Gramma's 75 Firebird: the new project
 

It's been slow around here so we decided to do a little engine work on the 1975 Firebird that my grandmother bought new from Ruckles Pontiac in Yonkers, New York back in September 1975. My grandfather traded in a 1969 Thunderbird plus cash for the Firebird and drove it off the lot. Gramma Rose drove the car for several years and then ended up giving us the car in the early 1980's when the door just got way too heavy to pull shut. (Anyone with a second gen F-body will know exactly what I mean).

We got the car with 38,000 miles and my brother drove it for a few years til it ran up 70,000 miles. At that point it just sat around and I ended up taking it and repainting the car and giving it back to my father as a gift. He proceeded to park it in the garage and throw all sorts of things on top of it and drag garden hoses across it. So I reposessed it in 2004 and brought it back to my house.

Anyway, Since my daughter helped rebuild the engine in the 72 T/A back when she was 8, I figured it was time to let my son try his hand at rebuilding the original 350.

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First thing we did was a compression test on the engine. Here's the results:

cyl 1: 125 psi
cyl 2: 120 psi
cyl 3: 125 psi
cyl 4: 115 psi
cyl 5: 115 psi
cyl 6: 120 psi
cyl 7: 115 psi
cyl 8: 125 psi

I then sprayed some oil in the low psi cylinders and retested with negligible improvement. (So that means it's the rings, not the valves - more on this later).

Since there was more than 10% variation between the highest and lowest pressures, it was time for a freshening.

I unplugged everything rather uneventfully in a day and got it out of the engine bay with the help of the wife and the kids.

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Other than a change to a 1972 cast iron four barrel intake and a camshaft/valvespring/timing chain swap in 1994, nothing has ever been done to the internals of this 350 engine.

With the boy by my side we pulled the engine apart and did some forensic examination of the parts. I'm a firm believer in actually examining what you have as you take it apart and not just throwing everything in a pile in the center of the garage. We found some interesting things.

The lifter valley was reasonably clean with a little tarnish on everything. Cam looked fine.

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The double roller timing chain was stretched quite a bit. When you set it at "0" on the timing mark and then tried to rotate the crank, you get the mark on the balancer to line up with the "4" degree mark before the distributor rotor would move. Thats a bit too much slack.

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Pulled the 6X heads and it looked like a bit of oil was burning in some of the cylinders. If you looked into the exhaust ports you could see the oil sludge seeping though the guides.

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A bit of carbon on the pistons but the bores looked beautiful - a mirror finish with no scratches anywhere.

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The bottom end showed quite a bit of tarnish on everything, the results of years of sitting with old oil, I imagine.

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Take a look at the piston and tell me what is wrong with this picture....

http://i20.photobucket.com/albums/b2...8/SDC10362.jpg

Yeah, nice factory alignment of the ring gaps. All eight pistons had the gaps on every compression ring and every oil ring lined up with each other. It defies logic. Every kid learns in high school shop class that you have to stagger the ring gaps in different locations to avoid loss of compression and high oil consumption.

All I can think is this was some type of job action or purposeful sabotage by the guy at the engine assembly plant back in 1975.

No wonder the car never had any ooomph when you hit the gas.

(Original machine marks on the piston skirts look nice, though)

We removed the compression rings and checked the ring gaps:

Cyl 1: .032, .030
Cyl 2: .032, .032
Cyl 3: .030, .032
Cyl 4: .032, .035
Cyl 5: .035, .032
Cyl 6: .030. .035
Cyl 7: .028, .028
Cyl 8: .025, .030


I believe the spec is supposed to be .019 plus/minus .010.

Main bearings/journals looked beautiful:

http://i20.photobucket.com/albums/b2...8/SDC10342.jpg

The rod bearings/journals looked just as nice. Oil clearance was still within spec. And yes, I stamped each rod with the numbers. They were all unnumbered when we popped the pan off.

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It still had the original asbestos rear main seal which was leaking badly along with the timing cover seal, oil pan gasket, torque converter seal, tailshaft seal, rear pinion seal.....

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Here's the empty block awaiting a trip to the shop:

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and all the parts:

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And of course the typical monkey wrench in the ointment...cracked exhaust manifold.

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If I can't find a replacement I might upgrade to the repro ram air manifolds.

Looks good, can't wait to follow this one :)

Steve, that is a nice bird :)

Maybe I'm missing something, but that's 8% difference. If it wasn't using oil, I wouldn't have rebuilt as it's only virgin once. Bore and bearings would seem to indicate that there were no issues.

As to why it was gutless, the tiny cam they put in those from the factory is the culprit I'm sure. I hope you're planning at least a mild upgrade in that area. Very cool car.

Doh!


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I was never too good with math, especially percentages.

I also needed an excuse to freshen up the engine especially with all the seals leaking from sitting so much.

And it's a good father/son project for the summer.

:-)

Cool project, and sweet car.

I noticed that too, and thought I was missing something. LOL

I've got a few manifolds down in the basement, i'll check the #s for you ...I hope you're not going to go any further than cleaning up and freshening the mechanicals on that time capsule ....

I'm sure you know this but rings rotate while the engine is running. Believe it or not, they don't all rotate in a beautiful symphony of synchronicity. They end up where they end up. I would say it was a coincidence that they were all lined up.

I understand the rotational effect but that's just too bizarro to have the gap on every ring, on all 8 pistons within a half inch of each other. If the universe has that much synchronicity i think i should go out and buy a powerball ticket (or 8 tickets) right now. :-)

Please check, that would save a bunch of time and effort if you have something.

And yes, we are just cleaning, replacing rings, bearings and swapping in a Melling SPC-7 068 cam and reassembling. I ordered the correct 1975 blue paint yesterday from Bill Hirsch, here in Jersey yesterday. Too bad it comes only in quarts and isnt available in a spray can.

(of course, I did break off a stud on the pass manifold. Got that side, too?)

You just can't sit down & relax - can you? :noidea:

Really nice car Steve, going to be a nice little ride with the freshen-up!

You're right, I can't just sit around. :-)

It's our family heirloom. I dont know if I told you guys of this episode:

When Gramma Rose had the car she always had the strangest way of shifting the car into gear. She would be sitting behind the wheel and would take her left hand and reach all the way across her body to push the gear selector knob down on the console shifter and then use her left hand to pull the selector into drive. Her right hand stayed on the steering wheel the whole time. It was the weirdest, most unnatural action you could think of. (Any of you with an automatic in your Firebird, try it. It's just about impossible to do).

Anyway, when it was time to teach my daughter how to drive, (mind you she is named after my grandmother, her great-grandmother), she sat behind the wheel, started the car and the reached over wth her left hand and duplicated exactly, the same bizarre method of shifting that Gramma Rose used. She had never seen her great-grandmother drive the car and would not have known of this procedure.

The hair on the back of neck stood up and I swore I could hear the Twilight Zone theme playing somewhere.

I know Gramma Rose was smiling up there, too.

You might be in luck. For some reason I think these are A-body logs. I've got a driver's side 499624A, date code k124 and a passenger side 496002A, date code L034. The heat valve is in very good working order both have flanges, the one still has the head pipe attached, it was cut off at the down pipe, the crossover is still good.