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Author Topic:   383 stroker help.
Dirt Roller

Total posts: 18
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.

Dirt Maniac

Total posts: 103
posted April 07, 2001 04:34 PM
Did you experience any engine vibration?

Dirt Roller

Total posts: 20
posted April 07, 2001 07:52 PM
Did you check the main bearing clearance? Sounds like the main bearings might be too tight.

Dirt Administrator

Total posts: 3279
posted April 07, 2001 08:26 PM UIN: 16262997
Yeah...sounds to me like there is something on the bearings also.....I would make sure first that they gave you the right 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.


Dirt Newbie

Total posts: 3
posted April 09, 2001 09:41 PM

Dirt Roller

Total posts: 20
posted April 10, 2001 08:28 PM
No, because the oil has to go through the main bearings and the crankshaft to get to the rod bearings.

Dirt Full Roller

Total posts: 34
posted April 11, 2001 08:52 AM
Did you check the side clearance on the rods? You should have a minimum of .018-.020. Max is about .040, but you better have a good oil pump with that much side clearance. If you don't have enough side clearance, it won't allow the volume of oil necessary to keep the bearings lubed.

Dirt Roller

Total posts: 14
posted April 12, 2001 08:34 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.

Dirt Freak

Total posts: 213
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

Dirt Full Roller

Total posts: 50
posted April 13, 2001 10:19 AM

Dirt Administrator

Total posts: 3279
posted April 13, 2001 10:50 AM UIN: 16262997
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...


Dirt Roller

Total posts: 8
posted April 13, 2001 06:24 PM
Just one more thing too check.There is a little plug underneath the the rear main cap.It's hidden kind of deep in the block,if this little plug is not in place all the oil gets pumped too the top of the engine.At idle you will have oil psi,but run it for a while and you will lose presure. It happened too me but now I always check just too make sure it's there in my new engines. This may or may not be your problem But it's an easy check.
Pull your rear main cap and shine a light through your oil psi sending unit hole,if you can light through the hole tap the hole and plug it.Like I said this is just a place too check since you'll be there anyhow. Good luck!

Dirt Full Roller

Total posts: 52
posted April 14, 2001 03:04 AM UIN: 1986763
What oil filter are you running? Don't run the PH13's...they are known to collapse. Run the HP4's. You can pick them up for about $7-$9 at most auto parts stores. I woudl mention the brand, Fr**...there we go, and I think it'll fly on the post. What weight oil are you running? Are you running the oil bypass plugged? I suspect you are running 20-50 or 40 or 50weight and the oil bypass plugged...and that the filter is collapsing. Just an idea. I never run the bypass plugged, run the HP4's, and run Mobil 1 synthetic...never had a problem.

Dirt Full Roller

Total posts: 52
posted April 17, 2001 10:05 AM
Is this a cast crank 383 ? If so you are taking a risk. I have recently had and have talked to many racers that are having trouble with 383 cast crank.

Lots of the local machinist/engine builders had told us the horror stories about eagle/scat/cat cast 383 cranks, but we installed one anyway.

The eagle crank we had lasted one night! Motor was balanced and assembled firat rate no corners cut. I will not build another 383 without an internal balanced steel forged crank.

I reccomend the same to anyone thinking of running a 383, if you go with a cast crank you are playing with fire and it will burn you it a matter time.

So with this in mind I would keep a good eye on the crank for cracks,defect etc.

[This message has been edited by fury (edited April 17, 2001).]

Dirt Roller

Total posts: 12
posted April 17, 2001 04:28 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

Dirt Newbie

Total posts: 1
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 ( 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!

Dirt Maniac

Total posts: 141
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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