Hanging valve?...NO, and another update

[chris401]

If you went 1 full turn down on the adjustment why dont you back them off a quarter turn. 3/4 turn should be plenty.

I hear you. .050” should have put them in the middle of the plunger travel, but I obviously F’d up at least one. And it runs so well once at temp, I’m convincing myself I either stopped for a beer and added another turn to one or just got way off on determining zero before adding a turn. Not like me to miss the basic stuff, but I’ve had my moments.

I have a laser temp gun arriving tomorrow to determine if it’s just one cylinder and then I’ll back that one off. Otherwise, I think I’ll just start completely over and reset them all. At this point, I’ve spent more time talking about it than getting off my ass and doing something.

I’ll report back what I find. Thanks to all for the comments.

Good idea. Find the cold exhaust port. Can you hook up a laptop or scanner into it and see what your temperature sensor values are when cold? If it has a MASS the quickest thing to look at is the air intake or ambient temperature. If it is off that usually causes full time performance issues but won't hurt to see.

[My427stang]

Did you check all the wires with an ohmmeter?

I really doubt it’s a dual plane issue, if you think it is, slap a 1 inch open spacer under it and see what it does

I think vacuum leak or dead wires

[Pentroof]

Did you check all the wires with an ohmmeter?

I really doubt it’s a dual plane issue, if you think it is, slap a 1 inch open spacer under it and see what it does

I think vacuum leak or dead wires

Swapped wires...same issue. New plugs, cap and rotor.

I believe the issue is the progressive linkage on the Sniper. This is a change from stock to alleviate the abrupt tip-in the Sniper has because all four throttle blades roll in together. I have modified the software and added a progressive link that starts activating the rear blades at about 40% of the fronts, to act more like a 4-barrel (and keep my daughter from unexpectedly lighting up the tires). This change and link is available from Holley, but “not advised”. Well, the damn thing is way too touchy with all four barrels opening together.

Anyway, the rear barrels have no fuel being introduced at idle now. I currently have a 4 hole, 1 inch spacer that may be making it worse. The Sniper injects fuel above the blades, so it bounces off the blades, pools momentarily, and then gets sucked in.

I think I have a lot of pooling and condensing going on in the plenum at cold start. 3 minutes later and all is good.

I’m going to try an open 1” spacer instead of the 4 hole. The problem is, the Sniper is known to have an annoying whistle related to the IAC in this configuration. If the cold fuel distribution is better but I get the whistle, I’ll add a 1/8” steel 4 hole plate between the spacer and the throttle body.

[Cyclone03]

Jim I have FAST ez efi .
Back in ‘14 I installed it . It had some oddness to the throttle tip in. The tech guys are,mostly,thinking electrical or setup problems . After almost 2 years I went on Power Tour,I marched right up to the FAST trailer and said hey this thing hates low throttle tip in from a start,it bucks jerks hates life. He asked did you adjust the blades so they move together ? No. Do that and set the IAC just out of the green. Green gives IAC counts between 15-20 if I recall correctly. He suggested 25-30. This closes the throttle blades more and uses more air from the IAC. I did all the above the next morning just as the temp came up but before the fans came on,lowest load possible . Seat of the pants 90% better . The next 8% came from ditching the four hole for an open. I admit I still have a tiny hick up,but it could be the driver forgetting how to modulate the clutch.

I think setting the linkage up to slow the throttle and running all for barrels 1:1 with the blades “more” closed for higher IAC at idle would help.
I have not flipped the Holley TBI over but I think the MAP sensor only reads 1 pair of throttle bores. If so a four hole spacer of any kind would effect performance.

[1968galaxie]

I guess all idling issues are not solved with these electronic carbs.
Electronic or old school carbs seem to require some tuning.

Anyhow - fiddling with cars is half of the fun

Cheers

[Pentroof]

I think setting the linkage up to slow the throttle and running all for barrels 1:1 with the blades “more” closed for higher IAC at idle would help.
I have not flipped the Holley TBI over but I think the MAP sensor only reads 1 pair of throttle bores. If so a four hole spacer of any kind would effect performance.

The Holley IAC procedure is a bit different, but I have it dialed nicely and I’ve never had any issues like you describe. My comment on tip-in was more about how much power came on quickly because of all four barrels at 1:1 and a linear , short throw. Lots of guys are adding an extension to the throttle arm, but that fix results in longer pedal movement. That means either an awkward pedal start location or not accessing full throttle.

[Pentroof]

I guess all idling issues are not solved with these electronic carbs.
Electronic or old school carbs seem to require some tuning.

Anyhow - fiddling with cars is half of the fun

Cheers

I would not consider my situation normal and measure all Sniper installations by this. I could have left the direct linkage alone and it would be fine if this were a hot rod. My problem is this is a 390 in a daily driver F100 I built for my daughter.

The reality is, after it’s warmed up for 3 minutes or so, everything is perfect. In warmer months, it’s a non-issue. My problem is, I want it perfect all the time.

[Pentroof]

Swapped the 4-hole for an open spacer and all is well.

Dead steady AFR gauge from the start and all 8 header tubes equally heating, instantly.

[Cyclone03]

Good job!

[Yellow Truck]

Interesting thread, glad you shared it.

[cammerfe]

Way back when I was first fooling with Holley EFI, there was a guy who made a cam/cable link that moved the throttle slower in the first part of it's travel. It was a sure cure for 'touchy' throttle foot. Worked a charm. I used one on Brother Lon's dual Holley TBI application on his 427 '67 Mustang.

KS