Is my "Crutch" too big?

I have an annular booster BLP (Holley HP) 850 with Brent's work on top of a 215 cc head 224/224 .520 114 cammed 383 SBC. Turbo stuff is a set of home made 1 3/4" headers, Garrett 88mm from Dave, 4 inch down pipe. I am having trouble getting it rich enough despite having HUGE PVCR holes. The brass set screws in the PVCR holes are drilled to the max, anymore and it would be geting into the allen head part of the plug(have not measured the size). Also there were 2 small holes drilled above the PVCR holes, this is how I got it from Brent so I don't think it's a combination problem with my car since he obviously needed large holes to get it to flow for him also. I have since opened the second set of PVCR's to 0.073". On the main jet side it came with 75's IIRC and I have upped them to 85/86 to get some more fuel to it but for anything out of boost they really need to go back to the 75's maybe 78's. On the last trip to the track I rolled into it off the line, let it come up on boost by the end of first, shifted second, shifted third then lifted. Boost was between 23-25 and afr's rose from 11.6 to 12.3 where I rolled out. Fuel is 110 octane Sunoco, and I am spraying washer fluid at it with 3 nozzles: 1 pre-compressor, 2 pre-hat. Timing under boost is 20*. The engine ran well, plugs don't show "nibble" marks or detonation but I haven't shut it down clean so I am just going off of what the wide band is telling me. One thing I might add is while doing a burnout when I get to the activation RPM of the power valves the engine will bog down and die and the AFR's correspond with off the chart rich, so the crutch system is activating and I have no bleed valve on the crutch so the power valves are getting the 50psi that the little air pump makes.

Am I just not getting signal to the boosters? Do I just keep drilling bigger PVCR's?

-Eldon

 

Re: Is my "Crutch" too big?

why are you spraying washer fluid when you have racefuel in the car??? just run c-16 and forget about the washerfluid.

 

Re: Is my "Crutch" too big?

What size are the booster passages? Might be a bottleneck if all this jet and PVCR changes aren't affecting your AFR.

Another very important thing to look at is your flowing fuel pressure under max load.

 

Re: Is my "Crutch" too big?

what size carb 750 or 850 ?

I have the same problem with my 383 sbc go figure





Gino

 

Re: Is my "Crutch" too big?

NITROUSKINGZ, I don't have an intercooler so that's why I am spraying some water at it, when it's in boost and spraying the car is running strong, I don't think that's causing the lack of flow through the PV.

jameskirk1: The fuel pressure is raising appropriately as the boost raises. I am not sure which booster passages you are refering to. The small fuel discharge holes or the physical booster it's self? Is there a rule of thumb or a formula for them?

04mx: I have an 850 cfm. I have been watching your posts like a hawk hoping you would find something that would help me also. Any ideas? Carm has all the fuel he needs with his 850 and his jets and PV's are tiny comparatively. Maybe his 400 inches and big heads are just moving that much more air.

I am thinking about going straight meth in my water injection bottle to richen up the mixture and make it through the end of the season, then maybe get a 750 main body this winter if that's what it needs. I have a 650 here I could try Brent's blocks on maybe. Just spit balling here.

-Eldon

 

Re: Is my "Crutch" too big?

What does Brent have to say about it? I am sure he could figure it out.

 

Re: Is my "Crutch" too big?

Bingo
Fwiw, my C&S had 4 holes per metering block behind the PV's.

 

Re: Is my "Crutch" too big?

I sent Brent a message this weekend but haven't heard from him yet, no biggie. I am planning to call him this afternoon, just thought I would check here in case I was missing something remedial.

10secgoal, nice to hear others have multiple PV holes. It was the first time I had ever seen that. I will post up what Brent says.

Thanks for the responses.

-Eldon

 

Re: Is my "Crutch" too big?

I have 79 front, 82 rear and the PVRS is .118 and .150 needle and seat , bowl extensions , 10an from pump to reg ,10an back to tank, 8an feed to carb and it is good to about 10 to 12 psi of boost after that point it goes lean .

Carm let me put his carb on my combo and I still went lean ( BIG THANKS TO CARM) and he goes low 8's with the AFR in the 11's

I do know fuel psi is going up because i log them with the LM1 so i can rule out the pump+reg issue .

next time i'll try some vent tube extension just to see if it makes it better or not ?

I would like to try a 750 VS my 850 maybe it will pull more fuel through the boosters then the 850 ,I don't know ?

I have issues with boost the MSD 7531 is saying like 12 psi boost peek and the LM1 is saying 18+ again but when i test them with compressed air they are the same

and this weekend when i went out to the track and the dam aerospace brakes locked up on the passenger side scraping the right front tire POS brakes >

it went 6.34 at 119 with a not so good 60 ft on (I think ) 12 psi peek boost if I can rely on the MSD box


Gino

 

Re: Is my "Crutch" too big?

10secgoal you wouldn't happen to have any pics of that sir would you ??

Gino

 

Re: Is my "Crutch" too big?

That was going to be what I was leaning towards. If carms didn't work, I'd say it wasn't given the fuel it needed. The first pump I had with blo thru did the same exact thing. Had the pressure and it showed in the gauge, but not the volume to keep the carb full. What's the pump ?




Sorry o4mx, no pics, got rid of the carb.

 

Re: Is my "Crutch" too big?

I have an A1000 on mine, -12 to the pump, -10 to and from the Aeromotive reg. .150 needle and seat standard bowl.
If I pulled the PVCR screw in plug completely out and made a test hit that would basically tell me if my carb/fuel system is capable of the fuel flow needed? It should go rich but if it didn't I am not going to get it with drilling PVCR'S, there is another issue. Would this be something try or is it just stupid?

Gino, that's very interesting about Carms carb not working on your setup. Like 10secgoal asked, what pump do you have Gino?

-Eldon

 

Re: Is my "Crutch" too big?

I have a magna fuel 500 pump with a 12 an feed to the pump also .

I tried that also, no PVRS's at all 4x .250 holes + the jets and it was still going lean ,that was last year tho.

this year i tried the same .250 PVRS and 79f and 84 rear and with the 84's it would not even want to spool at all ,went home and put in some 82's and now it will come up and at least let me make an 1/8 mile pass with it being in the low 12's at the end BUT with little boost .

when i test the pump in a 5 gal can and put compressed air on the reg the fuel that comes out of their should be enough to feed the dam space shuttle ??? it fills that can in no time .

Gino

 

Re: Is my "Crutch" too big?

I left a voice message for Brent to call me so I can pick his brain. If lack of vacuum signal is causing this then maybe wiring shut the secondaries would force the engine to pull through half of the carb. If that produces a richer fuel curve then I would be led to believe that either the fuel system can't keep up or the carb isn't getting enough signal. Any objections to this thinking?

-Eldon

 

Re: Is my "Crutch" too big?

If they are #6-32 tapped then that would be about a .093 to .096 pvcr with the set screws removed .

 

Re: Is my "Crutch" too big?

The fuel PSI may be going up with boost, but is it going up high enough? I would be looking at where you are getting your boost reference for the regulator vs. where you are logging your boost pressure. Having your fuel pressure low by only 3psi low under boost would make a HUGE difference in the amount of fuel flowing through a needle/seat and could also exlplain why you are seeing the same issue with two different carbs.

 

Re: Is my "Crutch" too big?

04mx ,

Have you ruled out the LM-1 ?

 

Re: Is my "Crutch" too big?

Gino, maybe check the MSD distributor and make sure the rotor is phased properly

Check the plug gap - set em to 0.025"

Try changing the total timing to a lower value - say locked @ 32* then take 8* more out under full boost with C16 and see if it clears things up

Change the 02 sensor

As mentioned, Gino bolted my carb on as it came off my car......it maintained 11.6 AFR @ 164mph @ 3580# all day.....it went lean on Gino's car

Something is not right, and i'll tell you 100% it IS NOT the carburetor

-Carm

 

Re: Is my "Crutch" too big?

what size vent lines on your tank or fuel cell? should be equal to feed line 10an, might be causing a suction in the tank.

 

Re: Is my "Crutch" too big?

jameskirk1 I have the fuel set to about 6 psi base and it rises a little more then 1 to 1 so at 12 psi boost the fuel is at 20 or so fuel psi this is normal with the magna fuel 500 pump and the 132-02 reg .

I log the boost under the carb and have the fuel boost port to the hat witch should give me 1 or 2 psi over having it under the carb.


blown385 NO man i have not ,I did change the sensor and moved it farther away from the turbine and still leaning out . It seems to be working ok when not into boost or low boost , when i cal the sensor (free air)it say's 20.9 afr .

Mabe it is the dam LM1 i tested the boost logging tonight using compressed air and adjustable reg to the map sensor and looking at the msd dials and at the same time recording with the LM1 and 5psi=19.5 , 10psi=24 ,15=29.5......... all is good but when i make a run down the track they don't match dam POS LM1 crap.

I am going to try vent tubes to see if that richens things up with boost pushing fuel out to the boosters ?

I'm just thinking out loud here 1 x .150 needle front has to feed 2X 79 jets + 2 x .118 PVRS woundering how the needle can flow all that fuel ?


Gino