79 Aisan carb install

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Jan 5, 2008
Summerville Sc
79 Aisan carb install
( this post is originaly from the 40 forum but it was suggested to me to try the 60 forum due to lateness of carb)Hiya- I'm plodding along on my carb install project and have hit another snag. After scouring the posts for anything carb and vac related, I found this thread which worked out the vac lines in an almost identicle situation. Almost. Evidently, my 79 carb is just differant enough to be a pita. Honestly, I have only a very basic knowledge on carbs and vac theory- I just want to finish my installation.I understand that there will be adjustments,etc but I'm under no deadline.(though I miss my dd) OK- Heres the issue- connection F is different on my carb.Instead of 1 line coming out, I have 2 vac ports there.It is either that,or that one port in the middle replaces F.None of these connect to the down angled port which the 78 carb has ( connection "F").
If I have gathered correctly,all the connections I need are as follows:
1. vacuum advance from dis. to connection
2. fuel in- connection
3. switched power to fuel cut sol.
4. my missing F connection
I have capped all else, w/ the exception of 2 ports on insulator block.Can someone help me work out that "F "connection? Thanks to Trollhole and co. for the excellent thread I've been working from. (the diagrams were most helpful)

NOTE: Pics from Trollholes thread have been deleted, as I was told that carb was significantly differant from my 79. Therefore, references to "lettered" connections were not applicable. To see the post w/ quoted pics intact, look for same named post in the 40 tech forum. My god, that confuses me just writing it.

Attached Images

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Will do asap Jim- Thnx
79 carb as installed

Here are some pics of the 79 carb as it sits in engine compartment.You can see the disconnected fuel line laying across the front of rocker arm cover. The vac advance line also lays across cover , connected to nipple @ right of adjustment screw in carb base.I'm sure I can find a switched wire for solenoid somewhere near carb. I wasnt sure what all you would like to see in engine compartment, maybe the absence of smog equipment. Thanks! :meh:
The ICS power connection is somewhere in the harness, there beside the brake MC. The other side of the ICS just needs grounded.

Cap the two open fittings on the top front of the carb. They are for the missing HAC.

The HIC (boxy thing on top of carb) connects to air cleaner on top, and down to carb insulator base on bottom.

I will hook it up this PM as described-

In my newb enthusiasm I'll go ahead and say:

YOU DA MAN! Thank you so much for your patience. Please pm me if you ever need anything in Charleston SC area.:clap:
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My enthusiasm was short lived! ;) I finished connecting the carb and cranked her up-very briefly. The truck tried to start,running very rough and exhausting black smoke,then died. On second attempt,she tried to crank,then shot an awesome flame out of carb. I thought this was enough for tonight .
So,should I begin w/ timing adjustment? The truck ran fine w/ old carb.(comparatively). can a differant carb require a differant timing setting? Im curious how the mechanical relationship between 2 gears @ timing can be affected by a carb. I know timing affects when valves open and close,thus their ability to receive fuel, or expell gas,but dont understand relationship to introduction of fuel mixture @ intake.
Plan B would be to begin adjusting carb settings. Whats your opinion? Thmx!
The black smoke usually indicates engine is drowning in fuel (check sightglass level on carb).
But the carb flameout indicates lack of fuel to the cylinders.

Carb settings do not have significant effect on timing setting. If the engine ran & started OK, before the carb swap, don't mess w/ the timing.

This kinda sounds like a flooding carb (needle stuck open, possibly w/ FOD) combined w/ a vacuum leak?

Edit: Are you getting power & groundto the ICS? Does it make audible click noise when connected?
Will check this pm -Thnx
Hiyas- Power was not correct to solenoid. 1 side of jack I attatched was not a ground. I rigged up a temp. ground and got 12 v. across jack. This seemed to improve starting attempts. Fuel in window was splitting dot before cranking,but quickly rose above it and dissapeared past top of window. This was after several cranking attempts.W/ full choke, motor would fire off and rev real high, but imediatly die down regardless of what I did. It seemed to be running smoothly during rev up after choke. Other times it just cranked and cranked,just short of starting. I was feeling optimistic- but then starter died.Unbelievable. It only clicks once when key is turned.Could be grounds,etc.. I will eliminate all that and repair as neccesary. If I have proper 12 v. @ starter, I will replace it. Then I can resume carb tweekage. Thank you all for your help!
Carb install pt.2

Hiya- I resolved the starter problem. I could have fixed it w/ a 20.00 cable instead of 80.00 starter.Ended up w/ both,chalk one up for experience. I switched the vac line going into carb to the center port, and capped the one one right that was connected. These are the 3 ports above idle adj. screw. This made a big difference- the truck cranks and almost starts w/ just a few pats on accelerator. If it does start, it immedietly dies. If started w/ choke, it revs up high,then dies. The level of gas @ sight glass also dropped when I changed the vac line,its now closer to center dot.I have correct switched power to solenoid, but have yet to hear audible click when powered up. How loud is that thing?I also have not connected vac line fro HIC to air cleaner,with removing the top of it so many times. Is that connection critical?
Anyway, thats where I am w/ this thing. Anyone have any ideas?:p
If it does start, it immedietly dies. If started w/ choke, it revs up high,then dies. I have correct switched power to solenoid, but have yet to hear audible click when powered up. How loud is that thing?
Starting symptom and lack of sound both indicate lack of ICS operation.

I also have not connected vac line fro HIC to air cleaner,with removing the top of it so many times. Is that connection critical?
No, connections to the air cleaner are usually not critical, since the air cleaner is atmosphere.
It is critical to have the HIC hose connected down to the fitting on the carb insulator.
Heya- Confirmed operation of ICS by removing it and connecting it to power while holding it. Felt it jump when I connected it. Re-installed it,still no dice. tightened all carb studs sequentially, no go again. Completed HIC connection-no change. Removed vac lines , inspected, re-installed. Freaked out and removed carb and then air horn. I did see a few black specks in bowl,and some sort of funk (slime?) floating in bottom of bowl. I removed all, then blew compressed air through ports in bowltill they were clear. re- assembled carb and installed (much easier second time!). Still wouldnt idle. saw same slimey stuff in fuel filter, so I replaced it and the last section of line, and drained bowl,blew through jets, etc. No idle.- HA-HA_HA-HAH!!! Its possesed!Frustration critical mass! I left her sitting alone in the dark garage.I'm going to seek a local mechanic who can come to truck. I know several,actually one who works on the new Buffalo military vehicles. Those trucks have very little in common w/ my 30 yr old cruiser motor though.I also know a drag racing mechanic (no kidding) who said he'd help.At least I know his vehicles have carbs. I dont know, something will pan out. I am not giving up-I'm just trying to get her running- whatever it takes. Thank you for all the help-I'll continue to post w/ progress.

Briefly- all carb needed to idle was a new gasket between insulator and intake. A stuid mistake ,but understandable w/ my inexperience. Idle is very high- still trying to adjust-will post w/ progress.

Edit- Truck will idle now-Im still trying to get it right. If I adjust curb idle to acceptable speed ,the truck stalls on deceleration. If I raise idle towhere it wont stall, its almost racing. Started idle mixture screw seated- then backed it out 1 1/2 turns. Backed out fast idle 1/2 turn, and idle speed 1 turn. Have adjusted fast idle and idle speed a lot. Can get curb idle correct, but then stalling @ stops begins. Have tried to find any vac leaks w/ methods from forum: covering air intake to idleing engine and listening for speed up as it dies ( none noticable ) and have sprayed idleing motor w/ water mist @ vac junctions to cause stall-again,no noticable change. I have also read a faulty EGR valve can cause these symptoms, but can find no reference to this valve in Haynes manual, and can not locate it .(pics on SOR didnt help much). Lastly,I read there is a switch which cuts fuel upon deceleration which can be faulty, but the only electrical on my carb is the ICS.(replaced). Any insight would be welcome, and I thank you all for the help already provided.
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Bump- lookin for help!
Close to done!

Adjusted carb per Jim C.'s direction and added beefier return spring @ carb (horizontal spring firewall side @ bottom-connects directly to accel. linkage).Truck drives well-great acceleration-and stops w/ out stalling-:D. Pesky idle is still screwy- can adjust it down to curb level no problem-but when I back out of garage,idle jumps up a good bit.Put her in gear, clutch out, and she runs well. When clutching to brake,idle jumps up again until I apply brake- then it drops down. Fast idle screw is maxed out,barely touching cam below.Idle adj. screw is also 3-4 turns out. I read that having accel. rod backwards can cause racing-there are 2 arms on it,1 long and 1 short.Evidently the short one should be @ firewall side. Mine is backwards. I wonder if this is worth reversing? Any thoughts on this would be appreciated-Thanks!
Yes, the thottle torque rod needs to be installed correctly.

Also, back off the hi-idle screw. It should not be touching anything w/ the choke off. Adjust the hi-idle screw to give 1800RPM w/ choke pulled, engine warm.
Pulsing @ idle/ vac readings

Hi- I have reversed torsion rod and backed out fast idle screw.The truck has returned to dying @ stops.I backed out mix adjustment 1/2 turn twice to try to fix this- no dice. The idle starts pulsing after running for a minute or so.I noticed that the pulsing stops with air cleaner removed ( it idles quite nicely then).But when replaced, it pulses and stumbles,sometimes dying. Vac gauge fluctuates between 17 and 21- it kind of builds with a rough idle to ~21 then falls to ~17- unless it dies. I am going to appeal to some local members for advice on a local tech. Thanks for all help so far!

Edit- I have also hose clamped all large vac connections and replaced any suspect small ones. Cannot find any leaks using water method.
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I went to give him a hand Saturday and all the vacuum lines look correct to me. Fuel filter is new and clean. Carb is clean inside. He is not getting a steady spray of fuel out of the needle. Since the carb is new I doubted the needle is clogged. I think the fuel pump is dying and its starving for fuel at low RPM. Once it gets up and the RPM's build it is able to pump enough fuel to run good. Sound reasonable to anyone else?

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