Convert to replaceable idle air bleeds?

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I don't think the in-the-well IFR position is as subject to reversion as the top position.

Again this is more radical than anything I've dealt with. So I would go want to see what is repsonding.

a. Exactly as it is, stick some wires down the secondary IABs. See how the AFR, vac and engine responds.
b. Open the primary throttles a 1/4 turn, and close the secondary throttles about the same.
- then see whether the idle mix screws are responsive
- try (a) again.
c. if opening the primary throttles and decreasing secondaries increased engine rpm, then reduce secondaries more or reduce timing a couple degrees.

There's nothing sacred about a square transfer slot. It's just an easy way to visualize a typical starting point.

(I'll cross post to RFS later if the discussion hasn't already moved beyond)
 
DrCharles said:
OK, so maybe I won't move the IFR
Click to expand...
The primary blocks are in the well too ?
Once you get a hang of drilling and tapping, its not that hard to return it to the high position if needed.
 
DrCharles said:
OK, so maybe I won't move the IFR ;) What cam are you running again?

First thing is to fix the wideband. Probably carbon on the sensor tip. Without the gauge, tuning is unnecessarily difficult!

The return of the dreaded flat spot may be related to t-slot exposure on both primary and secondary. My new baseplate does not have holes in the butterflies... but since I drilled my main body for bypass air, I only have to add holes to the adapter in the air cleaner stud opening.
Click to expand...


I would try lowering it because that is really where it SHOULD be.

I'm 281/281 255/255 .620/.620 on a 105 in at 105.

I pulled the intake tonite, and tomorrow I'll look and see how my much work it is to fit that antireversion plate on it. If it's a couple of hours of TIG welding and a couple of hours of grinding, I may go for it.

If it looks like more than that, I'll put it back on and run it until next winter.

I suspect that's why mine wanted them up higher even though it shouldn't want that.

I think some of that reversion is pissing it off and keeping the IFR up seems to dampen that.

Obviously I'm guessing at what's happening, but right now, that's my working theory.
 
Mattax said:
I don't think the in-the-well IFR position is as subject to reversion as the top position.

Again this is more radical than anything I've dealt with. So I would go want to see what is repsonding.

a. Exactly as it is, stick some wires down the secondary IABs. See how the AFR, vac and engine responds.
b. Open the primary throttles a 1/4 turn, and close the secondary throttles about the same.
- then see whether the idle mix screws are responsive
- try (a) again.
c. if opening the primary throttles and decreasing secondaries increased engine rpm, then reduce secondaries more or reduce timing a couple degrees.

There's nothing sacred about a square transfer slot. It's just an easy way to visualize a typical starting point.

(I'll cross post to RFS later if the discussion hasn't already moved beyond)
Click to expand...


I agree the lower IFR should be less subject to reversion. And it may be. I know my engine wants it up high and I'm blaming reversion. I could be way out in the weeds as to why. That's why I bought that antireversion plate. If I put that on and it doesn't help than my working theory sucks.
 
Ok, I'm as full of crap as a Christmas goose.

It's not an antireversion plate, it's a visner engine development SHEAR plate.

Not sure if that makes a difference, but I wanted to correctly say what I'm going to try.
 
yellow rose said:
Ok, I'm as full of crap as a Christmas goose.

It's not an antireversion plate, it's a visner engine development SHEAR plate.

Not sure if that makes a difference, but I wanted to correctly say what I'm going to try.
Click to expand...
I don't even know what that is!

I bought into Larry Meaux and even more so Calvin Elston's discussions about reversions on the exhaust side. I didn't go for a specific anti-reversion part, but in 2016 went all out on the small diameter tubes right off the head and the getting all the section lengths close to the numbers pipemax indicated. I *think* its helped. Car seemed happier but I didn't have time to try to quantify it. Logger was out, no time to mess with stuff and I needed the car, so just drove the heck out of it. :)
 
Mattax said:
I don't even know what that is!

I bought into Larry Meaux and even more so Calvin Elston's discussions about reversions on the exhaust side. I didn't go for a specific anti-reversion part, but in 2016 went all out on the small diameter tubes right off the head and the getting all the section lengths close to the numbers pipemax indicated. I *think* its helped. Car seemed happier but I didn't have time to try to quantify it. Logger was out, no time to mess with stuff and I needed the car, so just drove the heck out of it. :)
Click to expand...


I looked at several things to dampen some of the pulses the reversion causes. It seemed the shear plate was the best option.

What I'm not thrilled about is I'm out of room and can only squeeze a 1/2 plate in there. I'd rather have a 1 inch but I'd have to leave the hood partially open.

I like these shear plates because they not only have a groove around the holes (which is why I have to modify the top of the intake because it's blocking those grooves) they use a 7.5 degree (IIRC) taper on the holes to control the pressure waves in the plenum.

Again...this is a working theory and it's probable I'm way off the mark here. BTDT many times before, but at this point, it's the only modification I can think of to make it so I can lower the IFR's where they should be.
 
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