Deep Pulley Question for you '67 L78 Owners

[Chevelle SS 396 L78]

I've been researching parts for a build of an original '67 L78 block for my eventual clone build of original 1967 Chevelle SS 396 L78. It's been interesting researching the '67 L78 design and the appropriate part numbers and date codes for date correct engine build.


I actually have three questions for those of you who have or have owned L78 1967 Camaros:


1. Did your stock alternator from the factory (37 amp I assume) come with a deep groove pulley on it?


2. If your engine is still stock, whether original or rebuilt to stock specs, how does it perform on premium pump gas (91 to 93 octane)?


3. Any recommendations for an engine builder in central/sough central PA who knows the L78 engine thoroughly?


All input much appreciated,


John (in PA)

[DougA]

I've been researching parts for a build of an original '67 L78 block for my eventual clone build of original 1967 Chevelle SS 396 L78. It's been interesting researching the '67 L78 design and the appropriate part numbers and date codes for date correct engine build.


I actually have three questions for those of you who have or have owned L78 1967 Camaros:


1. Did your stock alternator from the factory (37 amp I assume) come with a deep groove pulley on it?


2. If your engine is still stock, whether original or rebuilt to stock specs, how does it perform on premium pump gas (91 to 93 octane)?


3. Any recommendations for an engine builder in central/sough central PA who knows the L78 engine thoroughly?


All input much appreciated,


John (in PA)

If you're looking for a quality machine shop, call Jim Bowen Racing Engines, Glen Rock, Pa.
Stellar reputation, knows BBC's well. Did my 427 in my drag Elky, been running strong for years. Know lots of people that are very happy with what he's done for them.

[Chevelle SS 396 L78]

Thanks Doug!

[plumL78]

They all had a deep groove pulley with #3844100AK on them except for the calif. smog cars. I believe some of them have been found to have a double groove alt pulley. they also could have been a 42 amp alt. when heavy duty battery was ordered

[Steve Shauger]

Here's some component #'s on my car.

[Chevelle SS 396 L78]

Thanks for the info so far guys! I've attached a pic of my '67 Chevelle L78 engine when practically new (you can tell the firewall is nice and fresh!). Note the alternator.....this appears to be a standard pulley arrangement. Either some L78's came out of the KC plant with non deep pulley alternators, or someone on the engine assembly line in Tonawanda screwed up!

I had problems with my power steering belt going off under hard acceleration [i.e. drag racing! :-)], and I've often wondered if the power steering pump also didn't have a deep pulley. This will always be a mystery to me. The crank pulley no doubt was the 3 groove deep pulley arrangement (the car had no smog & no A/C of course).

I thought I'd ask this question on this forum, since there were probably more L78 Camaros in '67 than Chevelles. Just looking for answers.

I am building an L78 engine to as close as my original engine's specs as I can get.

Thanks for the input,

John

[1967 4K]

Far fewer 67 L78 Chevelles than Camaros. I think the Chevelle # is in the 600’s, not certain.

[plumL78]

Jon Mello had a 67 Z survivor with around 11k miles that had a standard alt pulley on it with a heavy duty alt. He thinks they didnt have a heavy duty alt. with a deep groove pulley at the time the car was built so they just used what they had. Do you recall your orig chevelle having a heavy duty alt. option ?

[Chevelle SS 396 L78]

Jon Mello had a 67 Z survivor with around 11k miles that had a standard alt pulley on it with a heavy duty alt. He thinks they didnt have a heavy duty alt. with a deep groove pulley at the time the car was built so they just used what they had. Do you recall your orig chevelle having a heavy duty alt. option ?

No, I don’t believe it did or it would have been listed as an option on my order form & the window sticker, which I have. That’s interesting though! After all these years finding this out intrigues me. Times were much different back then & I suppose mistakes happened on the car assembly line!

[tjs44]

this is a older thread.I bought one of the GM 493243 pulleys and a std belt sits deep in it.Tom https://www.yenko.net/forum/showthread.php?t=122242

[jeffschevelle]

I've attached a pic of my '67 Chevelle L78 engine when practically new (you can tell the firewall is nice and fresh!). Note the alternator.....this appears to be a standard pulley arrangement. Either some L78's came out of the KC plant with non deep pulley alternators, or someone on the engine assembly line in Tonawanda screwed up!


The alternator was not assembled or installed at the Tonawanda engine plant. It was installed at the car assembly plant. As to when the pulley got put on it, see below.

Jon Mello had a 67 Z survivor with around 11k miles that had a standard alt pulley on it with a heavy duty alt. He thinks they didnt have a heavy duty alt. with a deep groove pulley at the time the car was built so they just used what they had. Do you recall your orig chevelle having a heavy duty alt. option ?

In 67 (and prior) the Alt pulley and fan were installed at the car assembly plant, not at the Delco alternator assembly plant. That's why there are no $1500 alternators for 67 and prior, like there are for later years where the alt part number depends in part on what pulley and fan it was assembled with (which makes the entire alternator rare and valuable if it came with a pulley and fan for a rare engine option). In 67, a 37 amp alternator is just a 37 amp alternator, part number 1100693.

So in 67, like any other sub-component assembled in the car assembly plant, standard 37 amp alternators, or any optional HD alternator, would have been assembled as a "job" for that particular car, with the fan and pulley combo specified for that car's engine (and other options that might affect the pulley). So there should not have been a situation where they were "out" of HD alts with a DG pulley. The pulley would have gotten installed for THAT job, and put onto a "pulley-less" HD alternator from inventory.

However, it is certainly possible (for John's Chevelle or for Jon's Z28) that (A) the plant was out of DG pulleys that day and used the specified back-up part, or (B) two alts got mixed up and the wrong alternator got put on that car (so the alt with a DG pulley got stuck on a 283 or something), or (C) the guy on the alternator subassembly line just messed up and put the wrong pulley on the alt for that job.

But none of those situations would make the non-DG pulley "right" for any OTHER L78 or Z28, unless there is solid proof that THAT car came with the "wrong" pulley.

[jeffschevelle]

Another interesting tidbit shown in John's early picture is the bypass hose clamp. It is a tower clamp rather than the usual flat style clamp. Assuming those clamps were not changed before the picture was taken (which John's post indicates would not be the case), this tells us his engine was built at Tonawanda somewhere between 5/1/67 and approximately 6/14/67 !

Per a Chevrolet service bulletin dated 5/22/67, 396 and 427 engines built on or after 5/1/67 through “approximately” 6/14/67 used a “new clamp” to prevent the bypass hose from blowing off. Up to that time, the nipples in the intake and water pump had no lips on the ends of them, which (per the bulletin) was occasionally resulting in hoses coming off. Then on “approximately” 6/14/67 a new nipple with a lip on the end went into use at Tonawanda, which allowed them to go back to the original flat style clamp.

The bulletin does not identify the type or the part number of the temporary clamp used at Tonawanda, but it does say that in service repairs if a hose comes off the dealer should use an AC hose worm clamp, part number 3840818 (which is the stainless AC worm clamp with a locator tab sticking out one side). So I had always assumed that Tonawanda also used an AC hose worm clamp on the engines assembly line between 5/1 and 6/14.

But John's picture suggests that they used a tower clamp instead during that period. So now the four NOS AC hose clamps that I had squirrelled away for my two cars with T0509EG engines will have to be put back with my AC parts stash!

[Chuck_Burg]

They do not perform well on premium pump gas. Been there done that, knock city. You need to mix in at least 5 gallons of 110 leaded on a full tank if you're using stock closed chamber heads and TRW pistons. If your block is decked and your heads milled you'll be well over 11:1 compression. If you want your motor to drive like it did in 67 and get enough timing out of it, around 36 degrees total with vacuum advance disconnected, you'll need better fuel. People say you can run pump gas on these motors which is probably true if you retard the timing and make it run like a dog.

I run 5 gallons of Sunoco 110 leaded mixed with 91 pump gas and it runs great!

[Chevelle SS 396 L78]

They do not perform well on premium pump gas. Been there done that, knock city. You need to mix in at least 5 gallons of 110 leaded on a full tank if you're using stock closed chamber heads and TRW pistons. If your block is decked and your heads milled you'll be well over 11:1 compression. If you want your motor to drive like it did in 67 and get enough timing out of it, around 36 degrees total with vacuum advance disconnected, you'll need better fuel. People say you can run pump gas on these motors which is probably true if you retard the timing and make it run like a dog.

I run 5 gallons of Sunoco 110 leaded mixed with 91 pump gas and it runs great!

Well, I was afraid of that, but I’ve still heard conflicting info on this. It certainly makes sense tho, as my original engine drank Sunoco 260 like water 50 years ago, but there was NOTHING like the feel & power of that engine! So, what do owners do who readily drop hundreds of thousands of dollars on original high performance muscle cars like Hemi Cudas, 427/435 Vettes and such at auctions? They seem to run fine across the auction block. Do all owners fill up at the airport to be able to enjoy their expensive rides! That includes owners of survivor hi-perf rides. I don’t consider this to be a dumb question! If I need to significantly detune my build it may not be worth it to me. If racing or airplane fuel is what I need to run I have no problem with that.

I’d appreciate more input on this. Thanks, John

[olredalert]

----Many places around here (southeast Michigan) carry 5 gallon cans of 110. One place about 20 minutes from me sells 110 at the pump. I have a fuel and oil distributer about 4 minutes from my house and he has 40 gallon drums as well as the 5 gallon cans that anyone can drop in and buy. We are blessed around here also because there are many non ethanol pumps at gas stations for us boaters. It's 91 octane but in combination with some 110 takes care of my cars that don't like ethanol.....Bill S

[GrumpyJeff]

Well, I was afraid of that, but I’ve still heard conflicting info on this. It certainly makes sense tho, as my original engine drank Sunoco 260 like water 50 years ago, but there was NOTHING like the feel & power of that engine! So, what do owners do who readily drop hundreds of thousands of dollars on original high performance muscle cars like Hemi Cudas, 427/435 Vettes and such at auctions? They seem to run fine across the auction block. Do all owners fill up at the airport to be able to enjoy their expensive rides! That includes owners of survivor hi-perf rides. I don’t consider this to be a dumb question! If I need to significantly detune my build it may not be worth it to me. If racing or airplane fuel is what I need to run I have no problem with that.

I’d appreciate more input on this. Thanks, John

I have a low mileage original 70 Z28 with 11:1 compression , and I drive it monthly when weather permits. I have run straight 100 LL from the local airport for over 20 years and the Car loves it ! I usually pay $5.00-$5.50 a gallon . I know not every body live 5 minutes from a airport ,but my Z is almost un driveable on 93 pump gas

[Xplantdad]

Any place that sells quads/ATV's should have racing fuel in 5 gallon containers as well.

[Chevelle SS 396 L78]

Good information! Thanks everyone!

[DougA]

I run 100ll in my 70 Chevelle LS-5 454. Original 290 casting iron heads, oval port, closed chamber, 101 cc heads. Around 11:1 CR.
Stock engine except for camshaft change, .544, 230 dur. @.050, hft. Probably don't need that much octane, but engine would ping horribly with crappy Md. 93 pump gas, even pulling the timing back to 32 degrees, it would knock. With 100ll, I keep the timing at 38, no knock, engine runs the absolute best it ever has in 20+ years. It loves that gas. Inside of the tailpipes are absolutely clean as a pin, not the slightest trace of any carbon. Engine starts instantly with the touch of the key, you don't ever hear the starter make a revolution. Happy BB.

$4.75 @ gallon last fall here in Md.

[Mr70]

Same here,run 100 octane in my L-78.

[x33rs]

We've been running nothing but the 91 octane available in AZ in our 69 Z since I refreshed the engine 5 years ago and have been daily driving it. Over 40k miles now, Runs perfectly fine, but these little engines actually have enough camshaft in them to bleed off quite a bit of cylinder pressure. But I knew that going in from building similar stuff like this in the past.

I built it back with exactly 11:1 compression, the original iron heads, a slightly tweaked version of the original 30/30 cam that has a little more lift and tighter lash, and a few subtle things internally for more performance. It loves 36 degrees of total timing with an additional 10 degrees dialed in with a vacuum can. In fact it gets 14 mpg around town and 17 highway with the muncie. After putting in a 5 speed highway mileage jumped to 22 mpg. It's been a fantastic running car on 91 pump.

On the BBC's like the L78's and LS6's, I could see where it might need some help in the gas department. Those factory cams didn't act quite as big in those engines.

[MYSTERYCHEVELLE]

I fill up at the ATM..... I mean the Sunoco Race Fuel Station 5 miles away for my little Black Bear!!