Mid-year HP engine code

[Chris D.]

Does anyone have some insight into the engine assembly content difference, as delivered from Flint, that was the necessity for the power steering specific HP code? '66 and '67 are the only years with a P/S specific engine code. Also, why would it change in '67 to be exclusive to P/S and AC in combination?

If all 350 hp engines were using the 5 qt. pan by '66, all the other differences that come to mind would be made in St. Louis.

This is not an issue with any car I'm working on just a curiosity I had.

Thanks,
Chris

[Gerard F.]

Re: Mid-year HP engine code

Could it be the difference in pulleys the engine came fitted with?

Just a thought.

Jerry Fuccillo
#42179

[Joe L.]

Re: Mid-year HP engine code

Jerry------

Pullies were almost always installed at St Louis (except crank dampers with integral pullies). No 1966 or 1967 used a crank damper with integral pulley.

[Joe C.]

Re: Mid-year HP engine code

Exhaust manifolds?

[John H.]

Re: Mid-year HP engine code

Chris -

I've wondered about that myself - I can't imagine any engine plant content-related differences in the engine assembly as-shipped that would make it unique to either A/C or P/S, as all of those components (including pulleys) were installed at St. Louis.

[Al G.]

[Terry M.]

Re: Mid-year HP engine code

Brackets too John? There has to be some difference in the engine for there to be a separate code. Any of the PS/AC brackets painted orange that would indicate a Flint install? What about the size of the oil pan? It had to be 5-quart for the PS ram to clear. We ran into that change in the C3s.

As you can tell, I am grasping at straws here because I have zero C2 knowledge. I'm just throwing out guesses.

[Joe L.]

Re: Mid-year HP engine code

Terry------

As far as I know, no 1966 or 1967 small block used anything other than the 5 quart GM #3820000 oil pan, so that can't be the difference. I have heard that some 1966 L-79 may have used the 6 quart 3820001, but I've never confirmed that.

The only engine-mounted brackets involved in the power steering system were the pump brackets. However, those were installed at St. Louis. I don't even see it as practical for them to have been installed at Flint.

All of the C-60 engine brackets were installed at St. Louis. This even included the studs that replaced bolts on the exhaust manifolds. However, I suppose it's possible that the engines destined for C-60 applications had the bolts deleted for the positions that were going to later receive studs. Seems unlikely, though. If they were going to do that, why not just install the studs at Flint?

One other possibility: due to the pulley configurations used with C-60 and/or N-40, it may have been necessary to use a waterpump with a different hub spacing than cars not so-equipped. However, to my knowledge only 1 hub spacing for waterpumps was used after 1965 but it's possible that it continued through 1967. In that case, the different waterpump hub spacing would have required that different waterpumps be installed at Flint and, therefore, the engines be differently suffix-coded.

[Chris D.]

Re: Mid-year HP engine code

Joe,

You shared a thorough water pump part chronology a few weeks back that did suggest the possibility of a later overlap in the transition of the two hub spacings.

I'm reasonably convinced that the new for '66 single groove base engine pulley, 3905995, had the newer forward spacing so that, by a wide margin, the largest volume of small block pumps were then standardized on that hub position.

There are some earlier pulley application overlaps, though, that do suggest the early hub spacing might have crept into '66 or later for some less common option combinations.

Looking at pulleys in the P&A for an indication has been an exercise in confusion. I find only two w/p pulleys shared with earlier pumps that theory suggests would need the earlier, rearward hub location. Without a '66 AIM these are only P&A service approximations: please correct where you see errors.

3790356 - base engine 63-65 plus 66 327 w/A.I.R., (exc.C.A.C., Sp.H/Per)
As it sat on my 63, the rearward hub location was required to line up. So this would be one early hub position that overlapped into '66. However, it has no use on L-79 w/power steering which started this conversation.

3890419 might. It shows up as service for 64-68 base engine C.A.C. as well as 66-68 Sp. H/Per,P.S.,& C.A.C. and also '69 - '70. This seems a bit shakier with application all the way to '70 and a 1st design note about which shaft (water pump?) this is used on. Also, '65 AIM shows the base engine AC pulley as 3850680. So it's not clear if the '419 exactly duplicates the original or if service swagged it. This does apply to HP engines so maybe it drives the early hub location and the need for a separate engine code.

What waterpump pulley do you see was originally released for both '66 base with AC as well as '66 350 hp with AC & PS?

Thanks,

Chris

[Joe L.]

Re: Mid-year HP engine code

Chris-----

I agree with you that it's extraordinarily confusing. However, I do think that this waterpump hub spacing thing might very well have been the reason for the different engine suffix codes used for certain 66-67 327 applications.

I believe that the w/p pulley used for both 1966 base engine with C-60 as well as L-79 with C-60 and N-40 was the GM #3890419. However, that number IMPLIES that it might not have been around at the beginning of the model year. So, it's POSSIBLE that some other pulley was used for early applications. IF so, I believe that pulley would have been the 3850680. However, the 3890419 and the 3850680 are supposed to be functionally identical. Whatever the difference is, I know not.

The 3890419 was used through 1970 for many PRODUCTION small block applications. It was replaced in December, 1971 for SERVICE only by the GM #3995643.

If we think that this pulley issue is confusing now, imagine what it must have been like at the time for the folks in St. Louis trying to build cars?

[Joe R.]

Re: Mid-year HP engine code

Hi Joe:

I am in the process of investigating this question, but I won't have all the data for a couple weeks. I'm gathering together samples of the two different pulley sets used on the crank and water pump on the L79 without A/C and the L79 with A/C. I plan to make some careful dimensional comparisons on the following two combinations:

3850838 crank plus 3890419 water pump
3858533 crank plus 3770245 water pump

Since the face of the harmonic balancer was in the same position for both configurations, it should be possible to determine whether the water pump pulley flange needed to be in a different place for one of the configurations to line up.

I will let you and Chris know (probably with a new post) when I get all the parts together and make the comparison.