Getting manifolds to fit properly. Thursday, 11-Jan-01 11:56:11 writes: I was trial fitting my carbs to my engine last night and I was having a tough time getting the manifolds not to interfere with the cyl tin. I dimpled the tin so I could at least get the manifold on, but it is still too tight and I think I might have a manifold leak if I leave it like this. I was wondering what you guys do for this since it is a lot harder trying to get this to fit when in the engine compartment. I have German tin and the manifolds are CB Performance aluminum. Do you recommend filing some of the aluminum off of the mainifold? Any suggestions would be appreciated. Brandon Sinclair

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I trimmed the tin so that the manifolds fit easily but still a good, close fit. Do it all while the engine is out, its nearly impossible to fit the tin once the engine is in. (n/t) (Ed) (11-Jan-01 12:57:46)

I had to trim the tin on the underside then bang it in with a hammer and punch (in a sock) (n/t) (Matt Harris) (11-Jan-01 13:39:44)

I cut out a section of sheet metal that made it easy. Looking at the end of the cyl tin. Make 4 vertical cuts where the round sparkplug holes are. Now you should end up with 2, up-side-down "U" shaped slots instead of round holes. Now you can easily ben in the center section to clear a manafold. You may even have to trim the bottom off of the center section so it doesn't interfere with the head. (n/t) (Ohio Tom) (11-Jan-01 17:14:00)

Art Thraen did a killer modification for me... Little or no modifications to the Tin just some bending. he machined the manifold flat where it sits against the tin, and he sort of spotfaced the bolt holes so the nuts and washers sit flat. It works awesome!! I highly recommend it. (n/t) (Harrison Miller) (11-Jan-01 17:40:41)

Oh yeah, they were CB Performance manifolds too. (n/t) (Harrison Miller) (11-Jan-01 17:43:29)

Re: Getting manifolds to fit properly.More>>> (Gary Cooper) (11-Jan-01 19:49:35)

all these modifications didn't specifically mention if the cylinder tin has the internal air vane that routes cooling air directly over the spark plugs (more) (dan ) (11-Jan-01 23:56:50)

I just took my rotory file and cut material off the manifold- here is why I think it's better to modify manifold instead of tin>>>> ( James2) (11-Jan-01


Trimming the tin is not an option and not nessary.

Take and put rags in intakes holes ( to keep unwanted things out). This can be done in car but not too easy.Take short wooden dow about 1 1/2 dia I do this on engine stand so I use hammer handle.Put handle under spark plug hole and hit very hard (once should do) to each hole.Then once inbetween holes at this point you should see the shape (if this is not enough) then you have wide base manifolds and cutting is a must. To cut small slice about 1/4" in the bends to the inside of the spark plug holes then repeat above proceedure and the area will open up for you. The reason I say dont cut up the tin is so you will keep as much cooling as possible for the heads and spark plugs Dont forget to seal around plug boots.

Gary Cooper


nearly all the taiwan tin i've seen lacks this critical factory sheetmetal piece.

the sheet metal i'm running is real german tin, brand new, and it could only be pounded in a minimal amount, because the air vane hits the head.

in order to clear the dellorto manifolds, i had to first grind off part of the air vane where it makes contact with the head, then pound the tin in a little bit, then grind some more on the air vane, little by little.

grinding on the manifold isn't always a good idea, because it may compromise rigidity... and eventually break off the tab(and stud hole) where the manifold bolts down to the head. this is very irritating, if you have ever had it happen...




First off, there is a bunch of extra material in the manifold so that it can be matched to heads with large ports. if your ports are not that big you don't need that extra meat anyways. Cutting the extra material off makes it a LOT easier to fit and remove the manifolds.

Also, if you cut or bend the tin, you are taking a chance of breaking one the spot welds loose, or changing the cooling air flow in a way that's not good.

Of course, if have huge ports in your heads, then you have no choice but to bend the tin.


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