I decided to pull my heads to check my compression ratio and see what crank was in it.

I think it’s a Bergmann full circle welded crank, but I can’t find any ID numbers or a name on it. The case is defiantly clearanced but still not sure what stroke the crank is. Looks like stock clearanced vw rods. I have no idea what’s up with the pistons. Looks like the pistons were machined to change the compression ratio but how do I figure the deck height with them like that?

Let’s here what you think The good, bad and ugly.

i believe your right about the stock rods not sure about those machined pistons though
and as for the crank i dont know about it unless there is some way to hold the rod and measure its travel while rotating the crank other than splitting the case

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Just Stand On It!!!!

Chris

I just checked the stroke. I put a piece of tape across the upper and lower head studs with the rod at TDC. Then I moved it to BDC and measured with a digital caliper and came up with 83.87mm. It’s a 84mm stroke or at least an 82mm.

Do you think the pistons are non stroker clearanced pistons?

not sure on that one u can take a known stock style piston and let the wristpin stick in one side of each piston
and see what the difference is to the top of the unmachined portion of piston is

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Just Stand On It!!!!

Chris

Both my Bergman cranks are stamped with his name on them, but not the stroke.

You could push the top of the piston into some clay, then move the piston and measure the cc's of the impression of the "raised" part of the piston with a graduated syringe (like cc'ing a head), then subtract that amount from your chamber volume when you go to figure compression.

Larry

Good idea Larry.
Where is the name stamped on the crank?

DPR and DMS also make a full circle crank.
Usually not necessary until about 88 or more in stroke.
Just adds more rotating weight and lightens the wallet by another $200 or so more........

I've got some pistons here I can measure from the top down to the ring land to see if they are taller than yours.
They should be.

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Gary

Turbo VW Sand Racer
Polaris Ranger



"If you don't run into the Devil every once in awhile, you must be going in the same direction!"

Davis Motorsports FaceBook Page

Seems like it was on the backside of the last (closest to flywheel) counterweight. Or maybe the front of the first one. Sorry, its been awhile.

DId you discover this before or after the porn brad?

my buddy had a crank called a perfect circle 82mm stroke from scat and it had no markings on it what so ever and it looked alot like yours just thought i'd tell ya.chad

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NOW GAS IT!!!!!

I thought the PO (Blake) said it had a gene berg roller crank, but now that I think about it he said a Bergman full circle crank. He also said the pistons and cylinders were just replaced but didn’t say anything about machining the piston. I’m going to try to figure out the CR tomorrow and I’ll post it.

I have been building the air cooled vw for over 30 yrs.Hers what i would do put the barrel back on make sure its seated get a syringe at least 60cc put the piston on tdc make sure of this by putting a dial indicator on the piston now you are sure of tdc.Stand your engine on its side make sure the cyclinder is perfectly level. Fill the cyclinder with alcohol take the reading this will tell you how many cc's are in the deck height.Do the same with the the combustion chamber in the head.Now at this point measure with a dial or digital indicator the top of the barrel to top of piston write this down as you did with the cc volumes of the cylinder and head.Now rotate engine to bdc measure with the indicator write it down now subtract the top of barrel to piston measurement from the bdc measurement this will definetly tell you the stroke of the crank.If they are stock rods the engine would have a bunch of cylinder shims under the barrels.Not unless the case was machined.

On the samba they said I could just measure the position and do the math. I don’t know what math I need to do so help me if you can so I can figure the CR.

This is what I came up with if anyone can help me figure out the CR it would be greatly appreciated. Sorry for the crappy drawing.

I put your measurements in here http://www.cbperformance.com/enginecalc.html

I subtracted the cc's of the raised portion of you pistons (which is 3.117cc, pi x r x r x ht.) from your 55cc head chamber. The calculator asks for combustion chamber cc's, but I think it actually just wants head cc's because I think the calculator figures the rest of the combustion chamber cc's using the deck height and bore size. If it does, then your CR should be 11.4

Larry

I came up with 11.1 without subtracting the raised portion.

That sounds about right, the raised portion occupies more of the space in the chamber.
It seems like the sharp edges of that raised area might be a bad way to develop hot spots,though, which can cause predetonation or cracking. But if it aint been pingin all along, maybe its fine.

Larry

Thanks for the math help Larry. I plugged it into CB engine calculator and got this.

Engine Bore [94mm]
Engine Stroke [84mm]
Deck Height * [.38mm]
Combustion Chamber CC's [51.883]
Your Compression Ratio is [11.7]
Number of cylinders [4]
Your Displacement is [2332 CC's or 142 C.I.]

So is this correct? I have 11.7 to 1 CR

My conversion was wrong on the deck height. It should have been
0.38mm = 0.014960629921276001 inches

I mess up again. I guess I shouldn't be watching my 2 young kids while I try to measure stuff on my engine. I probably would be better off if I gave my 3yr old son the calipers and told him to tell me the numbers.

The deck height was measured in inches not mm. So it should have been .038 inches witch changes my CR to 10.9 to 1.

What gas should I run with 11 to 1 CR?

93 with booster or 50/50 mix would be nice.

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2332cc Air Cooled Screaming Meanie. Predator Singleseat.

"Lets go get stupid"

I think a mix would be better. Or just run straight 110 fuel. I do not think it would hurt it. My wifes buggy has 10.9/1 and if I mix 93 with 110 at a 50/50 rate it will ping in the hot summer. I mix hers 50/50 with 116 and 93. But I know of a buggy that has 11.5/1 and runs straight 93 pump gas with no problems. I think each motor acts different with different grades of fuel. I do not like the booster I was told it has some things in it that slowly eat up any rubber lines and seals. I do know this for sure, but price wise it would not be much cheeper to use it.

http://www.renegadepro1.com/racing_fuels.html

Watch your RPM's with those rods. They can't take the abuse that a good set of "H" beams can. I have seen many of them fail because of over revving them.

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Buy the best and cry once.

H beams also go bad. I had a Carillo rod crack through the big end using a FK 8 style cam, anything can and does happen. I agree it happens a lot less with H beams and high rpm engines and the low cost makes them very cheap insurance.
The VW rod can take 9,000 rpms with smaller strokes (69-78 mm) it it is the bolt that is weak. These days the Eagle H Beams everyone sells are about same price as a set of race prepped stock VW rods. My DeMello race prepped VW rods in my 2180 have 20000 miles on them, run hard with a VZ 30 style cam and they have held up. A set of Gene Berg race prepped stock rods $214 won't break as long as the rpms are held under 7000 rpms on a 82 mm stroker. Rimco also makes race prepped stock VW rods. Not being Chinese they are pricey at around $250. Revmaster $179, Scat $169 and CB Performance Unitech $90 would be cheap insurance over the stock bolts. The CB Unitechs are cheaper than a set of ARP or SPS rod bolts and nuts for the stock rod. Price wise I really like the Chevy journal CB race H Beam rod as they come balanced and have 3/8 ARP 2000 rod bolts for $250. 18 months the CB rods were a red hot smoking deal at $200.