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Help Needed on 202 Crank Decision

Started by _jklumpp_ , Sep 07 2012 09:22 PM

Whos advice do I follow?

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32 replies to this topic

#1 _jklumpp_

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Posted 07 September 2012 - 09:22 PM

I need some help in coming to a decision on my crank - I know what I know, and engine building is not my strong point, so I am relying on 'expert' advice - trouble is, I'm getting conflicting advice from several sources, and I trust all of them!

I bought a 2nd hand engine recently - it was a speedway engine that was 8 meetings old, and had been built by the owner (who was a mechanic) and from discussions with him, there was a lot of though put into the engine.
The crank that was in it was a counterweighted crank that has been knife edged & nitride, and It was a virgin crank (original journal sizes)

When I got it, the idea was just to have it re-balanced (with a new YT RPM flywheel), and give it some new rings & bearings.
When my mechanic pulled it down, he found the bearings were worn, and he told me he thought it would be a bearing chewer, and he suggested having the journals ground, and big end's closed & honed.

It went off the the machine shop, and after nearly 2 weeks I get a phone call to say "we've hit a snag - what other cranks have you got?"... once I was able to talk, and asked a few questions I was informed that the machine shop was reluctant to touch it, because the 'old guy' reckoned it would be a bearing chewer due to the knife edging.... to which my mechanic replied it already is!...
So his recommendation is to not use the crank, and as I have a virgin red motor sitting in the shed, he suggested I use the crank from that (low mile HZ Auto)....

I wasn't completely comfortable that this was the 'right' way to go, and I stopped and had a chat to an engine builder (who built my current engine), that has experience with speedway & NC engines. He is using knife edged counterweight cranks, and has had no bearing issues.

So I picked up the crank today, and toook it to him to have a look at, and he reckons it looks good, and he;d have no hesitation using it in his engine. Ialso showed hima couple of the bearings, and he said he reckons they look OK....

To try & get another opinion, I also spoke to the guy that built this engine, and asked him waht he would do. His response was he's 'mic it up' and if it was still within tolerances, he's just put new bearings in, and put it back together....

So I've got 2 engine builders saying 'it'll be fine', and my mechanic & the machinist saying 'don't use it' - all of them have extensie experience with Holden sixes...

My car get's used for supersprints - we do about 7 rounds a year, and my dad & I share the car. Each round we do about 5 x 6 minute sessions each.
The car also see's '2nd car' road duties, and on average probably get's driven once or twice a week around town.
I want an engine that performs well, but isn't a hand grenade, and I don't want to have to constantly be pulling it out to re-build it.
My current engine has been in the car for about 5 years without any major drama's, and ideally I would like to be able to run the engine for at least 2 years without having to strip it down...

Below are some pics of the bearings (from 2 & 3) and the crank itself.

My current feeling is to run the knife edged crank, and just check it in 12 months time & see how it's travelling.... next idea would be to search for a virgin counterweighted crank, and run that... and my last thought would be to run the red crank I have...

I'm really interested to hear thoughts from others with experience to help me make the final decision....

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#2 _202DOHC_

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Posted 07 September 2012 - 10:00 PM

Hi
Looking at your bearings you do not have enough bearing clearance, can you post some pictures of your con rod bearings.
As far as which crank to use I would use the knife edged crank first the the std 202 crank before using the std full counter weight one.
The full counter weight crank has to much counter weight and will have flywheel problems, knife edged cranks seem to help.
I always run a steel Romac balancer and a light flywheelto setting down crank harmonics .
if you check my reply to oiling 202, this will help you bearing last longer.
We machine and built our own 202 engines to race speedway and have set our rev limiter in the msd at 9500 rpm, and we change out our bearings every 4 years not because they are worn, just figure we should.

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#3 _ljxu1torana_

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Posted 08 September 2012 - 12:57 AM

Hi
Looking at your bearings you do not have enough bearing clearance, can you post some pictures of your con rod bearings.
As far as which crank to use I would use the knife edged crank first the the std 202 crank before using the std full counter weight one.
The full counter weight crank has to much counter weight and will have flywheel problems, knife edged cranks seem to help.
I always run a steel Romac balancer and a light flywheelto setting down crank harmonics .
if you check my reply to oiling 202, this will help you bearing last longer.
We machine and built our own 202 engines to race speedway and have set our rev limiter in the msd at 9500 rpm, and we change out our bearings every 4 years not because they are worn, just figure we should.

dont talk shit about 9500 rpm.

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#4 warrenm

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Posted 08 September 2012 - 08:53 AM

As has been mentioned above, measure the bearing clearances, no sense fitting bearings with the same clearance as the ones your taking out. Not sure how they came to the conclusion that the crank would be a bearing "chewer".

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#5 _PeteXU1_

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Posted 08 September 2012 - 11:16 AM

My 202 pulls 10500 rpm
I missed a gear once and hit 12000

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#6 Shtstr

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Posted 08 September 2012 - 11:26 AM

The bearings are not worn out. As menchioned before the clearance is not set proply on them. you should use the knife edge crank and get it all ballanced by anouther machine shop. Use the bloke who you bought it off as if he's a mechanic and he should offer look after you with warrenty that way as it was his own engine.
I have seen 186 engines spin to 8000, but never a 202 as the stroke kills them above 6500-7200. Pistons shit them selves or rods part company.
takes a lot of work to get a red,blue or black motor to spin to these rpms and stay togther.
from what i can see in you photo of the crank it hasn't been crossed drill to help with oiling problems at high rpm so i would question what rpm it was built for????
if you are only turning it to 5000 should be fine but if it is going to see 5000+ rpm regurly i would get a few things done.
1 cross drill the crank
2 improve oil flow to 1&7 main bearing
3 fit oil restrictors to limmit the oil to the top end or fit a oil spray bar over the rockers.
4 fit exturnal oil returns to the top end to the side plates and to the sump
5 fit a crank breather system.
6 modifi the block so when the presur reless valve opens it feeds the exta oil and foam back into the sump insted of back into the gears creating oil foaming in the oil galleries.
7 Drill out all oil galleries to next size up to improve oil volume to bearings.
8 std oil pump with a heavy spring is quite good enough but you can use a high volume if you want
9 fit an oil restrictor to the cam gear spray or block it off all together and fit you own spray bar.

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#7 _STRAIGHTLINEMICK_

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Posted 08 September 2012 - 06:52 PM

I agree it looks like a bearing clearance problem.get a machinist to measure the crank journals and check roundness and surface finish ,then verify crank tunnel alignment with a good straight edge and feeler guages,then ensure main caps are tight in their registers,then measure main tunnels in four places each to ensure a cap has not moved .If all is ok then assemble bearings in main caps and measure each one in 3 places with an inside micrometer.From this you can work out the main bearing clearances .Do the same with the conrods and crankpins and if it all checks out then the knifedged crank will be ok in that block.Also be sure to chamfer the oil crank holes ,Mick

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#8 _Agent 34_

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Posted 08 September 2012 - 07:14 PM

My 202 pulls 10500 rpm
I missed a gear once and hit 12000

?

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#9 _jklumpp_

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Posted 08 September 2012 - 10:17 PM

thanks guys.
to answer a gew questions, the guy that built the engine is a 7 hour drive away - so not really an option ( unfortunatly).
crank is not cross drilled, and this is something else that the local engine builder does to his.
I only rev my current engine to 6500 max, andi'm told the new engine doesn't need to rev past 6000.
will try & get photos of the big ends

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#10 _tryhard_

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Posted 08 September 2012 - 11:22 PM

the bearings in your picture are king bearings & always look like that, they haven't even worn yet put the bearings back in & get some bearing plastiguage or flexiguage I can't remember witch name it is you get it from repco you can measure them with it. I think it looks fine. With the right induction and someone who doesn't give a shit will rev there engine to any rev.

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#11 orangeLJ

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Posted 09 September 2012 - 09:14 PM

Im a little biased, but if dave says its ok to run, id be running it.

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#12 _qiksix_

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Posted 10 September 2012 - 07:29 PM

i agree with most of what has already been mentioned above, i would get it reground cause the journals aren't right after the previous owner has been linishing them they have been riding the edges of the bearings.

i don't think it should be cross drilled, try to get a set of full groove bearings as they will give oil pressure right around the journal. cross drilling was something done back in the old days, you wont find any scat/eagle/bryants cranks cross drilled now a days, don't hold me to this i thought i read something that it actually drops oil pressure or doesn't flow at high rpm.

we used run a 235 stroker to 7000/7500 with block mods(larger oil galleries and pick-up) and full groove bearings for 10 years only pulled it down once to re-ring. sold the bottom end, now running a dead stock throw together 202 bottom end(2nd hand bearings/pistons/rings) and won at the 6 banger nats.

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#13 greens nice

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Posted 10 September 2012 - 09:08 PM

i agree with most of what has already been mentioned above, i would get it reground cause the journals aren't right after the previous owner has been linishing them they have been riding the edges of the bearings.

i don't think it should be cross drilled, try to get a set of full groove bearings as they will give oil pressure right around the journal. cross drilling was something done back in the old days, you wont find any scat/eagle/bryants cranks cross drilled now a days, don't hold me to this i thought i read something that it actually drops oil pressure or doesn't flow at high rpm.

we used run a 235 stroker to 7000/7500 with block mods(larger oil galleries and pick-up) and full groove bearings for 10 years only pulled it down once to re-ring. sold the bottom end, now running a dead stock throw together 202 bottom end(2nd hand bearings/pistons/rings) and won at the 6 banger nats.

will my track record still remain after this year? :stirpot:

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#14 _jklumpp_

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Posted 11 September 2012 - 03:08 PM

Many people have mentioned bearing clearance as the likely reason for the bearing wear - So what's the recomendation on what clearances to run?

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#15 _STRAIGHTLINEMICK_

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Posted 11 September 2012 - 08:12 PM

Many people have mentioned bearing clearance as the likely reason for the bearing wear - So what's the recomendation on what clearances to run?

G'day mate,if you are running consistent high rpm and using mineral 20/50 oil like Castrol Edge then conrods .002" and mains .003" but first check all of the things mentioned previously to ensure the block and crank are good before assembly,also one more thing to check is that bearings are not riding on the crank radiuses, keep us informed,Mick

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#16 warrenm

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Posted 12 September 2012 - 07:36 AM

Like Mick said, .002" to .003" is good.

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#17 _qiksix_

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Posted 12 September 2012 - 06:15 PM

hey kevin, what record's that?

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#18 greens nice

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Posted 12 September 2012 - 06:32 PM

the n/a holden 6 one on the board in the scrutineering shed.
7.73 @ 87.8mph.

sorry for the thread steal.

Edited by greens nice, 12 September 2012 - 06:33 PM.

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#19 _qiksix_

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Posted 12 September 2012 - 08:06 PM

is that holden engine powered or holden car as i broke it last year with 7.43@94mph.

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#20 greens nice

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Posted 12 September 2012 - 09:55 PM

is that holden engine powered or holden car as i broke it last year with 7.43@94mph.

holden powered, im now confused, do you own the red v6 LJ or the purple one?
im sure purple LJ dialled in at 7.85 when i raced it in the semi's.

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#21 _deantl2003_

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Posted 12 September 2012 - 10:49 PM

Which or what type oil pump are you runing in your engine standrad or JP???

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#22 _qiksix_

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Posted 13 September 2012 - 02:22 PM

mines the red one, the purple one is the brothers.

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#23 _Bomber Watson_

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Posted 13 September 2012 - 05:47 PM

The red one had a chebby v6 didnt it?

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#24 _jklumpp_

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Posted 13 September 2012 - 08:38 PM

Which or what type oil pump are you runing in your engine standrad or JP???

sorry to get back on topic, but im still a bit undecided... the engine currently has a std pump with modified release valve, and i'm tossing up whether to keep it in, or use my jp hi-vol....