1978 tach redlines

[Charlie P.]

TM/JG shows L-82 with A/C should have 5300 RPM redline, without A/C should be 5600 RPM. At the Mid-Atlantic regional, there were four 1978 L-82s with A/C. Three of the four had 5600 RPM tachs. It's a small sample, but not likely all three were replaced with the wrong RPM tach.

Since there were few cars without A/C, is it possible they had an oversupply of high RPM tachs to use up? Other thoughts?

Thanks,
Charlie

[Mark E.]

Re: 1978 tach redlines

I believe 1979 L82 with or without AC redline is 5600 rpm.

So maybe this was a running change late MY1978? Just a guess.

[Charlie P.]

Re: 1978 tach redlines

Mark- The JG does say 5600 RPM for 1979 L-82 with a/c. My car is February '78 build, so right in the middle of the MY.

[Mark E.]

Re: 1978 tach redlines

Mark- The JG does say 5600 RPM for 1979 L-82 with a/c. My car is February '78 build, so right in the middle of the MY.

Mid-year change? You'll need more data points with VINs to check this theory.
M

[Tom R.]

Re: 1978 tach redlines

Charlie

Look at the last date of revision and I suspect it was twenty years ago. When these manuals were written, comprehensive vehicle surveys (Mark's point) were not one of the methods employed to fully understand production changes.

Too often, owners and judges take these things, manuals as gospel but TIMJGs are only guides and quite limited when the full production sequence is understood and how running changes were incorporated in an assembly line that was kept going at all costs. As a result, the knowledge base reflected in a manual is probably fifty percent of what the collective body of judges know about a particular aspect in the manual...believe me I know! Simply understand that manuals are limited...not comprehensive.

I share this as we work to update the 73/74 TIMJG and the degree to which this revised 3rd edition version will differ from the 2000 2nd edition is rather dramatic. Today's technical manual writers have the tools of this forum to work with and truly collaborate on the nuances of production. Plus the sharing of photographs allows team members to study differences from same model year, same month, same build cycle, etc.

For example for the past three weeks, the 73/74 team has been scrounging around look at the control valve dust covers and whether they were C or X, at what point did it change and why? The current manual has one lone paragraph dedicated to power steering. The new manual will have a page and a half. In fact, I'll upload and you can take a look. It actually rolls forward and comments through the end of C3 production.

The question you raise is important and one that requires further study. I always encourage members, when curious about a topic, to survey cars that are similar to understand these production changes. Then, share this with the membership through the Corvette Restorer with a technical article. It takes three years to get it in print, and hopefully, the board is recognizing that this is a limitation of the Corvette Restorer as a Corvette technical journal and working to correct that deficiency.

Case in point, I studied the Polyspare yellow rim introduced in 1978. The manual reports it this way "Some 1978's had the wheel painted wheel...but most later wheels were semi-gloss black." Well if this isn't mealy-mouth say nothing wording, I don't know what is. I published the results of my Polyspare yellow rim survey back in 2006. Essentially, my survey showed that the change over occurred in late March after the 22nd. A few Pace Cars shipped with yellow rims but the majority shipped with black. But yellow rims were shipped on Polyspare tires from what August well into March! Is this "some" as the manual states? Hardly not. The point, be skeptical as you consume these manuals and when doubt exists, trust your intuition!

Manual_Chassis_PSCV_25Sep18.pdf

[Charlie P.]

Re: 1978 tach redlines

Tom-
I am just getting back into NCRS judging with my '78 and I find that the TM/JG definitely needs some updating in the form of added information and expansion of discussions/descriptions. At some point, I'll submit suggestions for revisions.
Thanks,
Charlie