Type 4 2.0l Deck Height and Compression Ratio

@Gnasha The guys on STF are correct. @GARRICK CLARK is on TLB and posts occasionally but I don’t think he knows you’re in the UK.

There is something wrong with that crankcase (or cylinders) that is difficult to understand and I’d get another case or send it to Jim at Stateside to sort it out. And the rods need to be properly checked for bend and twist.

 

@GARRICK CLARK is up near Preston, think he has Bamber Bridge Beetles there..?


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I think you need another pair of eyes looking at it who has had this problem before.

My pistons on my motor be it at TDC or anywhere along the cylinders length will move top to bottom, but not horizontal.

ON a worn COLD engine that piston up and down movement is called piston slap.

Its common on NEW aftermarket type 4 piston kits as the skirt of the piston is real small , and NOT a full circle skirt.

Standard VW pistons have a full circle skirt and don't rock up and down as much.

Also when this case/cylinder issue is fixed you need to check the ring gaps as they can be too tight from the AA factory, this can result in a partial seizing of the piston rings in the cylinders.

 

@GARRICK CLARK I’ve been following your ‘Thinking of going large’ thread on STF. I’ve used an 80mm crank with 5.325” H-beam rods, 5/16” bolts, VW 2.0l big ends, 22mm pin in a standard case and standard base circle cam – no case clearancing was required and the rods clear the cam. Rod ratio is 1.69:1.

I’ve used AA 96mm Biral cylinders with KB pistons for 2316cc and needed a 0.090” base shim to get the deck height and CR I wanted. Standard length pushrod tubes were OK but I used spacers in the case to push the tubes further into the heads to get a good O-ring contact.

 

77 Westy . I might just go that route, Clearancing the inside of a case can be a pain.
What did the rod angle look like with out the pistons fitted .
How much larger could you have gone on the stroke without encountering clearance issues, 82 maybe
Did you use a big lift cam, as the lobes can get close to touching
Was it worth the effort/money.
Big torque increase over the stock 71 stroke.

 

The rod ratio is on the limit of what is generally accepted as maximum for rod angle, although there are plenty of engines with lower ratios without any problems and so far, mine is fine – about a year of use. Isn’t looking at rod angle without pistons a bit meaningless?

Minimum crank web to case clearance is 0.045” so an 82mm crank would fit, but only just and too close for comfort (I look for a minimum clearance of 0.040”).

Cam is a mild Scat C25 with 0.430” valve lift (standard rockers), #2 rod to lobe clearance is 0.047”, #4 0.070”. If I wanted more valve lift, I’d fit a cam with smaller base circle diameter, or relieve the rods.

Was it worth the money? Of course it was! What else could I say?

Loads more low-end torque compared to the 2.0l with the same cam and heads. 1971cc to 2316cc is a decent capacity increase and Displacement = Torque.

 

Cool, If your combo works for you that's all that matters, when you mentioned the 5.325 rod I did think that was on the limit to be fair . Myself I don't like a short rod, The longer the better with a big crank. Think I'd go for the 5.700 rods with the 200k bolts. The width of a type 4 engine in a bug like mine is isn't an issue .But with standard type 4 cooling and carb linkages etc it can be. There is other issues that crop up going longer on the rod , but there's always a way round it.

 

It’s a compromise, with short rods you have to make sure there is clearance between the rod and the piston skirt and the bottom of the cylinder. And a low rod ratio increases the side forces on the cylinder walls - but the engine will pull more vacuum at low revs, which improves throttle response and low-end torque. Long rods are probably better for a bug engine, the higher rod ratios make a bit more power from mid-range but low-end torque and throttle response suffers.

With 5.7” rods you’ll need cylinder spacers about ½” thick, longer head studs, longer pushrods and tubes. The tinware, throttle linkage and exhaust could be a problem too but as you say there are ways around it.

 

1/2 " spacers, not if you use machine to length DEUTZ cylinders.
I don't like using spacers to be fair.

 

I have stripped the engine and along with another case (that was ostensibly decked at the same place) and both sets of rods to a engine machine shop in Coventry (again highly recommended). Pending any virus symptoms I'm going to see collect these parts this week.

The machine shop owner asked for two barrels and the main case bolts and insisted the case halves were torqued up and faces checked (in my presence) as satisfactory prior to payment.

Talks cheap, and the proof of the pudding will be in the checking.

 

I managed to pick up the cases just before the lockdown period started. I'm pleased to say (with out prompting or prior notice) they "found" a defect on the No 4 cylinder deck height and angle on GE case.

Having previously stated the heights across the top of the the cylinders were ok leaves me to think a trip to specsavers may be required when time allows.

So, Ive assembled (without sealant) and torqued down the cylinders. The No4 readings are better and the cylinder heights are spot on.

So, how to resolve the deck height differences, I had initially thought to remove material from the piston crown and polish afterwards so all are equal and one size shim would suit all?

 

Shims come in sets of 4 usually so a "best fit" would be my guess.. unless you have a massive deck height difference across them don't think you'd notice the difference in CR from a small one

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So in packs of four it sounds like machining or emery cloth would get me close enough to use the same shim under all 4 pots.

I did calculate/estimate the drop in CR with 0.002" removed, it was small lol, I'm not that concerned.

thanks for the responce

 

If you're only looking at a difference of 0.002" accross the deck heights I really wouldn't bother personally.

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If the difference is between one side of the engine to the other just used different thickness shims. If the difference is between cylinders and the tops of the cylinders are flat, 0.002” isn’t worth worrying about. Don’t use emery cloth, it will end badly.

 

That's real close . in the past I've glued 1000 grit paper to a FLAT sheet of glass, oiled the 1000 grit paper and used it to slowly sand the top of the cylinder , position the cylinder on the glass and turn it by hand. Do it for a minute ,refit, repeat till your done. Sneak up on it. I did it on mine , and even put a straight edge across the cylinder's and shone a torch underneath the straight edge in a dark room to look for light showing through any low points in the cylinders heights.