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Author Topic:   383 stroker help.
Coolhand
Member
posted April 06, 2001 11:09 PM
Need some help. Just built a new 383 stroker engine. First time out it ran about 10 laps and lost all oil presure at idle. tore it down and found all crankshaft main bearing destoyed. took it back to the machine shop and they found that the crank was bent. Now all of the rod bearings looked fine and the pistons wernt hurt. this was a new stoker kit from paw. Went and bought another crank took it to the machine shop and had them turn it and check it out. Looked perfect. Installed all new cranksaft main bearing. put the engine back together with another new oil pump took it to the track ran about ten easy laps never exceding 4000 rpm and lost all oil presure at idle again. loaded it up and drove about an hour home started it up and had about 40 lbs at 1000rpm.Were runing a 3 spd manual trans with a 350 flywheel with the weight off a 400 flexplate welded on it in the same location as it was located on the flexplate. Have a 400 dampener on the front. Anyone have any ideas im going to tear it down in the morning and check the bearings and see if there hurt.


owracer
Member
posted April 07, 2001 04:34 PM
Did you experience any engine vibration?


CNC DOC
Member
posted April 07, 2001 07:52 PM
Yeah...sounds to me like there is something on the bearings also.....I would make sure first that they gave you the right sizes........you ask for a .010 is actually that....I had that happen to me recently....

Umm....I really sounds to me like it is a bearing problem to me also....make sure you mic the crank and confirm that the bearing size is the correct one for your crank.

jammin

SCOTT
Member
posted April 09, 2001 09:41 PM
WOULD A BAD CAM BEARING CAUSE THE MAIN BEARINGS TO GO OUT BUT NOT HURT THE ROD BEARINGS?


CNC DOC
Member
posted April 10, 2001 08:28 PM
i have a stroker motor also. the first time we put it together it ran great but wouldnt hold any oil pressure. we put new bearings in and had the crank checked. we ran three week. this past week we found the oil filter full of copper looking pieces. we havent tore the motor down yet but i am expecting to find a crack in the main journal. i have a friend who builds his own engines. he claims that strokers are known for that. he swears by the high-dollar cranks. that is what i am going to try with mine. my motor has the exact same symptoms. i will look into the bending crank and get back to you.


CUSTOMPERFORMANCE
Member
posted April 12, 2001 11:30 PM
did you have the entire assembly balanced with the flex plate and balancer before you put it together? i have all my engines balanced regardless of size and power. just good insurance


2FAST4U
Member
posted April 13, 2001 10:19 AM
I WOULD HAVE TO AGREE SOUNDS LIKE SOMTHING ON THE BEARINGS TO ME


jammin
Administrator
posted April 13, 2001 10:50 AM
One more thing that comes to mind on here...just bothers me.....the block could have shifted, if you didnt have it line honed, you could be setting yourself for another let down if you build it again without having it done. That just keeps hitting me in the face on this deal...

jammin

mtnman
Member
posted April 13, 2001 06:24 PM
Do you have a oil temp gauge, if so what is the oil temp. I had the same problem with a 406 that was built by a very reputale shop and we had problems with the oil temp getting to hot and wiping out the main bearings and not affecting the rod bearings. We never could find the problem so we switched from conventional oil to Royal Purple synthetic and never had another problem.
This was our problem and our cure, just a thought that may help. Good Luck


vizdwiz
Member
posted April 17, 2001 07:36 PM
I read through most of the replys to coolhands problem. Here are a few of my thoughts. Dirt during assembly the first time around and not cleaned out the second. The possibly missing plug that was mentioned in another reply could also be a contributing factor. The oil pump may be sucking air. When the oil is thick and cold it could be OK but when hot and thin and subjected to cornering G's a small air leak may become uncovered even if only for a brief moment. Also if the crank is a regrind 400 crank check that the journals are round. An out of round journal will kill bearing quickly.
Our friend discussing the merits of a cast crank in a race motor, especially one with a longer stroke, has some very valid points. Remember all 400 cranks that have come out of a motor are likley to have a lot of miles on them and a good portion of their fatigue life used up. This makes it much safer to use an aftermarket crank but it has to be the right one. I have had some unfavourable results with undisclosed source 383 cast cranks. However in my capacity as tech Ed for Motortec Magazine (Motortecmag.com)I have had numerous occasions to build 383 and 347 stroker motors using Scats cast steel cranks. I have now used these for a number of years and hp levels up to almost 600 and rpms up to 7700 with no failures. The motors concerned really do take a beating on the dyno. Sometimes our project motors are on the dyno for three months (as when we tested over 4000 cam and rocker combinations in a SB Chevy)As a matter of interest the stroker crank Ford sells and quotes an rpm limit of somthing around 8000 is a Scat piece.I doubt they would sell it with such an rpm limit if it was about to break.
The additional weight coolhand used on the flexplate should be fine if it was installed in the right place. I have seen motors run with substantial out of balance without any appartent damage. Incidently the new Scat cranks will internally balance with most reasonable rod/piston weights so a 350 daper will work.
Bearing misalignment is often sited as a problem as is a bent crank. We have deliberatly bent cranks and tested the results. You will find it hard to believe but what you think might happen often does not. Back in the pre-war days manufacturs actually bent cranks in production motors to cut crank rumble and make the motor quieter. My guess is it is not the block or mains misaligned that is causeing this to fail so quickly.
To sum up my guess here is oil gally plugs left out, dirt, out of round journals, wrong bearing clearance - but thats just my opinon - for what it's worth!
vizdwiz


Limited5
Member
posted April 22, 2001 09:45 PM
I had a 383 and ran all season with no problems, I loved that engine! used Scat crank with speed-o-motive rods and KB pistons. Fluid dampner and balance plate with 350 flywheel. Engine had a good balance job and Dart heads. Engine looked brand new after a HARD season. Always used Kendall oil 50w and kept it cool on gas. Also used a Kevco oil pan.


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