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Engine Balance: 28oz-50oz questions.

fordfan

Contributor
Bronco Guru
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Sep 13, 2009
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3,503
Did Ford make a 4 bolt harmonic balancer for the earlier 28oz. balance?
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
Yes they did. Any 4-bolt off a 351W will be 28 oz-in.
Also 302 from '70 or so until about '81 will also be a 4-bolt. I believe there are about 3 different offsets on the 4-bolt line of dampers based on the spacers offered by Ford Motorsports.
 

Quick & Dirty

Sr. Member
Joined
Feb 15, 2004
Messages
826
Most small blocks switched to driver side water pump inlet and 4 bolt damper in '70.

The Bronco kept the passenger side inlet water pump and 3 bolt damper.

Putting a 4 bolt damper on an engine with a passenger inlet pump means the timing marks will be in the wrong place.
 
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fordfan

fordfan

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OK..Thanks for the info. This is what happened: Rebuilt C4 and t case in a new(new to me Bronco), while trans was out, installed a new flex plate (for a '77 Bronco). After trans and t case was installed... (not run during this time), installed a new 4 core HE brass radiator. This Bronco has an old A/C and the pulleys are a hodge-poge (mess). The crank pulley is a 3 groove pulley, and the water pump is a single groove. My idea was to install original pulleys; two groove crank pulley and two grove water pump pulley. When pulling the crank pulley off, found it is a 4 bolt pulley (the harmonic balancer looks different from the standard balancer, has a thick part in just one area).

So, I am wondering if the engine is a 50oz balance, and I have installed a 28oz flywheel. The flex plate looked like the one I pulled off, and I have cranked it today; I has a little vibration, but it is running terrible...skipping...running on maybe 6 cylinders. You can idle the engine up to say maybe 1500rpm and it is smooth. It has one little bit of vibration at maybe 2000-2100 rpm, and then smooths out again......Just wondering.
Thanks for the help!!!!!!
 

Quick & Dirty

Sr. Member
Joined
Feb 15, 2004
Messages
826
There should be a casting number somewhere in the outer ring. If it starts with a C or D it will be a 28 oz-in. If it starts with an E, it could be 50 oz-in. The 302 switched in '82, the 351 stayed 28 oz-in.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Most likely when ac was installed they swapped to a 4 bolt balancer because it was hard to find a 3 bolt pulley for the AC. Or the engine was swapped out and had the 4bolt pulley.
Most likely you have a misfiring issue that is causing all the vibration. Could be igintion problems bad cap, wires or plugs, could be valve issues or even old gas.
Even then some engines will just have a vibration as the factory balance is not perfect and harmonic balancer is not always able to dampen vibrations at all engine speeds.
 
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fordfan

fordfan

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The engine looks completely original, but you never know what has been done by a PO. The intake and heads are original, the balancer is a E4#, the oil pan is a 11-73..(in a '77 Bronco). Someone has ground a fine line in the balancer and painted it yellow and it is close to 180 degrees from the original markings on the balancer. Thanks for the input!
 

75junebug

Sr. Member
Joined
Jan 10, 2008
Messages
587
Loc.
NW Houston Tx
Check and see if the block has the boss for the Bronco factory clutch bracket. Most all 50 oz engines I have seen do not have the hole drilled out. Not a sure way to identifye but its a start
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
You can also pull the starter and check the casting number of the block. But E4 is for 1984 which if its a 302 balancer its 50 oz but they could have used a 351W balancer and its 28 oz like the pre 82 302's are.
Another thing that could cause your misfires is wrong firing order especaily if its a 5.0 engine and wired like a 302 or vise versa.
Most of the parts between 302's and 5.0's interchanges so intake or oil pan casting numbers mean little.
 
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fordfan

fordfan

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The balancer is specific to the crank.... Right? ....if the crank is a 50 oz balance, I have to maintain the 50 oz balancer..? could not install a 28oz balancer?..... I still not sure exactly what the crank is....It appears that the balancer may have been changed to a 4 bolt balancer so a 3 groove pulley could be added for the A/C..?.... I am going to try to build the carb this weekend and get it running better to check the vibration. It seems to be smooth once off idle (where it will run..because of the carb problem).. and I feel a slight vibration ....probably 1700-1800 rpm and then it smooths out again. I have not spun it faster than probably 2500 rpm..... Thanks for all the technical assistance...I knew there was balance issues with pre 80's and post 80's- just never exerpienced it first hand. Thanks! By the way.....I am also going to check the casting # on the block NAZ! Thanks!
 
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