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Intake Manifold
Posted: Mon Jul 07, 2025 3:20 pm
by No More Landy
Hi Guys
I am again having problems with spark plugs dying/breaking down due to previously suggested overheating.
My beetle was modified by previous owner from 1,3 to 1,6 litres I assume with only the barrels and pistons as the intake manifold and carb (31 ICTH)
are pointing to it being a 1,300 as well as the deck lid decal.
Is it possible to get second hand intake and carb from a 1,6 or should I rather add one carb per cylinder head to get it running proper.
Don't know why I didn't go this route long a ago !
Re: Intake Manifold
Posted: Mon Jul 07, 2025 10:06 pm
by Haans
Hi, don't know your problem background,......and do not proclaim to be a "ghuru" on aircooleds. but !
You goto make sure that ALL the tins are inplce and seal properly,....for starters
My 1600 SP is running on a31 pic carb with no issues .....to date......hoping it to stay that way

Dumping plugs ?.....too rich / lean ?
Overheating ? .....fanbelt tention ? ,....ignition timing ?
Hopefully all these remarks will trigger you to dig deeper into your grey matter, and /or some ghuru will guide you,... & me to solving your issue
Regards Haans
Re: Intake Manifold
Posted: Tue Jul 08, 2025 4:56 pm
by 73type2
You don’t mention if you have a 1600 single or twin port. If twin port, I’d get a 34 Pict 3 carb with matching intake manifold and distributor. I’m actually running a 1600 single port in my 1971 1300DP while I’m sorting out the 1300DP engine on the stand. The 1600 is running nicely with a cheap Chinese carb I bought off Amazon. Now I’m delaying returning the 1300DP to its rightful place!
Re: Intake Manifold
Posted: Tue Jul 08, 2025 5:58 pm
by No More Landy
It’s a twin port head and manifold risers
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Re: Intake Manifold
Posted: Tue Jul 08, 2025 9:29 pm
by 73type2
Twin ports are much more prone to vacuum leaks due to those damn rubber boots, thus playing havoc with your carb settings. Make sure there is no false air getting into the system, leading to a rich mixture.
Re: Intake Manifold
Posted: Wed Jul 09, 2025 2:51 am
by Tony Z
It could also be blowby that is adding oil into the chamber and fouling out your spark plugs.
Or weak spark.
What do the plugs look like when you remove them?
Re: Intake Manifold
Posted: Wed Jul 09, 2025 12:57 pm
by No More Landy
Thanks guys. When i rebuilt the motor with new rings and new cylinder heads I put new rubber boots on the manifold and new gaskets so don't suspect that.
Have new distributor cap and leads from ffr.
I suspect the jetting in the carb may be wrong possibly?
Have done the usual of setting the timing and tappets. She runs beautiful for 4 months and then slowly like a pig.
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Re: Intake Manifold
Posted: Wed Jul 09, 2025 8:27 pm
by 73type2
Don’t be too sure about the quality of parts we get nowadays. Rather check for vacuum leaks to eliminate that as a possible issue.
Re: Intake Manifold
Posted: Wed Jul 09, 2025 9:59 pm
by No More Landy
73type2 wrote:Don’t be too sure about the quality of parts we get nowadays. Rather check for vacuum leaks to eliminate that as a possible issue.
I did by using engine start spray all over intake to see if revs changed
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