Stroking a 302 Windsor - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
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post #1 of 5 (permalink) Old 05-11-02, 06:22 PM
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Stroking a 302 Windsor

Here is a link to those who are interested in stroking the 302 to a 331 or 347.

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post #2 of 5 (permalink) Old 05-12-02, 05:49 AM
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Join Date: Aug 2001
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3rd and 4th pages are password protected. :sad:

"To be afraid is to be alive - to act against that fear is to be a person of courage."

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Click on the above link to go to a site about my cars, old and new.
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post #3 of 5 (permalink) Old 05-12-02, 05:58 AM
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What's better a 351 4V Clevo or a Stroked 347 Clevo/Windsor?
351 for power and 347 stroker for torque?

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post #4 of 5 (permalink) Old 05-12-02, 06:09 AM
Two SC 61's = trouble
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Originally posted by Cobra
What's better a 351 4V Clevo or a Stroked 347 Clevo/Windsor?
351 for power and 347 stroker for torque?
Just keep in mind the 302 is strong for 500 H.P[more than that you are in the red] so if you want to blow[S/C] it in the future? A 351w is better it has much stronger webbing around the crank. Having said that a blown 302 with relativly std heads won't pull 500 h.p..
347's rev too!!They just don't have too...Ask A.P..

It has to be epa compliant these days so efi and Windsors are IN.But thank godness there are some good heads ,inlets $$ etc that we can get via the States.Sold here at some performance wharehouses...

Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic!
Tuned & maintained by "Peppertree Perfmormance". Dart block, Scat 4340 steel crank, Custom C.P pistons.Oliver rods.. Mal Wood twin plate clutch.. Twin SC61/2's,482 rwkw/ 645 rwhp..
Passengers, myocardial infarction material..
R.I.P Possum...
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post #5 of 5 (permalink) Old 05-13-02, 04:35 AM
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Originally posted by Grunter
3rd and 4th pages are password protected. :sad:
Yeah sorry about that I should have checked the whole lot they normally allow 1 page only and the rest password protected but this time they allowed 2 pages.
Page: 3

The 331 Kit Assembly
Our project will utilize a complete Scat 331 rotating assembly. We evaluated several 331 manufacturers on the basis of cost and quality of the components. We ultimately decided on Scat because their kit offered forged rods and pistons.

The crank is a Series 9000 cast steel crank, which will provide a significant increase in strength over cast iron, but without the expense of forged steel. Since we do not foresee power over 500 HP, or a poweradder, the cast steel will be more than adequate.

Scat offers either I beam or H beam 4340 forged rods. We opted for the I beam rods to keep cost down. Rod length is 5.400" for both their 331 or 347 kits, making it nice if we decide for more cubes in the future. The rods feature ARP 7/16" cap screws for superior strength.

Scat kits are offered with either hypereutectic KB pistons, or forged SRP pistons .The price difference is only $150, making it a worthwhile investment to step up to the stronger slugs. The pistons feature spirolocks for retaining the pins rather than a press fit.

Rings and Bearings
We will round out the bottom end with Clevite rod, cam, and main bearings. To control blow by and insure good compression, we went with Total Seal performance file-fit rings. We'll discuss the gaps later in the article series.

Most 331 and 347 kits on the market are recommended for 28oz (early Ford) balance factor. While some kits do come as 50oz, consensus is the lighter imbalance factor is better for bearing life.

In general stroker kits DO NOT come balanced, unless you specifically asked and paid for a balanced assembly. Because companies like Scat are manufacturing new cranks and rods, they simply are not going to be within production tolerances for a 28oz or 50oz rotating assembly.

Putting together a stroker kit without having it balanced is guaranteed to result in vibration and accelerated bearing wear and failure.

We recommend that you take your entire rotating assembly to a machine shop that is equipped to perform balancing. They should ask for your crank, rods, pistons, flywheel, balancer, pressure plate, and also one set of rings, and main and rod bearings.

The shop will weigh the ends of the rods and the pistons, and then modify them to match the lightest one in the set. Next they will calculate a "bob weight", the effective weight of the rod, piston, rings and bearings. From this the rotating assembly is mocked up and spun on a machine. If the shop is equipped with a electronic balancing machine it will pin point the out-of-balance location, and the machinist will modify the crank or flywheel to compensate.

We took our kit, as well as the harmonic balancer, flywheel and pressure plate, to Bay Area Balancing for an electronic balancing to within 3 grams. Factory Ford engines are allowed up to 5 grams variance.

We obtained a 28oz hub (right) for our Fluidamper harmonic balancer, which came originally with a 50oz balance (left). When balancing a Fluidamper, the hub must be separated from the outer ring.
It is typical to find slight deviance's in weight even when the piston manufacturer includes a sheet claiming all pistons in the set are within one-half gram. Our balance shop found a 3 gram difference from the highest to lowest in the set. A ball mill is used to remove a slight amount under the piston.
Bob-weights -the calculated sum of the piston, rods, and rings- are attached to the crank, along with the flywheel and balancer, to simulate a rotating assembly. This particular electronic balancer (Hines HC500) spins the crank at a specified rpm, and has a microcomputer which pin points the out of balance to within 1/8th of a gram. A drill press directly over the unit can immediately remove weight off the crank.
Nearly 70 grams had to be removed from the Scat cast steel crank in order to balance the assembly. (Note the large holes drilled in the counterweight.) That's a huge amount and goes to show you cannot just drop these kits in a motor and run.
We had just recently invested in a new billet steel 11" flywheel and clutch for our 50oz 302. We surely did not want to buy a new 28oz flywheel. Fortunately our balance shop could modify the flywheel to bring it from 50oz to 28oz.
In order to bring the flywheel to 28oz imbalance, material was removed from the opposite side of the 50oz counter weight. Compare to photo above.
Many balance shops don't even ask for the pressure plate. Good balance shops know they can be significantly out of balance (all clutches are supposed to come neutral balance.) Ours was five or six grams out, enough to cause a vibration. This was remedied by adding some weight. The plate is then indexed to the flywheel.

Many companies, including Scat, do offer balancing services at an additional cost. If you have them balance your stroker kit you MUST insist on sending them the harmonic balancer, flywheel and pressure plate you plan to use, or buy a new set from them. Do not allow them to balance your kit to their "shop standard" flywheel and balancer, since not all 50oz or 28oz balancers and flywheels measure the same. Continue

Page: 4

Engine Disassembly
One of the cost saving benefits of doing a stroker motor was the fact we'd use our old block as the foundation. The '89 5.0L block has never been bored over, and since we had been racing it for the past two years, we were certain there were no cracks or surprises.

We spent a weekend pulling and disassembling the old engine. In order to prevent interference with the rod bolts we clearanced the bottom of the cylinder bores- a common procedure for 302 based strokers. Finally we took a few measurements and dropped the motor off at the machine shop with our specifications.

1. It's hard to believe, but our "400 Horse 302" project is tired and ready to receive an overhaul.
2. With the engine bay of our '67 Mustang emptied out, we may upgrade the steering box and some other components. Look for related articles soon.

3. The old 302 comes apart. We'll reuse just about everything but the gaskets on the new 331 stroker.
4. It only takes about 30 minutes to tear down a motor. We'll knock out the freeze plugs before delivering to the machine shop.

5. The old main bearings were in surprisingly great shape -not bad for 200 passes shifting at 7000 rpm!
6. The old KB pistons show minimal wear, and signs of normal combustion (carbon build up is centralized around the exhaust valve.) These pistons and rods can be reused in someone's 302 with a little clean up.

7. We laid the new 331 crank, and a piston/rod assembly, in place temporarily in order to check for clearances as the crank rotates.
8. As suspected the rod cap screws just barely (0.005") clear the cylinder bore skirt.

9. Using some yellow paint the areas needed notching were identified. As you can see, every bore needs a little notch on the thrust side of the skirt at about the 12 o'clock position.
10. We rough cut the notch using a carbide cutting ball and an electric drill. We went back with a Dremel tool and stone bit to smooth it out. Only 1/8' deep notch is required, slighty more for the 347 crank.

11. While we had the carbide ball out, we chamferred the oil return holes in the lifter valley and also the oil filter mount. This simply helps the oil drain faster.
12. Before hauling the block off, we used a bore dial gauge to measure the taper in the bores, and also any out of round in the main bearing tunnel. We'll drop the block off and specifiy a 4.030" over bore, and no align hone on the mains since they checked out within specification.
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