I had been running a Holley 950 HP 4150 carb that was converted to E85, but was never happy with the cold starts and the idle characteristics with it. A week or two ago I picked up a new Holley Ultra HP 950 E85. It starts great, idles great, and is really responsive part throttle, but has a bog at full throttle. The accelerator pumps are adjusted correctly and it is like it came out of the box. It seems like it need more squirter when the secondaries open. I tried a few different pump cams, but have not got it right yet. Any ideas on where to start and what to look for?

The carb comes with 30 cc accelorator pump on the primaries and 50 cc on the secondaries, 45 squirter on the primaries and 50 squirter on the secondaries and 96 primaries and 106 secondaries on the jets.

It's most likely the idle and transition setup. What are the idle air bleed and idle feed restrictor sizes? How much of the transition slot is exposed at idle?

When you say full throttle are you still at low rpm...
have you jetted up yet... do you know what the high
speed bleeds are in it

AJ-I am not sure on the IAB and IFRs as I don't have the car at my house right not. I think I set the transition slot at .020, but I will have to check to make sure.

MR P- The carb is basically like it came out of the box. The bog is when I am footbraking the car. I launch at about 2000 rpms and when I hit the throttle there is a pretty bad bog.

I don;t think the carb specification are listed on line anywhere. I will not be able to look at the car tomorrow, but I pul the carb and look at how it was set.

Sorry guys the jet size I got before was from Summit Racing info, but was incorrect.

Here is the specs on the carb-

PRIMARIES SECONDARIES
IFR 56 56
PVCR 44 BLOCKED
PV 5.5 BLOCKED
JET 96 106
IAB 67 67
HSB 24 24
SQUIRTER 45 50
ACC PUMP 30 50
EMUL 1 BL BL
EMUL 2 BL BL
EMUL 3 62 62
EMUL 4 BL BL
EMUL 5 62 62

I used the numbered bit to measure all the sizes with the exception of the HSB and EMUL. All my small bits(60 and up) were out of order due to the case coming apart. I read what I thought was 62 on the emulsion bleed and 27 on the HSB.

The emulsion circuit a bit different than what I would run on that carb. It is main well dependent but not knowing main well size hard to tell. I normally would do blank, 028,blank, blank, 028.

From the specs on ifr and iab I would drop iab to a size 54-56. That will richer the idle circuit and help with the transition.


Those jets are rather large too. I normally end up about 8-10 sizes smaller. Normally on dominator cards I am not even that high.

What is the big like? Is it the motor cutting out then take off or blubbering then take off?

The bog is just a hestitation and then pulls hard. The bog is bad enough that it is effecting the reaction times.

What pump cams are on ot? Should have a pink in the front and brown or yellow out back. I would try dumping the iab to a 055-058. This will richen The idle circuit a bit and see if the bog gets better. Also can try to put an 050 squirter up front.

Also with e85 how much initial timing are you running? I have seen some cars with too low initial timing not launch.

Also be sure to have the car warm. I run it at 170 min when staging.

punt......lol

The pump cams are pink in front and brown on the rear. 20 degrees initial timing and I stage at 160. I will make the change to the iab and see if it helps.

I changed to the iab to 55 and the primary squirter to 50. This did not help, it is about the same. It still has a bog. Any other ideas?

Do you have a nice steady stream on the pump shot till
its gone(check with the engine off) and it does start as
soon as you start moving the throttle

Could be too much pump shot then. I have never run a 50cc pump on an e85 4150. Normally not needed.

Try going with a set of 042 squirter and put pink can in the back. The smaller squirter will lengthen the shot. The pink cam in the back will allow the 50cc pump to act like a 30cc. This is a big change and should see a difference. Worse or better. This will give you a direction.

I've heard nothing but bad things about the Ultra HP carbs. My friend bought a brand new 950 Ultra HP and had nothing but issues with it and Holley was no help. Turns out the front metering block was machined incorrectly and basically recirculated the fuel back into the bowl when you hit the throttle. Spoke to a local carb shop about it and he has had many complaints about these carbs. Hopefully you don't have a bad one.

Well I ended up putting a 50 cc pump on the primaries and it seemed to help. I drove it down the road and it felt pretty good. I plan to go out to the track Wednesday and make some passes. I will see how is does.

If more pump shot helps then that is telling us that the transition circuit is very lean. We need the huge pump shot to cover up the hole in the transition slot. What we need to do is make the idle and transition circuit richer. Where is the IFR located in the metering block? High or low? also how far are the 4 corner screws turned? Is the transition slot square? Turn the carb over and open the blades so the transition slot is showing a square with the blades.

If you get a rolling start say 3000-3500 rpm and mat it to the floor does the bog still exist? Is the bog only from a low rpm start?