Help with my new engine that runs like shit

[Mauidude]

Ok got your attention 😎 I’m quite depressed about my turnkey engine I recently installed. Builder will remain un named for now.
2110 82x90.5 chromoly crank , scat c45 cam and lifters. Empi big valve heads, Full flow Autolinea case. Dual HPMX 44, shockwave electronic ignition.
Drove for several trips to town no issues, lots of power happy with it.

Went on a VW cruise last weekend, ran great until it started popping on deceleration. Got to the second poker run stop, fortunately near my house , when I started it , it didn’t want to idle at all, if I throttled it it would run but very rough. Took it home. Total mileage is about 90 since install.
Pulled plugs, 3 black sooty , one grey. Plugged idle jets my first thought, texted builder, same assumption. Pulled carbs cleaned all jets , and circuits that I could , no noticeable dirt or crap from the gas..
Reinstalled ran the same. Didn’t.
Checked valve adjustment, all spot on.
Compression test all 150 ish.
Checked wires, all solid, good
Pulled distributor ,wires and coil and swapped with Pertonix from my old engine. Same issue !!!
I’m at a loss, it’s like only 2 cylinders are firing like timing is completely whack?
If it’s internal what could be the cause?
Thanks in advance for any ideas!

[Don Jones]

I have a very similar build as yours. I have cb's jet doctors and cb's float vent extender on my 44's. Same symtoms, if you throttle it, it runs fine.

Used my temp gun and checked the exhaust pipe temp and found (2) pipes were reading very low. Meaning they're not getting gas. This allowed me to determine what carb needed help. The temp gun is your best friend for diagnosing engine problems.

I even looked thru the jets and could'nt see any crud.

It was my idle jets, (2) of them, removed them and ran a fine wire thru them, removed the idle mixture screws and shot compressed air from top idle vent thru the carb and put finger over the idle jet hole and mixture hole intermittently. Whatever it was, was removed and engine runs great.

[RLFD213]

If the HPMX carbs are like real webers, I would check the idle gets for being plugged. If the builder is close go back to them and let them fix the issue. If you’re not running a good fuel filter run one. And try to keep good fresh fuel in the car all the time

[Brian_e]

Re-check the carb sync. Make sure the linkage is set up properly in the first place.

Brian
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[fl59bug]

Some things to check:

- possible vacuum leak at manifold to head or carb to manifold. A sync meter on venturies should should one or more carb barrels with markedly lower vacuum than the others

- dead cylinder: pull/reconnect plug wires to see if one makes no difference in rpm, or get a temp gun on each header pipe to see if any pipes cooler than the others

Ted

[Dauz]

If people would just learn to pull and blow our their idle jets with carb cleaner, I wouldn't sound like a broken record. An asshair follicle in that jet can ruin your day.

[Mauidude]

Thanks for the replies everyone , @ dauz. I did say that I cleaned all jets didn’t I? I’ll pull the carbs and try again, fingers crossed.
@RLFD213 nope I’m in Hawaii he’s on the west coast.
Don Jones thanks, going to do that today.
Fl59bug if only I could get it to run long enough to walk from the front of the truck to the engine compartment

[Dave Becker]

While you have the carbs off, put a new set of plugs in it, I've had a few new plugs fail, NGK's too, engine sounded like it had a plug idle jet and wouldn't idle.
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[liquidrush]

I learned this at an independent shop around 1980, we did tons of carburetor work and rebuilds back then. As we know, crud and carbs don't get along. Try this, rev that thing up to about 3500 rpm and put your hand over a carb sealing it off while opening the throttle. When it bogs down take your hand off and clear the engine out. Doing that draws a much higher vacuum all through that carburetor often times clearing out the problem. We called it blowing it's nose.

[Don Jones]

Mauidude,

Hope you have Weber Windows for easy access to the jets, mixture screws and spark plugs. If you don't, they'll make your life alot easier working on the carbs and plugs.

What plugs are you running? I use NGK D6ea's. Buy them off Ebay w/ free shipping.

Remove the top of both carbs and ensure that both carbs have the same fuel level in the bowls. Found out that the 12mm / 30mm float level shit resulted in different bowl fuel levels.

Remove the idle mixture screws & idle jets. Clean the jets with a thin guage copper wire.

Blow compressed air thru the idle vent in the top of the carb and periodically put your finger over the idle jet hole in the carb and idle mixture screw hole so that it can blow out any small debri out the carb.

44 idf's use a fairly small idle jet usually 50, 52 or a 55 so they're pretty small and clog up easily. I run telephone (inside wiring) thru the jet. i strip the insulation off and it fits nicely in the idle jet and it's copper so it soft to prevent scouring inside the jet.

[oprn]

[Mauidude]

Aloha all, Got it running again! Woo hoo! Pulled the carbs again and cleaned again, blew cleaner and air through the jets and air hole for the idle circuit, alternating as suggested between the mixture and idle openings, also used a thin strand of copper wire. What really worked I don’t really know. Oh and to
Don, that’s my single cab engine compartment before the new engine. This is the new one. Plenty of access 👍🏼 and yes same spark plugs as you . Thanks for all the help!

[Dauz]

[Don Jones]

Glad to hear you got it fixed. If it ever happens again you know what to do. I use the CB Fuel Bowl Vents and CB Jet doctors to try and prevent rubbish from entering the carb, may want to look into them.

Does the single cab have a removal cover above the engine?

[Mauidude]

Don, no access from above, I think the vanagon truck got that. The new HPMX already has the jet doctors or a copy of it installed.
what is the advantage of the float bowl vents? Seems like that’s intended for off roading.

[Don Jones]

[nextgen]

Don Jones think you saved .me time and money with your temp gun, use idea.

I did a valve job before I put my bug away for the winter and when I recently started it for the winter it bucked from side . and it ran but my idle was very low!!! Thought I screwed up my valve job. So I double checked it and it was fine.

Took my wifes temp gun, it did not go high enough to get a reading. So I used my hand and and got burnt on the 3 and 4 side exhaust , then went to the 1 and 2 side and that side was cold !!!!!

At first I was freaked out thinking it was some thing really bad. ( actually still don't know ) I have 36 Dells will check them tomorrow.

Oh yes that is the T-4 engine I wrote my manual about in 1993

Thanks

Joe
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[Don Jones]

[nextgen]

Thanks for the advice, what is funny is I installed a Fuel Cut off switch, I was told it was better to run them dry for long time rests.

So worked good for years. I used my Snail Carb tester and both are pulling the same amount of air. So I figured it was not the carbs. May not have the time today to check the carb today. Will let you know.

I may have the time to blast the carb intake . with starter fluild, at least to see if it will make the carb run.
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[nextgen]

OK did a quick test and shot some carb cleaner and starter fluid into some jets .

It started to stall but then it started to run a bit better. Slight back fires and engine started to run smoother. Put in half a tank of gas and took it for a rice. Better not perfect. Will pull the carb and clean it out.

Thanks
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