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1966 Pontiac Tempest Custom Coupe
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Discussion Starter #43
I might have missed it but..what rear gears came on it?
Still need to determine that. Read that it'll either be stamped on the axle on the "flange" side, if memory serves, and/or on the ring gear. I just read the original owner's manual in the glove box (which also has a small comb and old style can opener in it) and it says SAE-80 or -90 (and add LSD lubricant; might find gear oil with it already added). I'll get under there and try to find some numbers. Or, just turn the wheel and count the rotations of the driveshaft.

I suspect it's a high gear...doesn't feel like rpms are that high at freeway speed.
 

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May I ask why you chose to stick with 14" vs. 15" wheels? I see Summit has 15x7 Rallye I, which would require/allow for a 60-series tire. Is it just that you like the "possibly OE" look of the 14" wheel, 70-series tire combo?

When inspecting the shocks, I saw coil spring spacers (rubber block that sits between two coils) or stiffeners, which is probably a band aide for old, fatigued springs. It's ride is good, but very soft. Fatigued springs and old Gabriel shocks (a tiny bit of rust on them) are surely responsible for the boat-like ride. Fresh springs and KYBs are on the list.
Rim size was only due to a friend offering a full set off his '65 at a price I couldn't refuse.
They just needed some love and have been a major improvement along with other mild upgrades.

New springs and some KYB shocks will make you and your '66 very happy (y)

RALLY ONE (1).jpg 109.JPG 3X.jpg
 

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Get the PHS documents for your car which will tell you all the specs and options.

The rear gear with a 3-speed seems to generally be 3.23's. Use the 80-90 gear oil and if adding to the rear if flushing/changing, add a can of additive for the posi. I use Lucas brand gear oil.

The engine is a lower compression and should run OK on pump gas. Would not worry too much about octane/lead additives. However, this additive has been suggested to my by a Pontiac engine builder/shop. It is a lubricant and octane booster - and can add a little extra octane. Not too expensive and you might only want to use it every other fill up, or so. You can use it every fill up, of course.

Pontiac engines are known for torque and built for torque over HP. The 326 has a small bore, so it is not favorable in adding the larger 2.11" later valve heads - but not needed either. The 326HO was designed to compete against the Chevy Hi-Po 283 option back in 1964. You can keep your heads, add larger valves, I recall you can use the Chevy Hi-Po 2.02" intakes, and do the usual head mods to get a decent head. A good cam, dual exhaust, and I might add a later factory cast iron Q-jet intake and carb. Would make a nice, fun, street combo that won't break the bank at the gas pump, especially if gas prices continue to climb, and still smoke tires.

 

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1966 Pontiac Tempest Custom Coupe
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Discussion Starter #47
Get the PHS documents for your car which will tell you all the specs and options.

The rear gear with a 3-speed seems to generally be 3.23's. Use the 80-90 gear oil and if adding to the rear if flushing/changing, add a can of additive for the posi. I use Lucas brand gear oil.

The engine is a lower compression and should run OK on pump gas. Would not worry too much about octane/lead additives. However, this additive has been suggested to my by a Pontiac engine builder/shop. It is a lubricant and octane booster - and can add a little extra octane. Not too expensive and you might only want to use it every other fill up, or so. You can use it every fill up, of course.

Pontiac engines are known for torque and built for torque over HP. The 326 has a small bore, so it is not favorable in adding the larger 2.11" later valve heads - but not needed either. The 326HO was designed to compete against the Chevy Hi-Po 283 option back in 1964. You can keep your heads, add larger valves, I recall you can use the Chevy Hi-Po 2.02" intakes, and do the usual head mods to get a decent head. A good cam, dual exhaust, and I might add a later factory cast iron Q-jet intake and carb. Would make a nice, fun, street combo that won't break the bank at the gas pump, especially if gas prices continue to climb, and still smoke tires.

That's all great info...thank you Jim!

Neither Advance Auto or O'Reilly's had an oil filter in stock. Auto Zone (and NAPA) had it, so I got a Mobil One (M1-701, if memory serves) filter. Got that, Castrol 10W30 dino oil and zinc additive. Actually, the oil looks only medium brown, so while I normally change the oil immediately on any newly purchased vehicle, I'll wait a couple hundred miles and see how it looks. Also got Mobil One 75W90 "LS" gear oil. Waiting for Advance to have a diff cover gasket delivered later today (depending on the weather, might wait until it's warmer and the residual snow melts, just washed 'er!). Also got lead substitute (forget the brand).

I'm at about 5,700 ft elevation here in Colorado, so regular octane in this region is 85 octane. I filled it with mid-grade (87) a few days ago. Is 85 or 87 is okay with this (lower compression) motor? Normally, I wouldn't need to ask...I know when and when I don't need it (for my turbo cars or Z06; 11:1 CR), but just want to be sure there's not something I don't know with that Pontiac motor.

Thanks again for the good info...
 

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Discussion Starter #50
take a peek at your rear end cover and make sure they get you the correct gasket,
I think your gasket should be the one with the ears cut off see below View attachment 140815
Thanks for the tip. Indeed it is as such. And as we can see, those bolts suggest that cover hasn't been removed in potentially decades (possibly 5.5 decades?). I think back in the day (including myself), many weren't too good at changing the gear oil. I had my Chevelle 10 years and never did (was young and naive).
140817
 

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Discussion Starter #51
Your tip is now doubly appreciated. Advance had the wrong (like above) one sent over from another location. He couldn't find the correct one at first but went into a different section in the system (?) and found it...getting couriered to my local store tomorrow.
 

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Welcome.. Thats a beauty. I always say Got to Love a Post. I'd leave it. Just get rid of that red heater hose.
O ya, the fuel filter too. Just a little detail under the hood, not much.

Sent from my SM-G970U using Tapatalk
 

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Thanks for the tip. Indeed it is as such. And as we can see, those bolts suggest that cover hasn't been removed in potentially decades (possibly 5.5 decades?). I think back in the day (including myself), many weren't too good at changing the gear oil. I had my Chevelle 10 years and never did (was young and naive). View attachment 140817
You might try to loosen your fill plug before emptying your diff. Just in case your plug wont come out. Ask me how I know. Had to drill mine out, don't want you ruining your gasket.
 

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Discussion Starter #56
awesome it still has the posi tag intact the rear cover should clean up nice, after you remove the cover you can find your axle ratio divide higher # into lower #
Right...was happy to see that tag as well. Though no reason to suspect the numbers won't be there, I learned they're simply the number of teeth on the ring gear and # of teeth on the smaller vertical gear (directly connected to the axle shaft).

As I've done w/past diff covers, I'll repaint it (after hitting it with a brillo pad (or ?...maybe a drill bit style abrasive disc?) to get the surface rust off. I'll also rinse out the gears with plenty of brake cleaner to get every last bit of nasty old gear oil out. Not too optimistic, but I'm hoping the fresh gear oil will quiet the whining down a bit. If it doesn't, I'll have it rebuilt.

And though one can only see a bit of it, that gas tank has lost its youthful beauty, so its time has come. Spectra (Canadian company) makes repro tanks for it, so I'll get one of those (and new straps) and get a nice new tank installed.
 

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Discussion Starter #57
You might try to loosen your fill plug before emptying your diff. Just in case your plug wont come out. Ask me how I know. Had to drill mine out, don't want you ruining your gasket.
Great tip. I'll presoak it with WD-40/parts loosener. Don't have a blow torch, but do have a heat gun. I could hit it with some heat prior as well. Thanks for the forewarning...
 

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Discussion Starter #58
Welcome.. Thats a beauty. I always say Got to Love a Post. I'd leave it. Just get rid of that red heater hose.
O ya, the fuel filter too. Just a little detail under the hood, not much.

Sent from my SM-G970U using Tapatalk
Speaking of heater hose...since I wasn't getting any heat into the cabin (though the vent fan works), I checked to see if the heater hose was hot. It definitely was not. The main radiator hoses were, but both heater hoses in and out of the firewall weren't even warm.

That's perplexing to me...but hopefully clues someone into a solution to get some heat goin' in the cabin.
 

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Discussion Starter #59
Maybe I should mention the upper lever on the vent/heater controls will only move between off and heat...clicks to there, but will not move to the deice on the right. The fan definitely produces air flow on the floor...and at the windshield (which it shouldn't if deice isn't selected, yes?
 

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That's all great info...thank you Jim!

Neither Advance Auto or O'Reilly's had an oil filter in stock. Auto Zone (and NAPA) had it, so I got a Mobil One (M1-701, if memory serves) filter. Got that, Castrol 10W30 dino oil and zinc additive. Actually, the oil looks only medium brown, so while I normally change the oil immediately on any newly purchased vehicle, I'll wait a couple hundred miles and see how it looks. Also got Mobil One 75W90 "LS" gear oil. Waiting for Advance to have a diff cover gasket delivered later today (depending on the weather, might wait until it's warmer and the residual snow melts, just washed 'er!). Also got lead substitute (forget the brand).

I'm at about 5,700 ft elevation here in Colorado, so regular octane in this region is 85 octane. I filled it with mid-grade (87) a few days ago. Is 85 or 87 is okay with this (lower compression) motor? Normally, I wouldn't need to ask...I know when and when I don't need it (for my turbo cars or Z06; 11:1 CR), but just want to be sure there's not something I don't know with that Pontiac motor.

Thanks again for the good info...
Your 326 will be the 250HP version with 9.3 compression, so at your altitude, pump gas regular should be no problem. You may have to adjust the carb for the higher altitude, but try it the way it is and see how it goes.
 
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