1800 Top End, Deck & C/R

[borninabus]

i am doing a top end on an ED 1800 T4 using the (formerly FI) 022101371H original heads and AA 93mm P&C kit.

the heads have a .090" step
the chamber CCs--step included--are 56cc
the dished AA pistons are 9cc and deck @ the cylinders is .005"

assembled as it sits, i would have a compression ratio of 7.8:1.
too much

if i add .030" shims under the cylinders i hit the target of 7.3:1, but now i have a total deck height of .125".
not so good from an efficiency stand point.

i will NOT be splitting the case
i will NOT be going gun-ho on porting the chambers to add CCs
i COULD enlarge the piston dish, but don't think that 5cc is attainable.
split the diff: 2.5cc in the heads & 2.5cc in the dish
even if i do some custom work to gain some CCs and lose some of deck, the heads still have the .090" step and this is seeming like a LOT of work for naught.

should i just assemble it with the monster deck-height, seeing as this is how VW did it?
i don't really see too many options here...
maybe the more learned than i can offer some advice.
_________________
88 Van WBX, A/T - 13 JSW TDI 6M/T - 2012 Touareg TDI Sport

[timvw7476]

What's wrong with "old school" pre-technical bulletin head gaskets?
I had a 1800 with stock pistons & heads, kept the gaskets because
I don't care for slobber from the cylinder/head junction.
It was the nicest, fastest (90-91mph) stock type 4 engine I ever enjoyed operating.
And no, the head gaskets never "blew". Blow-by and piston slap took
it off the road.

[Tcash]

[raygreenwood]

To expand on what Tcash "showed" you......the head gaskets were a fairly defective design. Since they are multi-ply......essentially large crush washers.....they flatten under head pressure at max expansion rate....and do not expand and contract to prevent leakage when cold.

That fuel and oil forms carbon that props the gasket up. Eventually they create a leak that literally burns through the head gasket area like a cutting torch......permanently ruining the head...and no...welding will not fix a burn through area. It changes the metal.

This is common. Its also why many old school mechanics. ....jncluding dealers (but never the Bentley).....recommended head gasket changes along with general valve service at 50k miles. This was well known on type 4 cars long before the bus ever got the type 4 engine.

The later way is actually better. Delete the head gasket.....shim the cylinder base to get proper deck.....and lap the cylinder to the head with valve frinding paste.

The lapping in is key...it prevents leakage. Ray

[timvw7476]

My 1800cc "shim/headgasket" heads, after 90,000. miles
No blown out aluminum.
Gaskets are intact too, but I don't want to bore you people.
The torque/de-torque sequence takes 24 minutes or so at assembly.
Some people consider it tedious/ridiculous, but there are some people
who would rather lap barrels & heads than run headgaskets, personal choice,
I suppose.
The headgaskets/shims are still available....
Someone is using them.

[busdaddy]

OK, so the question wasn't particularly gaskets Vs: commando, it was more in regards to that rediculous step and the resulting loose deck. Was it some magic trick employed by VW to compensate for all the smog gear that those engines were saddled with?, or does it play a bigger part in something I'm missing?, or would it be better to tighten it up with shims at the base?
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

Слава Україні!

[Wildthings]

Add head gaskets to a head that has a step designed into it and you will have a really loose deck. My old 1800 made it over 250K miles with head gaskets, but they were on the verge of squishing out when the engine was torn down.

[borninabus]

the question is: is this engine meant to run .125" deck height?
and if so, why?
being that it would take a TON of custom work to eliminate the step--that's the way it will go together today.
without head gaskets, BTW.

if it explodes halfway home to CA, I'll let you guys know and you can offer your conjectures as to why.
_________________
88 Van WBX, A/T - 13 JSW TDI 6M/T - 2012 Touareg TDI Sport

[raygreenwood]

[raygreenwood]

To the original question.....the part I dont think anyone answered....nd I dont have enough bus experience to address.....is whether he will be fine with 7.8:1 compression or will it be critical that he gets it back down to 7.3:1.

My issue that I can see is that a large deck can run hot even when compression is good. A large deck with lower compression (whether its correct compression or not)....is a recipe for hot running.

The step is not the whole problem here (please correct me if you see that I am wrong)....but is the piston dish a little smaller than normal on the AA 1.8L pistons? Just from dim memory I thought the original KS or Mahle were about 12-13cc.

In my estimation 7.8:1 should present few tuning issues and may actually be an improvement in power and efficiency.....but those with experience with 7.8:1 in a bus should chime in.

I say this because the difference in weight and gearing...the 1.8 with L-jet and 7.8:1 in a 412 and 914 was a miserable inefficent hot runner. The 7.3:1 version of the 1.7L was even worse in these cars.

However.... In the bus...with different gearing, torque band etc.....its the correct range to be in. Ray

[Wildthings]

My old 1800 with Kolbenschidt dished piston, stock heads, sealing rings, and gaskets ran awfully good, very resistant to knocking and gave good power and gas mileage. Did have a slight cam upgrade. Didn't check the deck height when I took it apart, but wish I had. Should have been stock though, same for head volume.

[Tcash]

According to this article, in the absence of the head gasket. VW recommended installing a 1.6 mm (.063") barrel gasket. This would affectivley reduce the compression ratio to "(approximately 7.3:1 to 7.0:1)".
So the .030" you are installing will not be a problem.

Thanks to mayor ratwell
Head Gaskets

Good luck
Tcash

You do not mention if you are running carbs or FI?

[Wildthings]

[mnskmobi]

[Bleyseng]

At 7.8 to 1 CR he will be fine. The numbers seem off to me especially with a DH of .125". Get it down to .040-.065"!
Remeasure everything, check everything....
6.8 to 1 and it will be a dog plus with a deck ht of .0125 run hot as that will ruin the efficiency.

I am running a 7.8 to 1 CR with 94mm 914 pistons (small 10cc dish) and 1800 AMC heads and it runs fine.
_________________
70 Ghia Black convert-9/69 build date-stock w/133k 1600 SP-barn find now with a rebuilt tranny and engine
77 Westy 2.0L w/Ljet, Camper Special engine-95hp and with LSD!(sold)
76 Porsche 914 2.1L L20c, 120hp Djet (sold)
87 Syncro Westy Titan Red 2.1L 2 knob 100k miles

[Tcash]

[Tcash]

[borninabus]

hello Gents

Tcash has the numbers really right--not illustrated in the above calc because piston dish is not added in.

effective CCs are 65:
56cc chambers--including the .090" step--and 9-10cc piston dish.
022101371H cylinder heads; AA 93mm T4 kit.
.005" cylinder deck installed with no spacers anywhere which equates to 7.8:1 compression ratio.
i will need to add at least .030" additional deck to lower the compression ratio to The Bentley spec of 7.3:1........

according to the provided link, VW specified a .063" cyl shim for a total deck height of over .180"!!!!
WTF, mates

the bus and engine came to me "running" a seized exh valve & PRO carb after recent "top end work" in the LA area.
_________________
88 Van WBX, A/T - 13 JSW TDI 6M/T - 2012 Touareg TDI Sport

[timvw7476]

Sorry about the photos & 'deviation" from topic,
my post was aimed at headgaskets as a means to get below 7.8/1,
as wildthings stated, the KS dished piston 1800cc set up is one place
where these units held up, I don't believe the VW head shims alone will get you any where near 7.3 to 1, but a lot of VW operators want to run
more than 87 octane fuel, so headgaskets are one way to do it,
and no, not every type 4 engine melts when they (headgaskets) are
installed. consider my images mere documentation,just like any image(s)
posted hereabouts.

[Tcash]