here. I have a 72 F500 with a 330 in it. It rarely gets driven but is almost mint condition. I've owned it over 20 years. It has a 330MD in it that I dont believe is original.

Anyway, it sat for a long time and when I got it running it had very little power and was burning fuel really badly. So I changed it over to electronic ignition. No help. Then I went thru the carb (2100 2bbl) and other than a little dirty, it was fine. Gave up on it and put it away.

Last winter, I got it out, pulled the engine and had everything machined and I overhauled it. Used the same crank, rods, pistons and cam. Had heads gone thru and reassembled everything. It still wont run right.

I'm very mechanically inclined but I feel like I'm missing something here. I have no idea why it will barely run. It sounds way retarded to me. It will run and idle but doesnt have enough power to move itself. I set initial timing at 8 degrees and full advance is at 36 degrees.

I sent the carb to a carb shop and they say it looks good except that the idle screw was turned way up, which that's the only way I can get it to idle

The timing chain is in correctly. I leaked all the cylinders down and they look great. Internal vacuum leak somewhere? Any help is appreciated!

 

Bump to top 😎

 

It may well be retarded. The Tune-Up manuals which you should already have - and the shop manuals - are excellent though one issue is the assumption that the mechanic is dealing with a reasonably new piece of equipment.

So there are a couple things that need looking at, that experience has shown here at FTE over the years are very common and cause mucho headscratching. The heavy balancer steel outer inertia ring - where the timing marks live - is prone to slipping off axis or its "clock" position relative to the crankshaft keyway, timing set, etc. In this situation the "0" or TDC mark is way off.

Setting the ignition timing with a timing light will consequently be way off as well. A good check on an engine tune-up is to measure the manifold vacuum at factory idle RPM with a mechanic's vacuum gauge. This inexpensive tool is like a steampunk Scangauge, or OBD-0. A healthy stock engine in good condition and properly timed will pull 19" to 21" at Sea level. A correction factor is applied for altitude but this is what you want to see. Accuracy of the TDC "0" mark, should be part of the plan before diving into a "new" engine or performing a Tune-Up. An inexpensive Piston Stop Tool is the best way to do this. An engine that pulls 19" to 21" steady needle (or its high altitude equivalent) can be assumed to have the ignition timing set very close to optimum, and at least reasonable valve timing, and cylinder compression, no major vacuum leaks or exhaust restriction.

If the motor doesn't achieve the correct manifold vacuum at idle, find out why, because it will not run right and can't be made to run right. It may be the ignition timing is severely retarded, or other defects, or a combination of problems. Generally speaking the higher the manifold vacuum # the better, but it is also very important that the gauge is absolutely steady. If vacuum is even a single 1" lower than the spec, that's a lot, and it will be noticeable.

The carburetor in particular is calibrated for a specific air flow or velocity through the venturi at all times under all conditions, from idle to steady cruise, wide open throttle, etc., and it will not achieve performance or economy with incorrect ignition timing. There is a direct relationship between ignition timing advance and manifold vacuum.


Welcome to FTE, btw

 

Agree with the timing and balancer slipping. Use a positive stop in a plug hole and find TDC. Also look at the distributor gear. Did the roll pin break and the gear slip on the shaft?

 

Tug300L, welcome to FTE.

Ok so it sat for a long time and when started it had no power and could not figure why so it sat again till pulled out and motor rebuilt right?
Tedster posted how to do the timing even if the marks are off using vacuum gauge.

So I got to ask what fuel are running this thing on hope not the fuel in the tank that has been sitting for who knows how long.
Bad fuel will make any motor run bad if at all. Get a can of fresh gas and some hose to fit the fuel pump and run the hose from pump into the can of fresh gas and run it till fresh gas is in the carb and see what happens.
Dave ----

 

Think I figured it out.

Theres a 5/8 vacuum hose plumbed into the manifold right behind the distributor, runs over by brake master cylinder to what looks like a check valve? Then runs down under the cab and comes back inside the truck behind the back seat to a canister. Obviously brake related, very early power brake assist? That check valve mist be bad because I unhooked that hose and hooked my vacuum gauge to that port, fired it up to check vacuum and it ran way better (once I turned the idle down a lot) LOL!

Pulls 20 inches at idle drops to around 15 under throttle and is way smoother and way more responsive.

So that leads me to figuring out where to get that check valve, assuming that is a check valve. I think it has to be.

Probably a good time to replace the single master cylinder on this truck with something a little safer. Any referrals yall can send me on finding this check valve and changing the brake master to a dual without cutting the truck up?

Thanks for the help!!

 

 

Thanks for the update.

Are those "Widowmaker" 2 piece wheels?

Those need to go bye-bye, if so. Those are dangerous. Split rims to be clear are not inherently dangerous as such. Widowmakers though, are a different deal altogether.

 

Educate me. I'm familiar with typical split rims bit how do I determine if these are widowmaker? This truck is primarily used for parades but I'll admit, it needs tires. (I was born in 76. These tires are from about 1980) So widowmakers are before my time.

And any input on this check valve? I'd like to find one for it.


Thanks!

 

The vacuum hose for the brakes: Look under the cab inside the frame rail. You should fine a remove "hydro-vac" brake booster. The line from the manifold supplys vacuum for boost. The line into the cab is a vent line. A better explanation can be had once you look at it and compare it to this starting at about 57 seconds:

 

As for widow maker wheels, do your wheels have split locking rings visible on the front wheels like so:

https://www.alibaba.com/product-deta...805014911.html

If so, you are "good" Tubeless with one piece wheels is best.

Widow makers--worst:

https://www.jalopyjournal.com/forum/...nting.1083358/

 

Interesting. So my problem is likely the hydrovac itself, not the check valve. In any case, does anybody make a conventional master cylinder / booster combo that will allow me to get rid of the single master / hydrovac setup without having to cut into the firewall? This truck should have a dual feed master on ot rather than a single... imo

 

I'll look at my wheels tomorrow and post some pics. Thanks everyone for all your help and advice!

 

You might have some luck with later if not really late model F350/450/550 masters. Firewall mounting is a question mark depending on the diameter of the booster section. If you can overcome that, you would be in business. You will have to fiddle with pressure differential unless you can find one for all drum brakes.

Under cab setups hold a lot more fluid than the firewall mounts of "the day" and with some of those (all, many?) haveing two cylinders per wheel, more fluid is needed. On the parade route? As long as you check religiously for leaks, you will be good.

 

Are these the widowmaker wheels?