Holley 870 street advenger - junk?

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Retroboy

Retroboy

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Hello. I'm not a novice to engine stuff but can't get this thing to idle properly and it's rich as anything at idle. I have 24 deg timing at idle, 36 total, transfer slots properly adjusted, and .014" stainless restrictors in both idle jets in both metering blocks. I have an EGT probe close to the header flange which is reading high which would normally tell me it's lean but I'm thinking the probe is in the flame so reading high. The air burns your eyes and is stinky as. Bit more info on my set up - It's a .040 over 360 about 11:1 with a Comp Cams solid roller, a Super Victor and a Vertex internal coil Mag. I have a belt drive pump with aHolley bypass regulator with a #70 jet in the return running 6 psi. I'd be happy to have a clean idle at around 1000 rpm.
Anyone used this carb successfully?
Cheers
 
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Retroboy said:
Hello. I'm not a novice to engine stuff but can't get this thing to idle properly and it's rich as anything at idle. I have 24 deg timing at idle, 36 total, transfer slots properly adjusted, and .014" stainless restrictors in both idle jets in both metering blocks. I have an EGT probe close to the header flange which is reading high which would normally tell me it's lean but I'm thinking the probe is in the flame so reading high. The air burns your eyes and is stinky as. Bit more info on my set up - It's a .040 over 360 about 11:1 with a Comp Cams solid roller, a Super Victor and a Vertex internal coil Mag. I have a belt drive pump with aHolley bypass regulator with a #70 jet in the return running 6 psi. I'd be happy to have a clean idle at around 1000 rpm.
Anyone used this carb successfully?
Cheers
Click to expand...


Uhhhhh a lawn mower won’t run on a .014 idle feed restriction. Stop looking at the EGT’s. They respond way too slow and they will jack you up.


You have enough pump to support 1000 HP. I doubt a .070 bypass t is near enough. You have multiple issues, none of which sound like a carb issue.
 
Maybe not the carb. OTH I dont trust any of these new carbs. And even old ones sometimes have odd things inside.
It wouldnt hurt, and may make you less anxious, to note the locations and measure all of the restrictions.
I think Mike and others on RFS forum have posted about finding odd calibrations in the street and truck avengers.

Typical idle feed restrictions on a 4150 type carb are around .028 to .038" dia with idle air bleed restrictions around .070" to .076" dia. Although I've seen smaller and larger used that's the typical range. .014" is way too small.
 
Last edited:
Retroboy said:
Hello. I'm not a novice to engine stuff but can't get this thing to idle properly and it's rich as anything at idle. I have 24 deg timing at idle, 36 total, transfer slots properly adjusted, and .014" stainless restrictors in both idle jets in both metering blocks. I have an EGT probe close to the header flange which is reading high which would normally tell me it's lean but I'm thinking the probe is in the flame so reading high. The air burns your eyes and is stinky as. Bit more info on my set up - It's a .040 over 360 about 11:1 with a Comp Cams solid roller, a Super Victor and a Vertex internal coil Mag. I have a belt drive pump with aHolley bypass regulator with a #70 jet in the return running 6 psi. I'd be happy to have a clean idle at around 1000 rpm.
Anyone used this carb successfully?
Cheers
Click to expand...
too much timing , start over -----------
i ran a 870 on a hot 406 sbc in a 92 gmc shortbed , got 16.1 if I kept my foot out of it , of course it ran faster w/ an 800 double pumper on it .
 
yellow rose said:
Uhhhhh a lawn mower won’t run on a .014 idle feed restriction. Stop looking at the EGT’s. They respond way too slow and they will jack you up.


You have enough pump to support 1000 HP. I doubt a .070 bypass t is near enough. You have multiple issues, none of which sound like a carb issue.
Click to expand...


These carbs do not have removable or adjustable idle jets or air bleeds. The restriction is inserted in the jet in the metering block.
Belt pumps are the best thing since sliced bread. Never had a problem with this setup so don't think that is the problem but still ready to look further at the return jet
 
Retroboy said:
These carbs do not have removable or adjustable idle jets or air bleeds. The restriction is inserted in the jet in the metering block.
Belt pumps are the best thing since sliced bread. Never had a problem with this setup so don't think that is the problem but still ready to look further at the return jet
Click to expand...


Yeah, I know they don’t have adjustable IFR’s. You drill them out to 6-32 and make them replaceable.

I’ll look in my notes and see what the last one I had apart had for IFR’s. I can’t imagine that it came with .014’s, but I’ve seen goofier crap than that.

How many GPM does that pump produce at 1000 RPM crank speed? I mean a 3.5 gallon pump will easily do 800 HP on alcohol.
 
Mattax said:
Maybe not the carb. OTH I dont trust any of these new carbs. And even old ones sometimes have odd things inside.
It wouldnt hurt, and may make you less anxious, to note the locations and measure all of the restrictions.
I think Mike and others on RFS forum have posted about finding odd calibrations in the street and truck avengers.

Typical idle feed restrictions on a 4150 type carb are around .028 to .038" dia with idle air bleed restrictions around .070" to .076" dia. Although I've seen smaller and larger used that's the typical range. .014" is way too small.
Click to expand...

The quality of the carb is suspect from the get go. I've had to replace the threads in the main body for the fuel bowls and the locating dowels for the secondard metering block fell off the casting with the gasket.


The idle jet and air bleeds are fixed, so dont confuse my inserted restrictions with adjustable factory stuff.
 
famous bob said:
too much timing , start over -----------
i ran a 870 on a hot 406 sbc in a 92 gmc shortbed , got 16.1 if I kept my foot out of it , of course it ran faster w/ an 800 double pumper on it .
Click to expand...

This is in a fly weight race car with a 5200 stall converter. I used to run locked out ignition so I'm being kind at 24 deg. No reason in this universe a car will run faster with a DP
 
"and .014" stainless restrictors in both idle jets in both metering blocks."

Are you sure?
 
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Retroboy said:
Yes I put them there
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Why? There's a relationship between the IFR and IAB with the T-slot that needs to be balanced not only for AFR but also for where it begins to taper off for the start of primary booster flow. Not having a go just trying to understand what you're trying to achieve with the changes.

Also when you run locked timing you assume the engine wants that timing at all rpms to produce peak cylinder pressure which is not the case.
 
Retroboy said:
The quality of the carb is suspect from the get go. I've had to replace the threads in the main body for the fuel bowls and the locating dowels for the secondard metering block fell off the casting with the gasket.


The idle jet and air bleeds are fixed, so dont confuse my inserted restrictions with adjustable factory stuff.
Click to expand...
None of us were confusing anything. We all know this carb as well as the 'old school' carbs come with pressed in restrictions. On the newer ones they all need to be checked right out of the box.
 
Retroboy said:
This is in a fly weight race car with a 5200 stall converter. I used to run locked out ignition so I'm being kind at 24 deg. No reason in this universe a car will run faster with a DP
Click to expand...
Sure about that?
 
I would check the basic stuff float level make sure the seats are clean and seating correctly also replace the power valve any of those failing could produce the symptoms you are describing
 
Hysteric said:
Why? There's a relationship between the IFR and IAB with the T-slot that needs to be balanced not only for AFR but also for where it begins to taper off for the start of primary booster flow. Not having a go just trying to understand what you're trying to achieve with the changes.

Also when you run locked timing you assume the engine wants that timing at all rpms to produce peak cylinder pressure which is not the case.
Click to expand...


I second the why. That is way too small for most anything, even IF you squeeze the IAB down.
 
Hello rather than get into debates about various pros and cons can we hold replies to those who actually have first hand experience with these particular carb please.
 
What size is the IAB?
 
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Street Avenger. It's got a snappy name so it'a gotta be good, right?
 
Retroboy said:
9


I took this idea from Gale Banks and have used it since the late 1970's when necessary. You may have heard if him lol
Click to expand...


I’m out. There is NO WAY it will run with an IFR that small. And you want help, but you don’t listen. Don’t matter to me but you don’t make enough power for a pump like that and I don’t care who told you to put an .014 IFR in there is WRONG.

You aren’t reinventing the wheel. You don’t have some outrageous combination that no one has never seen. It’s rather basic. The pump is too big AND you have a tune up issue. It’s not the carbs fault you don’t listen.
 
yellow rose said:
I’m out. There is NO WAY it will run with an IFR that small. And you want help, but you don’t listen. Don’t matter to me but you don’t make enough power for a pump like that and I don’t care who told you to put an .014 IFR in there is WRONG.

You aren’t reinventing the wheel. You don’t have some outrageous combination that no one has never seen. It’s rather basic. The pump is too big AND you have a tune up issue. It’s not the carbs fault you don’t listen.
Click to expand...

I just left responding on another thread. I don't understand why people refuse good advice. All they want to hear is what they want to hear. Not what they need to hear. I feel your pain.
 
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