Aluminum SBC exhaust
02-26-2008, 05:43 PM
#32
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I see that a lot of theese companies who are offering "mid level performance" exhuast have notes that they are only to be used with stock cams. Most seem to be setup with stock style risers.
Are the riser designs the culprit for reversion issues?
Could I go with a "mid level" manifold with a stainless tubular riser and still be safe with a bigger cam, or am I way off base here?
Are the riser designs the culprit for reversion issues?
Could I go with a "mid level" manifold with a stainless tubular riser and still be safe with a bigger cam, or am I way off base here?
The farther away from the motor the water and exhaust mix the less chance of reversion. Buying a mid level manifold like the Rev's, Kodiak, EMI, etc and having a custom long riser made is going to be $$. Your better off paying upfront for Lightnings or CMI's or getting the Imco or EMI's with the long risers made for larger cams.
I've found that 350 ci SBC with stock manifolds, risers and thru hull revert right around the 224* duration range. It's mainly the fuction of the overlap the cam has. A 224/224 114+5 did not revert while the 224/224 112+4 did.
My last 355 I ran a 226/230 112+2 hyd roller with aluminum Glenwood Magnaflow manifolds and FastGlass stainless short risers. I had tiny droplets of water in the center runners at idle. I used stainless tubing and welded on 8" extensions to mix the water and exhaust further back. No reversion after that.
My current 385ci with a 234/240 112+4 hyd roller with the same setup has a few small droplets in the center runners. I will be extending the exhaust portion another 4" right into the tip to kill the reversion. It will be a virtually dry system as water does not mix with the exhaust until the tip.
Doing this you must keep the extensions from touching the exhaust hose as it will burn thru quickly. Makes it tough when your tips are not at stock location like mine.
02-26-2008, 06:38 PM
#34
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KE, thanks for the read. Now you really have me wondering. Theese are going in a 28Cig and the engines are being built now, we havent decided on a cam or exhuast yet.
The boat sits extremely low in the water and under normal load the exhaust tips are submerged to the tops of the tips.
The first pic is the stock exhuast setup and thats pretty much exactly how it sits in the boat, the seccond two pics give you an idea of how low it sits and the angle it sits at. From some rough measurements and guessing I would say that this is a little short of the 13" minimum between the riser tops and the waterline. The ***** is there is no room under the existing hatch for riser extensions.
The boat sits extremely low in the water and under normal load the exhaust tips are submerged to the tops of the tips.
The first pic is the stock exhuast setup and thats pretty much exactly how it sits in the boat, the seccond two pics give you an idea of how low it sits and the angle it sits at. From some rough measurements and guessing I would say that this is a little short of the 13" minimum between the riser tops and the waterline. The ***** is there is no room under the existing hatch for riser extensions.
