I just replaced the intake manifold on my 351 W. converted it over to a 4bbl. It had a rough start but finally smoothed out. seemed to be doing fine until it warmed up. The oil pressure dropped on the gauge and began hearing valve tap. I turned it off, came back a little while later after it had cooled and started it again. same thing happened. good oil pressure in the beginning then nothing after it warmed up. when i replaced the manifold i did away with the smog stuff and capped off the vacuum switches that control it. I can't think of anything i might have done while replacing the manifold that would have caused this. it must be a coincidence. right? i had great pressure before i replaced. any ideas?

 

There isn't really anything in the oil system that has any direct correlation with the intake manifold. Was the old manifold installed with silicone sealer on the ends? I'm thinking that some silicone or old gasket materiel got past you and was sucked up by the pump and has now taken up residence in the filter screen.

I assume you yanked the distributor to make it easier to change the manifold. If you had knocked the pump shaft out you wouldn't have any o/p at all, but that's another pathway for debris to have gotten into the pan.

 

Yes I did use some sealer on the ends of the manifold. I didn't think there was any way for stuff to get into the oil. Where would it have gotten past me and into the oil supply?

 

I was thinking more in terms of old sealer from the old manifold, that perhaps a chunk fell off when you removed the manifold and went down one of the oil drainback holes. Any time you open up an engine there's the risk of debris falling down into some convenient opening that leads to the oil sump. It happens.

 

When i removed the pan that is between the manifold and the heads there was carbon that had accumulated in the area where you can see the pushrods. There were also about a half dozen 1/4" holes in between the two banks. Do these holes lead to the oil supply? When i was removing the carbon i would bet that some small pieces fell in these holes ......

I've drained the oil twice and both times a lot of small carbon pieces and a few large (1/4 round) peices were in the drained oil. This is obviously bad. I guess I'm going to have to drop the pan and check it out. there isn't any other way to clean the pickup screen without removing the pan is there?

 

Pan between the manifold and heads...? Are you sure you have a 351W, not a 351M?

Anyway, yes those should be the oil drainback holes for the oil that drains from the heads to return to the pan. Chunks of carbon, hmm? Sounds like our culprit!

Now, I had a thought but I'm just winging it here so bear with me... The first place the oil goes after leaving the pump is up to the filter. (Which may be partly plugged itself.) If you remove the filter, drain the oil and leave the drain plug out, take a look at the filter boss on the block. The lower, outer hole is the one that leads from the oil pump, not the inner one inside the threaded filter adapter. If you were to flush some solvent and then blow some compressed air though that hole, it might flush the crap out of the pick-up screen and back into the pan, then hopefully out the drain hole. Follow with compressed air to blow other stuff loose and dry the solvent. Compressed air by itself may do the job but I'm thinking some solvent to loosen things up. I have also heard of people sticking a wire or long, thin screwdriver through the drain hole and scraping the filter screen with it. Worth a shot?

 

The information sticker on the valve cover says 351(W) I was just assuming that meant Windsor.

Hey we think alike, I already forced some hot oil down that hole and yes, some carbon did come out. I had thought about the solvent idea also but wasn’t sure if any leftover solvent would harm anything? Compressed air is an excellent idea I’ll try that next.

Yes I tried coming in from the other end. Exit only. There is some sort of cover behind the hole that is raised off of the bottom of the pan about a half-inch. I could drill a hole in that cover but I think I could make my problem worse with adding metal shavings.

Thanks for the info Dan, if anything else comes to mind let me know..

 

Hot oil? Hmm...Hot Oil Treatment for your engine...with good marketing, you could make a fortune selling it to the yuppies!

Yeah, there's a cover around the screen and it has to sit pretty close to the bottom of the pan. The solvent shouldn't really harm anything, just make sure you get it flushed out, maybe pour some Marvel Mystery Oil down after it and use lots of compressed air. Me, I'd probably even shoot some carb cleaner down there, but I'd for sure dry it really well and pour oil in there afterwards.

Yes, W does mean Windsor, I just haven't seen one with a valley pan. Is the thermostat in the front of the manifold or in the block?

 

It’s in the front of the manifold, that is the reason I had to replace this manifold. The guy that had it before me broke the bottom of the cast iron bolthole and JB welded the thermostat housing to the manifold, then sold it to me. It then started overheating so I went to replace the thermostat and I found his quick fix. I tried to copy what he did but I couldn’t get a good seal. I then started pricing out manifold and found a guy who was getting rid of his 4bbl setup. I had a 2bbl, so what the heck I’ll put the 4 bbl on it. I push snow with this truck I could use the extra umph.

The hot oil treatment worked! I started it up this morning and drove it around for about an hour. Kept good oil pressure the whole time. I’ll probably drain it use some carb cleaner like you said and force some more oil down there just in case. Thanks for the advice your check is in the mail.

 

Thanks, but we poor moderators work for free...!

Glad it worked out. Sure beats the heck out of dropping the pan!

Sounds like you do indeed have a Windsor. I'll have to look into that valley pan thingy though...

 

Thanks again.