Matching Ports And Shortening Side Bolts

[c_r_thomson 0]

I got my inlet manifold for my Carb conversion today and i have to match up the ports as expected. Can i just use a dremel to widen the ports on the manifold to match the ones on the head?

 

Also, the bolts at each end of the intake prevent the manifold from fitting flush. What's the best way to adjust for this? Hack off a bit of the original bolt or "make" a shorter one from a new M8 bolt?

[c_r_thomson 0]

Someone must have been through this.

 

Any ideas?

[Ahl 4]

I got my inlet manifold for my Carb conversion today and i have to match up the ports as expected. Can i just use a dremel to widen the ports on the manifold to match the ones on the head?

Shouldn't be any problem with that, just make sure you port match it first and that you do it carefully.

[Beastie 1]

Shouldn't be any problem with that, just make sure you port match it first and that you do it carefully.

 

 

Also take care to note how repeatable the fit of the inlet manifold is to the head. If it bolts up in a different place every time due to clearance in the bolt holes then it's going to be pretty difficult to know whether the ports are matched or not on final assembly. Traditionally the solution to this is to arrange for dowels or else a pair of dowel - bolts to locate the position of the manifold in a positive fashion.

 

More recent thinking tends to render the port matching and the dowel theory somewhat obsolete though: The intake obviously should flow only in one direction ie: from the atmosphere into the engine. Therefore a port mismatch is not a problem provided that the step is only encountered in the reverse direction (eg: the hole at the port end of the manifold is widened in excess of the diameter of the port in the head). This design will flow well in the direction intended but will flow badly in the reverse direction. This can be helpful when trying to counter reverse flow caused by valve timing overlap.

[Jonmurgie 2]

A picture speaks a thousand words... get some posted and I'm sure more people will pipe up with their thoughts

[Guest ashnicholls]

I did the port matching as described. and just just cut the studs down to suit on either end.

[c_r_thomson 0]

Ok, shortened the two bolts at each end.

 

After reading Beastie's post, I left the ports alone.

 

I'm sure any difference will be negligable. I hope!