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I was surprised to see metric fasteners when I removed the headlight assemblies from my newly acquired '85.
I'm assuming everything on the car is metric other than maybe the engine?
That is what I have found to be true on my 85. The bolts that go directly into the block are English, the bolts on the engine accessories and rest of the car are metric.
I have even used my 3/4" drive torque wrench on the car. I have a 1/4" drive, a couple 3/8" drives, a 1/2" drive and the 3/4" drive torque wrench. Before it is all said and done, all will be used.
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Originally Posted by drcook
I have even used my 3/4" drive torque wrench on the car. I have a 1/4" drive, a couple 3/8" drives, a 1/2" drive and the 3/4" drive torque wrench. Before it is all said and done, all will be used.
pretty much everything on the C4 is METRIC except the engine (long block), and anything that attaches directly to that engine block - all that being FRACTIONAL. things get a little screwy with engine accessories and associated brackets. the brackets attach to the engine with FRACTIONAL fasteners, but accessories that attach to those brackets are METRIC. a good example is the PS pump and bracket - look at parts 2 ands 21 -- a mixture of fractional and metric.
off the top of my head, i'm thinking the lower intake manifold is another component that has a mixture of fractional and metric fasteners. same applies to the AC compressor mounting. exhaust manifolds attach to the engine with fractional fasteners, and the exhaust pipe(s) attach with metric.
bolt or screw heads may be hex, torx, or allen, but they would still fall into the fractional or metric family. anytime working on the engine, brackets or accessories, it's a good idea to "bag and tag" all fasteners and attach that bag to the part or component. take notes, make drawings, and take pics - it pays to be **** -
ha ha ha ha ha - one of the best truthful statements I have read in a long time
After fussin' with C3 and C4 Corvettes since 2002 and buying everything under the sun at one time or another to wrench 'em, I had to buy a "Highboy", roll-away tool chest to hold it all! Separate drawers for metric and English and "other" stuff like torks, etc.
Come on guys, quit complaining because you need SAE and metric. My Jaguar XK150 I used to own was Whitworth, and my 1939 Delage D6-75 I used to own was a mixture of metric, Whitworth and SAE.
When I owned the Jag the only Whitworth tools I could find were Snap On. Expensive.
pretty much everything on the C4 is METRIC except the engine (long block), and anything that attaches directly to that engine block - all that being FRACTIONAL. things get a little screwy with engine accessories and associated brackets.
This is the most accurate answer yet.
Here is the deal on C4's...and all other "domestic" GM: If it's designed before 1980 it's standard. If it's designed after 1980, it's metric.
Obviously, engine block was designed in '55....that's standard.
A/C compressor bracket? Designed after '80....Metric
Steering column? Designed before '80....Standard.
Now here is the thing about tools: For all wrenches and sockets, buy metric! ...then add a 1/4" and 3/8" to those sets. Nearly all metric work on nearly all standard cap screws and nuts, except 1/4 and 3/8". This is how your wrench set/socket racks or trays should look:
Now, "=" means in practice. Someone is probably going to point out that 13mm is not exactly the same as 1/2" and that is true, but in practice, a 13mm wrench or socket works on 99.9% of 1/2" bolt heads or nuts. So, you buy metric tools + the 1/4 and 3/8 and you end up with a more versatile tool set, for less money.
I distinctly remember blue-colored sheet metal bolts under the hood of my dad's new 78 Grand Prix.
The sae/metric thing has more to do with assembly plant tooling and production change-out than calendar dates.
I wouldn't doubt that. "1980" was something that I heard from one of my auto tech prof's back when I was in school. I'm sure that figure is not hard and fast....we're talking GM here. I think it's a pretty good guideline to keep in mind when working on these things, however.
Have found this rule to true with the Vette and other cars and things needing repair;
the thing your fixing now is SAE. You finally have it done. You move on to the next thing (which might be right next to the thing you just fixed) only to find it's metric. Ths forces you to get out from under the car, go get the metric sockes, find out one lousy bolt needs an open end to get to. Back out from under to get the wrench from the chest. By the time you finish the repairs or whatever, half the tools from your roll around are under the car. So, rule of thumb, whatever your working on now, metric or SAE, the next thing to do in the repair will be the oposite. Live it, love it, know it.
a 7 mm and 10 mm socket will get you long ways along with quality torx head kit with angle extension. Torx heads on C4's demand the good stuff, strip easy. Don't Harbor Freight those ones for sure! (interior and body wise)
Last edited by corvette95; 05-08-2018 at 07:29 PM.
Have found this rule to true with the Vette and other cars and things needing repair;
the thing your fixing now is SAE. You finally have it done. You move on to the next thing (which might be right next to the thing you just fixed) only to find it's metric. Ths forces you to get out from under the car, go get the metric sockes, find out one lousy bolt needs an open end to get to. Back out from under to get the wrench from the chest. By the time you finish the repairs or whatever, half the tools from your roll around are under the car. So, rule of thumb, whatever your working on now, metric or SAE, the next thing to do in the repair will be the oposite. Live it, love it, know it.
05-07-2018, 02:00 PM
What's metric on a C4?
I think it's a pretty good guideline to keep in mind when working on these things, however. 
