352ci 65 F100
Engine was running fine. Piddled with carb a little, replaced points, condenser, cranked and is running on what sounds like 4 cylinders. Sounds like it's hitting on 4 consecutive cylinders and then missing on the next 4. It causes truck to rock back and forth while running in idle. I pulled each plug and found that all 8 are firing, so my problem is not ignition. The exhaust manifold is corroded badly on the passenger side and leaking as well. But this should just cause noise....right? Does it sound like the head is not sealed and sucking air, thus leaning out fuel mixture and not firing? What's going on? Any ideas are greatly appreciated......Gary

 

it may be an intake leak, torqe down your intake bolts to specs and see what happens. was it running fine befor you messed with the carb? you may have improperly adjusted the carb. also were the plugs fouled or clean? i doubt the head is leaking and causing the problem as ive never heared of it happening. it may be an intake leak though.

 

Did you remove the plug wires from the cap when you changed the pionts? What did you set the point gap at and what is the Dwell reading you are getting on them now? Did you remove the carb or just piddle with it on the motor. You will hear a more pronounced air sucking if you have the air cleaner off. Becasue you indicate it ran fine before you worked on it, what ever you worked/reworked is causing your problem.

--Mike

 

Good idea, I'll try the intake. The plugs are new. The new and old points make no difference. Could the carb cause this? Remember, the plugs are firing on all cylinders. I hope the carb is the problem, and I suspect that the carb is shot for other reasons. However, it did run ok before. Thanks

 

i would guess the most proably explantion is the carb imporpely adjusted or damaged because it ran good before you twaked it. id start with the carb, rebuild it for 20 bucks and a days worth of time it will be like new. then move on to the intake.

 

Are the plugs firing in the correct order?

 

The intake manifold is configured so that one side of the carb fuels two inside cyls on one bank and two end cyls on the other. If you can isolate which cyls are not firing, you will have a better idea on where to look. If you messed with the carb, maybe you affected one side of it, thus affecting 4 cyls.

 

Those technical terms like "Piddled" throw me.
While piddling could you have twiddled some crud loose that affects one main jet, &/or fuel feed galley resulting in what you seem to describe, and is what instig8r63 is talking about.
Sounds good to me anyway.
FBp

 

Sorry for using such technical term on you guys. laugh....Got with a mechanic today and you are correct. The carb was the problem. Probably something blocking one of the intake banks, and the linkages were loose on the throttle shaft which further screwed things up. He says I should have a PCV valve installed also. Thanks for your help

 

gwp,
You definitely should have atleast 1 PCV Valve, or 2 if you can work it out. The engines sort of quit using road vent tubes in the mid-late 60s and there is No Way for an engine to relieve internal pressure build up, and all engines have internal pressures.

In fact the older & more used an engine gets the more pressure we can expect. Not having any PCV system can result in leaky front & rear main crank seals, leaky rocker cover gaskets and leaky intake manifold end seals. . .so PCV is really important and 2 are even better as they create Postive Crankcase Ventilation (ergo PCV) by valving the innards & using intake manifold vacuum to do it.

ALso FWIW the best set up is the one that draws from a spacer plate that goes under the carb. The good news is that spacer need not be from an FE engine as almost all FoMoCO V8's use the same carb bolt pattern for all 2V (2Bbl) carbs. Same goes for 4V (4Bbl) carb, all have/use same bolt pattern, so you can use a spacer/draw plate off a 302, 351, etc whatever year you can find with your bolt pattern.

You got a 2V right?

A simple Tee fitting and 2 rocker covers with pcv grommets should work, & if your oil filler is in a rocker cover, you can bore a grommet hole in an extra one of them, bafffle it so your PCV Valve doesn't get or sick raw oil, and replace your existing rocker cover with the custom vented one I'm talking about.

FBp

 

Yes, it's a 2V. Your advice is exactly as the mechanic I spoke with regarding the PCV situation. He emphasized coming from the carb spacer too. Look at the pic below. I can't figure how to install a PCV with the crankcase breather that's installed now. Can I buy a PCV which inserts into the same hole as the breather? The engine is a total mess on top and bottom.....oil everywhere. I hope you are correct about the PCV adding to the leaks. The engine has lots of miles, but has very good oil pressure and runs and sounds pretty good. No smoke except when it's cranked after sitting a while (valves I guess). I hope to get a few more years of service from it. Not sure what a rocker cover is. Thanks much....Gary

 

How old is the cam? I had one with 3 flat lobes and 5 collapsed lifters. It sounded just like that.....

 

Ops....I forgot to included the pic. Still unsure of how to set up the PCV. Thanks

http://www.angelfire.com/falcon/gwp36530/04150005.JPG

 

Gary E-Mail me & I'll get back to you ASAP I have not got the time to try to post pictures here. It's too involved!

I can show you what the PCV should look like, and I'll discuss the smoke when you first crank it up, it's NBD (as in No Big Deal). . . .

Your posted pic is of the Rocker covers, I might be splittin' nit but I think they cover the rockers because I believe the valves are inside the combustion chambers & the head has to come off to get at 'em. . . . But the rockers will come right off after the rocker covers are removed. . .

Anyway those are early style rocker covers, my digi pic will make the difference evident kwik!

I can't post my Email Here. I'll post it in an eMail through here though
FBp