Slant Six Forum
https://slantsix.org/forum/

Intake/Exhaust Port Tolerances
https://slantsix.org/forum/viewtopic.php?t=49875		 Page 1 of 1
Author:  MLC Duster [ Sun Sep 23, 2012 7:40 am ]
Post subject:  Intake/Exhaust Port Tolerances
I did a bench dry fit test of the my super six intake/exhaust manifolds. I looked at two perspectives, 1. the horizontal alignment, and 2. the vertical alignment (from the perspective of the head). A straightedge along the horizontal plane (with exhaust ports 1 and 6 as reference) reveals a 1/16" gap in the remaining ports. Obviously this exhaust manifold is somewhat warped. However, is it warped beyond servicibility? The manual gives no reference to this, however, Dan pointed me to this article that does http://www.slantsix.org/articles/manifo ... unting.htm. In the article, a unitless measurement of 0.1 is said to be tolerated in this horizontal port opening variability. Is this 0.1 inches? If so, I am below that and everything will seal?!

The vertical plane shows the exhaust has a uniform gap. I thought that I read somewhere that this gap is necessary to permit proper movement while heated. Do these tolerances look acceptable to those with experience here?

Image

Image

Image
Author:  MLC Duster [ Sun Sep 23, 2012 8:17 am ]
Post subject: 
I placed a gasket I had on the mated manifolds. The two end holes line up well, but the center hole is a little off. All the ports seem to be adequately surrounded.

Image
Author:  Doctor Dodge [ Sun Sep 23, 2012 8:49 am ]
Post subject: 
Try to get the intake and exhaust "faces" on the same plane, the exhaust manifold will 'adjust" for expansion once it heat cycles a few times.
You may need to "adjust" (ream-out) the 3 intake to exhaust mounting holes in the intake, to allow the exhaust manifold to shift outward, even with the intake manifold port 'face' surface.

Also do a little "off-set" reaming of the centre intake manifold mounting hole, to get the best "horizontal" port alignment possible... and run it.
Basically, "fit & fiddle" to get the best port alignment and gasket compression / clamping forces.
DD
Author:  MLC Duster [ Sun Sep 23, 2012 11:00 am ]
Post subject: 
Thanks. I thought the two outboard holes that hold the manifolds together were threaded in the exhaust manifold. If I ream them out, I'll have to tap for larger bolt. Or can I just ream them larger and use a nut on the opposite side without rethreading them at all?
Author:  Aggressive Ted [ Sun Sep 23, 2012 9:26 pm ]
Post subject: 
Quote:
Thanks. I thought the two outboard holes that hold the manifolds together were threaded in the exhaust manifold. If I ream them out, I'll have to tap for larger bolt. Or can I just ream them larger and use a nut on the opposite side without rethreading them at all?
I reamed mine out as Doc suggested and used two long stainless steel bolts, lock washers and nuts. Also reamed out the center hole and used a large stainless steel bolt to get everything to line up. No leaks!
Author:  65Dodge100 [ Tue Sep 25, 2012 3:49 am ]
Post subject: 
Move your gasket in the last picture so that the center hole in the intake lines up - then grind out the two end exhaust holes and ports to match instead of vice-versa. Everything lines up by the center hole in the intake.

That will get you pretty close. It should line up fine on the intake but I found on mine that I had to remove way too much metal on some of the exhaust ports.

In my case it was best to make a cardboard template of the head ports and use it instead of a gasket. Everyone uses a gasket and gets away with it so mine may have just been made way off.

A template is easy. I used a shirt/gift box. Trace out that gasket you have with the center hole and the two end holes. Cut them out square with an exacto knife. I had a plan for holes for all the other studs that is more complicated and maybe not needed. Maybe best to just hack them out for clearance.

Place it on the head and go around the head ports with a ball-peen hammer just to make an impression in the cardboard. Then cut the ports out with the exacto.

For each exhaust port eg. #3, #2 &#1 cut out an extra .021, .055, & .088 (respectivly) on the inboard side for expansion clearance minimum. Then .097 for the end hole.

Do the same for #4, #5, & #6 and the end hole on the other end. I added an extra .050 to each measurement just in case and still cut out less metal than going by the gasket.

The less metal you remove, the more you have sealing against the gasket.

If your head ports are already ground out to match the gasket forget the whole thing and use the gasket.

You will still need the expansion clearance though or part of your port will be blocked when the manifold is hot. Exhaust hitting this little wall deposits crud and could keep the manifold from moving back as it cools without eating the gasket a little or just hanging up, tearing the gasket or breaking the manifold.

It may not be for everyone. I'm the only one that I know of that has ever mentioned it. I just wanted to do everything I could to make sure I didn't have to do this job again anytime soon.

Danny
Author:  DadTruck [ Tue Sep 25, 2012 9:14 am ]
Post subject: 
65Dodge100

I matched the intake to the cylinder head the exact same way you describe.. a sheet of construction paper, located by the center bolt hole in the cylinder head face, then used a ball peen hammer to mark the port openings. Tapping on the construction paper with a light ball peen, against the edge of the port exits,, preforated the paper nicely,,
then transfered the finished template over the intake manifold, was not much, but there were a few intake inside permiter edges that I had to open.

the exhaust openings in the Dutras had more than ample coverage over the head exhaust port openings.
Author:  Doc [ Tue Sep 25, 2012 10:08 am ]
Post subject: 
Quote:
Thanks. I thought the two outboard holes that hold the manifolds together were threaded in the exhaust manifold. If I ream them out, I'll have to tap for larger bolt. Or can I just ream them larger and use a nut on the opposite side without rethreading them at all?
I ream-out the through holes, in the intake, to give myself additional adjustment "movement" in the direction needed.
DD
Page 1 of 1 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/