I’m wanting to identify what flywheel is on my stoked 351. When looking at int and ext online pics they appear to look very similar with drilled holes etc. Not like comparing bbc which is really obvious. I wanted to identify by dropping the inspection cover. Manual transmission.

The car is a 69 Mach 1 and I’m thinking I may have put a neutrally balanced flywheel on many years ago thinking the new engine was internally balanced. Now street ready and has a very noticeable vibration on the steering wheel and shifter. The harmonic balancer that I’m pretty certain came on engine is ext balanced. (Long time project)

Been a few years since I went through this but Ford used a couple different balance weights and you had to make sure flywheel and balancer matched. That may have been 302 only,…. if only I could remember.

Go over to correctcraftfan.com and ask. The 351w in the ski boats has a flywheel from a 1969 mustang with manual trans.
those boats are direct drive w/ borg warner. i needed a ring and a new flywheel was cheaper.
Even tho neww flywheel was 157 tooth, it was wrong (balance/counter weight) and bolt hole size.

Member 'Keno' over there knows the finer points front to back & inside out.
if it's a cleveland, Keno will still have the answer.

EDIT IN ; this is a copy and paste from my flywheel fiasco, sorry if it doesn't help now that i read it.

Well............ there's some bad news to be given here
You have a flywheel for a later 302 when they liked to call them 5.0 engines and it takes metric fasteners.

It's also 50 oz imbalance on that flywheel and you want one with 28 oz imbalance otherwise you'll be able to make milkshakes on top of the engine if you were to install it and the damper plate with some bolts that would fit. Or in other words.........don't even think about trying to use that flywheel.

The changes happened around 1983 or so for reasons known only to Ford

The earlier 157 tooth flywheel that was on your engine was, like mentioned earlier a cross reference to a 67 Mustang with a 289 and a 4 speed which had 28 oz imbalance.

So.........you either need to get your old flywheel back or go back in this thread to the part numbers for the right flywheel and get one of them, then your SAE bolts will fit and you already know you need to trim it and use only 3 bolts and you'll be back in business. .

Just tell the parts guy what you need with the part numbers given earlier because the Ford marine 351 flywheel isn't on any 351 automotive engine. Once again only Ford knows why they did things the way they did

you say it is a stroker motor so what crank is in it? also what year is the engine? ford used 28 oz imbalance on the early 302 and 50 oz on the one piece seal 302 but the 351w were all 28 oz. the boss was the exception as it I think was internally balanced. if it is an after market crank then all bets are off as they may use a different imbalance than the original it is replacing.

Like comp said you really need to know what crankshaft is in it. A lot of stroker cranks are internal balance now days. The ones that are not are generally 28 oz. How long ago was the engine built ? Any chance your machine shop would have records ? I have a card on every balance job I have done since 1997 or so when I bought my balancer.

Other than finding a part number on the flywheel it will be hard to determine what it is.

I have actually used a wheel balancer to determine the imbalance. And even used it to balance one that was wrong for my application (it was in a pinch late on a weekend and beer may have been involved!)

All good points and the engine is a 94/95. Ben at precision offshore built it way back when he worked for Valako but I spoke with him yesterday and he couldn’t say enough great the engine was built and power it should have but didn’t remember much else. I was hoping he was able to resolve.

At the time when I was rigging engine for install I assumed it was internally balanced cause most strokers were internally balanced so went with a neutrally balanced flywheel I’m 99% certain. Now almost 2 decades later I see the balancer on it is ext balanced. Fk wish my brain went back that far.

I can relate and can't help not saying;
It does go back that far, but that's just where you left it.

Yup

Update - Valako remembered who did the machine work and balancing and by surprise the shop was still in business so made a ph call and they said to lower pan and get the stamped numbers off the forward counterweight. I called them back with the number and they were able to reference it to their card file.

HB is ext balance and the flywheel is to be neutrally balanced. I had an ext balance one on it. Problem solved. This went back to 2001. I had received the engine with the HB minus flywheel.