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bygddy 05-14-2013 06:19 PM

Hp body upgrade
Look what i got today, Holley HP mainbody upgrade. Went together really nice, unfortunately didn't come with smaller bleeds so I have to wait until tommorow to try it out.
They come set up for 4 corner idle with 75/36 and 75/36, need it to be 75/36 and 36/36
So will see how it works then. Tonight I'm installing an accel adjustable vacuum canister. Woo

Richiehd 05-15-2013 05:46 PM

This whole thing sounds interesting, but not sure what you doing? Do you take a regular double pumper and replace the body of the carb? whats the 75/36 36/36 all about? And so now this becomes a Holley hp, but only 2 idle screws?

bygddy 05-15-2013 07:44 PM


Originally Posted by F-BIRD'88 (Post 1675739)
When I did mine I had to fine tune the primary idle air bleeds further.
(My donor carb was a 700DP).. Needed a slightly smaller primary idle air bleed to get it just right.
Soldered up the 75 and redrileed with a .062" 1/16" drill bit. Then hand honed it to the size needed with the drill bit until it was dead nuts. It is about .064" +/-. The AFR gauge allows you to really dial in the idle circuit.
It was balky off idle. Off idle lean spot ....Now it is very sharp and smooth.
Depends a lot on which metering blocks (donor carb) you use.

the idle air bleeds in the stock donor carb body are your clue. Have a look.

Yah, i found the post from when you first did yours, I'm likely going to order an AFR guage next month and work on fine tuning....I had a btch of a time finding bleeds today, I did eventually find some and will pick them up tommorow. For now I'm just going to run the reccomended 75-36-36-75 primary and 36-36-36-36 secondary (for 2 corner idle). It pisses me off that Proform includes the extra bleeds for their mainbody for 2 corner idle but the genuine Holley ($40 more) didnt. The metering blocks are from my 4779

bygddy 05-15-2013 07:51 PM


Originally Posted by Richiehd (Post 1675904)
This whole thing sounds interesting, but not sure what you doing? Do you take a regular double pumper and replace the body of the carb? whats the 75/36 36/36 all about? And so now this becomes a Holley hp, but only 2 idle screws?

Yah, you can use a 650, 700, 750 vacuum or dp and upgrade it with either a proform or Holley HP mainbody. Chokless, smooth entries, downleg boosters and adjustable air bleeds are the biggest benefits. Much more tunable. For 650 guys its an easy upgrade to a 750 for $150
The high speed and idle air bleeds are the numbers I listed. A standard Holley has to be drilled to make changes, generally only pricey "race" stuff has removable bleeds.

bygddy 05-16-2013 08:22 PM

OK, so its on and it runs, I installed 36's instead of the 75 iab's as per Holley for a 2 corner idle. Its still pig rich at idle. Went back to the 75's and no real change. Almost as if the Carb isn't responding to the change.
Timing is at 26* initial, with an additional 10* of vacuum.
36* total. On test drive its unreal, snappy, power everywhere, no bogs stumbles etc. Part throttle in OD it pulls clean from low rpm etc. So it seems right across the board, and is def making more power then it was. Any suggestions from anyone who has done the HP or proform upgrade to help my idle? I'm a few weeks at least from getting a wideband so i can't make drastic changes but do wanna clean up the smelly idle.
Here is the set up.
355, 10:1 comp
Pro-filer 195 heads.
454/454 lift
Performer rpm
4779 with HP main body upgrade with screw in bleeds
Primary are 75 hsb and 36 iab
Secondary are the same.
Any suggestions?

bygddy 05-16-2013 10:01 PM

Would lowering my floats help the rich condition at idle? Right now fuel comes trickling out the sight plugs. So i could go lower. Forgot to mention i did replace the PV so its isn't blown.

bygddy 05-17-2013 03:59 AM


Originally Posted by F-BIRD'88 (Post 1676272)
Define: too rich at idle.... How are you determining this?

Are the idle mix screws active? can you stall it by turning in the idle mix screws?
How many turns out are the idle mix screws when the idle is set correctrly, using a vacuum gauge.?

The float height has a minor effect on the whole fuel curve.

Mixture screws are app 1 turn out, maybe 1 1/4. Yes they are responsive and will shut the car off when dialed too far in. Using a vacuum guage I'm showing a steady 15hg in drive at 650rpm.
By "too rich" I'm saying it makes your eyes water anywhere near the back of the car, and very very minor dark smoke at idle at the tailpipe.
Your Canadian, you know how some mornings its just cold enough to very lightly see your exhaust when the car is warming up, that's what its like.
Yes I nknow I need a wideband but can't make that happen until next month.

ap72 05-17-2013 09:31 AM

a wideband won't help you at all on your idle. In fact it can make things worse as they do NOT give an accurate reading at idle, use your vacuum gauge.

bygddy 05-17-2013 04:27 PM


Originally Posted by F-BIRD'88 (Post 1676359)
By "too rich" I'm saying it makes your eyes water anywhere near the back of the car, and very very minor dark smoke at idle at the tailpipe.

Yes I nknow I need a wideband but can't make that happen until next month.


This does not indicate a "rich" idle. What it indicates is raw unburned fuel in the exhaust.
Poor combustion at idle. Misfire... late combustion.
If the idle screws are active like you say then the idle circuit is not too rich.

But the combustion is not complete. One or more cylinders are misfireing at idle
one or more cylidners getting a different afr mix at idle (leaner,,,,vacuum leak.)
manifold plenum too cold. poor fuel mix/vapourization... fuel pudding in the manifold. Cold...
late spark advance at idle. Ignition system fault causing missfire... cross fire spark scatter. cap coil rotor wires
leak in the header gasket at the head.
all these will throw off idle idle. leaky valve. liquid fuel will not burn. poor fuel mix (there is enough fuel but it is not mixed well-evenly to all 8 or vapourized well)

A simple heated narrow band will do 98% of the job for you, for peanuts.
A wide band is nice but the simple home built NB gets it done.

Blue smoke burning oil
black smoke misfire
white smoke water leak, cold engine, water vapour, water in exhaust
white smoke trans fluid burning.

You cannot smell a "rich" or a lean air fuel mixture.
A stinky exhaust/burning eyes is incomplete poor combustion....
start with the ignition system.
Do not idle or try to tune you car in the garage, even with the door open.
Take it outside.

check for a header gasket leak. check for correct throttle position at idle.
check condition of the igntion system "new" is always suspect.
Possible rotor cap phasing alignment issue Scatter/misfire
do a simple cylinder balance test to find the weak cylinder(s)

Again : look at the idle air bleeds on the old stock donor holley carb body.
What size are they? pri/sec.


OK, so ignition is "new" and worked before my changes, its actually not as bad as I thought, yes its smelly, but black smoke when rolling and getting into the seconadties. Plugs look dark and rich, idle isnt as bad as I thought and I will measure the old bleeds when i get something to measure with. I changed plugs just now, and jetted down a touch, it was 72/80, I'm now 68/76 and going to go drive, pull plugs and see what it looks like. Miss fires are not present, it idles calm and smooth with no stumbles. Ground is something that got my attention tho now that u mention it. It was grounded at the cast heads and I did reinstall the same ground on the alum head. Now I wonder if its not sufficient.

bygddy 05-17-2013 04:28 PM

Oh and vacuum is rock steady at 20 in park, 15 in hear. Does not move at all. Mixture screws are very responsive. 1 and 1/4 out on each side.

bygddy 05-17-2013 09:43 PM

70/78 seems to show the best results with the plugs, and no more black smoke when I jump on it. It does now have a tip in stumble, almost like a lean bog for a second....may try changing the pump cam to #2 position and see how it works.

bygddy 05-20-2013 09:00 AM


Originally Posted by F-BIRD'88 (Post 1676964)
I often find a 750 holley likes 70 pri and 80 sec jetting.
It is well within what I find to be normal jetting for that carb..

The slight lean stumble is that on the primary throttle tip in or when getting into the secondaries from cruise? Or from rugging it from a stop?

If it is a primary offidle tip in response issue the throttles may be out of position at idle. (T slot exposure) can be eithe thte primary or the secondary throttle position that is the one causing the flat spot ...or both LOL.

It also indicates the the idle circuit fuel curve trim (idle air bleed size) is not quite right and may need fine tuning. It is slightly too big.

Look at the origional stock carb body. Look at the size of the primary and secondary idle air bleeds on it.
I bet they are smaller than the 75's you got in the new carb body.

It could be a air leak too.

When i did my upgrade using the Proform HP carb body I had to tune it a bit too.
Once you get it dialed in, it is very sharp and smooth.
The afr meter/gauge really lets you fine tune the idle air bleeds so that the throttle tip in transition is nice and smooth right from idle thru to when the main jets starts to flow fuel, as you get further into the throttle..
The 75's they give you are just a rough base line. idle air bleed.

I ended up back at 72/80 actually, the bog is all over the place really, if I rug it out of the hole its fine, nothing weird at all. But any kind of cruising speed and you tip in it stumbles/bogs noticably. I do have a box of blank bleeds but without an afr meter I'm hesitant to make any changes. I looked for air leaks and couldn't find any. I hate admitting this because it just sounds so stupid, but this thing makes a god awful sucking noise anytime you lean on it at all. I have had holleys on everything and not once heard one that sounds like this does. Picture a qjet when the secondaries open only much much louder....this is why I have kept looking for some place that it could be pulling air in. Doesn't do it until you lean into a bit. It also did the same noise with the old main body as well. And yes....I know its a Carb, and air does get pulled in lol....its just real loud. The only other thing i thought might be causing the noise is the little bit of epoxy on the throttle blades from when i filled the holes the original owner drilled. They aernt perfectly smooth so maybe that's my sound.....I dunno.

bygddy 05-20-2013 11:02 AM


Originally Posted by F-BIRD'88 (Post 1677096)
"Bogs every where from cruise"

I would take two of the blank air bleeds and drill with a 1/16th .062" drill bit.
Install in place of the primary 75 IAB and try it. Increase the primary jet from 70 to 72 and try it.

Going bigger on the iab's leans and smaller richens correct?
The proform body comes with,and I bought for the Holley, an extra set of 36's for the secondary outers when used with 2 corner idle like mine. I was concerned that these would richen the idle up way too much and never actually drove it I don't think when i had them in there. I just stayed with the 75 outers on the primary and secondary, and 36's on the inners. It takes about three seconds to swap them over tho so maybe I will try that this afternoon. My blanks are at work and were closed today so can't do much else for now.

bygddy 05-25-2013 12:10 PM

OK, so small update. Switched the secondary iab's to 36's. So front are 75 for the high speeds and 36 for the idle, rears are all 36. That didn't change much, this morning set the floats again, and I guess I wasn't setting them with it warmed up enough. Once up to temp the rear would be more then a trickle out of the sights. So I lowered it a bunch, now giving the car a good nudge some will dribble out. This has cured a few things.
1: it no longer bogs anywhere, even cruising in OD at 1600rpm it will pull clean.
2: it no longer stumbles when turning and accelerating.
3: it doesn't stall when i pound on the brakes.
4: when it got hot, it would idle high, 1100 in park, 800 in gear. Now it was too low, but no longer effected by temp. In had to increase it to get back to 900 in park, 600rpm in gear. Much more stable as well.
Still chasing a very rich condition. Driving around town and any moderate and up throtlle input brings black smoke from the exhaust.

Only once, but it was weird, it would want to just shut off. Pulling to light, it would just want to shut off. Had to 2 foot it to keep it running. The fuel level was very low, less then an 8th of a tank, so maybe it suffers a pressure drop at that point? I got gas and it didn't do it again.....yet.
And all in all it actually feels stronger, which I have no idea why an improper float level would effect, but it does....with 327 gears and an OD it an absolute animal on the highway....I have buried the speedo in a heartbeat out on the country highway where I live....and it still keeps pulling. Kinda neat
The stock 750 bleeds were actually richer based on size then the current ones. So I have 10 blanks now, I'm going to use what I'm running as a starting point and start opening them up a bit at a time and see if I can eliminate the smoke and rich condition. Im not sure if i should open the high speeds up, or just the idle bleeds. Or all of them in small steps. Indomt believe its a jet issue, I'm running 70/80's in it now and any less in the primary and it develops a lean surge condition.
So that's my novel, I'm sure nobody has time to read it all and add input....but I need to write stuff down to get a grasp of things so this is my way to do that.

bygddy 05-25-2013 01:19 PM


Originally Posted by F-BIRD'88 (Post 1678706)
Do not use a 75 as a high speed air bleed. Use a 36.

What is the size of the primary and secondary idle air bleeds in the stock carb body?
Guestimate using a1/16th and 1/32 drill bit. or a straight pin that you can mic ,,etc.
This is your start point.

The final pri and sec IAB sizes will be very close the IAB sizes in the stock body.

Ya the float level matters.

The stock bleeds are
70 idle, 31 main on the primary,
28 idle and 25 main in the secondary.

But these bleed sizes will be richer across the board compared to what I'm currently running.
Right now I'm 75 idle, 36 main and
36 idle and main on the secondary
Bigger is leaner correct?
I was shocked to see the difference float level made.
I was going to start with opening up the fronts to 80 and 40
Secondaries to 42 on both primary and secondary
This should lean it out a bit for idle and high speed bleeds.
I have read to try and get it to a point where it has a lean surge while cruising, then go back a bit in bleed size.
What do you think?
Or should I try and take some jet out of it first? With the floats wrong I wasnt getting an accurate test before so I could go back and try 68/76 again and see how it feels and how the plugs look.

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