Flexplate for 225 Dauntless V6

[masonmoa]

This is a hail mary post.  Praying somebody can help me with this.  

I've got a Buick 225 Dauntless out of a 67 CJ5 I inherited.  Wife's uncle bought the CJ brand new off the lot.  Had the motor rebuilt and am trying to mate it to a 700r4 tranny.  I have gone through 5 different flex plates that are all supposed to fit, but none of them do.  Neither the center hole is big enough for the crankshaft, and the bolt holes do not line up.    

Both me and my buddy who's helping me with the project can't figure out what is the problem.  Engine block numbers confirm it's a Dauntless, as do all the other parts I've bought for it.  I've reached out to Novak, and the flex plate they gave me the part number for doesn't fit.  Flex plate for a Buick 300 doesn't fit.  Flex plate for even fire Buick V6 doesn't fit (tried for the hell of it.)  

If anybody has any ideas or suggestions on what could be wrong, I'd very much appreciate the advice.  It appears I've got the one Dauntless crankshaft that's not stock. 

Thanks.

[Moses Ludel]

masonmoa...The 225 V6 was used in the Jeepster/Commando with a THM400 GM transmission behind it.  That would be one source or method for identifying the correct flexplate.  The other approach would be Buick Special passenger car applications for the 198 V6 and 225 V6 (both odd-fire).  Buick used these engines from 1962-67 in the Buick Special.  THM transmissions were used in the later Buick Special applications.

Kaiser/Jeep would not have done anything unusual with the 225 crankshaft flange.  There was no need to match any other engine or transmission type.  The 225 Dauntless was purchased from GM in crate form.  This would have involved a GM flexplate for the THM400.  Buick used the THM400 in heavy cars and muscle cars behind 400, 430 and 455 V8s.  The 350 Buick V8 was used in the Jeep J-truck/Wagoneer models from 1968-71 with both manual and THM400 transmissions.

To your immediate need, I found this flexplate at The Jeepster Man.  It should be what you need if your torque converter will bolt to this flexplate properly.  Explain that you're mating a THM700R-4 when ordering:

https://www.thejeepsterman.com/products/2514-flex-plate-225-v6-1966-1971-jeepster-commando-cj5-cj6/

Parts Mike also offers a flexplate but is currently out of stock according to his website:

http://www.partsmike.com/index.php/products/g106-flywheel-buick-v6-oddfire  [Says "flywheel" in the link but is actually a flexplate.]

This should put you on the right path.  Let us know if these leads work.  I have additional thoughts if they do not.

Moses

[masonmoa]

Thank you for the response.  I do appreciate it.  

Unfortunately, I've already ordered the flex plate advertised on Jeepsterman and it did not fit.  

The one from PartsMike is not in stock.

We've ordered 3 different flex plates from TA Performance as well, and none fit. 

Novak informed me that I need the ATP Z-117 flex plate for my application.  I just ordered one, but will not get it for a few days before I can check if it fits.

Thanks again.

[Moses Ludel]

masonmoa...I went to the ATP website with this ATP Z-117 part number.  The flexplate fits 1975-77 (early 1977) Buick odd-firing 231/3.8L V6s.  An odd-fire 231 should have the same crankshaft flange pattern as your 225 Dauntless, so this should work. 

According to a reputable resource, the Jeep/Buick 225 and odd-fire Buick 231 crankshafts can interchange.  There is one GM crankshaft number common to both engines:  1357898.  The 1357898 crankshaft is distinctly 225 Jeep/Buick and also appears among the 1975 to early 1977 odd-firing V6 crankshafts.  The ATP flexplate should fit:

https://atpautomotive.com/flexplate-z-117

Here are some specs on the flexplate you've ordered.  Take a close look at the torque converter mounting hole spread, the outer diameter of the flexplate, the crankshaft flange pattern and the tooth count (160).  Compare this with your 225 V6 engine and the 700R-4 transmission:

Part Number

Z-117

Name

Flexplate

Additional Details

Torque converter mounting hole spread is 11.75 inches

Flywheel Pitch

12 TO 14

Outer Diameter (in inches)

13.42

Teeth 

160

 

Late 1977 and 1978-up 231s are even-fire.  The later front-wheel drive 231 V6 engines have a smaller crankshaft flange and bolt pattern design.  The ATP Z-117 flexplate is designed for an odd-fire, RWD V6 engine.

 

The balancing formula is similar between the 225 and 231 odd-fire V6s, but the formula is different for the even-fire 231 V6 (introduced mid-year 1977 and up).  This ATP flexplate for an odd-fire 231 should be similar to a Jeepster/Commando 225 flexplate.  (As you know, the Dauntless 225 V6 with automatic transmission was only available in the 1967-71 Jeepster/Commando C-101 and not in the CJ models.)  The Buick V6 odd-fire crankshaft is externally balanced.  Factory method was to balance the crankshaft, flywheel/flexplate and vibration damper as an assembly before building the engine. 

Footnote:  In the early nineties, I toured the GM plant that built the redesigned Chevrolet L35 90-degree 4.3L CPI V6 engines with a counter-balance shaft.  At GM, externally balancing the engine was done with the flywheel or flexplate in place on a completely assembled engine.  The assembled engine was fired on natural gas, and a strobe light indicated where to punch or drill the flexplate or flywheel for crankshaft balance.  (In the sixties, Buick and Jeep technology likely did a manual bob-weight balance of the crankshaft, damper and flywheel or flexplate before the engine assembly.)  When rebuilding these V6s and other externally balanced engines, the damper, crankshaft and flywheel or flexplate are balanced together before the engine assembly.  (The clutch cover may be included, too.)  Today, if a quality machine shop rebuilds a 225 or 231 V6, the damper, crankshaft, flywheel/clutch and flexplate components get balanced.  The odd- and even-fire engines, due to their different crankshaft phases, use different balancing formulas.  If needed, I have the formulas for primary balancing either engine type.

 

You're using the original 225 damper/pulley, right?  Since your engine is assembled, the flexplate cannot be balanced with the crankshaft and damper.  As a direct replacement part, the ATP flexplate likely has some balance formula.  If there is any imbalance, a flexplate contributes far less vibration than an out-of-balance, heavier flywheel/clutch assembly.  The flexplate does not have anywhere near the mass.  It also benefits from the fluid torque converter.  You may not have any issue.  If you're not familiar with the odd-fire V6 running "rough as a cob" (as one sixties GM engineer called it), get ready for the natural odd-fire rumbling.  This is different than an imbalance vibration.

 

Out of curiosity, I looked at Fluidampr's current catalog.  They don't offer a Buick V6 damper now.  There was a time when they did, and these dampers come up at eBay (used).  If you need that kind of aid, make sure the Fluidampr will fit your engine and benefit an odd-fire V6.  Contacting Fluidampr tech support might turn up ideas.

Let us know whether the flexplate works and how this all turns out...You should be able to confirm the fit in a few days.

Moses

[masonmoa]

Thank you sir.

Yes, I'm using the original damper/pulley.  I just ordered a Z117 flex plate and will report back once I get it.

I have one question for you though.  The one possibility I came up with is this: Is there any possibility the Dauntless had one crankshaft for manual and another for automatic?  That's the only explanation I can come up with for why the 5 different flex plates that are for a 225 Dauntless don't work.  

[Moses Ludel]

Masonmoa...Your question is well reasoned...Some manufacturers will not drill a pilot bearing/bushing bore for their crankshafts intended for use with an automatic transmission.  Their manual transmission crankshafts have a drilled bore to accept a pilot bearing.  This gets discovered while trying to install a manual transmission in place of an automatic.

However, this is not typical for GM.  The only crankshaft that shows up for the 225 Jeep applications is the 1357898 casting.  And we know your crankshaft has the pilot bore for the CJ's manual transmission pilot bearing/bushing).  GM and others generally make a standard diameter indexing hub for the flywheel and flexplate.  This matches the hole diameter at the center of the flywheel or flexplate.

Are you finding that the bolt circle/pattern is correct but these flexplates are not fitting onto the crankshaft's indexing hub? 

I just went to the Clegg Engines website.  (Clegg is a large engine reman facility.)  Their crankshaft catalog lists odd-fire Buick 225/231 V6s this way:

64-67 BUICK 225/3.7L V6 Crankshaft Kit (BU-10220-225)
75-77 BUICK 231/3.8L V6 Crankshaft Kit (BU-10220-231)

For the odd-fire 225 engines, here are the core casting numbers Clegg associates with their kit.  These numbers are also 1975-77 (early '77) odd-fire 231 crankshaft castings:

1255645, 1357898, 1378351, 1378354, ODD FIRE ENGINES  [Note the 1357898, which shows up for both the odd-fire 225 and the 1975-77 odd-fire 231 V6s.]  1967 was the last year Buick used the 225 V6.  Kaiser bought the tooling and continued building these engines.  This is likely why the 1357898 crankshaft is shown for all Dauntless applications.  This might have been the 1967 prototype casting.

Both crankshaft kits spec as Clegg's part #10220.  The 225 and 231 odd-fire distinction may simply be for catalog purposes due 1) to Buick's V6 hiatus from 1968-74 and 2) the bump in cubic inch displacement when Buick bought back the tooling from AMC and transformed the 225 into the odd-fire 231.  Clegg will accept a 1357898 core for either engine application.  There is no distinction for "Manual" versus "Automatic" transmission on any of the Buick listings.  All odd-fire crankshaft cores either have the pilot bearing bore or, in the worst case scenario, can be drilled for one.  Your current concern is the crankshaft flange's indexing hub diameter and the bolt circle diameter.

Since Kaiser/Jeep was using the THM400 behind the 225, as well as with manual transmissions, it's highly unlikely they would have the crankshaft flanges machined differently for each application.  (The first Dauntless 225 V6s were assembled Buick crate engines.)  The usual protocol for GM was one crankshaft that fits all applications.

Moses