Author Topic: Adding 428 counter weight to 390 FLEXPLATE- balancing (Read 5633 times)

dozz302 · « **on:** October 15, 2018, 12:58:44 PM »

Just wondering if anyone knows of a source to find counter weight you can add to a 390 flexplate to be used on a 428 motor. I want to use a 390 flexplate for the strength but need proper weight to add. I know you can buy an aftermarket but would rather stick with ford parts OEM. Thanks

cjshaker · « **Reply #1 on:** October 15, 2018, 01:26:07 PM »

What is your reasoning that a 390 flywheel is stronger than a 428 flywheel? If you want strength, ditch the factory cast flywheel and get an aftermarket steel one. If you want something that you can beat on and still be safe, it's the only wise choice.

BattlestarGalactic · « **Reply #2 on:** October 15, 2018, 01:30:59 PM »

Agree, your best bet is use an aftermarket steel wheel.

I know they offer aftermarket small block steel flywheels with bolt on weights for use on early or late 302's. Nothing for the FE that I'm aware of.

blykins · « **Reply #3 on:** October 15, 2018, 01:39:40 PM »

You can probably have a balance guy drill the poop out of one side of it to make it off-balance, but why would you want to spend that much money/time on an old cast iron flywheel?

I have respect for guys who just want to use OEM Ford parts, but "vintage" cast iron flywheels with stress cracks are not my idea of fun.

Rory428 · « **Reply #4 on:** October 15, 2018, 10:48:55 PM »

When I bought a new McLeod steel flywheel for the 428 CJ in my 59 Ford, it did come with a counterweight piece that can be added for a externally balanced 428 application. I suppose unlike years ago, when McLeod offered a different flywheel for a 428 vs a 352/390/427 etc, it seems now they only need 1 part number, and include the bolt on counterweight in the package. My aluminum "soft Lok" flywheels also have bolt on counterweights, the aluminum flywheel for my SB Ford came with both the 28 oz and 50 oz counterweights, depending on the version of crankshaft used.

KMcCullah · « **Reply #5 on:** October 18, 2018, 09:37:55 AM »

When I built my 416 I used a 390 flywheel with this counter weight bolted to it:

https://www.summitracing.com/parts/mcl-563333

It took a little weight added to an existing hole in one of the cheeks to make it balance. Easy peasy balance job. That was with an 1UB crank though.... I've always suspected 1U was balanced for 410 internals. And 1UB for 428 internals. The only 410 I've torn down had a 1U crank.

I don't mind running an old iron flywheel on the street. Spun them to 5500+ many times. I treat them like old grinding wheels that could possibly be cracked. Give it a whack, it should have a ring to it if not cracked.

wayne · « **Reply #6 on:** October 18, 2018, 11:15:32 AM »

Save your legs and buy a steel wheel or a scatter shield i run both.I lost a flywheel a 3500 rpm years ago i got lucky it went down and to the right cut the new hooker header clear off broke 4 speed case ect A guy in town had a small block let go it took the dash windshield put holes in the roof he junked the car a 62 fairlane he had a few cuts .

428 GALAXIE · « **Reply #7 on:** October 18, 2018, 02:10:53 PM »

Those old cast flywheels Look horrible when scuf them a little.
I got me a new steel flywheels.

fryedaddy · « **Reply #8 on:** October 18, 2018, 02:51:40 PM »

i had my 428 crank internally balanced so i could use a 390 flywheel on it.no more worries about it being out of balance

dozz302 · « **Reply #9 on:** October 25, 2018, 01:40:50 PM »

Sorry I meant FLEXPLATE. Now lets start again. Thanks for responses.

My427stang · « **Reply #10 on:** October 27, 2018, 10:06:27 AM »

I don't think you are going to get a different answer, why not buy the correct flex plate?

If you need SFI or just want strong aftermarket, they make them

https://www.summitracing.com/search/part-type/flexplates/make/ford/engine-size/7-0l-428/safety-rating/sfi-29-1?N=4294949307%2B4294663890

dozz302 · « **Reply #11 on:** October 29, 2018, 10:26:41 AM »

The ford 390 flex plate is plenty strong- the aftermarket plates are heavier thus slow the car down a hair. Thanks

blykins · « **Reply #12 on:** October 29, 2018, 11:08:45 AM »

Do you bracket race or heads-up race?

Rory428 · « **Reply #13 on:** October 30, 2018, 01:28:52 PM »

I would not be too concerned about the strength of a factory 428 flexplate. Even with the triangular cutouts the OE 410//428 flexplates have, I have never seen any issues with them, strengthwise. I raced my Fairmont with a 428 and C6 for about 10 years, most of that with a transbrake, launching at WOT against the transbrake at 5200 RPM, running mid 10 second ETs, and I used the same old factory 428 flexplate that entire time. I think if you buy a new stock replacement aftermarket flexplate for a 428, like maybe from Pioneer, they use a solid 390 style flexplate, and weld on the counterweight to work with the externally balanced crank.
By the way, when Ritchie Pauley was still racing his 428 69 Torino in NHRA Stock Eliminator, I was at a race when they were removing the transmission, and it appears that they had spent a considerable amount of time drilling dozens of holes in the factory 428 flexplate, I would assume to lightened it. If you had ever seen some factory flexplates , like a Buick V8, they have huge cutout sections in them.

GJCAT427 · « **Reply #14 on:** October 30, 2018, 03:47:14 PM »

Rory, I just tore a 410 down this past weekend. The flex plate in it was a solid disc with the reinforcing ring. The counter weight was welded to the outer most edge next to the ring gear. It was most defiantly factory as I found the Ford stamp. The 428s I have seen all were the triangle openings. Make me wonder if the 410 was unique with the solid disc?

Rory428 · « **Reply #15 on:** October 30, 2018, 03:58:44 PM »

Is it a 1 piece or 2 piece flaxplate? I have had some 428s from 1966 that had a 2 piece flwxplate, which was heavier than the more common 1 piece unit. I have only owned 1 410, from a 67 Mercury, and it had a spoked 1 piece flexplate, with a welded on counterweight, that looked the same as the 428 flexplates I have.

GJCAT427 · « **Reply #16 on:** October 30, 2018, 04:11:51 PM »

Nope its a one piece. It looks just like a 390 solid, but it has the counter weight. I`ll see if I can post a picture this week.

My427stang · « **Reply #17 on:** October 30, 2018, 07:20:05 PM »

This is a Ford one out of a 410

GJCAT427 · « **Reply #18 on:** October 31, 2018, 04:40:35 AM »

Exactly what I have, But with the separate bolt reinforcement ring.

dozz302 · « **Reply #19 on:** October 31, 2018, 01:12:05 PM »

That's interesting-I've never seen one of these. That is definitely factory-I can tell by the welds- same as the CJ flywheel I have. I guess the 410 just used a 390 flywheel and put the counter weight on. As far as one breaking I have seen one out of a bracket car years ago that completely broke free in the spoke area where the big holes are- probably had a lot of runs on it. I was in a 1969 must. running 11.50's.

GJCAT427 · « **Reply #20 on:** November 02, 2018, 01:06:54 AM »

my427stang, question for you, does your 410 crankshaft have the standard 428 markings on it? I got to cleaning mine up and found a stacked YJ on it. No other marks so far. This motor has been punched to .060 so the block is more or less junk. It supposed to be 10/10 according to some stampings but the bearings are not marked as such. Still needs more cleaning before I measure it . This YJ has me scratching my head.

My427stang · « **Reply #21 on:** November 02, 2018, 04:15:43 AM »

I got that one off of a propane irrigation 428, and it had junkyard yellow marker "410" written on it, so no idea what it came off of.

Never saw the YJ marking though

GJCAT427 · « **Reply #22 on:** November 03, 2018, 07:37:41 AM »

My427stang, after some cleaning I found the crank # 1U. It has a small counter weight on the middle main cheek. Don't remember see that before. Anybody have picts of the 428 variations of those cranks?

cammerfe · « **Reply #23 on:** November 03, 2018, 09:59:07 AM »

Ford calls the automatic transmission 'flexplate' a flywheel. I believe 'flexplate' is GM terminology.

That said, when we received one of the first dozen CJ Mustangs, we built the transmission for it at T&C Livonia. We used a 390 flywheel, to which the ring gear is 'electron-beam-welded'. Our first outing with the new parts was to the drag strip across the river in Windsor. On the first pass, the starter came loose from the C6 at about the 60' mark. We replaced it and on the second pass the same thing happened. This time the starter pocket in the case was ruined and the case split back at the crown section.

On tear-down we discovered that the counterweight was welded to the flywheel 180 degrees out of place. (In our quest to have it right, it was a carefully-done hand job---just not in the right place.) OOPS!!!

KS

wayne · « **Reply #24 on:** November 04, 2018, 11:59:22 AM »

Jegs sell a steel flywheel with a bolt on weight hays makes it. I am older then dirt and its a long time ago when we raced what has changed back then we got the heaviest flywheel we could get.Now everyone runs the super lite stuff.

jayb · « **Reply #25 on:** November 05, 2018, 09:22:18 AM »

Quote from: GJCAT427 on November 03, 2018, 07:37:41 AM

My427stang, after some cleaning I found the crank # 1U. It has a small counter weight on the middle main cheek. Don't remember see that before. Anybody have picts of the 428 variations of those cranks?

All the 1U and 1UB cranks have that little counterweight. The 1UA cranks don't, so they are the SCJ cranks and are worth more. Go to 428cobrajet.org for some good pictures of the crank differences.

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Author Topic: Adding 428 counter weight to 390 FLEXPLATE- balancing (Read 5633 times)