Another question for anyone who's dissected a Keel twinscrew manifold
06-18-2009, 09:35 PM
#1
Three Wheelin'
Thread Starter
Another question for anyone who's dissected a Keel twinscrew manifold
I'm having new plates made for the lower section of my Keel twinscrew manifold. I'm going to have 1 flat plate made (in case I ever decide or need to ditch the intercooler) and a "regular" replacement one.
These will be thicker to resist warping, and milled, to be flat.
The Keel manifold has very big holes on the bottom plate relative to the size of the bolts that go through them.
The OEM manifold has rubber inserts which (could) permit the manifold to float above the heads. It also probably makes it easier to align the bolts when installing the the intake, and permits some variation between engines.
We noticed that it's possible to make a plate that lines up perfect with the bolt holes implied by the original manifold, or possible to make a plate that lines up perfect with the bolt holes in the heads, but not both. The difference between the two is not large, but somewhere between 1 and 2 mm.
I recall other posts that said the timing between cams is different, and that the timing becomes more closely aligned as the engine warms and expands.
I was theorizing that the OEM manifold has the rubber inserts in order to permit the distance between the heads to widen as the engine expands, without putting an inordinate amount of stress on the manifold, which because it's located between each bank, effectively ties the two halves together.
Does this sound plausible?
I'd like to keep the bolt holes as small as possible, but I don't want to create potential stresses as the engines warms.
I thought that Andy was just being lazy/imprecise in making the lower bolt holes much larger than they needed to be, but perhaps there was a good reason for doing so, which was giving the engine/manifold the ability to expand at different rates without binding or stressing the contact/mounting points.
Thoughts on the above are appreciated, especially by anyone who's actually BTDT.
These will be thicker to resist warping, and milled, to be flat.
The Keel manifold has very big holes on the bottom plate relative to the size of the bolts that go through them.
The OEM manifold has rubber inserts which (could) permit the manifold to float above the heads. It also probably makes it easier to align the bolts when installing the the intake, and permits some variation between engines.
We noticed that it's possible to make a plate that lines up perfect with the bolt holes implied by the original manifold, or possible to make a plate that lines up perfect with the bolt holes in the heads, but not both. The difference between the two is not large, but somewhere between 1 and 2 mm.
I recall other posts that said the timing between cams is different, and that the timing becomes more closely aligned as the engine warms and expands.
I was theorizing that the OEM manifold has the rubber inserts in order to permit the distance between the heads to widen as the engine expands, without putting an inordinate amount of stress on the manifold, which because it's located between each bank, effectively ties the two halves together.
Does this sound plausible?
I'd like to keep the bolt holes as small as possible, but I don't want to create potential stresses as the engines warms.
I thought that Andy was just being lazy/imprecise in making the lower bolt holes much larger than they needed to be, but perhaps there was a good reason for doing so, which was giving the engine/manifold the ability to expand at different rates without binding or stressing the contact/mounting points.
Thoughts on the above are appreciated, especially by anyone who's actually BTDT.
06-18-2009, 10:16 PM
#3
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
I suspect you are right. The thick rubber-like gaskets between the S4 manifold and the heads is more edidnece that they knew it as all going to adjust itself some as relative temps changed.
06-19-2009, 12:49 PM
#4
Three Wheelin'
Thread Starter
Thanks, Dr. Bob.
I think Andy was never in a position to turn this into a "serious" business like Tim or D.R. The kits went thru a lot of variations (though I think each variant was an improvement over the prior one), there were delays in getting kits shipped, there were some issues re: quality control/completeness of the kits, and I think Andy was trying to keep the costs low so he ended up taking a pretty big financial bath on the project.
He was a little on the thin skinned side, but I remain impressed with what he was able to accomplish as a DIYer. The kits do work, and work pretty well. He flew out from Atlanta to help Pete Watson and me install our kits, which I always thought was a pretty stand-up thing to do.
I think Andy was never in a position to turn this into a "serious" business like Tim or D.R. The kits went thru a lot of variations (though I think each variant was an improvement over the prior one), there were delays in getting kits shipped, there were some issues re: quality control/completeness of the kits, and I think Andy was trying to keep the costs low so he ended up taking a pretty big financial bath on the project.
He was a little on the thin skinned side, but I remain impressed with what he was able to accomplish as a DIYer. The kits do work, and work pretty well. He flew out from Atlanta to help Pete Watson and me install our kits, which I always thought was a pretty stand-up thing to do.