Before doing my port matching I made some collars for the exhaust manifold and locating pins for the intake. Now I can be sure they go on in the same position every time.
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| gasket matching https://slantsix.org/forum/viewtopic.php?t=59624 |
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| Author: | Dugr [ Tue May 10, 2016 12:45 pm ] |
| Post subject: | gasket matching |
When it comes to a bit of porting, and more specifically gasket matching should the gasket be raised up on the bolts before scribing the ports? I see comments about installing the intake on the engine stand with the engine upside down so the intake will hang at a slightly raised position. |
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| Author: | CNC-Dude [ Tue May 10, 2016 1:58 pm ] |
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Unless you verify the port alignment of the intake and exhaust manifolds to the head ports when you bolt them together, you may need to make them align to the head first. Otherwise, port matching to the gasket may be futile. Since these engines and most other inlines don't have a way to accurately index the intake/exhaust to the head when you bolt them together, you may have to get creative to make sure they bolt back together indexing the ports to each other so you can get the best benefit from port matching if you do it. |
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| Author: | Joshie225 [ Tue May 10, 2016 2:10 pm ] |
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Who says the gasket ports are the correct size? The exhaust ports should be a little smaller than the ports in the exhaust manifold. The intake ports at the head are already slightly larger than down the port. There's generally no good reason to be grinding in there. |
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| Author: | ProCycle [ Tue May 10, 2016 2:27 pm ] |
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Before doing my port matching I made some collars for the exhaust manifold and locating pins for the intake. Now I can be sure they go on in the same position every time.
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| Author: | CNC-Dude [ Tue May 10, 2016 3:13 pm ] |
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ProCycle, a lot of people just don't realize what is involved in properly gasket matching a head and intake/exhaust ports. That's the only way to make it worth the effort and of any benefit. |
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| Author: | 1930 [ Tue May 10, 2016 3:31 pm ] |
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Quote: Before doing my port matching I made some collars for the exhaust manifold and locating pins for the intake. Now I can be sure they go on in the same position every time.
Great job
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| Author: | slantzilla [ Tue May 10, 2016 3:34 pm ] |
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David Vizard's Holley tuning book has very good directions about how to lay out the head and intake for matching. On a fairly stock motor it can cause more problems than it helps. |
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| Author: | Badvert65 [ Tue May 10, 2016 3:41 pm ] |
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I figured, if they expand and contract so much that they have the special fasteners, what's the point of matching the ports? I'm jus sayin... |
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| Author: | CNC-Dude [ Tue May 10, 2016 6:07 pm ] |
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They don't expand enough to become mis-aligned, cast iron manifolds expand the same as the cast iron head. Even an aluminum intake doesn't expand enough to cause any issues with port alignment. With that logic, no head and intake/exhaust ports on any engine could be port matched, and that simply isn't the case. |
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| Author: | Badvert65 [ Tue May 10, 2016 6:47 pm ] |
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OK, I'll concede that point. Port matching can be effective but I don't really know how much things move around on a slant. I just know they move enough that I tightened the fasteners down too much and the manifold cracked. |
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| Author: | Joshie225 [ Tue May 10, 2016 6:54 pm ] |
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The exhaust manifold sure expands a lot more than the cylinder head. |
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| Author: | Jerame_c [ Tue May 10, 2016 9:40 pm ] |
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when I port matched my head i used the stock steel gasket as my guide, it has smaller port holes than a modern style gasket and guarantees the new gasket won't protrude into the flow area which is counterproductive. Also based on what i saw port matching will help even if it isn't perfect. I had some ports i took almost an 1/8 inch out of one wall because they were so filled in. while you are at it, even if you don't take much of anything off of the valve guide bosses, at least deal with the major casting flash on some of the seams in the ports. |
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| Author: | Killer6 [ Fri May 13, 2016 11:10 am ] |
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Quote: The exhaust manifold sure expands a lot more than the cylinder head.
Josh is 1000% correct on this one, the special flat sleeve washers on the ends w/lock nuts and the torque specs given are specifically there to allowfor expansion, and to reduce the tendency to crack. Port match is simple, holes in the head bigger for the intake,holes in the manifold/header bigger for the exhaust. Performance offsetting "UP" is only effective if you can realistically assemble things that way in the vehicle,which leaves out most headers. The best thing you can do is to mod the intake center hole to raise it so that it can't "drop" on you while installing, same for the exh. outer holes, that doesn't mean to make them tite,just lower so the mannys sit higher. The gasket should be resting as it would on install,if it's not high enuff at the ports you need a diff./modded gasket. Left & right align will be OK if the holes are centered as ported as they will want to center naturally in the upper radius. Intake manny "tilt" can be a small challenge,most of us I'm sure have done the "all the way up,then all the way down,then just split the diff. by eye" job, align. pinning the cool int. should be fine. |
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