Help with a Pontiac Straight-8

[MercMontMars]

Hi there, I have a 1952 Pontiac Chieftain with a swapped 1954 Pontiac Straight-8. I’ve posted about it before, but I’m getting deeper into it and need to know more technical data. I’ve only worked on older V8s so far and this motor is still a bit alien to me. I’m trying to learn as much as I can about it. I do plan on rebuilding it soon as it will need it, but for now I need to at least get a little bit out of it until I have the time and know-how. I’ve been able to run and drive it, but air-fuel mixture has been a continuous issue along with other things related to age such as fuel making it’s way through the piston rings. Runs cold as ice though and I’m in Florida!

I need to know some general things such as the best oil to use for this motor, suggested oil or fuel additives, and some Dos/Don’ts from experienced Straight-8 owners. I know these motors like thick oil but how thick should I go? Any quirks or things I should worry about upon disassembling the engine? Tips on timing adjustment and tuning? I also need to know the bolt torque specs if anyone out there has info on that.  
 

If anyone knows more about Pontiac’s hydramatic transmission I’d also love to learn some more on it as I want to rebuild it. It shifts well and does the job but 3rd gear seems to take it’s time. From what I’ve felt while driving, I believe the trans has 3 gears plus overdrive. (Felt 4 shifts.)
 

That about covers what I need to know. I’m all ears to any wisdom someone is willing to share about this car and it’s motor. Looking forward to learning something new and getting this motor purring as it should!

 

[rocketraider]

The HydraMatic is a four-speed unit. No overdrive. 4th gear ratio is 1:1 direct drive.

 

Suggest getting an original print copy of the 1952 Pontiac factory service manual. You'll learn more about the car from that than anything else. Since you have a 54 engine and transmission might pay to get a copy of the 54 book for those. 

 

Looks like 49-54 are covered in one book.

[Oldtech]

Before getting too crazy on the engine do a compression test,  and what is the oil pressure?  A good tuning may be all it needs. Check the ignition timing and that the advance mechanism is working correctly. 

As far as oil for the warm climate goes I'm sure straight 30 was recommended. You could go 15-40 if the engine is a bit worn. 

Transmission... that's a whole 'nuther science. the shift from 2-3 on those is always the fussy one as it is disengaging a band and a clutch, and engaging the other band and clutch. You may only need a band adjustment. Or... after this long it may need everything. Go at it slowly... one thing at a time. and yes, it is a 4 speed with a very low first gear and no overdrive. 

[Bloo]

This. Get the manual(s). There's bands to adjust and linkages to adjust. It all matters. There might very well be nothing wrong with the transmission. The engine originally used rather ordinary oil (probably 10W30 or 20W20 or so in 54. Maybe SAE20). They didn't use heavy oil originally, but it might not be a bad idea in hot weather especially if it has trouble holding pressure when hot.

[Ben Bruce aka First Born]

Yep, what Bloo said.  

  Nice car.

 

  Ben

[Rusty_OToole]

Multigrade oil and detergent oil debuted about the time your car was built. It was the default choice at every car dealer and gas station from the fifties thru the eighties. Chances are your car has never used anything else but 10W30.

 

If the manufacturer ever recommended 30 oil it was only for the most severe hot weather conditions, when 10W30 was not available.

 

Thick oil won't fix a worn out motor. If anything it will make it wear out faster. But it may quiet things down a bit. I would try the 15w40

 

Your engine has low compression and will run fine on the lowest octane regular gas.

 

The transmission is a 4 speed with fluid coupling, not a torque converter. It may be necessary to adjust the bands for more positive shifting. This is a normal service procedure that is required from time to time.

[hook]

They run quiet, solid and vibration free. When tuned properly you could balance a nickel edgewise on the fender, The only noise you get at idle is that wide fanbelt. If you hear a slight ticking noise starting, it's not the valves. I turned one of those straight eights into a straight 7. It happened very quick.

[MercMontMars]

@Bloo Thank you for the reply! I’m in Florida and it does get pretty hot, I’ll try your suggestions of 10-w30. I have dash gauges, but they are reading inaccurately (temp gauges instantly rises over 230 after motor gets to temperature, which is inaccurate as I have a temp cap on the radiator and I have a temp gun. Runs around 160-180.)  I will test the accuracy of the oil pressure gauge next time I run it as it does move but I’m not sure if it’s correct.  Didn’t know about the bands, that’s very good to know. Will adjust them as soon as I can.

[MercMontMars]

@Oldtech Good to know! It will definitely need an adjustment as it was very fussy from 2-3. Was afraid to push it, but I’m relieved to know it’s a matter of tuning. Will run all the tests as soon as I can, trouble is I’m in the process of moving to a bigger shop. I know for sure the timing is way off, I got it a lot better than it was but the previous owner had this motor running at about almost 1200 RPM IDLING! I had it down to about 400-500 idling now. Im sure she’ll come around, just a fussy ancient motor that is giving me a run for my money. 

[MercMontMars]

@Rusty_OToole Thanks for the reply! I’ll give 10-w30 a shot, glad to hear that bit about the detergent oil. I always hear back and forth rumors about what you should use, non-detergent being better for them etc. My belief is, they had what they had at the time, but anything we’ve got is astronomically better now! Good to know about the fluid coupling, I wasn’t sure about that before. Will adjust the rings on it as soon as I can.

[Bloo]

In my 1936 Master Six, a very closely related engine to yours, I am running 20W50 in late summer when it is getting over 100F constantly. According to the shop manual, I shouldn't need to be doing that. I probably wouldn't need to if the engine was fresher.

 

Since you have a temp gun, check at the back of the engine. Your temp gauge is most likely at the back of the head, and that is the hottest spot in the engine. The most common cause of overheating in these engines is a rusted out water distribution tube. The symptom is the back of the engine runs too hot, and that's where your gauge is. If it's not boiling over, it's probably fine. It was @Rusty_OToole who advised me to check mine with a temp gun, and it was marginal. I replaced the tube and... yeah, there were rust holes.

 

[Rusty_OToole]

To answer your questions in more detail, first you should get the factory repair manual for your car. They printed thousands of them, at one time every dealer had them, and they turn up on Ebay and at antique auto literature dealers usually around $50 to $75. If you don't have one, the MoToR Manuals are good, although not as complete, since they cover all makes of cars.

 

One unusual feature of your motor is the built in oil filter in the crankcase. It should be cleaned out at overhaul time. Otherwise does not need to be serviced.

 

Some people recommend adding a little upper cylinder oil to the gas, such as Marvel Mystery Oil, Bardahl, Redex, or maybe some 2 stroke oil. Today's gas is very dry and a little extra lube will double the life of rings and valves, and prevent sticking valves when the engine is out of commission for long periods.

 

How is your oil pressure? Have you done a compression test? Oil pressure should be 35 PSI hot when running at 30 MPH or more. If you have 15 at idle that is pretty good. Ideally, compression should be around 110 PSI and not vary more than 15 lbs between cylinders. But if you have 90 or better that is enough to be going along with.

 

1954 was the last year for the straight eight Pontiac, in fact the last straight eight on the market along with Packard. They were known as a smooth, reliable, long lived  motor. Many mechanics bought Pontiacs because they knew they were one of the best, most trouble free cars on the market.

 

Most times, on an old car like that, you need to go over it and make a lot of small repairs, that don't necessarily cost much money but do take some time. It is incredible what a difference it makes to have everything working right and adjusted to factory specs. One thing often overlooked is to fill the shock absorbers with oil, if it has the refillable type, and to get a front end alignment. Shock absorber oil is not readily available but hydraulic jack oil is a good substitute.

[57j2olds]

@Rusty_OToole

 

 

Your comment about additives to the engine oil makes me wonder......I have a 48 Olds with a straight 6. 

 

Would adding 2 stroke oil to the fuel help? What do you recommend?

 

The motor was from a 49 replaced in the late 50's however all original.

 

Thanks 

[Rusty_OToole]

Do you believe Jay Leno knows a little about old cars and old motors? Here is a video in which he gives his views on today's gas and whether you need additives. I suggest using some type of upper cylinder lube in the gas, like Redex, MMM, Bardahl or your favorite brand for better valve and ring life and to prevent rings and valves from sticking when in storage.

If you want Jay's opinion on this question skip ahead to the 30 minute mark.

 

 

 

[R Walling]

 I have a straight 8 Chrysler and one of the first things I did was to install a new gauge set under the dash. I would never trust a 70 year old oil or temp. gauge.

 

 If the stock gauges read the same as the new ones, then I would be really happy!