1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fins"?

[Terry M.]

Re: 1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fin

Excellent observation Joe and accurate description on the factory balance process.

[John M.]

Re: 1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fin

Scott,
Regarding your engine "builder" I think you made a wise move getting your engine out of there. There are hundreds, maybe thousands, of L79s out there rebulit with OEM or OEM replacement internals that run great on todays pump gas. Start a thread asking the question about this and you'll get some great information. I'ts amazing how many builders know so much more than Detroits automotive engineers.

[Joe L.]

Re: 1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fin

I have removed it 3 times, engine rebuilders 3 times, I was not gentle with it

Jack

Jack------


Why didn't you use a balancer installation tool and why didn't the other engine builders that installed it use such a tool? These tools are not a "new-fangled" device; I used my first one about 40 years ago, and I'm sure they were around well before then.

With a crankshaft that does not have a balancer bolt tapping (i.e. most 250 and 300 hp 327's as well as all 283's) one doesn't have much choice except to use impactive force (i.e. no one has the huge press-device the engine plants used). However, all SHP 327's used a balancer bolt-style crankshaft. So, using a balancer installation tool is the way to go. I absolutely CRINGE at the prospect of having to install a balancer using impactive force. I would much rather have any crankshaft without a balancer bolt tapping converted at the time the machine work is performed than risk damage later by "pounding on" a balancer. However, as I say, that's not even necessary with a SHP 327 or any 69+ 350.

Using impactive force to install a balancer risks damage to the balancer, damage to the crankshaft snout and, especially, damage to the crankshaft thrust flange and rear main bearing thrust surface. In fact, personally, I consider such damage, to one degree or another, not a possibility but a virtual certainty.

[Scott S.]

Re: 1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fin

I have a very original L-79 '67.My balancer is non finned with "1266" stamped on the back of the outer wheel.The engine build date is B-15-7.It went thru judging with no deduct.....Paul....

Hi Paul, thanks for your post. If mine had a date on it somewhere that might settle the issue, but I can't find one. Still good to find out that non-finned balancers made as early as December 1966 were being used on at least some 1967 Corvettes. As a recap , my engine was cast on December 27, 1966 with a car assembly date Jan. 11, '67. Non-finned balancer with no date code.

Jim Schwering (post 2): "I can not speak to the 67s ,but the book appears to be incorrect in re finned balancers ending in 65. Here is a shot of one I have purchased for my 66 , dated C-66."

Chris Enstrom (post 4): "The harmonic balancer you have looks just like the one I took of my almost completely original 67 a few years ago. My family has owned the car since 1973."

Randy Renfandt (post 23): "The balancer on my L79 looks like yours. The car is a May 67 built car W/O A/C or PS. I have had the car since 68 and do not recall changing the part in question."

Jack Panzica (post 24): "My L79 327/350 Build date 4/07/66 has the 8" fined balancer. #3817173 Its is not suppose to be according to Colvin, but it came with the car from the factory. Original engine , and balancer. see photos, you can read numbers if you enlarge"

Paul Dogali (post 31): "I have a very original L-79 '67.My balancer is non finned with "1266" stamped on the back of the outer wheel.The engine build date is B-15-7.It went thru judging with no deduct....."


[Note: the "post" numbers referenced above seem to change as new posts are added, I'm accustomed to Forums where each new post is added at the end (sequentially according to date and time), but it appears that this Forum inserts replies just below the post being replied to, and adjusts all the post numbers accordingly.]

[Scott S.]

Re: 1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fin

Scott,
Regarding your engine "builder" I think you made a wise move getting your engine out of there. There are hundreds, maybe thousands, of L79s out there rebulit with OEM or OEM replacement internals that run great on todays pump gas.

Thanks for the encouragement John, I was in a bad spot, and I sure didn't enjoy picking up a disassembled engine from a reputable engine builder. My knowledge and understanding of engines is growing but still very limited. I wasn't able to explain very well to the engine builder what I was learning on the Forums, and even if I could, I don't think I would have changed his mind.

Basically, I knew in a general sense what I wanted to do, which is to rebuild the engine with the correct cam and using OE equivalent parts (and maybe the Crower Sportsman connecting rods). According to what I've read on the Forums, from Duke and others, the original 11:1 CR L79 was in reality most likely closer to 10.25 or 10.5:1 off the assembly line. If I understand correctly, the engine can be built with correct, forged, 11:1 domed pistons and end up with a SCR of 10:1 or 10.25:1 after minor pocket-porting and other adjustments. That would put me on the low side of the true CR factory output in 1967, and if it was really needed (which it shouldn't be), I may be able to lower CR up to another quarter to half a point with gasket selection.

I'm working within what seems to me a very narrow "range". The engine builder wanted to go 9.2:1 CR, but I read that was too low for the L79 cam, and the engine wouldn't run properly. But if I build it with too high of a CR, I'll have to track down high-octane fuel and additives for every fill-up. If the L79 cam with OE equivalent internal parts will run fine on 93 octane premium pump-gas at a true, measured 10:1 SCR, that's only a quarter to a half-point below what it was in 1967 (factory advertised 11:1 notwithstanding).

So in the final analysis, the engine builder wanted a 9.2:1 SCR engine with a 'modern' cam. I wanted a true 10:1 SCR because I wanted OE equivalent parts and I had read that the L79 or "151" cam needs higher than 9.2:1 SCR. I couldn't go the way the engine builder wanted to go, and if I let him build the engine his way, I wasn't going to be happy with the finished product, and that wasn't fair to him or me.

Start a thread asking the question about this and you'll get some great information. I'ts amazing how many builders know so much more than Detroits automotive engineers.

I've been putting out other fires the last two weeks, but I will do that soon. I think I will need to find an engine builder who already understands these 40+ year old Corvette engines, and why they should run fine on premium pump-gas if properly built, and then do it. If my engine builder doesn't already understand this, I'm not going to change his mind, and I don't think I have the right engine builder.

That's where I'm at in the process so far, anyway. Lots more to learn.

[Jack P.]

Re: 1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fin

Jack------


Why didn't you use a balancer installation tool and why didn't the other engine builders that installed it use such a tool? These tools are not a "new-fangled" device; I used my first one about 40 years ago, and I'm sure they were around well before then.

With a crankshaft that does not have a balancer bolt tapping (i.e. most 250 and 300 hp 327's as well as all 283's) one doesn't have much choice except to use impactive force (i.e. no one has the huge press-device the engine plants used). However, all SHP 327's used a balancer bolt-style crankshaft. So, using a balancer installation tool is the way to go. I absolutely CRINGE at the prospect of having to install a balancer using impactive force. I would much rather have any crankshaft without a balancer bolt tapping converted at the time the machine work is performed than risk damage later by "pounding on" a balancer. However, as I say, that's not even necessary with a SHP 327 or any 69+ 350.

Using impactive force to install a balancer risks damage to the balancer, damage to the crankshaft snout and, especially, damage to the crankshaft thrust flange and rear main bearing thrust surface. In fact, personally, I consider such damage, to one degree or another, not a possibility but a virtual certainty.

The truth is , I did most of the damage the first 10 years I owned the car. It was my every day car and had to get me to work. There was always something breaking. I remember taking off the balancer to replace the plastic timing chain at about 60,000 miles. Who had tools, I used the curb in front of the house as a jack.

I know better now... I use two cylinder blocks....

Jack

[Larry M.]

Re: 1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fin

Neat car, 67 350 horse air coupe.

The harmonic balancer you have looks just like the one I took of my almost completely original 67 a few years ago. My family has owned the car since 1973.

I think you have the right one, but let's let the thread develop. I've been proven wrong before.

My 1967 327/350 HP (factory air) car has the factory balancer WITHOUT any fins. 26,000 mile car, engine never apart. Late March 1967 build, VIN 14,845.

Larry

[Joe L.]

Re: 1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fin

...to replace the plastic timing chain at about 60,000 miles.

Jack

Jack------


Yes, those plastic timing chains don't last very long, at all. However, I think you really mean the nylon plastic-toothed camshaft sprocket. Those have a short life, too (but definitely not as short as plastic timing chains).

Believe it, or not, but 1966 was the first year for the use of the nylon-toothed camshaft sprockets on small blocks (Mark IV big blocks used them from the get-go in 1965). So, if you had bought a 1965 small block instead of a 1966 small block, you never would have had a problem with the dreaded "shedding" of camshaft sprocket teeth. And, you would have thus had one less reason to remove the balancer.

In fact, the 1966 small block camshaft timing sprocket was unique to 1966 in two ways. First, it was the first use of the nylon camshaft timing sprocket on a small block. Second, it was the last year to use the "wide tooth" camshaft sprocket on a small block. So, it was the only year small block to use the nylon-tooth, wide-tooth camshaft sprocket. Most folks replace these with cast iron sprockets as used for pre-66 small blocks and I'll bet you did, too.

[Jack P.]

Re: 1967 L79 Harmonic Balancer I.D. - Book says "no fins" - NCRS JG & Forum says "fin

Jack------


Yes, those plastic timing chains don't last very long, at all. However, I think you really mean the nylon plastic-toothed camshaft sprocket. Those have a short life, too (but definitely not as short as plastic timing chains).

Believe it, or not, but 1966 was the first year for the use of the nylon-toothed camshaft sprockets on small blocks (Mark IV big blocks used them from the get-go in 1965). So, if you had bought a 1965 small block instead of a 1966 small block, you never would have had a problem with the dreaded "shedding" of camshaft sprocket teeth. And, you would have thus had one less reason to remove the balancer.

In fact, the 1966 small block camshaft timing sprocket was unique to 1966 in two ways. First, it was the first use of the nylon camshaft timing sprocket on a small block. Second, it was the last year to use the "wide tooth" camshaft sprocket on a small block. So, it was the only year small block to use the nylon-tooth, wide-tooth camshaft sprocket. Most folks replace these with cast iron sprockets as used for pre-66 small blocks and I'll bet you did, too.

Yea Yea Yea, your right , I meant sprocket, I told everyone I, was young, sprocket , chain , it was all the same, something to keep me from getting where I had to go.

Don't we just love our cars,

Jack