Heat crossover blowby...

-
Ben A...

Ben A...

Well-Known Member
Joined
Jan 14, 2020
Messages
147
Reaction score
53
Location
Los Angeles
Took off the intake manifold on the Duster (LA360) I just picked up
Looks like the heat crossover was blowing into the block? Is this a common issue?
This is an old Holley Street Dominator.

How does this happen? Bad gasket? Installation? Time? Kinda rattled here... I haven't driven the car, but in testing I did notice fresh engine oil was immediately disgusting and I also suspected a vac leak somewhere....

Keep in mind this is AFTER cleaning... there was gunk all over this.

Anything else to look out for now?

Thank you!

IMG_7094.JPG


IMG_7093.JPG
 
If you are referring to the discoloration in the lower middle area, that would be "normal.". It gets fricken hot in there, bein' exhaust 'n all. And cooks oil splashing up against it.
 
67Dart273 said:
If you are referring to the discoloration in the lower middle area, that would be "normal.". It gets fricken hot in there, bein' exhaust 'n all. And cooks oil splashing up against it.
Click to expand...
Okay, that's good to know. There was a decent amount of dark crust also but i cleaned that off.
 
"There could" possibly be a pin hole there "somewhere". I would literally get a magnifying glass out and look very closely. I've seen it before.
 
On aluminum intakes, I like to use putty epoxy and a piece of aluminum flashing to make a plug for each side of the crossover, and then use these gaskets. Fel-Pro Performance Intake Manifold Gasket Sets 1213
The homemade plugs act as a reinforcement for the gasket to keep from it blowing through at the crossover. If your feeling froggy, you could port match the manifold out to this gasket size but it would be quite a bit of material removal because your intake has smaller ports than a set of 318 heads intake ports.
 
Garrett Ellison said:
On aluminum intakes, I like to use putty epoxy and a piece of aluminum flashing to make a plug in the crossover, and then use these gaskets. Fel-Pro Performance Intake Manifold Gasket Sets 1213
If your feeling ambitious, you could port match the manifold out to this gasket size but it would be quite a bit of material removal because your intake has smaller ports than a set of 318 heads intake ports.
Click to expand...

Thank you! That seems a lot more reliable than the sheet metal solutions I've seen :/
Unfortunately I have no choice but to reassemble tomorrow and I probably can't secure that gasket in time. But that's a different problem...
 
I don't like blocking that cross over at all. Heating the carburetor sounds non productive, but it actually helps fuel atomization on a street car. Plus, living in Toronto, you need all the cold weather help you can get, so I'd leave it unblocked. Just one peon's opinion.
 
RustyRatRod said:
I don't like blocking that cross over at all. Heating the carburetor sounds non productive, but it actually helps fuel atomization on a street car. Plus, living in Toronto, you need all the cold weather help you can get, so I'd leave it unblocked. Just one peon's opinion.
Click to expand...

Yup, just a mild -14C out right now... :/ Realistically I don't have time to do it properly anyway and I'm scheduled to get this car safety inspected on Monday.
 
Yes, in that temperature for a steady driver leave the heat crossover open.
 
I would want to check the valve guides and stem seals. Inside the port looks like a bit of oil. Since the crossover is common w 2 exhaust ports, I'd start there. Maybe time to do a set of heads.
 
Just out of curiosity, what prompted you to change the intake gaskets and how long has the intake been on and in use?
 
It would probably be a good idea to put some adhesive backed 120 grit sand or emery paper on a true flat surface (A framing square on a hard flat surface works!) and drag the manifold flanges back and forth to check for high and low spots to check for warpage. That manifold looks like it has non production marks on the flange and may need to be tried or at least need two sets of gaskets to take up the difference.
 
Dana67Dart said:
Just out of curiosity, what prompted you to change the intake gaskets and how long has the intake been on and in use?
Click to expand...

I have no idea how long its been on, but ballpark guess is 15 years? Hard to say.

I purchased a new carb and thought I might as well pop the whole intake off because I had a feeling there was a small vacuum leak (idle high, even with throttle adjust full backed off). Cleaning up, swapping gaskets and reinstalling.
 
High lean idle can also be bad PCV so change the valve while your into it if you haven’t already .
 
Garrett Ellison said:
It would probably be a good idea to put some adhesive backed 120 grit sand or emery paper on a true flat surface (A framing square on a hard flat surface works!) and drag the manifold flanges back and forth to check for high and low spots to check for warpage. That manifold looks like it has non production marks on the flange and may need to be tried or at least need two sets of gaskets to take up the difference.
Click to expand...

im leaning over the car right now! that will be my next step. thank you.
 
Demonic said:
I would want to check the valve guides and stem seals. Inside the port looks like a bit of oil. Since the crossover is common w 2 exhaust ports, I'd start there. Maybe time to do a set of heads.
Click to expand...

I hope you're right because I need an excuse to look for new heads! :)
 
And it’s probably best to assume that it has the stock smog distributor, too. If you choose to advance it past the stock settings, first bear in mind if it’s an EGR unit that it’s not uncommon for them to advance up to 63 degrees of combined mechanical and vacuum advance. They don’t work too well without EGR and could cause overheating and heat warpage with an aluminum manifold. I do know from experience that a 1972 D or W200/W300 3/4-full Ton distributor has a decent non egr emissions exempt curve while being an electronic unit. It’s one you can put on and run and get pretty decent performance with.
 
Last edited:
15 years... that crossover looks normal to me. New gaskets and run it.
 
You must log in or register to reply here.
-

Back
Top