302 stock crank

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302 stock crank

Post  gmsmkr on May 3rd 2016, 11:45 am

Ok I have some questions on the strength on a stock 302 crank.

I/we have split lots of 302 blocks from 350hp to 700hp do to rpm's not really the hp but the cranks have always been ok which brings me to my first question...

1) how strong do yall think they are

2) would it be safe to say the stock crank with a zero balance combo would last along time with good rods and light pistons in a good block that is rpm reliable

When I say rpm I'm talking 7k plus with good valve train light valves etc..
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Re: 302 stock crank

Post  maverick on May 3rd 2016, 6:35 pm

Way back when I was a whippersnapper, I spun factory 289 and 302 cranks like they were routers. (These were late '60's era deals, so this info may not relate.) My most common failures were split blocks or windowed cylinders.. I thought the cranks were pretty damn good for factory stuff. I guess the big question is "What rpm reliable block are you thinking of?" If it's a Dart or something similar, it sounds like you're gonna be testing rotating assemblies to failure. Razz
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Re: 302 stock crank

Post  rmcomprandy on May 3rd 2016, 7:47 pm

gmsmkr wrote:Ok I have some questions on the strength on a stock 302 crank.

I/we have split lots of 302 blocks from 350hp to 700hp do to rpm's not really the hp but the cranks have always been ok which brings me to my first question...

1) how strong do yall think they are

2) would it be safe to say the stock crank with a zero balance combo would last along time with good rods and light pistons in a good block that is rpm reliable

When I say rpm I'm talking 7k plus with good valve train light valves etc..

There are 2 different O.E.M. crankshafts for the 302 engine.
One for a 28.2 in/oz external balance and the one called the lightweight which uses 50 in/oz external balance.
The "lightweight" crankshaft is not very strong but, is required by a lot of racing class rules.

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Re: 302 stock crank

Post  slurm on May 3rd 2016, 7:51 pm

I will regret typing this for i have yet to have any crankshaft failure with a 302. We run dirt modified and have been for the last 20 years. 1 of our older engines was built in 1996 and has been refreshed twice as it is just a backup engine. 1968 block  with stock rods and cast trw pistons, ported 351w heads. With a 600 gear and a 3/8 track has seen north of 8 many nights. Before this engine my father only had problems with dropping valves and reused the crank. This engine is now in a 72 f100 i use to haul grass to the dump. Makes alot of bad noise on cold start up but still like to leave in 1st and drive to the dump just screaming.  Built right i think and a good tune no problem. This engine is 28 oz all new ones are 0
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Re: 302 stock crank

Post  gmsmkr on May 3rd 2016, 9:24 pm

Our 312" deal is a stock crank with 28 oz balance and it has taken a beating like a champ and we got to talking about getting it zero balance but wanted to ask
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Re: 302 stock crank

Post  supervel45 on May 3rd 2016, 9:39 pm

Try to find a sixties or early 70's block they are stronger. Don't remember the Casting numbers but, you can find the info easy enough. Never much heard of the cranks failing either, it was always the block splitting in half down the valley and most of the ones I've seen where do to heavy nitrous use.

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Re: 302 stock crank

Post  FalconEh on May 3rd 2016, 10:42 pm

gmsmkr wrote:Our 312" deal is a stock crank with 28 oz balance and it has taken a beating like a champ and we got to talking about getting it zero balance but wanted to ask

You have the right crank, no harm in zero balancing it, add a few mallory slugs and there should be less harmonics at the plus RPM, but even if you leave it 28oz the crank should handle the duty cycles reliably.
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Re: 302 stock crank

Post  whatbumper on May 4th 2016, 1:55 am

supervel45 wrote:Try to find a sixties or early 70's block they are stronger. Don't remember the Casting numbers but, you can find the info easy enough. Never much heard of the cranks failing either, it was always the block splitting in half down the valley and most of the ones I've seen where do to heavy nitrous use.

That's really just rumors. Those blocks are heavier but not really any stronger.



I've broke as many 302 blocks as anyone and usually it is cause by one of three things: cylinder shifting (due to the inherent design of the lightweight casting design of this block), detonation or pre-ignition.

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Re: 302 stock crank

Post  supervel45 on May 4th 2016, 8:02 am

whatbumper wrote:
supervel45 wrote:Try to find a sixties or early 70's block they are stronger. Don't remember the Casting numbers but, you can find the info easy enough. Never much heard of the cranks failing either, it was always the block splitting in half down the valley and most of the ones I've seen where do to heavy nitrous use.

That's really just rumors.  Those blocks are heavier but not really any stronger.  



I've broke as many 302 blocks as anyone and usually it is cause by one of three things:  cylinder shifting (due to the inherent design of the lightweight casting design of this block), detonation or pre-ignition.

^^^^^Maybe I would still rather an older heavy block. Opinions are all over the place on the SBF's . This pretty interesting and a Lot of guys used to use them that were on a budget.

http://www.oldwestracing.com/index.html?http://www.oldwestracing.com/articles/mexican.htm

It seems to me if you are going to spend good money on a good block good rods and good pistons you might as well go the whole 9 Yard's and get a good/Forged crankshaft and be done with it.

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Re: 302 stock crank

Post  turbo2256b on May 7th 2016, 10:24 am

Around 78 Ford took a lot of weight out of the mains and cylinder walls of the 302. In the mid 90s they put material back in the cylinders so they coud bore and hone them quicker without as much distortion of the cylinder walls. Because the mains ended up so much weaker in he newer blocks the HO versions changed to the 351W firing order to remove stress from the no 1 main. Back in the early 70s built most all my 302s with the 351W firing order never had any issues running into the 7000 to 9000 RPM range wit ha factory crank and reworked rods.

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Re: 302 stock crank

Post  dfree383 on May 7th 2016, 12:09 pm

If it's not broke don't fix it........
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Re: 302 stock crank

Post  gt350hr on May 9th 2016, 6:45 pm

Hydraulic roller blocks are pathetic. Adding a 50 oz crank is the kiss of death when extended rpm and time at elevated rpm is there. Girdles won't save them either.

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Re: 302 stock crank

Post  dfree383 on May 9th 2016, 6:49 pm

gt350hr wrote:    Hydraulic roller blocks are pathetic. Adding a 50 oz crank is the kiss of death when extended rpm and time at elevated rpm is there. Girdles won't save them either.

They live pretty well under 450-500 hp from my experience.

Most of the ones I've seen split have been with NO2 or Boost and poor tuning.
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Re: 302 stock crank

Post  gt350hr on May 11th 2016, 4:20 pm

Sure! I ran one for five years as a 347 with 28 oz balance , 6,000 rpm limit and about 450 hp. freshened it up sold it and it has another six years of street use on it. Just like glass , it will take allot but too much will make it shatter. An early block has been in my race car as a 331 for 16 years , revs to 8,000 through the lights and makes around 525. The 5.0 block would not do that and survive. Some people think it's the motor mount location that causes it and I call BS. You can't remove 25-30 lbs if iron unless the change is made to compacted graphite and expect to have the same strength. Simple physics.

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