| Author |
Message |
Rob Combs
Samba Member
Joined: December 30, 2020
Posts: 587
Location: South Bay LA, California
|
 Posted: Wed Aug 06, 2025 7:16 am Post subject: Re: Overheating Help |
 |
|
Aluminum tape for HVAC ducting is stick as hell, tough, and works great if you have holes to plug and ducting to seal, which should be minimal for a non-doghouse.
Jimbo is right. You’re lean. Look to the electrodes in the center of the plug, NOT the threaded area. You want that pale white center to be light to medium brown to get you in the ballpark.
High compression plus too lean can seriously increase combustion temps, deck height notwithstanding.
Whoever said you need lower compression for higher-alcohol fuels, soory to say, is incorrect. Alcohol has less BTU than straight gasoline, so when you cut straight gas with alcohol you decrease BTUs. This works in your favor WRT compression, and AGAINST you WRT carb jetting. You need bigger jetting all other things equal.
Start with getting your jetting squared away and make sure you’re feeding the engine compartment plenty of air - cheap(er) place to start, effective, and doesn’t require you to wrestle another fan shroud on there - yet.
Make sure your oil pressure isn’t so high you’re bypassing the cooler.
Let’s do that and take it from there. |
|
| Back to top |
|
 |
Rob Combs
Samba Member
Joined: December 30, 2020
Posts: 587
Location: South Bay LA, California
|
| Posted: Wed Aug 06, 2025 7:21 am Post subject: Re: Overheating Help |
|
|
| Snoopy1971 wrote: |
| VW_Jimbo wrote: |
| Snoopy1971 wrote: |
The plugs look lean?? I though lean is covered in white/light gray ash? ... These plugs look neutral colored/ tannish to me |
Those plugs are lean. Fix that first.
Good luck. |
Sounds good. I'll clean the plugs up and back the mixture screw out a little and see what it does. Or would you suggest a bigger main jet? I already have a 135 in there, not sure what size my idle jet is, I have to look. |
I run a 142 main on a 1600. But I also have a 28mm venturi and fairly low compression/pumping pressure. |
|
| Back to top |
|
|
Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 26084
Location: Olympia Wash Rinse & Repeat
|
| Posted: Wed Aug 06, 2025 8:26 am Post subject: Re: Overheating Help |
|
|
| Snoopy1971 wrote: |
Are the flaps and thermostat needed? Mine never had them in since Ive had the car. I know some guys run them and some dont. |
If you mean "Needed" by that the engine will run better and last longer, then yes.
_________________
In Stereo, Where Available! |
|
| Back to top |
|
|
Rob Combs
Samba Member
Joined: December 30, 2020
Posts: 587
Location: South Bay LA, California
|
| Posted: Wed Aug 06, 2025 8:27 am Post subject: Re: Overheating Help |
|
|
One last point or two and I’ll shut up.
1) Sounds like your total timing (rev until it stops advancing) is in the ballpark but easy enough to print off the degree wheel over in the technical information section (i think that’s where it is anyway), laminate it, and ACCURATELY place it on your crank pulley with 2-sided gorilla tape, and then you can be sure.
2) Yes, at ~8.5:1 with presumably a stock cam for God’s sake run the best damn fuel you can buy!!!
Good luck with it! |
|
| Back to top |
|
|
Snoopy1971
Samba Member
Joined: May 15, 2020
Posts: 329
Location: Parkville, Maryland
|
| Posted: Wed Aug 06, 2025 5:07 pm Post subject: Re: Overheating Help |
|
|
| Rob Combs wrote: |
One last point or two and I’ll shut up.
1) Sounds like your total timing (rev until it stops advancing) is in the ballpark but easy enough to print off the degree wheel over in the technical information section (i think that’s where it is anyway), laminate it, and ACCURATELY place it on your crank pulley with 2-sided gorilla tape, and then you can be sure.
2) Yes, at ~8.5:1 with presumably a stock cam for God’s sake run the best damn fuel you can buy!!!
Good luck with it! |
Yeah I didn't advance it all the way to 32° because others have said too far advanced causes overheating. But I already have a degreed pulley on the engine.
And yes, I already have 93 octane in the car
_________________
1968 Bug |
|
| Back to top |
|
|
Snoopy1971
Samba Member
Joined: May 15, 2020
Posts: 329
Location: Parkville, Maryland
|
| Posted: Wed Aug 06, 2025 5:18 pm Post subject: Re: Overheating Help |
|
|
Checked my idle jet ... So a 135 main jet and a 65 idle jet
Are the main jets interchangeable? My carb is a Weber Redline 34 Pict-3, but I cant find jets for that particular Weber line ... Would one for Solex work? They look the same by the pics, but it's hard to tell.
https://www2.cip1.com/c13-43-5137-s/
Another question ... I'm going to try to source original parts for the doghouse shroud, fan etc ... What is the difference between a doghouse fan and a non-doghouse one, beside a slight size difference ... If I'm looking at one online at pics, is there a way to tell?
_________________
1968 Bug |
|
| Back to top |
|
|
Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 26084
Location: Olympia Wash Rinse & Repeat
|
| Posted: Wed Aug 06, 2025 5:35 pm Post subject: Re: Overheating Help |
|
|
| Snoopy1971 wrote: |
Another question ... I'm going to try to source original parts for the doghouse shroud, fan etc ... What is the difference between a doghouse fan and a non-doghouse one, beside a slight size difference ... If I'm looking at one online at pics, is there a way to tell? |
VW used a 29mm wide for the 1500 & single port 1600 engines (earlier fans are even narrower), as measured between the two round plates that make up most of the fan. When DH came out it started with 33mm, went up to 34, and finally 35mm. Other than these width changes there is no obvious other changes in the 1500/1600 single port, and the doghouse fans.
The below we posted a few years ago, but is still relevant about the thermostat:
Piston rings do not 100% seal the head chamber, cylinder and piston top from the engine inner case and oil sump. When any internal combustion engine that uses piston rings is not up to proper operating temp the rings seal even worse. The reason why an ACVW engine is more (clattery/tapping) noisy when first started up and quiets way down about ten minutes later is because the aluminum pistons need to swell up till they properly fit inside the cast iron cylinders. Aluminum swells up faster and more than cast iron does, so the designers of these parts had to compromise in this way. Cold pistons not fitting properly in the cylinders literally ever so slightly flop inside the cylinders, not good for ring sealing when this is going on. Which is also why the thermostat with flaps or the early throttle ring is so important for engine longevity for any ACVW engine using a carburator. Additionally gasoline is very non-lubricating, so too much fuel will both wash away the oil that should be lubricating and sealing the piston rings to the cylinders, and cause the rings cylinder surfaces to wear, thusly seal again even worse.
On top of the above, back when I was much younger and dumber, I ran my ACVW engines without thermostat system. This resulted in too much fuel getting into the engine oil and that caused the oil to turn acidic even with regular 3,000 mile oil changes and daily driving. This showed up most visually with the oil strainer in the sump getting very pitted up. Once I installed thermostats the used sump oil stopped smelling of fuel at each oil change and sump strainer stayed looking like new over many tens of thousands of miles. Once an ACVW engine reaches a minimum of 160F oil temp the fuel and water from burning fuel that gets past the piston rings can be vaporized out of the sump oil.
_________________
In Stereo, Where Available! |
|
| Back to top |
|
|
Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 26084
Location: Olympia Wash Rinse & Repeat
|
| Posted: Wed Aug 06, 2025 5:39 pm Post subject: Re: Overheating Help |
|
|
| Snoopy1971 wrote: |
| Are the main jets interchangeable? My carb is a Weber Redline 34 Pict-3, but I cant find jets for that particular Weber line ... Would one for Solex work? They look the same by the pics, but it's hard to tell. |
Have yet to deal with Weber jets, but by your image the VW main jets do not have that angled area just under the head of the Weber jet. Would check the bore the jet goes into and if that has a chamfered matching hole, then the Solex main jets will not work.
_________________
In Stereo, Where Available! |
|
| Back to top |
|
|
Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 26084
Location: Olympia Wash Rinse & Repeat
|
|
| Back to top |
|
|
Rob Combs
Samba Member
Joined: December 30, 2020
Posts: 587
Location: South Bay LA, California
|
| Posted: Wed Aug 06, 2025 6:34 pm Post subject: Re: Overheating Help |
|
|
| Snoopy1971 wrote: |
| Rob Combs wrote: |
One last point or two and I’ll shut up.
1) Sounds like your total timing (rev until it stops advancing) is in the ballpark but easy enough to print off the degree wheel over in the technical information section (i think that’s where it is anyway), laminate it, and ACCURATELY place it on your crank pulley with 2-sided gorilla tape, and then you can be sure.
2) Yes, at ~8.5:1 with presumably a stock cam for God’s sake run the best damn fuel you can buy!!!
Good luck with it! |
Yeah I didn't advance it all the way to 32° because others have said too far advanced causes overheating. But I already have a degreed pulley on the engine.
And yes, I already have 93 octane in the car |
Excellent. I agree, stay at 29 or 30 for now. We’ll sneak up on optimal later.
Everything said so far about running a thermostat is correct. Big thing to remember is they help to keep heat in the engine, not to remove it. If you’re overheating without one, adding one won’t be the solution. But if you’re going forward with converting to doghouse save yourself a shitload of trouble and put in the flap system while it’s already apart.
If you have a way to measure the main jet size, great! Verify it!
If you can’t easily get replacement jets in a variety of sizes, you can always ream them larger ever so slightly a bit at a time and sneak up on the size you need.
65 sounds kinda big for the idle/slow speed on your engine but that circuit is low load so not where you need to focus, at least yet. I wouldn’t try to enlarge the idle jet any more at this point.
Still feels like you’re way lean on the main. |
|
| Back to top |
|
|
Snoopy1971
Samba Member
Joined: May 15, 2020
Posts: 329
Location: Parkville, Maryland
|
| Posted: Wed Aug 06, 2025 6:38 pm Post subject: Re: Overheating Help |
|
|
| Eric&Barb wrote: |
| Snoopy1971 wrote: |
Another question ... I'm going to try to source original parts for the doghouse shroud, fan etc ... What is the difference between a doghouse fan and a non-doghouse one, beside a slight size difference ... If I'm looking at one online at pics, is there a way to tell? |
VW used a 29mm wide for the 1500 & single port 1600 engines (earlier fans are even narrower), as measured between the two round plates that make up most of the fan. When DH came out it started with 33mm, went up to 34, and finally 35mm. Other than these width changes there is no obvious other changes in the 1500/1600 single port, and the doghouse fans. |
Wait, so there's 3 diff sizes of DH fans? But the DH fan shroud dimension stayed the same? Sounds like I cant just get a random DH fan ... sounds like I need to get a fan and shroud that were already used together.
_________________
1968 Bug |
|
| Back to top |
|
|
Rob Combs
Samba Member
Joined: December 30, 2020
Posts: 587
Location: South Bay LA, California
|
| Posted: Wed Aug 06, 2025 6:41 pm Post subject: Re: Overheating Help |
|
|
I have serious doubts there are 3 different shroud thicknesses, so at what point are we belaboring the point and splitting hairs?
EDIT: 3 different doghouse fan shroud thicknesses is what I meant.
Put more succinctly, do we really need to induce this poor soul into hand-wringing anxiety over the width of the GD [edit: doghouse] fan?
At some point, practicality has to win the day.
Last edited by Rob Combs on Wed Aug 06, 2025 7:20 pm; edited 1 time in total |
|
| Back to top |
|
|
Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 26084
Location: Olympia Wash Rinse & Repeat
|
| Posted: Wed Aug 06, 2025 7:17 pm Post subject: Re: Overheating Help |
|
|
| Snoopy1971 wrote: |
Wait, so there's 3 diff sizes of DH fans? But the DH fan shroud dimension stayed the same? Sounds like I cant just get a random DH fan ... sounds like I need to get a fan and shroud that were already used together. |
Or take a measuring tool to the next VW swap meet or ask any seller in the classifieds if they would measure the width of the fan they are selling.
Personally have carried a 6" measuring caliper in the back pack at all the swap meets for 30 years or so to sort out parts like this.
Know a fellow that converted to the DH cooling system, but used the 29mm wide 1500/1600 single port cooling fan he already had. The engine that ran fine with the non-DH shroud all the sudden was over heating with DH shroud. Once he upgraded to one of the larger DH fans, it ran cool again.
_________________
In Stereo, Where Available! |
|
| Back to top |
|
|
Nitramrebrab72
Samba Member
Joined: November 10, 2018
Posts: 901
Location: France
|
| Posted: Wed Aug 06, 2025 11:49 pm Post subject: Re: Overheating Help |
|
|
| Snoopy1971 wrote: |
I thought it odd and quite coincidental that the fuel pump worked fine and the engine ran outside the car a week or so earlier, but now it wouldn't run in the car, but OK, I guess it was a coincidence.
|
What are the odds of it failing at the same time as you overheating???
More than 9 times out of 10 double failures are linked not coincidence.
The fuel pump was already on it's way out , no longer able to keep the carburettor bowl fully brimmed all the time, pumping enough fuel to keep you running but not enough to stop the carburettor leaning out and the engine from over heating.  |
|
| Back to top |
|
|
Snoopy1971
Samba Member
Joined: May 15, 2020
Posts: 329
Location: Parkville, Maryland
|
| Posted: Thu Aug 07, 2025 3:29 am Post subject: Re: Overheating Help |
|
|
| Nitramrebrab72 wrote: |
| Snoopy1971 wrote: |
I thought it odd and quite coincidental that the fuel pump worked fine and the engine ran outside the car a week or so earlier, but now it wouldn't run in the car, but OK, I guess it was a coincidence.
|
What are the odds of it failing at the same time as you overheating???
More than 9 times out of 10 double failures are linked not coincidence.
The fuel pump was already on it's way out , no longer able to keep the carburettor bowl fully brimmed all the time, pumping enough fuel to keep you running but not enough to stop the carburettor leaning out and the engine from over heating. |
Makes sense, but I do have a new fuel pump installed and still overheating
_________________
1968 Bug |
|
| Back to top |
|
|
Nitramrebrab72
Samba Member
Joined: November 10, 2018
Posts: 901
Location: France
|
| Posted: Thu Aug 07, 2025 7:11 am Post subject: Re: Overheating Help |
|
|
| Did you check the fuel line is running free and not bunged up somewhere ?? |
|
| Back to top |
|
|
Snoopy1971
Samba Member
Joined: May 15, 2020
Posts: 329
Location: Parkville, Maryland
|
| Posted: Thu Aug 07, 2025 10:31 am Post subject: Re: Overheating Help |
|
|
| Nitramrebrab72 wrote: |
| Did you check the fuel line is running free and not bunged up somewhere ?? |
Bunged up? I guess that means bunched up, kinked, bent, etc ... nope its all straight and free-flowing and all newish as I just replaced last summer.
_________________
1968 Bug |
|
| Back to top |
|
|
VW_Jimbo 
Samba Member
Joined: May 22, 2016
Posts: 11242
Location: Huntington Beach, CA
|
| Posted: Thu Aug 07, 2025 10:15 pm Post subject: Re: Overheating Help |
|
|
| Rob Combs wrote: |
| Snoopy1971 wrote: |
| Rob Combs wrote: |
One last point or two and I’ll shut up.
1) Sounds like your total timing (rev until it stops advancing) is in the ballpark but easy enough to print off the degree wheel over in the technical information section (i think that’s where it is anyway), laminate it, and ACCURATELY place it on your crank pulley with 2-sided gorilla tape, and then you can be sure.
2) Yes, at ~8.5:1 with presumably a stock cam for God’s sake run the best damn fuel you can buy!!!
Good luck with it! |
Yeah I didn't advance it all the way to 32° because others have said too far advanced causes overheating. But I already have a degreed pulley on the engine.
And yes, I already have 93 octane in the car |
Excellent. I agree, stay at 29 or 30 for now. We’ll sneak up on optimal later.
Everything said so far about running a thermostat is correct. Big thing to remember is they help to keep heat in the engine, not to remove it. If you’re overheating without one, adding one won’t be the solution. But if you’re going forward with converting to doghouse save yourself a shitload of trouble and put in the flap system while it’s already apart.
If you have a way to measure the main jet size, great! Verify it!
If you can’t easily get replacement jets in a variety of sizes, you can always ream them larger ever so slightly a bit at a time and sneak up on the size you need.
65 sounds kinda big for the idle/slow speed on your engine but that circuit is low load so not where you need to focus, at least yet. I wouldn’t try to enlarge the idle jet any more at this point.
Still feels like you’re way lean on the main. |
Agree with the idle and bumping up the main. I would jump to 150 on the main and see what happens. I would rather see it a little fat than too thin. I bet you will get down in the 140 - 145 range.
Idle is good at 65, but some motors respond well to a fatter idle jet. Once you get the main closer to “good”, I would try a 70 idle jet to see what happens. The motor is always pulling from the idle so why not feed it a tiny bit more. If it starts talking back, you can always reduce it!
Check the float is floating, not getting stuck on its swing. I have been baffled once by each issue. Also that it is set to the proper level and that there is no obstruction in the float valve. Also be sure the float valve seals well.
Double check that fuel pump pressure. 2.5 - 4psi. I like 3.5psi. Also volume. I use an oil quart to catch the fuel in a 15 seconds period, cranking at normal speed. Take the measurement in an old oil quart container so you can read the volume. Then multiple by 4, so you get a minutes worth of cranking calculated from the 15 seconds. Because in a full minute, the fuel pump should flow .6 to .8 gallons of gas.
Somewhere in that range works.
_________________
Jimbo
There is never enough time to do it right the first time, but all the time necessary the second time!
| TDCTDI wrote: |
| Basically, a whole bunch of fuckery to achieve a look. |
| 67rustavenger wrote: |
GFY's Xevin and VW_Jimbo!  |
|
|
| Back to top |
|
|
Snoopy1971
Samba Member
Joined: May 15, 2020
Posts: 329
Location: Parkville, Maryland
|
| Posted: Fri Aug 08, 2025 4:57 am Post subject: Re: Overheating Help |
|
|
| VW_Jimbo wrote: |
Agree with the idle and bumping up the main. I would jump to 150 on the main and see what happens. I would rather see it a little fat than too thin. I bet you will get down in the 140 - 145 range.
Idle is good at 65, but some motors respond well to a fatter idle jet. Once you get the main closer to “good”, I would try a 70 idle jet to see what happens. The motor is always pulling from the idle so why not feed it a tiny bit more. If it starts talking back, you can always reduce it!
Check the float is floating, not getting stuck on its swing. I have been baffled once by each issue. Also that it is set to the proper level and that there is no obstruction in the float valve. Also be sure the float valve seals well.
Double check that fuel pump pressure. 2.5 - 4psi. I like 3.5psi. Also volume. I use an oil quart to catch the fuel in a 15 seconds period, cranking at normal speed. Take the measurement in an old oil quart container so you can read the volume. Then multiple by 4, so you get a minutes worth of cranking calculated from the 15 seconds. Because in a full minute, the fuel pump should flow .6 to .8 gallons of gas.
Somewhere in that range works. |
Oh yeah I had checked the float previously. It didnt seem to be sticking, although I wasnt sure what I was looking for. I filled the bowl up with a syringe of gas ... eventually the float came up. It seemed like I had to fill it for a while until the float moved, but I chalked it up to starting with an empty bowl.
Yeah I have to call Weber Redline to see if they have jets for this carb. I'm not seeing anything on their website that looks like the tapered geometry of the jet I pulled out of mine. Their website sucks ... no search feature on it.
Yeah I have to look up how to check the pressure of the fuel pump .. I know I saw it somewhere. It's a rebuilt Pierburg pump from Sparxwerks. Just put it on a couple weeks ago. I had gotten it because my engine ran fine outside the car, but when I put it back it, it wouldnt stay running. Would start and run 2-3 seconds and die. After some troubleshooting, I figured my fuel pump had taken a crap, so got the rebuilt one.
_________________
1968 Bug |
|
| Back to top |
|
|
Snoopy1971
Samba Member
Joined: May 15, 2020
Posts: 329
Location: Parkville, Maryland
|
| Posted: Fri Aug 08, 2025 6:25 am Post subject: Re: Overheating Help |
|
|
| Snoopy1971 wrote: |
Yeah I have to call Weber Redline to see if they have jets for this carb. I'm not seeing anything on their website that looks like the tapered geometry of the jet I pulled out of mine. Their website sucks ... no search feature on it.
|
Interesting ... the guy in this thread says he took a jet out of a solex and put it in his Weber Redline 34 PICT-3. Thats weird because the jet in mine has the tapered part, but all the jets for a Solex I see online are flat under the head like here:
https://empius.com/products/112-5-main-jet-for-empi-40k-kadron-brosol-solex-carburetors-14/
_________________
1968 Bug |
|
| Back to top |
|
|
|
