Harmonic Balancer size ???? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mdazb · 01-04-2009, 06:28 PM

I have a 72 C10 350/350 2wd. I'm currantly changing out the H Balancer. The one I got from the local parts store measures 6 3/4", The one I just removed from my engine measures 8". The parts guy swears that the 6 3/4" is the one that should be on the engine. Any help to correct this would be great.

Thanks

**leddzepp** · 01-04-2009, 06:46 PM

Quote:

Originally Posted by mdazb

I have a 72 C10 350/350 2wd. I'm currantly changing out the H Balancer. The one I got from the local parts store measures 6 3/4", The one I just removed from my engine measures 8". The parts guy swears that the 6 3/4" is the one that should be on the engine. Any help to correct this would be great.

Thanks

If what came off your engine was 8" and it ran fine, then that is what I would replace it with....regardless of what the parts guy told you (especially if it is autozone or another chain store)

piecesparts · 01-04-2009, 07:24 PM

There ARE two sizes and They both will work. You have to get a different pointer for the smaller balancer. It bolts onto the bolts that holds the timing chain cover. The 8" is what most trucks used in the past, but the smaller balancers give you some extra room. I changed over from my bigger one to a smaller one,when I built my stroker motor.

**WIDESIDE72** · 01-04-2009, 08:55 PM

Did you go by the year model of the engine, or the truck? Is the engine original to the truck? Either will work as long as you have the same type of balance, internal or external. IMO, keep the same size that was on it.

piecesparts · 01-04-2009, 09:53 PM

The GM SBC is not particular on balancer size. If you want a performance unit, the smaller diameters are the most prevelant. It is easier to see and time the bigger ones if you have a lot of attachments on the front of the engine, but it is really the choice of the buyer.

1968SWBBigBlock · 01-04-2009, 10:26 PM

GM used the larger balancer on high performance / heavy duty applications

mdazb · 01-04-2009, 10:46 PM

Thanks for the info guys. I went ahead and ordered the 8". Is there a way I can tell what year the motor is?

70GMCer · 01-05-2009, 08:24 AM

Isn't the 8" ones thicker than the 6 3/4" ones? Wouldn't that cause the pulleys to be offset? Doesn't it also depend on what size water pump you have (long or short)?

1968SWBBigBlock · 01-05-2009, 09:36 AM

mdazb - if you look on the back "ledge" of the motor(right in the area that your tranny bolts to but on the block and facing up towards the hood) you will find a casting code that is in larger numbers - you will also find a date date which is alpha-numeric which is 4 or 5 digits long
If you can find that it is you date code
1st digit is Alpha
A= Jan
B= Feb
L= Dec
Second will be a pair of digits which will equal the day of the month
01 = 1st
31 = 31st
the last number will be a single or a pair depending on how the block was cast and when - sometimes you need to be able to identify the time frame the motor is from to confirm what year - ie look at the casting number - does it match numbers from the 60's if it does the the date code is C168 we can figure the motor to be made March 16 1968.
Sometimes GM was nice and cast C1678 (normally in and after the 70's) we know this motor to be made March 16 1978

1968SWBBigBlock · 01-05-2009, 09:41 AM

70GMcer - You are correct they are thicker - but all the thickness goes towards the timing chain cover - the pulley alignment is based off the end of the crank which will be the same no mater what balancer you run.
Water pump length has nothing to due with the balancer diam or thickness - the old rule of thumb was Hipo and HD motors recvd the larger balancer - std passenger cars recvd the smaller thinner unit - I assume it had something to do with the RPM's and maybe compression ratio that had to have the better balance?

el curioso · 01-05-2009, 01:56 PM

Im no engine expert but to what I have heard...
The 6 3/4" is for two bolt mains and the 8" is for four bolt mains...
Once again im no engine expert...

71 super · 01-05-2009, 05:41 PM

el curioso, I have a 3970010 block which is a 2 bolt main and it has the 8 inch balancer from factory. Motor has not been touched except to remove.

70GMCer · 01-07-2009, 12:48 PM

Quote:

Originally Posted by 1968SWBBigBlock

70GMcer - You are correct they are thicker - but all the thickness goes towards the timing chain cover - the pulley alignment is based off the end of the crank which will be the same no mater what balancer you run.
Water pump length has nothing to due with the balancer diam or thickness - the old rule of thumb was Hipo and HD motors recvd the larger balancer - std passenger cars recvd the smaller thinner unit - I assume it had something to do with the RPM's and maybe compression ratio that had to have the better balance?

ok....that makes since.......I just thought the 8" would stick further out from the crank. So, you're saying it will be the inside offset the still will align the bottom pulley with the top pulley of what ever pulley setup you are using?

LOW DOUGH · 01-07-2009, 01:17 PM

I have the small balancer (listed for an 85 Caprice) and a stock timing cover for the bigger balancer. The timing table is attached to the cover not the bolts for the cover. Makes it really hard to time because the tab is not by the balancer. So, you can use what ever one you want.

The auto parts guy wouldn't know anything about it if he is not familiar with these aplications. He could have been a ricer guy or just not have much experiance with any of this. It's not hard to get a job at autozone. I know, I am a part time auto parts guy at autozone. We got some guys that make you wounder how they ever got a job there.

I would look for the right balancer for my applicaton but it dosen't matter. It runs fine. and they cost alot. alot to me.

01-04-2009, 06:28 PM	#1
mdazb Registered User Join Date: Oct 2004 Location: Nor Cal Posts: 75	Harmonic Balancer size ???? I have a 72 C10 350/350 2wd. I'm currantly changing out the H Balancer. The one I got from the local parts store measures 6 3/4", The one I just removed from my engine measures 8". The parts guy swears that the 6 3/4" is the one that should be on the engine. Any help to correct this would be great. Thanks

01-04-2009, 07:24 PM	#3
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: Harmonic Balancer size ???? There ARE two sizes and They both will work. You have to get a different pointer for the smaller balancer. It bolts onto the bolts that holds the timing chain cover. The 8" is what most trucks used in the past, but the smaller balancers give you some extra room. I changed over from my bigger one to a smaller one,when I built my stroker motor.

01-04-2009, 08:55 PM	#4
WIDESIDE72 Senior Member Join Date: Aug 2008 Location: Cedar Park, Texas Posts: 7,494	Re: Harmonic Balancer size ???? Did you go by the year model of the engine, or the truck? Is the engine original to the truck? Either will work as long as you have the same type of balance, internal or external. IMO, keep the same size that was on it.

01-04-2009, 09:53 PM	#5
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: Harmonic Balancer size ???? The GM SBC is not particular on balancer size. If you want a performance unit, the smaller diameters are the most prevelant. It is easier to see and time the bigger ones if you have a lot of attachments on the front of the engine, but it is really the choice of the buyer.

01-04-2009, 10:26 PM	#6
1968SWBBigBlock Active Member Join Date: Oct 2006 Location: Ohio Posts: 1,643	Re: Harmonic Balancer size ???? GM used the larger balancer on high performance / heavy duty applications __________________ 1968 SWB 454 + .040, 490HP x 540 FT pounds of Torque 10-1 Kb Forged pistons, recon rods w/ ARP wave loc bolts 781 heads Ported with 2.19/1.88 SSTvalves Lunati 60204 cam, Micro Trol lifters, Ported Edelbrock Performer Rpm manifold armor coated, Pertronix Triple Strike Ignition Holley 770 Street Avenger carb,Headers armor coated Built by Watson Ruppel Performance in Sarahsville Ohio. Hardshift Tranny Built Turbo 350,TSI 10" 3000 stall 12 Bolt Eaton Posi 4.10 Richmond Gears moser axles 18.5" x 31" Hoosier Pro Street Radials ET Classic 5 Wheels - polished Power Steering, Power Brakes,Disc Brakes,Tach & Gauge Dash, Tilt,Factory Air (gone) Custom Paint & Body Work Special thanks to my wife, my son and my money tree

01-04-2009, 10:46 PM	#7
mdazb Registered User Join Date: Oct 2004 Location: Nor Cal Posts: 75	Re: Harmonic Balancer size ???? Thanks for the info guys. I went ahead and ordered the 8". Is there a way I can tell what year the motor is?

01-05-2009, 08:24 AM	#8
70GMCer Senior Member Join Date: Apr 2005 Location: Joppa, Maryland Posts: 4,408	Re: Harmonic Balancer size ???? Isn't the 8" ones thicker than the 6 3/4" ones? Wouldn't that cause the pulleys to be offset? Doesn't it also depend on what size water pump you have (long or short)? __________________ 1997 GMC Sierra Ext 1965 Mustang

01-05-2009, 09:36 AM	#9
1968SWBBigBlock Active Member Join Date: Oct 2006 Location: Ohio Posts: 1,643	Re: Harmonic Balancer size ???? mdazb - if you look on the back "ledge" of the motor(right in the area that your tranny bolts to but on the block and facing up towards the hood) you will find a casting code that is in larger numbers - you will also find a date date which is alpha-numeric which is 4 or 5 digits long If you can find that it is you date code 1st digit is Alpha A= Jan B= Feb L= Dec Second will be a pair of digits which will equal the day of the month 01 = 1st 31 = 31st the last number will be a single or a pair depending on how the block was cast and when - sometimes you need to be able to identify the time frame the motor is from to confirm what year - ie look at the casting number - does it match numbers from the 60's if it does the the date code is C168 we can figure the motor to be made March 16 1968. Sometimes GM was nice and cast C1678 (normally in and after the 70's) we know this motor to be made March 16 1978 __________________ 1968 SWB 454 + .040, 490HP x 540 FT pounds of Torque 10-1 Kb Forged pistons, recon rods w/ ARP wave loc bolts 781 heads Ported with 2.19/1.88 SSTvalves Lunati 60204 cam, Micro Trol lifters, Ported Edelbrock Performer Rpm manifold armor coated, Pertronix Triple Strike Ignition Holley 770 Street Avenger carb,Headers armor coated Built by Watson Ruppel Performance in Sarahsville Ohio. Hardshift Tranny Built Turbo 350,TSI 10" 3000 stall 12 Bolt Eaton Posi 4.10 Richmond Gears moser axles 18.5" x 31" Hoosier Pro Street Radials ET Classic 5 Wheels - polished Power Steering, Power Brakes,Disc Brakes,Tach & Gauge Dash, Tilt,Factory Air (gone) Custom Paint & Body Work Special thanks to my wife, my son and my money tree

01-05-2009, 09:41 AM	#10
1968SWBBigBlock Active Member Join Date: Oct 2006 Location: Ohio Posts: 1,643	Re: Harmonic Balancer size ???? 70GMcer - You are correct they are thicker - but all the thickness goes towards the timing chain cover - the pulley alignment is based off the end of the crank which will be the same no mater what balancer you run. Water pump length has nothing to due with the balancer diam or thickness - the old rule of thumb was Hipo and HD motors recvd the larger balancer - std passenger cars recvd the smaller thinner unit - I assume it had something to do with the RPM's and maybe compression ratio that had to have the better balance? __________________ 1968 SWB 454 + .040, 490HP x 540 FT pounds of Torque 10-1 Kb Forged pistons, recon rods w/ ARP wave loc bolts 781 heads Ported with 2.19/1.88 SSTvalves Lunati 60204 cam, Micro Trol lifters, Ported Edelbrock Performer Rpm manifold armor coated, Pertronix Triple Strike Ignition Holley 770 Street Avenger carb,Headers armor coated Built by Watson Ruppel Performance in Sarahsville Ohio. Hardshift Tranny Built Turbo 350,TSI 10" 3000 stall 12 Bolt Eaton Posi 4.10 Richmond Gears moser axles 18.5" x 31" Hoosier Pro Street Radials ET Classic 5 Wheels - polished Power Steering, Power Brakes,Disc Brakes,Tach & Gauge Dash, Tilt,Factory Air (gone) Custom Paint & Body Work Special thanks to my wife, my son and my money tree

01-05-2009, 01:56 PM	#11
el curioso Registered User Join Date: Dec 2004 Location: El paso, Tx. Posts: 428	Re: Harmonic Balancer size ???? Im no engine expert but to what I have heard... The 6 3/4" is for two bolt mains and the 8" is for four bolt mains... Once again im no engine expert... __________________ 1969 Chevy C-10 350/700r4

01-05-2009, 05:41 PM	#12
71 super Registered User Join Date: Sep 2005 Location: Canton North carolina Posts: 3,079	Re: Harmonic Balancer size ???? el curioso, I have a 3970010 block which is a 2 bolt main and it has the 8 inch balancer from factory. Motor has not been touched except to remove. __________________ 67 blue step side- bb 68 gold and white swb cst anniversary 68 custom swb hot rod Ls swap 69 swb cst 6 cylinder/ overdrive 69 black/black cst bb swb 70 orange and white cst Canada built truck swb bb 71 black and white super swb bb 71 red and white super swb 72 green and white super swb 4x4 62 nova wagon 400 series Ls swapped 68 Camaro 327/4 speed- 1 owner, original paint 66 Volkswagen bettle 69 auto stick Volkswagen Beetle

01-07-2009, 01:17 PM	#14
LOW DOUGH I'M TRUCK CRAZY! Join Date: Oct 2006 Location: Sachse, TEXAS Posts: 1,737	Re: Harmonic Balancer size ???? I have the small balancer (listed for an 85 Caprice) and a stock timing cover for the bigger balancer. The timing table is attached to the cover not the bolts for the cover. Makes it really hard to time because the tab is not by the balancer. So, you can use what ever one you want. The auto parts guy wouldn't know anything about it if he is not familiar with these aplications. He could have been a ricer guy or just not have much experiance with any of this. It's not hard to get a job at autozone. I know, I am a part time auto parts guy at autozone. We got some guys that make you wounder how they ever got a job there. I would look for the right balancer for my applicaton but it dosen't matter. It runs fine. and they cost alot. alot to me.



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