89 Formula 350 Guage Question 140 or 120 Speedo? - Third Generation F-Body Message Boards

JP007 · 10-20-2009, 05:23 PM

Which speedometer gauge came factory on the 89 Formula 350 cars? A car I am looking at shows a 120mph speedo with an 8k tach. The 8th digit is an 8 shows it is a factory 350 car but the speedo tach combo looks wrong as all others cars I had looked at had a 140mph speedo / 8K tach. It does have the dual cat exhaust, 4 wheel disc, 3.27 rear. Super clean and drives out good.

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Ward · 10-20-2009, 05:50 PM

I'm pretty sure a formula should have the 140 speedo, and a 6k tach. I'm not sure what the 8k tach could have come out of, maybe a V6 car. No stock V8 that ever came in our cars would live to 8000 RPM, I don't even think a 2.8 or 3.1 would. Come to think of it, the only 8k tach I've seen is the one that came in the 89 TTA.

berlin305 · 10-20-2009, 05:56 PM

Okay well on my 91 firebird i am donoring the parts out. Has a 140mph and 8k tac. Its a formula 305 tpi. And i believe its original.

Ward · 10-20-2009, 06:03 PM

Hmm, I could be wrong on the tach, it's been a while since I've looked at one. I have the digital gauges :P

RPM WOT L 98 · 10-20-2009, 09:26 PM

The 8K tach and 140 is correct for the L98 Formulas.
I hate to speculate, but someone might have changed the speedo on the car and not paid attention to the different mph. The question is, does the speedometer seem to read accurately?

JP007 · 10-21-2009, 06:36 AM

The speedo reads accurately. The drivers door has almost little or no drop when I open it, so the top hinge bushings seems good considering being that old. Been looking all year for a clean & tight car. I was curious if the RPO codes in the console would indicate corrct gauge cluster? Otherwise a pretty decent vehicle. After 8 GTO's I kind of like a change and really like the 3rd gen Formula & IROC cars. The 86 Firebird I bought new and drove it 227,000 miles. Learing a lot from this site. Thanks for the information.

xcalibur · 10-21-2009, 10:29 AM

ALL 1989 Formula 350s came with 140 mph speedo.
Someone swapped yours out for NAR. I ordered an '89 Formula 350 and had if for 6 yrs. That's why it also came w/Z-rated rubber !

Mudskunk · 10-21-2009, 10:52 AM

i have an 89 formula 350 and its got the 140mph speedo. 120mph came on the non 350's.

okfoz · 10-23-2009, 11:37 AM

Here:
This is from a bunch of research, debate away, it is from GM documentation.
http://www.3rdgenformula.com/all%20y...tachcombos.htm

John

RPM WOT L 98 · 10-23-2009, 09:31 PM

I thought I remembered the LB9 M5 cars having the 140/8K combo but was not sure and did not want to speak out of my a$$. Thanks John.

JP007 · 10-23-2009, 10:49 PM

Very good information. The tach combo's link from okfoz was very good and did copy & paste on that one, impressive and Thank You! I passed up a 88 Formula 305 TPI 5 speed car with 77K in Chicago with 140 speedo and 8k tach this last summer, the info in these replies really tells me a lot. The basic RPO codes N10, G80 & G92 and the 140 speedo with 8k tack would indicate a very desireable car. The Formula I found with the 120mph speedo with 8k tach is in really nice shape so I think checking the all RPO codes would be a smart idea. Pretty obvious speedo has been changed. These last couple of posts really cleared up a lot and with a quick look at the RPO codes and speedo & tach combo says a LOT! Again thanks for the updates.
JP

okfoz · 10-25-2009, 08:44 PM

It is defintaly something that is not correct. There could be a ton of reasons why it is incorrect. The factory could have run out of the correct IP, so they installed that one instead, it is unlikely, but possible. As would be the possibility that the original Speedo was defective and changed under warranty. It really throws up a red flag in my book that is for sure. I would probably personally pass, at least do a CARFAX on the car and an Autocheck to see if there is any information...

John