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who has a good stock of cylinder base shims? Type 4
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SGKent Premium Member
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PostPosted: Wed Aug 19, 2020 7:33 pm    Post subject: who has a good stock of cylinder base shims? Type 4 Reply with quote

Running CR numbers today and the Mahle piston set had 11 cc dish but the new factory KS has a 15 cc dish. Need a different shim or I will be at 7.0:1 with the new pistons, which is too low. What I have is .071" shims. I need essentially .050" although it looks like no one sells them. Anyone know who has high quality shims that hold up well? .040" will give me 7.4:1 which I could live with. A .050" shim would be a deck of .080". A .040" would give me a deck of .070.
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old DKP driver
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PostPosted: Wed Aug 19, 2020 9:17 pm    Post subject: Re: who has a good stock of cylinder base shims? Type 4 Reply with quote

AC.Net has a good selection and European motors does as well
Oh wait a minute ............never mind Cool
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PostPosted: Wed Aug 19, 2020 10:06 pm    Post subject: Re: who has a good stock of cylinder base shims? Type 4 Reply with quote

thanks Chris. did you get your flywheel shims? I never heard back from you if any of those would work for you.
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RalphWiggam
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PostPosted: Thu Aug 20, 2020 5:23 am    Post subject: Re: who has a good stock of cylinder base shims? Type 4 Reply with quote

I could be wrong, but even with the .040 shim, isnt a deck of .070 a bit high?

I was under the impression that somewhere around .050 deck is about where you want to be. Im running .040 on my 1.7L.
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old DKP driver
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PostPosted: Thu Aug 20, 2020 8:32 am    Post subject: Re: who has a good stock of cylinder base shims? Type 4 Reply with quote

I received them from the type 4 store. Len shipped them pretty quick too !
Thanks for remembering.
86-A CAM & Lifters also came a day later. I’m stoked ! Except for orange sky
& the white westy I saw on the news this morning getting ready to burn up
In the fire north-west of Santa Cruz. Evil or Very Mad
Now I wonder who owns it and really feel bad for their loss.
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PostPosted: Thu Aug 20, 2020 9:21 am    Post subject: Re: who has a good stock of cylinder base shims? Type 4 Reply with quote

RalphWiggam wrote:
I could be wrong, but even with the .040 shim, isn't a deck of .070 a bit high?

I was under the impression that somewhere around .050 deck is about where you want to be. Im running .040 on my 1.7L.

The combustion chamber on a 1.7 is a different size than on a 2.0. As long as the piston clears the valves and head as it wears in, generally you go off the final compression ratio you want, and totally ignore the parrots. It is the CR that makes heat before any gasoline is even burned. Put an IR thermometer on an air compressor sometime, it is too hot to touch.

In 1991 on a 2L VW recommended an aluminum base shim of 1.6mm and no head gasket. 1.6 mm is .062." That would give a totally stock deck of .092." The deck is about .030" with no shim. But that new CR would be 7.1 if you used all new factory parts. If instead you used the 11 cc dish Mahle pistons the CR would go back to 7.3. KS pistons are a 15 cc dish.

I don't want to mislead anyone that the "squish" in a cylinder doesn't make a difference in the mixing of air and fuel. Honda added a 3rd valve to their engines back in the 1970's to create turbulence that helped mix fuel and air to make a leaner burn. My sources in the racing world tell me that "squish" has to be around or under .040" to get real benefit. The problem is that in a 2L bus we really can't go to high CR's without other consequences. My source, whose father was my mentor, reminded me that his dad not only worked with Super Vee type 4 motors, he was the guy behind Super Vee type 4 motors during their development. He indicated that thermal coatings were the only way his dad got heat under control in a type 4 motor. John at ACN made a great suggestion, which would be to open up the chambers and get the CR back down that way. At age 70 in a couple weeks, and with heart conditions, I'll leave that development to you younger folks.
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Last edited by SGKent on Thu Aug 20, 2020 11:43 pm; edited 3 times in total
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raygreenwood
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PostPosted: Thu Aug 20, 2020 10:23 am    Post subject: Re: who has a good stock of cylinder base shims? Type 4 Reply with quote

SGKent wrote:
RalphWiggam wrote:
I could be wrong, but even with the .040 shim, isn't a deck of .070 a bit high?

I was under the impression that somewhere around .050 deck is about where you want to be. Im running .040 on my 1.7L.

The combustion chamber on a 1.7 is a different size than on a 2.0. As long as the piston clears the valves and head as it wears in, generally you go off the final compression ratio you want, and totally ignore the parrots. It is the CR that makes heat before any gasoline is even burned. Put an IR thermometer on an air compressor sometime, it is too hot to touch.

In 1991 on a 2L VW recommended an aluminum base shim of 1.6mm and no head gasket. 1.6 mm is .062." That would give a totally stock deck of .092." The deck is about .030" with no shim. But that new CR would be 7.1 if you used all new factory parts. If instead you used the 11 cc dish Mahle pistons the CR would go back to 7.3. KS pistons are a 15 cc dish.


Yes...but factually the father down the bore you start combustion....the less efficient the combustion process and the hotter the top end of the cylinder runs....and thats no from the "parrots" thats from experience.

Its not just a total compression thing...its a distance and time thing.

A deck of 0.70" is a big deck. A better method would be to decrease deck and increase chamber size. With a 2.0 as compared to a 1.7L....lots of meat to do that with.

I am saying it will not run well?...not at all. But it could run better. Ray
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PostPosted: Thu Aug 20, 2020 11:27 am    Post subject: Re: who has a good stock of cylinder base shims? Type 4 Reply with quote

Ray - read the 1991 Factory directive VW issued to stop bus pistons from melting because like we have discussed before, bus problems are totally different than 411 or 914-4, or 912e issues. You have to put on your bus thinking hat. The combustion chambers are different on 1700 vs 2L. The stock 2L deck with no shim is about .029" plus a thin paper gasket. VW deleted a small head gasket, the paper base gasket, and added a 1.6mm aluminum shim at the base. That 1.6mm converts to .063." Add .063" and .029" and you have a deck of .092" as the new factory base. That gives a CR of about 7 : 1. That is down from the 7 : 3 that these buses were issued with. In fact I just measured the dish on my old Mahle set and they are 15 cc and not the 11 cc that was published for them.

Using your logic as an absolute we would all still be driving flatheads with bowl pistons and little to no deck. The hem-spherical head allows for better flow of intake and exhaust from the cylinder. The deeper the deck the less gasses are expelled. While it makes for less power on the next charge, the remaining heat helps warm the incoming mixture and improves efficiency. Over all the amount of new heat generated is slightly less, lowering the risk of a melted piston.

The big question I have now to make is do I want to use the lower CR of 7 : 1 or do I want to go back to the 7.3 : 1. Right now with these shims I am at 7 :1. I thought the Mahle dish was 11 cc so that had me at 7.3 : 1 but I never measured the new Mahle set which was a mistake. This bus makes really good power at 7 : 1.
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PostPosted: Thu Aug 20, 2020 12:53 pm    Post subject: Re: who has a good stock of cylinder base shims? Type 4 Reply with quote

SGKent wrote:
Ray - read the 1991 Factory directive VW issued to stop bus pistons from melting because like we have discussed before, bus problems are totally different than 411 or 914-4, or 912e issues. You have to put on your bus thinking hat. The combustion chambers are different on 1700 vs 2L. The stock 2L deck with no shim is about .029" plus a thin paper gasket. VW deleted a small head gasket, the paper base gasket, and added a 1.6mm aluminum shim at the base. That 1.6mm converts to .063." Add .063" and .029" and you have a deck of .092" as the new factory base. That gives a CR of about 7 : 1. That is down from the 7 : 3 that these buses were issued with. In fact I just measured the dish on my old Mahle set and they are 15 cc and not the 11 cc that was published for them.

Using your logic as an absolute we would all still be driving flatheads with bowl pistons and little to no deck. The hem-spherical head allows for better flow of intake and exhaust from the cylinder. The deeper the deck the less gasses are expelled. While it makes for less power on the next charge, the remaining heat helps warm the incoming mixture and improves efficiency. Over all the amount of new heat generated is slightly less, lowering the risk of a melted piston.

The big question I have now to make is do I want to use the lower CR of 7 : 1 or do I want to go back to the 7.3 : 1. Right now with these shims I am at 7 :1. I thought the Mahle dish was 11 cc so that had me at 7.3 : 1 but I never measured the new Mahle set which was a mistake. This bus makes really good power at 7 : 1.


Yep....read that and your other post.

The question is not that the mods in the 1991 bulletin may have kept some engines from seizing.....bit since "seizure" was the issue.....I do not see definitive information that greater deck.....was by itself a key part of that equation.

Doing three things/mods....all at one time to produce one specific result.....is not proof that all three mods COMB8NED were needed or ideal. The oiling changes alone reduced piston temperature and increased cylinder oiling.

L-jet runs leaner than ideal in some rpm ranges. That can make heat. Just lowering compression can help....but no always....when you are producing more heat from another factor.....combined with the already restrictive exhaust.

A big plus factor.....is that you are running a better breathkng than atock cam...right? That alone reduces some of the inherent trapped heat from the exhaust sysytem.

I would say run it at 7.3:1 and keep your deck as tight as possible.

Ray
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PostPosted: Thu Aug 20, 2020 1:04 pm    Post subject: Re: who has a good stock of cylinder base shims? Type 4 Reply with quote

the original question of who has a good assortment of shims that they can deliver in a day isn't really answered.

nearest shop who does blanchard grinding on the ones I already have is 100 miles away in Oakland.
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