Vacuum lines & tuning 73 F100 302

[Mispeld]

I instaled a new HEI, plugs, wires and just replaced the 4bbl Holley with a brand new 2bbl 2100 carb. It was molested. The vacuum lines are hooked up all over, and some are capped off. I timed the engine with the vacuum advance disconnected at 6°. I put a spacer in that came off a 1977 truck between the carb and intake but I'm not sure what engine it was. I know it wasnt a 302 or 351w. The truck hesitates about 1/4 throttle. It did that with the holley too. Is there supposed to be a spacertain or does the carb bolt right to the intake? The intake is a 2bbl by the way.

I'm thinking I need to simplify the vacuum lines. The distributor is hooked up to the manifold behind the carb. Thats just how they had it. I'm thinking the distributor needs to go to the ported vacuum on the carb.

What about the rest? Can I cap the pcv? What about the one at the intake where the heater core hose connects? It looks like there are two transmission lines hooked up to a vacuum. One is capped off under the truck. It's a C4 tranny.

Can I cap off everything except the distributor? PCV? What should go where? Is it correct at 6° vacuum unplugged and ported?

It idles and revs great in the driveway. But under load it sputters and hesitates. Thanks.

[71Fe2O3]

I can't speak to the other things, but it would be unwise to cap off the PCV. It allows oil vapor and blow-by a way to get out of the crankcase. If you cap it off, those gases will exit by some other pathway, making the engine run poorly and perhaps damaging gaskets or seals along the way. Some photographs would make it easier to understand the vacuum line situation.

[Mispeld]

I was thinking the same thing. Here's what I'm thinking...

The spacer has a nipple, so I'm going to run that to the PCV. The base of the carb in the rear has a large nipple so I'll plug that. The truck has manual brakes. I'll run the distributor off the ported nipple I beleive on the passengers side towards the front. I'll cap off everything else. The only vacuum I'll be using is PCV, and ported distributor.

I sprayed carb cleaner on the rear base of the carb and the idle lowered a little so I'll address whatever small vacuum leak that could be. Am I on the right track? The truck wants to stall about 1/4 throttle, but if I can get beyond that, 1/2 - WOT is fine. Is feels like an accelerator pump but it did it with the holley 4bbl, and this new carb. Looking inside, it squirts nice steady streams into the carb when hitting the gas.

Sorry for the looooong write up. I like to be thorough.

[Ranchero50]

Yeah, bump the timing to 15 degrees too.

[Mispeld]

15 BTDC? With advance unplugged to set it? Oh, and the timing tab... I'm aligning it to the right side of the tab above the harmonic balancer; with the sharp point not the rounded edge? Sorry, just never played with Fords.

[71Fe2O3]

The only vacuum I use is for the PCV and the distributor vacuum advance-I plugged the port behind the carburetor.

I know my 360 has a spacer between the carburetor and the intake; I will have to check the 302.

Once you get the timing right-I believe I also have mine at or around 15 BTDC, hook up a vacuum gauge and adjust the mixture screw on the carburetor to maximize vacuum while the engine idles. You may have to readjust the idle speed afterward. It will also pay to get the dwell angle set correctly-you should be able to find the correct setting by searching this site.

It takes a bit of fiddling to get everything working right, but it is satisfying, and very educational.

[Ranchero50]

Yep, max vacuum and then go a little bit rich, 1/8 turn or so. Engines tolerate rich better than lean and it'll help you idle quality.

You have a '73 so post a pic of your timing setup. Been a long time wince I played with one of those.

Your C4 needs vacuum too. Without it, it won't shift correctly, but a lot higher revs.

[Mispeld]

Hopefully this picture works. The timing tab has a round edge to the left, and a sharp right angle on the right. I assume I use the right side where the sharp corner is?

[image] [/image]

[Ranchero50]

Yep. Pop you dizzy cap off and rock the crank back and forth between rotor movement to see how much slop you have in your timing chain (you can measure it on the balancer). A lot means it's time for a replacement.

[Mispeld]

I was told if the timing marks are moving around when the timing light is on, it means the timing chain is worn. The marks are spot on and I just put it at 15° btdc. I'll check by turning the crank like you mentioned. I found 2 vacuum lines, one to the trans, and another with what looks like burn marks so they were leaking. I got everything plugged except pcv, distributor and trans and she's purring at idle. I'm about to go out and hook up the vacuum guage, set the carb, recheck timing and see how it goes. I appreciate all the help.

[Ohiotinkerer]

I was told if the timing marks are moving around when the timing light is on, it means the timing chain is worn.

Not always - my 360 was dead on at idle and good when accelerating but when I would be cruising at a steady speed you would feel a little hesitation or "hitch"........pulled the cap and moved the crank and sure enough had just enough play that it was causing it to jump around........good old nylon gear timing sets - they might have kept the noise down but didn't wear worth a s**t...........

[Ranchero50]

I was told if the timing marks are moving around when the timing light is on, it means the timing chain is worn. The marks are spot on and I just put it at 15° btdc. I'll check by turning the crank like you mentioned. I found 2 vacuum lines, one to the trans, and another with what looks like burn marks so they were leaking. I got everything plugged except pcv, distributor and trans and she's purring at idle. I'm about to go out and hook up the vacuum guage, set the carb, recheck timing and see how it goes. I appreciate all the help.

That or the vacuum can is leaking. Suck on the line to it. Should be able to see the plate shift with the cap off. If it won't hold vacuum you need to replace it.