Manifold Hitting the Block

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vames

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72 Swinger. 318 Long story short: I had a reman 318 put in the car and it came back with a cracked driver exhaust manifold near where one of the center bolts went through. I obtained a good manifold (same stamp 2951123) from a kind forum member here and brought it all to an exhaust shop that deals with old cars.

The guy at the exhaust shop told me that the manifold is hitting the block (or maybe the head) where it curves down and around to connect to the pipe. He says the old manifold has marks on it where it was ground down to fit at some point. It appears that the old one cracked because it got torqued down when there was still a bit of clearance issue on the reman engine. He is going to attempt to grind some material off the manifold in a similar manner that the old one was ground, but warned me that there's a chance we ruin the manifold in the process.

I don't know the # of my reman 318 block, (I assume it was from a year close to 72), and I wasn't aware that there is an issue of block/manifold compatibility (i.e. I thought manifold differences were about clearing the PS box, not about whether they actually fit on the engine).

Has anyone run into a similar problem?

I know some will tell me to get headers and that may be the ultimate answer, but I'm really just trying to get a nice driver going. Performance is not my goal here -- just a working car without an exhaust leak -- and I assumed that stock components were the most surefire way to get there.

I'd be thankful for any and all advice here. The car is at the shop and I'm at work, so I asked him to send me pictures and I'll add them if he does.
 
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Having the same problem with 318 manifold hittin 360 head it never hit the 318 head don't know what the problem is. I bought a log style gonna see if that will work
 
Okay, here goes:
A reman engine can be other than your specific year. Most likely yours has later heads on it, say '73 and later. These have extended exhaust port surfaces on them, some may be drilled for air injection systems, some may not.
Early style heads/exhaust ports:
OIP.9ZnKL5WUjsf_0-4B4o8PJQHaDP?w=350&h=153&c=7&r=0&o=5&pid=1.jpg

Later style heads with larger exhaust port surfaces and air injection holes drilled:
upload_2021-11-3_16-4-5.jpeg

The issue is where the driver's side manifold drops down to it's exit- it is, out of necessity, very close to the cylinder head in order for it to clear the steering column.
OIP.BFpnR8q7_UWzHXteFBxYTwAAAA?w=199&h=159&c=7&r=0&o=5&pid=1.jpg

This can often result in clearance issues with the head's #7 exhaust port surface.
The solution, as tempting as it may be, is not to grind the head- there is a water jacket not far beneath the surface, and if you cut into the jacket, the head is junk. Yes, I've done it. If the interference is extremely minimal, you may be able to barely touch the offending area with a grinder- but no more than that. A bit can also be taken off the manifold, but again, don't get carried away- too much can weaken the manifold and it can crack after a few heat cycles.
Try a nice, thick exhaust gasket- sometimes it gains you just enough room to clear everything.
OIP.Y_IAZvFXhVuzn4xNBxtmYAAAAA?w=142&h=159&c=7&r=0&o=5&pid=1.jpg

Make sure you get 273/318 specific gaskets, the larger port 340/360 gaskets can have sealing issues on the 318 heads/manifolds.
If that's still not enough clearance, then you need to get a "header flange"- a piece used by guys who fabricate their own headers. They're typically 5/16-3/8" thick.
upload_2021-11-3_16-25-39.jpeg

Sandwich it between the manifold and the head (no gaskets), and your interference issue goes away. You *may* need longer exhaust studs & bolts for this.
The last option would be to use a '73 and later manifold, made to clear the newer heads.
I have also run into a similar issue when using 340 manifolds on Magnum engines. I had to use the header flanges on that, too.
 
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72 Swinger. 318 Long story short: I had a reman 318 put in the car and it came back with a cracked driver exhaust manifold near where one of the center bolts went through. I obtained a good manifold (same stamp 2951123) from a kind forum member here and brought it all to an exhaust shop that deals with old cars.

The guy at the exhaust shop told me that the manifold is hitting the block (or maybe the head) where it curves down and around to connect to the pipe. He says the old manifold has marks on it where it was ground down to fit at some point. It appears that the old one cracked because it got torqued down when there was still a bit of clearance issue on the reman engine. He is going to attempt to grind some material off the manifold in a similar manner that the old one was ground, but warned me that there's a chance we ruin the manifold in the process.

I don't know the # of my reman 318 block, (I assume it was from a year close to 72), and I wasn't aware that there is an issue of block/manifold compatibility (i.e. I thought manifold differences were about clearing the PS box, not about whether they actually fit on the engine).

Has anyone run into a similar problem?

I know some will tell me to get headers and that may be the ultimate answer, but I'm really just trying to get a nice driver going. Performance is not my goal here -- just a working car without an exhaust leak -- and I assumed that stock components were the most surefire way to get there.

I'd be thankful for any and all advice here. The car is at the shop and I'm at work, so I asked him to send me pictures and I'll add them if he does.
Yes, depending on what heads you have and what manifold you are trying to install, you may have a issue.
 
On my 273 with later 318 head I had to double up the gasket on the drivers side to get clearance.
 
Thanks everyone -- especially Professor Fate -- for the input. I'm guessing that as you said, I have a '73+ head that has those extended ports. If the shop grinds the manifold and ends up ruining it or not being able to make it fit, I'm trying to prioritize my next moves.

1) Obtain a 73+ manifold. Would I have problems with clearing my 72 car's power steering box? Any other considerations?

2) Similar manifold with a fatter gasket -- does anybody have any gasket suggestions?

3) Similar manifold with a spacer (Header Flange). Seems like this would move the manifold out for clearance, but the ones I see do not look like they would cover the extended exhaust port surface on the 73+ head. Would this be a problem?

I say it all the time, but this forum is fantastic. Thanks all for paying attention to me and my car!
 
Glad that I just read this. I just overhauled my '72 318, not in yet, and just have 2 nuts on finger tight holding the left exh manifold on. Looked at this area and yes it is tight, but OK. What I did notice is the manifold is ever so slightly warped, and definitely will need to have a gasket. Going to post the passenger side manifold problem, heat riser.
 
Thanks everyone -- especially Professor Fate -- for the input. I'm guessing that as you said, I have a '73+ head that has those extended ports. If the shop grinds the manifold and ends up ruining it or not being able to make it fit, I'm trying to prioritize my next moves.

1) Obtain a 73+ manifold. Would I have problems with clearing my 72 car's power steering box? Any other considerations?

2) Similar manifold with a fatter gasket -- does anybody have any gasket suggestions?

3) Similar manifold with a spacer (Header Flange). Seems like this would move the manifold out for clearance, but the ones I see do not look like they would cover the extended exhaust port surface on the 73+ head. Would this be a problem?

I say it all the time, but this forum is fantastic. Thanks all for paying attention to me and my car!
1) As long as it's an A body manifold, it will clear your steering with no issues. Unsure which year exactly they went to the larger port surface, but '73-'74 is a ballpark figure- I know for sure they were present on '75s, have one sitting in my garage.
2) Looking around to see what's available (lots of things out of stock right now...), something like the Fel-Pro MS90460 or similar should work.
PLYMOUTH Fel-Pro MS90460 Fel-Pro Exhaust Manifold Gaskets | Summit Racing
@66signet 's suggestion above- doubling up on the gasket (you'll have two anyway) can also work if you need a hair more clearance. I'm not fond of doubling them up, but you gotta do what you gotta do!
3) Shouldn't be a problem.
 
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OK it turns out the head doesn’t have those bigger exhaust ports. Just needed a thick gasket and the slightest bit shaved off the manifold. Now it’s sealed.
 
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