1600 dual port running on 2 cylinders

[67rustavenger]

Maybe you guys with later dual port single carb engines can help me out.

I'm working on a friends 66 beetle with a dual port 1600 stock engine, single carb.

I did the usual tune up and replaced the intake to head gaskets. Valves have been correctly adjusted.

The car ran fine when I drove it to my house for a complete new clutch install and to clean up some PO hacks that were making the car unreliable.

Put it all back together and installed the engine.
Fired it up and it runs on the 1-2 side only. After a minute of running. I can grab the exhaust pipe on the 3-4 side bare handed. The 1-2 side would produce 2nd degree burns instantly if I touched it.

So the suspect is a leaking intake gasket or a leaking intake boot.
I have not yet tried carb cleaner to find the leak as the engine dies unless I pedal it to keep it running.

I have had many beetles over the years. Just never a single carb dual port. All I have ever had were SP single carb and dual carb dual port engines.

This issue is a little baffling.
Am I on the right track suspecting the intake gasket and boot on the 3-4 side of the engine?

In the image, the 3-4 spark plug wires are temporary. I was trying to see if maybe the other wires were part of the problem. They weren't.

_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[Cusser]

In your photo, the #3 and #4 spark wires look correct in their temporary location. With a single carb, issue has to be not getting spark to #3 and #4, or a large vacuum leak. Wouldn't hurt to pull the plugs and take a look at those. Or to try to run at night and see if a spark is jumping.

I use aerosol starting fluid to try to find vacuum leaks, there are 3 potential sources for this on the #3 and #4 side of the engine.
1. manifold boot on that side
2. gasket between end casting and cylinder head
3. some manifolds have a nipple (which formerly connected to a compensator on the left firewall), usually these are capped off or closed off with a piece of tubing and a golf tee, can't see that area in your picture. Look at this photo, maybe that engine is pulling in air through that.

_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[67rustavenger]

Thank you for the input cusser.

I guess it's down to two possibilities.
The end casting does infact have the vacuum plug in place.

Thank you again.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[Cusser]

Yeah, I doubt that both #3 and #4 wires could be bad, and would run OK on 3 cylinders. An inline spark checker on #3 and #4 might rule out any spark issues for those two.
https://www.harborfreight.com/in-line-spark-checker-63590.html

_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[Eric&Barb]

You need the proper hard rubber grommet in the front engine tin where the metal fuel line passes thru. With no protection there the edge of the engine tin will saw thru the metal line.

In a pinch one can use a small section (about 2"long) of the German flex fuel line to protect that. Slit the flex line down one side, slip in place with slit on upside, hose clamp to keep in place.
_________________
In Stereo, Where Available!

[67rustavenger]

[ashman40]

Looking for common failure issues between cylinders #3 and #4...

Compression test cylinders #3 and #4 to make sure the head isn't loose. Between all four cylinders the compression readings should be within 10% of each other.

Remove the valve cover for #3 and #4 cylinders and manually rotate the crank thru two revolutions and confirm the valves open and close for both cylinders. Make sure the rocker arm assembly hasn't come loose.

As suggested, spray carb cleaner on the intake manifold junction points looking for a leak. If the idle changes at all (up or down) when you hit a spot with the spray you have found a leak.

Test the ignition for spark on the two cylinders. The best option is to use the actual spark plugs from each cylinder. You could find that distributor and plug wires all work normally but if you don't use the actual spark plugs you could miss that the plugs themselves have failed. I have seen spark plugs fail internally where the conductor inside the ceramic cracks. The plug looks completely normal but doesn't work.

_________________
AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[VW_Jimbo]

Sorry man, no fun chasing dead holes!

Experience says it a bad intake boot or gasket. Carb cleaner will make quick work finding it.

Seen the distributor cap break at the 4 to 3 side and ground to the distributor body, through a steel vacuum tube.

Seen flat distributor lobes on two out of four.

Seen hundreds of internally cracked heads.

Misadjusted valves.

Valves that do not close because of old crappy oil.

Just a few things to check!
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[VW_Jimbo]

Ditto
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[67rustavenger]

Ok guy's thanks for the hints.
Valve were adjusted yesterday afternoon. Oil was changed while the valve adjustment took place. Heads are not cracked. I drove this car to my house and it ran flawlessly. It's either the boot or the gasket (New) on the 3-4 side.

I just bought a new set of boots and will track down the leak and fix it.

That is after I unclog a left carb jet on my 1679 that's been giving me fits.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[andk5591]

Are you 100% sure the plug wires on on right....Not that I have ever accidentally reversed them But it has always been either a vac leak or reversed wires....
_________________
D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them...

[Cusser]

If he wasn't 1500 miles away, I'd love to take an in-person look !!!
_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[Dark Earth]

[67rustavenger]

Just to dispel the firing order comments.
I just went out and reversed the 3-4 wires. Started the engine and it runs the same as yesterday. Two cylinders and the 3-4 exhaust, I can grab bare handed no heat. 1-2 way too hot to hold onto.

Tomorrow, I'll remove the 3-4 intake manifold and replace the gasket and intake boot.

Hopefully that takes care of the problem.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[VW_Jimbo]

Good luck man! You’ll get it tomorrow!
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[andk5591]

The manifold boot leak can also be intermittent....Ran into that last year...Was not fully on..Depending on how warm the car was, it would run decent and then run like crap. And I have seen the rubber caps break down pretty quickly on the intake ports because they get pretty warm. Consider using high temp RTV or JB weld on a machine screw to seal it.
_________________
D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them...

[67rustavenger]

So I have the offending left end casting off. Nothing like using two wrenches and turning a nut 1/64th of a turn to get it off.

I noticed that the end casting and the intake runner don't align very well.
This car has an alt. on it and the intake runner cannot be raised to align it with the end casting. It's close but rides low in the boot.

When I install the new boot. Is the best technique to mount the boot on the end casting and then slide it onto the intake runner?
This seems logical to me as I will not have to fight to get the boot on the end casting once I have reinstalled it.

Make sense?

BTW, I did double check the valve adjustment. I am spot on in that regard.

Happy Fathers Day to all you Dad's.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[andk5591]

Is there a tab that bolts the center part to the top of the case? If so, 13mm socket to loosen it. Should go together like buttah....
_________________
D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them...

[67rustavenger]

Yep. I already loosened that tab. The intake runner is not going to rise due to it hitting the bottom of the alt.
To bad this can doesn't have a generator. I'd be golden.

Thank you for the tip.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!

There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!

[David_nc_72std]

Maybe if you loosened the intake on the opposite side it would allow enough movement to line everything up properly.