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Mon Oct 09, 2017 12:19 pm

Hi all can someone tell me whats the best plugs to use in my 1600 Duelport
Im seeing theres Borsh WR8AC-4 and 7908 are here any others if so whats the best Thanks

Mon Oct 09, 2017 12:37 pm

Problem is there are two different dual port heads out there. One requires the standard length spark plug. The other requires a longer spark plug at the threads for a 3/4" dimension.

Using the wrong length of spark plugs can cause you problems down the road. So you will need to figure out which head you have.

Do a search for "Dual Port Head" or "Spark Plug Length" and check the "Titles Only" box to cut down on having too many results.

BTW "Duel" is where people fight to the death.

Mon Oct 09, 2017 2:06 pm

Wennie, is your engine carbureted or fuel injection?

On my 1974 dual-port carbureted 1600 engine, I use NGK B5HS. NGK tends not to seize up as much as Bosch plugs.

Tim

Mon Oct 09, 2017 2:43 pm

I actually believe there were at least four (4) different spark plugs used in T1 heads. This is what I've learned over the years about T1 spark plugs:
1) Original spark plug: Bosch W8AC / NGK B6HS (notice these are non-resistor plugs)
W = 14mmx1.25 threads
8 = heat range (Bosch)
A = thread length is 1/2" with crush washer
C = copper center electrode

2) Mexican Beetle heads(?) : Bosch W8DC / NGK BP5ES
Stock diameter plugs but longer allowing for a thicker head
W = 14mmx1.25 threads
8 = heat range (Bosch)
D = thread length is 3/4" with crush washer
C = copper center electrode

3) Many aftermarket performance heads: Bosch X5DC / NGK DP8EA-9; (12mmx1.25 x 3/4")
These are smaller diameter (12mm) plugs with longer (3/4") threads allowing the head to have even more material above the cylinder/piston.

4) Over the years, aftermarket T1 heads may have also come with the following:
12mmx1.25 x 1/2" - Smaller diameter than stock (more material) but same short length

5) I also recall reading of heads that didn't use crush washers and instead used a tapered seat for the spark plugs. That makes a 5th style of head.

If you have an unknown head, you really need to measure the depth of the threads and their diameter. Diameter is not too hard. If it is the wrong side it will not fit.
You do NOT want to put a longer threaded spark plug into a shallow threaded hole. The exposes threads will collect carbon deposits over time and when you remove the spark plug you will rip out the head. That is if the piston doesn't smash the electrode closed on the plug end.
Nor do you want the spark plug to be recessed in the plug hole. This will shroud the compressed air-fuel mixture from the spark. Deposits will also form on the exposed threads in the threaded recess and reduce the effectiveness of the spark plugs.

You want the electrode to sit just inside the combustion chamber.

Here is a PDF with the description of how to translate the Bosch spark plug numbers:
https://www.euromotoelectrics.com/v/vspfiles/assets/images/superplus_designationcodes_10.pdf

Here is the same sheet for NGK spark plugs:
https://www.ngksparkplugs.com/assets/design_symbols_plugs.pdf

Mon Oct 09, 2017 3:13 pm

Pull a plug and see what you have if it worked before buy it again. You will see if it is short and fat or long and skinny.

Mon Oct 09, 2017 3:51 pm

Starbucket wrote: Pull a plug and see what you have if it worked before buy it again. You will see if it is short and fat or long and skinny.

Problem with that is the DPO could have installed short plugs in a head that needs the long reach 3/4" threaded plugs. Sure they worked before, but can carbon over if continued to be used. Also one head could be the short and the other the long. At this point, anything is possible.

Mon Oct 09, 2017 6:08 pm

so take a piece of wire, bend the tip so you have a shoulder, stick it in the plug hole and pull it tight, make a mark on the wire, and you should have a pretty good idea as to how long the plug threads need to be

Mon Oct 09, 2017 6:34 pm

Years ago I had two Bosch plugs bad out of the box. They only failed once hot, so the problem was veryt difficult to find.

I switched to NGK plugs and find that the B5HS (rather than B6HS mentioned by Taskb above) work better. Never had a bad one either.

And yes, the B5ES (or BP5ES) are the longer thread pugs (E for extended thread) for the replacement heads.

Mon Oct 09, 2017 9:14 pm

Rub a little antisieze on it before you stick it in.

Tue Oct 10, 2017 12:35 am

Is there a way to tell what plugs fit a 1600 single port?[/b]

Tue Oct 10, 2017 4:23 am

If you stick to Bosch or NGK plugs you won't go wrong. There are stories of some people having bad experiences with both brands of plugs but that is probably down to normal manufacturing failure rates.
I have heard that the Bosch plugs tend to be on the high side of the thread diameter tolerances i.e. they fit a bit more snuggly, but if your spark plug threads in the head are clean there shouldn't be a problem.
If the plugs are not easily removed by hand after a turn or two by socket and the plug threads are clean then you should probably run a spark plug thread cleaner into the heads to get rid of any buildup. Also make sure the plug seat is clean as a significant amount of heat is transferred at that point (when there is no buildup).
Some people recommend using an anti seize compound on the threads of a plug. I have never done this and never had a problem in 35 years - its a users choice thing and I don't think there is a right answer. The only issue is manufacturers torque settings for spark plugs are based upon a non lubricated thread. So if you use anti seize compound and torque the plugs to the manufacturers specification you will end up over tightening the plugs.

Given the tight area in the engine bay of a Beetle I wonder how many actually use a torque wrench to tighten the plugs? - how many actually own one or know how to use one properly.

Tue Oct 10, 2017 4:52 am

Here's a good pic that shows WHY you want to use the correct spark plug with your head:

Tue Oct 10, 2017 7:44 am

Meiang wrote: Given the tight area in the engine bay of a Beetle I wonder how many actually use a torque wrench to tighten the plugs?

Here in the states there's Harbor Freight Tools, which periodically puts its click-type torque wrenches on sale for $10 USD, and they are rated pretty good. Myself: I have one of 1/2" drive, one of 1/4" drive, and two of 3/8" drive. I used the 3/8" drive to torque the plugs on my 1835cc DP engine, after a solid threaded spark plug insert (NOT a TimeSert) vibrated loose after a few years, so I replaced the insert and plug, and this time used the torque wrench there because I hadn't been torqueing the plugs enough (because on VWs I had been wary about stripping out the threads in the heads).

So now I recommend using a torque wrench on VW plugs, even carry one of those torque wrenches and spark plug socket in that VW's trunk.

Tue Oct 10, 2017 12:21 pm

I like bosch platinum's, puttem in and never think about them again....untill somebody ask this question.

Thu Oct 12, 2017 11:12 am

Chris333 wrote: Is there a way to tell what plugs fit a 1600 single port?[/b]
Unlike the DP heads there wasn't much demand for performance SP heads (maybe back in the early '60s). So if you have a VW manufactured SP head it probably uses the same Bosch W8AC spark plug.
Again, measure the threads in the head for both size and depth. W8AC = 14mmx1/2"

I did a quick search and the '70 Beetle (1600 SP) Owners Manual lists the same Bosch plug as the '69 and '73 manuals (W145T1 = W8AC):