3.0 Exhaust Manifold install and bolt length issues.

[boater364]

I?m stumped?. I decide to change my exhaust manifold because I had no idea of the age. I purchased? GLM Part Number: 51214 replace Mercury Part Number: 806867A12 for my engine serial 0F356496, Model No: 430L100HS. I used a flat file to remove all the paint and cleaned up my block very well. I installed the Manifold with the gasket provided. I used the original nuts for the 2 studs in the front, then original 3 grade 5 bolts 3/8 x 4 5/8 . When I insert the 3 bolts, the rear bolt can be screwed in a few threads, the middle 2 I can only get it to grab maybe 1 thread, but I don?t want to try torque it down because I?m afraid ill rip the single tread out. .

The bolts are not bottoming out on the gasket, the head of the nut is hitting the manifold.

The manifold is setting tightly against the block. I did briefly check the block with a straight edge by eye,, no feeler gauges and it did not see it warped, especially not ? inch warped!

From what I see on the old manifold and the bolt discoloration, they should be inserted ? inch into the block. Correct?

GLM calls for OEM stud 10-53728 which I believe is 3/8 x 4 5/8 and have, my engine calls for Merc 52143 which is listed in part diagram as ?SCREW, (.375-16 x 4.75)?.

My gut wants to get a grade 5 3/8x5 bolt maybe 4 7/8 and try that and get back onto the water but the techie part of me wants to figure the root of the issue.
What do you think? Have you seen this before? Should I pull the manifold and take measurements and contact GLM. I did not want to pull the manifold because those rubber boots on the elbow are a pain and shift.

 

[alldodge]

Been several folks which have had issues with GLM manifolds fitting. Bondo mentioned he have to shave his down to flatten them out but didn't hear anything about bolt length. Did you try seeing how far the bolts protruded out through the manifold before installing?

 

[boater364]

I saw that post last night while researching. I'm probably going to pull the manifold at lunch measure the hole length and compare to the original. I'm also going to check the manifold for flatness. I take pictures... thanks for the reply.

 

[Bt Doctur]

While you at it, run a tap to chase the threads in the block

 

[Fishermark]

Definitely pull the manifold back off and see how far out the bolts stick through. You may have to buy longer bolts. Bondo's issue was at the top where the elbow attaches.

 

[boater364]

I pulled the manifold and took measures and all the holes are within a 1/10[SUP]t [/SUP] of inch different.

The matting service is flat and even.

Starting from the back, the last hole is, 4 3.2/10, the next hole is 4/10, and next hole is 4.2/10.

The engine block is 7.5/10 so it?s ? deep. And the gasket is almost 1/10 of an inch.

So what should I do? Should I try to return manifold. Should I get 5 inch bolts? If so will any grade 5 bolts work?

 

[alldodge]

I pulled the manifold and took measures and all the holes are within a 1/10[SUP]t [/SUP] of inch different.

The matting service is flat and even.

Starting from the back, the last hole is, 4 3.2/10, the next hole is 4/10, and next hole is 4.2/10.

The engine block is 7.5/10 so it’s ? deep. And the gasket is almost 1/10 of an inch.

So what should I do? Should I try to return manifold. Should I get 5 inch bolts? If so will any grade 5 bolts work?

Something doesn't add up, the old and new manifolds are within 1/10 of an inch. The pic of the old bolt above shows it has close to 1/2 inch thread being used. You put the new manifold on and you get only 1 to two threads. When you stick the old bolts through the old manifold do they show the same penetration?

 

[boater364]

Sorry bad wording, I do not have the old manifold to measure here today. I have it at my father in laws house. The difference of 1/10 is between the 3 bolts on the GLM manifold... I thought it was odd that I could get the last bolt to grab but not the front two.

 

[alldodge]

Sorry bad wording, I do not have the old manifold to measure here today. I have it at my father in laws house. The difference of 1/10 is between the 3 bolts on the GLM manifold... I thought it was odd that I could get the last bolt to grab but not the front two.

I would contact GLM or where you got the manifold and ask them why is the manifold thicker. If they cannot supply a good reason for it, either return or get longer bolts. About any Grade 5 bolt will work, Grade 8 is even better.

 

[Bondo]

Ayuh,.... So how much bolt threads protrude through the manifold casting,..??

Ya need 'bout 1/2" to 3/4",.....

 

[boater364]

Ignore the circular dial, its broken, look at the slide ruler.

This one i can get it to grab a few threads...






This one i think I feel it grab one thread but i dont wanna toque it...





This one went all the way into the manifold without hitting the threads and would just spin..

 

[Bondo]

Ayuh,.... That bolt in the pictures, needs to be 1/2" longer,.... gr. 5 are fine,....

 

[Alumarine]

1 is definitely too short, but aren't they all a bit short?
How deep are the threads in the block?

 

[boater364]

the block is 3/4 inch deep. I got over to my father in laws house and the old exhaust manifold are 4 1/10th, so these are roughly about 1/4 inch to wide. I have a email in GLM tech support, lets see how they handle this.

 

[fishrdan]

If all the bolt holes measure the same depth, I'd just buy new fasteners the correct length and bolt it on. If the holes are different depths (bolts sticking through more-less) it sounds like the casting may not have been machined parallel, same thickness all the way across.... Which might be the case as from looking at the pics from top to bottom the bolts threads sticking through are 4-3-2 (top to bottom)

 

[boater364]

I put 5 inch bolts on and it seemed to do the trick...

Here's the reply from the technician over at GLM:

I measured our 21745 and it measures 4-5/8? the stud 22475 measures 5-3/8? the bolt 21745 sticks out 3/8? and the stud 22475 I think is closer to 5/8? there has never been an issue with the bolts being too short if he needs a longer bolt we probably have something that will work.