Stroker kits

old bird

Registered User
Has anybody had any experience with stroker kits for 3.8 SC's?

Am considering a 4.2 kit from Morana.

Sincerely,

Old Bird
 
From what I've heard many times, the 4.2 truck crank in that kit is not strong enough. Cast steel vs. forged steel. Anyone have an approx on what the 4.2 crank can handle (hp)?
 
I think there are four choices when it comes to stroking your SC.

Use the cast crank from Morana.....I don't think it's strong enough.

Build-up weld on a forged crank and offset machine it....Fred's lasted 8,500 miles before it broke. I don't think anyone else has tried doing it since.

Offset machine the rod journals to a smaller diameter....Chris Wise did this, and it seems to be working. Requires custom pistons, rods and bearings. Some of the benifits are less surface speed on the rod bearings and wider rod bearings.

Custom forged billet crank....Fred did this on his most recent engine. I don't know much about it, other than it cost $3000-4000 just for the crank. He was able to get more stroke than offset machining would safely allow and there dosen't appear to be a down side except the cost.

David
 
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Cast crank?

Don't the SC's come stock with a forged crank? Someone told me that it did. If this is the case, why don't you keep the stock crank, have it ground/polished and get the oversized/undersized bearings for the main and rods?

Someone please correct me if I am wrong.
 
All 90 and up and most of the 89s (although some early 89s had cast cranks) do. We're talking strokers though, and a forged crank with a longer stroke isn't readily available. The 4.2 Truck crank is usually used in 3.8 strokers as the 4.2 and 3.8 blocks are the same, but a 4.2 isn't a forged crank and won't hold up to the pressure our cars run.
 
I think the cast crank would be handle the stress just fine. I have had vettes and camaros all running cast cranks and more than 400 hp in each, the vette being a 8500 RPM screamer, and i never had a problem with a crank. Maybe it was just luck, but if that is the case then there are a lot of lucky people running around with cast cranks putting down some serious power. But then again my experience with the Supercoupe engine is still limited so maybe you guys are right, but has anyone broken a crank on one of Morana's engines yet where it was a crank failure and not something like harmonic balancer. Please let me know because I planned on using one of these engines as well, also has anyone used one of the 4.4 stroker kits.
 
You're also talking V8's. A 400 hp V8 is considered mild by most. With a 4.2 Stroker in an SC motor, the potential for 400 hp is there without a whole lot of mods. I don't know of anyone breaking a 4.2 crank but I have heard of the majority of the cast cranks Ford attempted to get by with when they first produced the SC breaking. The early 89's had cast steel cranks and they were a bad weak point. To me it just doesn't make any sense to attempt to use a crank intended for NA duty in a forced induction car with as much boost as ours are capable of. There's no reason for Ford to make the 4.2 crank able to withstand our setup, and you know it would have cost them more.

Personally, If I'm going to do a custom setup it's all going to be forged, mainly because I don't want to have to worry about tearing the engine down later because I saved money using a cast crank. Doesn't sound like much of a deal anymore.

Plus, with the 3.8 SC and the 4.2 cranks both are neutrally balanced, as is the flywheel/flexplate and the balancer/crank pulley. The only way I can see them causing a problem is if they were improperly installed or worn out (in the case of the balancer).

You don't have any idea what the stroke came out to on his car??? I have an extra block to play with and am trying to get more ideas.
 
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Pardon my ignorance, but will the stock forged crank work with the 4.2 stroker with just different sized bearings? I'd also like to know this as I was planning on working with Morana on rebuilding my 90 SC engine.
 
I would talk to some of the guys in Canada. Tom Morana has been building the 4.2 stroker kit for some time now and I have never heard of one of his motors blowing up. I would say that with more cubic inches by way of a stroker it may be wise to keep the rpms. down. There is no replacement for displacement Tim
 
Stroker Cranks.

Morana tells me that 4.2 stroker is truck crank that has been cut down to fit SC block. He claims that with the right stuff, they are a reliable 400 hp engine. Does anyone have any experience with these people? I saw one reply from a canadian with a 4.2. Sure is tempting, little better than 10% more displacement, stroke not way out there.

Old bird.
 
If I was going to build my mortor all over again it would be a stroker. Cubic inches produce torque horsepower is a product of torque.Make sure you get a crankshaft Guridle good balance job and turn the engine slower. It should be a nice street motor. I wouldnt take a car with a cast crank and beat it to death or run 20 pounds of boost either. I know Tom has built more than a few of these engines. Tim And the reason that these engines cost so much to build is that there is not enough competation in the market for parts. Its more like I have the parts you need this is the price take it or leave it. Tim
 
I spoke with Tom, and he is very willing to talk to you to help you through the process and makes sure you get exactly what you want. He told me that the engine will live happy all day smacking a 6700 RPM redline. He is a cool old guy, who told me "nothing to worry about, it won't break, you can run it up to that redline as often as you need" Nice people up there
 
Well then if they are that durable, I just may end up with one. Anyone have an idea at how much hp this thing can take?
 
The cast crankshaft will not stand up to the pressure of boost, that is why Ford went to the trouble and expense to forge a crankshaft for the SuperCoupe, they even made the rear main different so that you would not put the wrong crank in your supercharged engine. Adding stroke will gain torque but all you need to do with a supercharged engine is turn the boost up and you can gain more torque than you will with the added stroke difference. The design of the 3.8 crankshaft is no where near as good as the small block Chevy, that is why the Chevy and other engines can get by with cast cranks to a point, it is due to design.

The idea that we don't want to take the time to work with some one is wrong. We did take the time to work with some one on this issue and it did not work, that is why I can tell you that it is not a good idea, been there, done that.

The other issue I would like to clarify is that we are not trying to compete with Morana or any one else on price. Our program is all together different. I know that we can not be everything for everyone. There are people that are more concerned with price and there is nothing wrong with that. I will be the first to tell you that we are not a price oriented bussiness. We could do it cheaper but it would not be the product we would want to be associated with. We build high quailty performance and racing engines and it costs money to do this type work, just like it cost us a LOT of money to buy the equipment like CNC machines and Dynos and such needed to do this type work. There is allso a lot of time in the development of products and engines that are factored into pricing. In other words there are burger joints and there are steakhouses, we are one of the steakhouses of the engine builders and that is why it cost more.

Coy Miller.
 
For josh

You can't change the stroke of the crank with larger bearings. All that does is take up the "slack" when you reduce the crank journals diameter.(keeping the same centerline)

Offest grinding involves grinding the journal down to a smaller size, but moving the centerline up. The "top" (end farthest from the counterweights) of the journal stays in the same place, but the "bottom" is ground so that the overall diameter is smaller. It also requires smaller (on the big end) rods and matching bearings.

Jeff

PS I thought that Fred broke the crank because of a driveline failure. Seem to remember the case broke on his AOD when the driveshaft broke. Was this what happened or what?
 
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How much of a stroke could you acheive on an SC crank by offeset grinding? How much smaller do the ends of the rods need to be?
 
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