1964 292 Y block in my F-100 I am at my wits end, I rebuilt the carb, installed new intake gaskets, and this thing still idles crazy, up, down, stalls when I come to a stop, it is acting like it has a big vacume leak. Or am I missing something,. I also am curious if these came with a factory PCV valve, for some reason this one has one screwed in to the manifold just under the front of the carb with a big rubber line going to a small canister on the back of the engine just behind the lifter valley pan. I'm not sure that these even had a PCV it seems to me that this is to early for one, and that it vents thru the oil breather. I know that early SBC had a draft tube (not comparing this to a SBC ) and thats why I am thinking that this PCV screwed into the manifold is cause vacume leak symptoms, Or am I way over thinking thing All PCV i have ever seen are pushed into the Valve cover and then routed to the aircleaner plus the earliest car I have had that had one was an early 70's Impala..I am all ears and would buy you a beer or 24 if your ever in the area of Cincinnati..

The "screws into the ('64 truck) intake manifold" design sounds correct to me.......plug that line and see what happens with your vacuum leak. That should make some things clearer to you anyway. Different sizes of PCV's have different amounts of "flow" - so they bypass smaller amounts of air at idle. The other systems you are thinking of had their "check valve" - PCV valve on the other end of the suction line but they work the same. The PCV valve acts as a "check-valve" so that if the enigne backfires - it won't be pressurizing the crankcase.

A small portion of the engine intake air is being siphoned out of the engine (the Y-block uses the valley space over the lifters to gather the "smoke") and "new air" is sucked in through the vented cap on its front stand pipe. In the later sixties, the stand pipe caps (Y-block was out of production by then) had a stand pipe cap with a hose that hooked back up to the air cleaner. That insured that even at full throttle - where an engine with blowby might be building a bit of crankcase pressure - all of the smoke was ingested by the motor....cough, cough.

 
 Steve Metzger       Tucson, Arizona

I removed it from the canister tube on the rear of the engine, and it was tube attached to the PCV valve was sucking hard ( VACUME) but the engine still seemed to be idling rough. I removed the whole deal and capped it off and still idleing rough (DAMNIT) I checked the cap,button and points and they seemed to be ok but I think I am gonna replace them and the plugs and wires, and go backt thru the whole timing process and see what happens, the wires are older . I guess my hopes of it being the PCV valve idea may be dashed as it did'nt seem to make a difference. Still idling rough, and stalling when stopping...ANY IDEAS?

How are your valve cover gaskets? new or baked? - pull the covers and make sure you still have a full set of pushrods. The "new" gas we have tends to make for sticky valves and eats pushrods...... can make things run rough in a big hurry.

Bad plug wires are a good guess too....especially if they've gotten pretty cooked over the years. You might pull one at a time and see if one of them makes "no change". Don't do this bare handed OK?

The carb rebuild you mentioned - have you done one before?

 
 Steve Metzger       Tucson, Arizona

Just shopping for ideas, if you cup your hand just above carb top, without a/cleaner on and lower hand slowly over carb opening, usually if vac leak, the engine will start to increase in revs as it pulls air from leak. This is assuming carb rebuild is not a problem. We await progress.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

The PCV setup you have is the correct one for 63 and 64 trucks.PCV was mandated by Uncle Sam on cars and light trucks starting in 63.

 

Paul,

Boonville,MO

I'd better correct a mis-statement I made about your setup being original.It is except that you said it had a rubber hose on it.It would originally have had a steel line from the valve to the fitting at the rear of the valley cover.

 

Paul,

Boonville,MO

Irs: Did this problem exist before you took the carb apart? If yes, continue looking, if not that's likely the problem...

Paul

Have you checked the basics, compression check for valve problems, or broken valve spring(s)?

John - "The Hoosier Hurricane"

Yes it was doing this before the carb rebuild. I've rebuilt several carbs before with suuccess, I made  sure I took my time with it.. Yes it will increase in idle if I cup my hand over it. I have search high and low for a vacume leak, with everything from brake clean, carb cleaner, starting fluid, hell even used my propane torch, and found no evidence of any leak anywhere. I used fel-pro gaskets on the intake, when I took the intake off I thought I found the problem as all the mating surfaces where painted, so I cleaned them off with a roloc gasket remover pad, and re-installed, still running rough, removed the PCV valve and capped it off with a plug and still running ruff. I am gonna do a tune up (plugs cap and such)this week and see if I can make some progress.. I got my timing set at 20 degrees, btdc. I will post an update as soon as I get back out there, thanks guys for trying to help, I really wanna get this thing right The more I drive it the more I love it, just need to fine tune. it.... Ryan