Cross Drilled Crank Questions Again...

[donforeman]

I searched here for cross drilled crank advice and read that it is looked down on now. Is there anyway it could be beneficial in a low hp small engine application or is it a bad idea in all situations? I am reassembling a small 1970's Honda used for SCCA racing. In the 70's Honda actually went to a lot of trouble designing a lot of parts for FIA racing. Its basically another car as many parts were replaced. One of the parts were the crankshafts. There are extremely rare now, but its not just an OEM crank with another set of holes punched in the other side, its a new casting. The production crank has oil galleys at least double in size and the oil routing is different. The galleys in the Mugen crank look to be copied from the bigger Honda motorcycles of the same era and those did not seem to have a reputation for oiling problems. Oil is fed though the center of the crank then with two smaller holes feeding each side of the journal with like a little trough at the end. Most real information on the engines has died over the last 40 years. So now I am stuck reading Honda's propaganda from the 70's or just winging it. Sometimes the winging it bites me and I learn the hard way. From the parts catalog "special 8 weight crank shaft offers better durability and silky turn of power unit" I have the 8 counter weight crank and the 4 counterweight crank that still has the oil galleys cast different than OEM. A lot has changed in 40 years so just asking for a more experienced guess/advise. The oil pumps do not have a lot of volume either so not sure if that adds to the problem or not. If cross drilling is taboo now. I can pass the cranks on to collectors without a problem. If something happens its a lot easier to find a production crank, easier on the pocket book too.

[Dave Koehler]

"silky turn of power" Can't say I have ever seen HP described as such,
Despite what you read here I don't see any issue in your case.
Throw a turbo on it to make the crankcase bulge and it may be another story.

[Racer71]

We had a similar issue with the watercooled Porsche engines. I put a 2nd oil hole at the outermost part of the throw of the rod journal so that centrifugal force kept the oil coming out. We called it perpendicular drilling them. Once I started drilling them we no longer experienced number two rod bearing failures/excessive wear on our motors that were in the auto X and road race cars

[donforeman]

Thank you both for the feedback.

[jed]

Most domestic engine builders frown on cross drilled crankshafts. Plenty of threads on ST concerning the hazards of cross drilling.
I listened to the top engine builders about this until the late 90s when I started doing machine work on imports, those nasty rice
Burners, and then I saw practically all had cross drilled crankshafts and guess what very little bearing issues. I began to question
That assumption about cross drilling. Those turbo 4 and 6 cylinder import engines were making 150/200 HP per cylinder with no bearing issues.
I still haven’t figured it out 30 years later. If you brought me the short block to set up I would use the stock crankshaft set all clearances
And make all necessary checks. Then all most guaranty no bearing problems.
I have all the faith in those era crankshaft.

[BCjohnny]

With such a small engine 'flywheel weight' (polar moment) probably counts for more than the niceties of oiling

With that in mind ..... and assuming the lighter four CW crank doesn't beat up bearings unnecessarily etc ...... I'd use that in preference

Unless you're maintaining a constant high rpm, and I doubt it in your case, the ability to gain rpm faster usually results in a quicker ride

[donforeman]

OK thank you sounds like I can pick anyone of them and be fine with such a low hp engine. The non cross drilled 4 counter weight cranks are the easiest to find as they are stock and there were millions of those made. All Mugen cranks were cross drilled but some came with 4 and some with 8 counterweights. The 8 counter weight crank is original spec for the Honda Mf318 engine, Hondas formula car engine from the 70s.