exhaust cross-overs??
 

Hello-
I recently had to pull off my upper & lower manifolds to fix a water leak at the rear of the lower manifold. I've only had my manifold off a couple of times since the rebuild so I'm not real familiar with my Edelbrock Performer RPM cylinder heads & the proper gaskets to use, etc. I did notice that in the middle of both of the lower manifold gaskets (that match up to the top of the heads) there is a hole about 3/4" in diameter inbetween the 2 center bolt holes, on both heads. I did not know until now that these holes need to be plugged with a heavy duty, coated, cardboard gasket insert thing that was supplied with my fel-Pro gasket part#1250. Last time I pulled off my lower manifold I forgot to install the insert to plug these exhaust cross-over holes. The result was excessive oil spitting out of my oil breather at full throttle. I knew something was wrong right away, even though power was the same and the engine ran perfect. I'm so glad I figured out the problem. But I still have some questions about these exhaust cross-over holes...so here they are:

What is function of these exhaust cross-over holes?

Why do I need to plug them on a 302?

I can't remember, it's been a while....but do the stock 5.0 cylinder heads have these same exhaust cross-oer holes?

The Fel-Pro gaskets set that I bought (#1250) had 2 different sets of these inserts. One to plug the exhaust holes, another to keep them open.
What kind of motor (or size?) would need to run with these exhaust holes open?

Those holes are for the EGR system. You will notice the same holes on your lower intake manifold. Thos holes go to the center of the intake (that little hole on the top of the lower, and on the bottom of the upper). Then there is a crossover that takes the gasses to your EGR spacer.

If you have it blocked off disconect the coolent lines to the spacer because they are not needed.

I should also add that you should keep it all conected. The EGR system dosn't function at WOT so it will not cause you a hp loss.


Wade

exhaust cross-overs??
 

Hmmm....
You got me thinking now. I've had my coolant lines that run through the EGR spacer itself, disconnected for years now. That was one of the old tips way back when, thinking that the coolant was heating up the EGR more when hooked up then when not. I've since read that that is really not the case. So here's a question for you:
If I simply hook my coolant lines back up to the EGR spacer...is that going to some how prevent oil from coming out my oil breather, like it has been?
Because that is the problem that I am trying to solve here. When the exhuast cross-overs were open, my engine spit out oil out the filler tube when the motor was at full throttle, With the exhaust cross-overs open my motor was even blowing out the cheaper cork style valve cover gaskets that I used to use. Blowing them right out from underneath the tightened down valve cover! I bought better ones with the metal going through them, but then had to switch from a screw on, stock style oil cap to a open filament breather to allow for the extra exhaust gases flying through my motor.
Please help.
So do the stock cylinder heads have these same exhaust cross-overs as my Edel. alum. heads?

The only way that the crossover could cause excessive presure in the crankcase is if the gasket did not seal around the port. This would allow exhaust gass to be pumped in your engne causing a positive pressure. This would be rare though.

If the EGR system is hooked up reinstall the coolent lines. The hot coolent is much colder then exhaust gasses.

The stock heads have the same crossovers as your performer heads. Performer heads carry a CARB# right? High performance/race heads and intakes will not have the EGR system.

Are you sure the problem is related to your EGR crossover? It could just be blow by, or the dreaded blown head gasket. Hows your coolent leval?


Wade

exhaust cross-overs??
 

What you said above, sounds like what happened to my motor. While I was having the oil blowing problem, I did both a compression test & a leak down test, and everything checked out a-ok. I even did each of those test twice just to make sure my oil problem wasn't being caused by "actual" blow-by (leaking ring, blown head gasket, etc.)

"The stock heads have the same crossovers as your performer heads. Performer heads carry a CARB# right? High performance/race heads and intakes will not have the EGR system."

I think you just nailed it right on the head. My heads do not have a CARB#. They are Edel. Performer RPM heads, part#6025, w/ 2.02/1.60 valves. So I beleive that these are considered performance/race heads, right?! So I guess that would make sense to block off the exhaust cross-over openings, correct?

Thanks for the info. Wade. I'm pretty sure I've figured out the problem. I just don't have time to finish putting my motor all back together until this weekend. I'll let you know how it runs after that. One more question though, if I'm going to block off the cross-overs...then should I still hook up the coolant lines to the EGR? The coolant lines have no effect on the EGR system, do they?

Thanks again-

If you are going to block it off then disconect the coolent lines, they will just heat up the intake for no reason.

I'm kind of confused though... you had the edelbrok heads on when you had this problem right? If so this tells me that your heads have the EGR ports on them and you can still hook up all your smog stuff. You may even pass the sniff test even though it is not CARB leagal.

exhaust cross-overs??
 

Yeah, I'm beginning to get confused myself. Here I thought I identified my problem...but I talked to the Edelbrock tech-line yesterday and he was saying that my #6025 Performer RPM heads might actually be the #6035 heads because those exhaust cross-over holes shouldn't be there on the race/non-smog legal heads?? I bought the heads new from a speed shop a few years ago, with the correct identification of the heads on both the box, and the heads themselves. Everything was marked #6025 though, so I'm pretty sure that information is correct. I think he just confused me more. But he said that if I do end up blocking off the cross-overs that I should keep the coolant lines disconnected from the EGR. But the tech guy also said that I shouldn't use those coated cardboard cross-over plugs that were included in my Fel-Pro #1250 gasket kit. He said eventually they would burn right through. Even though it seems like some type of heavy duty cardboard that is coated on both sides, that does seems logical. Instead, he said to use a small piece of sheet metal and cut it to the same size as the Fel-Pro cross-over plug, but a little thinner...to allow the gasket to compress some. What do you think? He was saying what you were, about how I should be able to leave the exhaust cross-overs open and everything should work fine. Maybe I need to plug them because I DID REMOVE most of my smog equipment, such as: smog pump, hard line from the h-pipe, and all of the plumbing coming from the rear of the cylinder heads. The rear of the heads were blocked off before I put the new motor in. So maybe that is why these holes should be plugged?? Not sure if I mentioned it, but the PCV is new and works fine. Sorry for the long post, and thanks for all the info. so far Wade.

Explorer parts
 

Sorry for the long postings guys. Just wanted let you know that I pulled the manifold over the weekend, changed gaskets, plugged the exhaust cross-overs...and all is well and running good. :D Thanks for the help WADS56!

Simi-