Welded German Stroker crank or Chinese?

[woodsbuggy1]

What is the best way to go for 82 or 84mm crankshaft? I have used Chinese 82mm cranks without any problems but plan on building a 275hp engine for new buggy(EFI/Turbo} I have seen several broken 90mm welded German cranks but was curious if there are any issues with 82 or 84mm welded cranks. Thanks for any real word experiences. This will be going in an off road buggy that will be abused at times with a 6K redline.
Kenric

[farmer]

Hard drag starts are usually what breaks cranks. A turbocharged engine is not so tough on the crank at starts because the boost and thereby max hp is delayed a couple of tenth´s. That said, my choice for a high hp engine is a DPR 82 mm with type 4 center main and VW type 1 rod journals. Such a crank will hold a lot of power.

T

[saltracer]

In my pinion, as soon as you weld on a forged part, any advantages of having a forged part are negated. The strength in forging is that all the metal is running in the same grain like a piece of wood at a molecular scale. As soon as you weld on something you have completely destroyed the grain structure so in the case of a crankshaft it becomes weaker than a one piece forging. Just my thoughts.

I've beat on several Chinese cranks making over 200hp and never had an issue, bar one. An empi crank was oversized on the rear main journal. I now buy the cranks from CB and never had an issue.

[woodsbuggy1]

Thanks for the great input! That is exactly what I was looking for. I do have and older Scat 82mm crank with wedgmated flywheel and Porsche journal rods but the rods are 5.354(stock Porsche) would prefer to run at least 5.4 or 5.5 rod. Maybe I should be looking for new connecting rods instead of a new crank. This build is about a year away so I have some time to evaluate my options.
Thanks
Kenric

[farmer]

Saltracer, that´s why a welded crank should be heat treated after the welding, to unify the metal structure. If you need it really durable you cryo treat it. Then the crank becomes very durable and withstands a lot of abuse.

200 hp with Chinese forged cranks is not a problem. When you hit 230 things begin to get a little "interesting" I have seen 2 86 mm and 1 84 mm crank w Chevy rod journals give up in engines that were pullking 230-240 hp. I have also seen a welded 86 DPR in a type 4 give up at 310 hp and 8000 rpm. not a pretty sight.

This leads us back to my recommendation above which is a very strong crank that will hold most within reason.

The old Scat wedge mated is a very strong unit. The weak spot is the rod bearings. See if you can source a set of Clevite bimetal bearings. To my knowledge they are the best you can buy.

[richie,uk]

I have dpr 82mm with t4 center main like farmer describes but with chevy rod journals in my 2276 nitrous engine in my street car for last 5 years and no problems at all, its gone as quick as 10.42 in 1/4 so gets a good work out

[gbaker770]

Welded

[Bruce2]

As soon as you weld on something you have completely destroyed the grain structure ..

This is not true.
Certainly, the welded metal added has no grain structure, but the original forging will retain it's structure.
In order to destroy the grain structure, it has to be heated all the way through to temps way higher than the crank will get during welding. Also, to fully anneal the crank requires holding it at that high temp for a lot longer than it takes to weld.
This is why a welded genuine VW crank has such a good reputation for strength.

[woodsbuggy1]

You have given me several points to consider, I would like to run a type 4 center main but am only seeing bearings for standard uncut case. Also after spending more time rereading Maximum Boost, I realized that I should be safe with nearly any forged crank as long as I limit RPM to 5800 or so and use a balanced assembly with strong rod bolts(ARP). At this point, I am leaning strongly toward a welded German crank with counterweights, heat treat and full balance with H beam Chevy rods and Type 1 mains with a lightened German 8 dowel (11/32") flywheel.
Thanks
Kenric

[Bruce2]

Where did you get the idea that you can't go more than 5800 rpm with a steel crank?

The industry standard for the 8 dowel pins is 8mm. Going to 11/32 at the start is a foolish waste of $. The only use of 11/32 pins is to repair a crank where the flywheel came loose.

[Ol'fogasaurus]

In most cases a simple fix of a crankshaft shouldn't require re-heat treating, they've been doing things this way for a long time. If stroking the crankshaft then you might need to but again, it is the heat put in during welding then by the grinding. Occasionally you do see a broken crankshaft but then the inspection of the old shaft before the machine work is important too. Do a search and there are videos on checking for cracks on crankshafts; its been a long time since I last did it so I don't remember (without watching the videos) what you need at home to check before you even take the shaft into the machine shop.

What I see (and that started a long time ago) is the importers not doing due-diligence to the incoming parts whether they are off-the-shelf from foreign countries or even here at home. There should be material specs going out as well as process specs than need to be adhered to.

One of the guys I know just had a very expensive stub axle bust on him while charging around on the dunes. While they were changing it out I (a 4 person job not including me ) got looking at the stub and noticed a black spot by where the flange joined the splined part and yelled out that there was a flaw in it from the Mfgr. which hadn't been noticed before. When they looked at it it was a "no wonder" situation.

Lee

[woodsbuggy1]

Bruce, thanks for your input. I have no reason to run high RPM and require low end torque so I like run a fairly small camshaft (probably an FK42 or similar for this engine) my off road experience has taught me that higher RPM shortens engine and transaxle life. I will stay with 8mm dowels, thanks for your tip.
Lee, you have also given me things to consider. I am in Indiana, so having a competent VW machine shop requires me to mail things to the west coast. I have tried multiple shops within driving distance (up to 5 hours drive) and have learned my lesson.
Thanks Again
Kenric

[Kafer_Mike]

I am in Indiana, so having a competent VW machine shop requires me to mail things to the west coast. I have tried multiple shops within driving distance (up to 5 hours drive) and have learned my lesson.

What part of Indiana? Have you tried Davis Motorsports in Morristown IN? Gary Davis (turboblue here on STF) is a long-time VW woods buggy and sand drag racer -- and all-around 'good people'. If he can't help you with what you need, he'll direct you.

[woodsbuggy1]

Mike, I am about 25 miles south of Ft. Wayne, almost exactly 2 hours from Davis Motorsports. Gary has taught me a lot over the years and is always my first call when I need parts or knowledge, he is the one that mentioned Brothers machine to me several years ago to fix an engine case that was improperly machined by someone else(not Davis Motorsports). Gary is a wealth of knowledge and a Great guy too.
Kenric