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Old 06-06-2008, 09:44 AM   #31
dlrecord
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Default Re: Holley 23XX Series Modular Carb Stuff

I haven't given up yet and I hope you all haven't written me off either as hopeless. I finally got out and ran though everything again based on all the threads. Here's the update:
  • Holley 7448 350 cmf w/ #58 jets and #65 primary
  • timing set to 5* btdc
  • idle at 500 rpms
  • Holley original points distributer with pertronix p/n 1481 ignitor
  • mechanic advance is Working (timing Mark advances as rmps rise)
  • vacuum advance not Working (put vacuum gauge on vacuum advance on dizzy and increased rpms: no change in vacuum).
  • orange accel cam set on the #2 hole
  • good steady stream of gas out the shooters when accelerator opened up
  • check ball under the shooter housing appears to be free and working

The unit still stumbles and hesitates upon tip in. Runs fine once past tip in. I am wondering if the accelerator pump cam needs to be adjusted to shorten the stroke? Could it be too lean on tip in and not getting enough gas to break past inertia? I am also wondering about the influence the vacuum advance has on this tip in issue...not sure if I can buy a vacuum advance or if I need a new dizzy.

As always, thoughts appreciated.
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Old 06-06-2008, 10:37 AM   #32
Michael Mayben
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Default Re: Holley 23XX Series Modular Carb Stuff

Hail no!!! We don't give up 'til it's either fixxed or permanent broke!

If the timing is now base at 5*btdc, then ya musta re-stabbed the distributor and got it right! Everything is now normal except for one thing.

Ya don't put the "test" vacuum gauge on the vacuum advance can nipple...if ya do, ya just removed the vacuum source from the advance unit! If you connect your vacuum gauge to the fitting on the passenger side of the metering block on that carb, you should see (at your noted altitude), between 1"hg and 3"hg at idle! That is the only "ported" vacuum source on that aftermarket carb! Once you are satisfied the ignition is dialed-in, then attach the vacuum gauge to the port on the bottom rear of the carb, that position will give only true manifold vacuum...and we need to know what that reading is at warmed up idle. That reading will be accurate only after you are satisfied that the idle mixture screws are properly adjusted and the idle speed is locked in. I'd really like to see an idle speed of 625rpm in neutral on that motor.

If the mixture screws are not set correctly, and idle speed is not set correctly, then tip-in cannot be achieved! Remember, this is a step-by-step deal, where every "adjustment" affects some other characteristic also! Tip-in/pump shot is finalized only after everything else is locked down!

To test the vac advance can for operation if you do not have a handheld vacuum pump (mity vac), then connect the advance vacuum tube to the can nipple. Start the engine and verify the timing Mark position using your timing light. While watching the Mark, suck on the open end of the hose...you can easily pull up to about 7"hg with just your lungs unless ya have emphysema (or smoke!!). While suckin' and releasin' and suckin' and releasin' you will see the timing Mark advance and retard, advance and retard, indicating it's working correctly. If the Mark does not move, then vac advance can is toast or the plate in the distributor it's attached too is frozen.

It's possible to have a vac advance unit that still operates, but has an internal leak...that will create a "phantom" vacuum leak that is somewhat hard to diagnose. All the more reason to make a mity vac part of your tool arsenal, those little gadgets are wonderful items to have for all kinds of diagnostic and service procedures!

New vac advance cans for the Holley distributors are not available from any source, we've been fighting that battle for several years now. Jeff does have some good used ones that I just recently tested and returned to him (including one for the very difficult to find parts for..."straight point Holley"). We have several more that are ng right now, but are boxed to go out to a service we use that re-manufactures those items, those will be available in the online store in the next 30 days we hope.

Adjusting the pump cam (or replacing) is gonna be the last step, we still have a few more tricks to go through though. At your altitude, it's "possible" that a different pump cam May be needed to optimize the setup, but do not go there until we go through the whole deal if ya wanna make it right!

Your are doing real well at stickin' with this...and I promise...I can outlast ya so don't give up! Bein' old does have advantages!

I'm in the office/shop until 9pm tonite, I'll continue to monitor this deal if ya have time to report back about the advance can.
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Old 06-06-2008, 11:16 AM   #33
dlrecord
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Default Re: Holley 23XX Series Modular Carb Stuff

Michael,

I'll get out there this afternoon and run a few of the vacuum tests.

If I drop out of teh thread suddenly for a little while, it is only because I'm probably in delivery with my wife. Our first baby is due any day now!

-dan
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Old 06-06-2008, 12:35 PM   #34
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Default Re: Holley 23XX Series Modular Carb Stuff

Ok dan! Best wishes to all involved!

Please...do not name tha poor kid "Scout"!
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Old 06-06-2008, 01:53 PM   #35
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Default Re: Holley 23XX Series Modular Carb Stuff

We got suck (I May try to get a vacuum pump this weekend).

I reset the curb idle to approximately 625 rpms in neutral as suggested. I disconnected the vaccum advance tube from the carb but left it attached to the can on the dizzy. With the timing light set (timing read 8* btdc with the Scout in neutral) and the tube handy, I sucked on it and watched the timing advance from about 8* btdc to 12*~15* btdc, so I now know the vacuum advance is working.

Alright. Next steps?

-dan
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Old 06-06-2008, 04:06 PM   #36
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Default Re: Holley 23XX Series Modular Carb Stuff

Ain't it great to suk sumtimes?? Great work grasshopper! Obviously ya don't smoke at your altitude!

The "spec" for the total amount of advance the vacuum can on your distributor can provide is 5*. If you remove the advance unit and flip it over, you will see a numeral "5" stamped on the actuator arm. Now you have really lernt stuff!!! "some" versions of that distributor (selected ihc oem distributor/engine/vehicles) use a vacuum advance with a 7* set point...another detail as to why the statement "all IH sv distributors are the same" is bogus!

The jetting sounds about right, and the #65 power valve is the most versatile for IH apps, that has nothing to do with what we're working through right now anyway, but it's good info to know!

An orange pump cam is correct for that carb outta the box and works perfectly at 0ft.>3000ft. I've not personally tried to tune one at 5,000ft. So I have no data in my notes. So what we end up with here will be real valuable for helping other folks!

Next...verify that the pump arm override screw is adjusted properly. To do this, hold the throttle lever to wot (yes it will squirt fuel down the gullet resulting in partial flooding at startup!), then with your other hand, depress the accel pump actuator lever down as hard as you can. With the lever held down, the clearance between thew override screw and the lever where it touches should be 0.015" using a feeler gauge. You can also "eyeball" that clearance, the whole idea is to make sure that the lever adjustment does not create a hard contact which ends up bending the lever and wearing the nylon cam very quickly. It also takes all slack outta the accel pump actuation system so that even one degree of throttle lever movement, results in a pump shot being initiated through the shooter nozzles.

I want ya to simply move the cam retaining screw to the #2 hole. That will give increased "lift" earlier in rotation, and provide a slightly heavier pump shot at tip-in. This will make it either...noticeably better...or noticeably worse! That is in relation to the fact that you know how it "feels" right now with the screw in #1.

Because IH sv engines have a very "high" rotating internal "mass" (comparatively speaking), and the vehicles themselves are superpigs (whether Scout II or fullsize stuff), they take a very healthy "pump shot" to cleanly/smoothly launch the rig at tip-in. Just winging the throttle at idle May appear that the tip-in is ok, but when ya actually do a "launch" (either gently or wot), the "hole" appears. That "hole" is what we are trying to eliminate.

And make certain when doing all this tuning...that the engine is fully up to temp. Don't just go do a quick test drive around the block and then condemn the problem...try it several times on both an uphill and downhill launch and be able to see a "pattern" which is repeatable.

Then we're gonna doubletask here...if it's a little better, then I want ya to advance the distributor timing to 8*btdc and go repeat the test. I bet you will see improved performance at your altitude! In fact, you can keep bumping the timing a degree atta time until the engine begins to detonate (ping/knock) under load, then back it off one degree...that's what we call "power timing" and has nothing to do with emissions or oem "specs" which are always the starting point.

If ya like it at that point, yore done. But...when ya go down tha hill to tha lowground (say 2000ft.), ya will have to back off the timing to 5* or ittle ping like a bitch under load!
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Old 06-08-2008, 06:13 PM   #37
dlrecord
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Default Re: Holley 23XX Series Modular Carb Stuff

Quick update (non-IH related): it's a girl! 6.5 pounds, 19.5 inches and huge appitite!

It might be a few days before I can get back out to the Scout... :-)

-dan
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Old 06-08-2008, 06:44 PM   #38
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Default Re: Holley 23XX Series Modular Carb Stuff

Congratulations!! To all involved in this deal!

Y'all are in for a real ride now!
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Old 06-08-2008, 07:16 PM   #39
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Default Re: Holley 23XX Series Modular Carb Stuff

Quote:
Originally Posted by dlrecord View Post
quick update (non-IH related): it's a girl! 6.5 pounds, 19.5 inches and huge appitite!

It might be a few days before I can get back out to the Scout... :-)

-dan
Huge congrats dan!
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Old 06-13-2008, 11:38 AM   #40
dlrecord
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Default Re: Holley 23XX Series Modular Carb Stuff

Thanks guys.

I have some time today so I'm going to play with the Scout and run a few of the adjustments. I'll get back again once complete.

-dan
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Old 06-13-2008, 12:28 PM   #41
dlrecord
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Default Re: Holley 23XX Series Modular Carb Stuff

Alright. I tried to check spacing on the pump arm override screw but had a lot more the .015. Even with the top nut loosened, the spring was not long enough to stretch the cam arm down enough to create the .015 spacing with wot and pump arm pushed down. I had a lot of play left...like a lot.

I attached a picture for you to see (and make sure I am working on the right stuff here). The cam is already set on the #2 hole as it is...

Let me know your thoughts. Thanks,

-dan
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Old 06-14-2008, 04:30 PM   #42
Michael Mayben
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Default Re: Holley 23XX Series Modular Carb Stuff

Great picture dan!

I wish everyone could/would post shots like that one...including myself!

I just received two new 0-7448, 2300 mixers yesterday from the warehouse, and have two freshly-built 500cfm versions of the same carb here now. None of those have the issue you describe, which will greatly affect what ya got going on!

I've just got home from "dave the gear man"'s shop where we rebuilt yet another 2300 for a close friend's sii, he does that under my supervision every two years now. And his pump system was just as we set it two years ago. While we rebuilt the carb, dave set up a fresh trac loc and replacement r&p in Matt's rear axle.

But...your issue is ez to correct!

First, remove the retaining clip and the accel pump arm from the shaft it mounts on.

Flip the arm over and closely inspect the area where the arm rides on the cam. You will prolly find it worn somewhat...maybe two distinct "divots" in the surface? If so, ya need to carefully grind/polish that area back flat, and leave a very slight "radius" to the grind. The worn area is caused by grit wearing the steel arm once it's embedded in the nylon cam surface, kinda like lapping compound.

Attached are two shots, the first is a badly worn pump lever. The second one shows how I recondition those levers.

Then...carefully "flatten" the bend in the arm next to the pivot pump to make it slightly "flatter". I do this by simply squeezing the arm inna vise with light/medium hand pressure on the vise screw handle. Do this very carefully, and flatten just enough to take out the "slack" in the override adjusting spring/screw/nut system. Keep doing that a scosche atta time until you can easily achieve the 0.015" pump lever clearance spec.

Don't know how the bend in that lever got magnified...but it did. I have seen one of those arms not bent correctly on a new carb out of the box. So this is not a normal sitch, but with the setup as it is, there is no wonder ya can't get the pump shot dialed in!

Great work and observation!
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File Type: jpg Worn Accel Pump Lever.jpg (474.0 KB, 758 views)
File Type: jpg Recondition Accel Pump Lever.jpg (377.0 KB, 581 views)
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Old 06-18-2008, 03:32 PM   #43
dlrecord
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Default Re: Holley 23XX Series Modular Carb Stuff

Michael:

adjusting the cam arm did the trick! I took the arm off, inspected for divits or other wear and didn't find any on either the cam or the arm. I gentle bent the arm a bit checked, bent a little more and was then able to tune the spacing in to .015 approximately. Put it back on fired it up, let it warm up and attached my vacum gauge to my new t-fitting off the back vacum port on the carb.

I was pulling about 10"hg so fined tuned the air intake screws to acheive about 12.5"hg with an idle around 540-550...the Scout just seemed to like that range better. Is 12.5"hg a good number by the way? Also, timing is set at 8* btdc. I'll power time that as I get to drive the Scout a little more. (let me know if I am off on this adjustment as well, but that seemed to be the most I could get out of the ole girl.)

on my test drive around the block, the tip in issue was gone; just nice acceleration with no stumbling or hesitation. I'll get back out there again and give a better test drive: up some hills and down some hills and really test it out, but I think the issue has been corrected.

A big thanks to you and Jeff for the advice, the patience and the instruction. I learned a lot about my carb and the proper way it should work through this exercise.

-dan
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Old 06-18-2008, 05:42 PM   #44
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Default Re: Holley 23XX Series Modular Carb Stuff

If ya keep chippin' away at stuff like this dan....usually ya git lucky and win most of tha time!

I been doin' these carbs for nearly 45 years now...and I learn new tricks every day! I'm real fortunate to have a great group of folks I call friends who share knowledge about old skool stuff like this, no matter what their age/background.

If there is a secret to this stuff, it's patience and doing one thing ata time and diagnose issues rather than just shotgun'in stuff like usually happens when dealing in "forums"!

On IH stuff with slushbox tranny I set curb idle rpm at 800 with full warm up, droppin' into drive should show about 600>625rpm. I bet you will gain another 1.5"hg at least with a slightly higher idle speed. But what ya got now ain't bad for yore altitude.

The power timing thing is something that is unique to each vehicle setup and I know ya can run more base timing advance at your altitude!
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Old 07-31-2008, 01:33 PM   #45
Drew Merrick
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Default Re: Holley 23XX Series Modular Carb Stuff

I thought I would contribute to the base here. I just picked up a rebuild kit from salem performance racing in salem, oregon. That guy has more Holley parts than any one else I can imagine. Instead of just giving him my list number I brought the carb in for exact kit fitting. Like a fine tailor he found exactly what I needed and pointed out some areas of concern right away. Then he adjusted the kit. A total of 32 bucks.

my carb:
  • list 2977 753
  • IH: 284545-c91

Holley parts kit #: 37-1543
2bbl carburetor kit

the kit came with two different size accelerator pump diaphrams. Steve took the one I didn't need and traded directly across for the proper valve seat adjuster nut and lock and didn't charge me extra. That's service!!!

performance racing equipment
2715 portland rd ne salem, or 97303-3168
(503) 371-8622
steve, owner.
I appologize if this competes with IHOnly north. Not my intention.
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