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Discussion Starter · #1 ·
I have a CJ-5 with a Chevy 350 bored .30 over. They guy I bought it from said it had a 400 crank in it (called it stroked I think) and I was just wondering what this means and what the implications of it will be. I don't know much about engines and after seeing the posts in here (especially Teamrush's) on engines I have know doubt you know what this means I just hope you can explain it to me in terms simple enough to understand.
Thanks for dealing with my engine incompetence,
Bill

/wwwthreads_images/icons/cool.gif78 CJ-5</font color=blue> all fiberglass, chev.350 .30 over, TH350
 

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This is a pretty common mod for SB Chevy's. It comes out to a 383 ci (I think, or is it a 377) anyways, you can swap alot of cranks into alot of different blocks to come up with different cubic inches, longer strokes for more torque (yours IS a stroker) shorter strokes for less mass & higher rpm's. A 383 is probably the most common. Although I don't know why they take cranks out of perfectly good 400's. Hope this helps!

Mike H.
1983 CJ-7 Laredo
1999 Dakota 4x4
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Discussion Starter · #3 ·
The 383 is a 350 block that has 400 crank and rods with 350 pistons. The crank main journals are turned down to fit the 350 block. You will be hard pressed to tell any difference, power wise or torque wise, between the 350, 400, or the 383.
Mizu

Visit my web site at My Jeep Site
 

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It depends on what rods were used.
If they increased the rod length, then the torque goes up dramatically on any small block.
The longer stroke on the crank will give you a little more HP and Torque, but you would have to take it to a really good engine tuner with a dyno to get top performance out of it.

If it's running alright, there really aren't any implications other than it is now an externally balanced engine.

350 CID chevy's and down were internally balanced, meaning that they could interchange flywheels, flex plates, and engine balancers.
(flex plate is the correct term for the 'flywheel' and ring gear for automatic transmissions)
You CAN NOT run either 350 or 400 gear, you stuff will have to be custom balanced for that particular engine. (between $150 and $300, depending on how perfect you want it, and what the going rate is. If it's within three grams dynamic, I'm happy...)
Don't accept a 'Static' balance. Won't work in your application. Get a 'Dynamic' balance.
That's where they spin the crank, with bob weights on the crank simulating the rods and pistons. They will need your rods and pistons, flywheel or flex plate, and your harmonic balancer.

Another thing you need to keep in mind is what kind of pistons and wrist pins you have.
Strokers have by definition, a longer stroke, that means the piston have farther up and down travel. That means they have to go, stop, reverse direction, cover more ground, and slow and stop, reverse direction, ect, ect.. Much faster than it's short stroke counter parts at any given RPM.
Piston velocities are greatly increased, and so are the forces exerted on them. If someone used weak pistons or pins to build a stroker, it can be bad...

(These are just a few things that have to be considered when someone tries to outsmart the factory engineers....)

If the engine seems to loose power as it goes up the RPM range, or seems to want to make power and just can't do it, or if it shakes or vibrates more than a stock engine does, it needs to be balanced...
Any shop with a dynamic balancer should have someone in house that can help with your carb setting and ignition settings, and it is worth the money! You won't believe the difference!

I'm guessing that about 34 or 36 degrees total timing, and all in by 2,500 to 2,800 RPM will give you the best zip...
(Take the advice of a good tune shop over these figures. I don't know what you have from here, so this is just a guess based on the stokers we do here...)
Use a limiter for the vacuum advance. With the extra stroke, you may not want the vacuum coming all the way in...

You may also take into consideration that with 30 more cubic inches to feed, you are going to need a little bigger cam than the guys with 350, a little more intake, and little bigger runners in the heads, a little bigger valves, a little more of everything...
You would be surprised how 30 CID will quiet a semi radical cam... Don't get too big though.

Most guys with strokers make the mistake of going too small instead of too big, and I don't know why that is...? Most of them stay very Conservative on intakes and cam profiles.
Stay with a cam you can use stock springs with. Stock springs will keep you out of trouble a bunch of times...
Use the Edelbrock Performer RPM instead of the regular Performer, or you will run out of intake at about 4,500 to 5,000
Set your RPM limit at 6,000 RPM, and stick to it.

Use a 600 to 650 CFM carb, vacuum secondary if possible.
600 will give you more drivability, and throttle response, (neck snap!).
The 650 will take some of the low end throttle response away, but will give more top end power and RPM.
I wouldn't go any higher than 650 or drivability will suffer quickly...
Have someone good with carbs tune it, and leave it alone...

Use free flowing exhausts. You have 30 more CID than the 350 guys, so expect to use the 1-5/8" headers or larger. Don't go beyond 1-3/4" inch tubes though... You will start to loose power in a street driven engine.
A good set of Flow Master mufflers should round things out...

Remember, ALL FACTORY 400 CRANKSHAFTS ARE CAST IRON !!
Most stroker kits use factory crankshafts.
They won't take detonation, and they won't take sudden shock loads very well, so no reverse drops or neutral drops, or anything else that shocks the crankshaft.
Otherwise you get to take the crank out in two or more pieces.
If you roll on the power, or power brake before you take off, the crank will be fine...
(I didn't say not to have fun, I said don't be stupid!)

A properly tunes stroker will let you know in the seat of your pants when you roll on the power throttle... It should torque right on down the road!

Does this answer some of the questions you had?
If you need more, just ask.
Aaron.


If Chris Columbus "Discovered" America (with 25 million already here), Can I Go "Discover" Florida?
 
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