410 cracked flexplate
Thread Starter
|
New User
Joined: Apr 2019
Posts: 6
Likes: 0
410 cracked flexplate
So, let's start from the beginning my truck had its 390fe engine built to a 410 using a 428 crank and new pistons at. 040. It was balanced assembled and stuck into the truck. A few years later I buy it and I get a horrible ear piercing turn over noise which I'm totally assuming is a cracked flex plate(this only happens when it's cranked). Now for my questions how will I replace this? I have the balancing sheet and the engine receipts. The hard part in my eyes is Rebalancing it. Would I absolutely have to pull the engine. And would I just need to find a 428flex plate with a certain weight?
This engines in a 74 highboy with a C6 if anyone cares
This engines in a 74 highboy with a C6 if anyone cares
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Don't assume it's the flex plate being cracked. It could be rubbing the separator plate because of crankshaft end-play, or it could even be the starter.
That being said, probably the only way to do it would be to take the old flexplate, balance a crankshaft to that flex plate, and then using a new flex plate, balance THAT to the spare crankshaft. Being that it's a 428 crank, this method is probably not feasible.
Check the paperwork - is your "410" crank still externally balanced? If not, the flywheel might be neutrally balanced.
I had this happen with an engine I built, a 289 for a specific vehicle I wanted to build. Was balanced, and some weight came off the flywheel to make it perfect. When plans changed, and I wanted to put it in place of a 1982 302 in a Ford LTD, it needed the flexplate for that AOD transmission. Only flexplates around were for externally-balaneced 302s. So I asked my machinist if it was possible, using a spare 289 crank I had, to balance the crank to the 289 flexplate, then balance the 302 flexplate to the 289 crank. He loved the idea, and took care of it. Worked out great. (He had to remove a whole lot of the weight on the 302 flexplate, but it worked).
That being said, probably the only way to do it would be to take the old flexplate, balance a crankshaft to that flex plate, and then using a new flex plate, balance THAT to the spare crankshaft. Being that it's a 428 crank, this method is probably not feasible.
Check the paperwork - is your "410" crank still externally balanced? If not, the flywheel might be neutrally balanced.
I had this happen with an engine I built, a 289 for a specific vehicle I wanted to build. Was balanced, and some weight came off the flywheel to make it perfect. When plans changed, and I wanted to put it in place of a 1982 302 in a Ford LTD, it needed the flexplate for that AOD transmission. Only flexplates around were for externally-balaneced 302s. So I asked my machinist if it was possible, using a spare 289 crank I had, to balance the crank to the 289 flexplate, then balance the 302 flexplate to the 289 crank. He loved the idea, and took care of it. Worked out great. (He had to remove a whole lot of the weight on the 302 flexplate, but it worked).
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Any scraping of the seperator plate, or look up around the crank flange and see if you can see any cracks. Maybe turn the engine over a few times - anything obvious on the flexplate might be on top where you can't see it the first go-round.
Lead Driver
Joined: Jan 2003
Posts: 9,893
Likes: 12
From: Ohio
Unbolt the converter while you are down there and slip it back the little it can go. Might give you a better look of the center hub and if it is cracked/damaged. Using a big screwdriver and gently pry against flexplate and block plate and see if it makes a cracking/creaking sound. Roll the engine around and test multiple spots. If it's cracked, it should make noise.
428's take their own flywheel/flexplate due to being externally balanced. Did the shop rebalance it for internal balance? That would eliminate the need for a 428 flexplate.
Have you pulled the starter to see if it is engaging improperly? That might be the screaming sound you hear. Something to check.
With the lower cover removed, can you see the starter nose? Maybe have someone crank it while you look/see. Might be able to narrow down the noise.
428's take their own flywheel/flexplate due to being externally balanced. Did the shop rebalance it for internal balance? That would eliminate the need for a 428 flexplate.
Have you pulled the starter to see if it is engaging improperly? That might be the screaming sound you hear. Something to check.
With the lower cover removed, can you see the starter nose? Maybe have someone crank it while you look/see. Might be able to narrow down the noise.
Trending Topics
Hotshot
Joined: Jul 2005
Posts: 13,834
Likes: 26
From: Middle Tn.
Simple and cheap first. If only when cranking the first thing I’d pull would be the starter. Have you checked that all 3 bolts are intact and tight? Then I’d pull the tranny and visually check everything. Look for obvious signs on the converter and check the flex plate. Yanking the engine would be my last resort.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Lead Driver
Joined: Mar 2004
Posts: 8,924
Likes: 153
So, let's start from the beginning my truck had its 390fe engine built to a 410 using a 428 crank and new pistons at. 040. It was balanced assembled and stuck into the truck. A few years later I buy it and I get a horrible ear piercing turn over noise which I'm totally assuming is a cracked flex plate(this only happens when it's cranked). Now for my questions how will I replace this? I have the balancing sheet and the engine receipts. The hard part in my eyes is Rebalancing it. Would I absolutely have to pull the engine. And would I just need to find a 428flex plate with a certain weight?
This engines in a 74 highboy with a C6 if anyone cares
This engines in a 74 highboy with a C6 if anyone cares
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
That depends on if the original balancer modified the balance of the flex plate or not.
Thread
Thread Starter
Forum
Replies
Last Post
Johnkimble
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
20
Sep 7, 2018 11:48 AM
GaryLP
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
3
Oct 11, 2014 07:20 PM
tommythomasson
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
3
Apr 8, 2008 11:36 AM
fordeverpower
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
5
Jul 31, 2005 07:25 PM
marty68
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
5
Oct 31, 2004 06:31 AM