Gramma's Car: the new project!

[njsteve]

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.

[njsteve]

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.

[njsteve]

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.



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" dgeree mark before the distributor rotor would move. Thats a bit much slack.



Pulled the 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.

[njsteve]

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



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

[njsteve]

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



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. [img]<<GRAEMLIN_URL>>/no.gif[/img]

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

(Original machine marks on the piston skirts look nice, though) [img]<<GRAEMLIN_URL>>/smile.gif[/img]

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.

[x Baldwin Motion]

Steve is that a Formula, or was there a hood swap?

[MosportGreen66]

10-1 odds you end up doing a 4 year frame off...

[Xplantdad]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MosportGreen66</div><div class="ubbcode-body">10-1 odds you end up doing a 4 year frame off... </div></div>

Dan...LOL

Steve wouldn't do that...would he? [img]<<GRAEMLIN_URL>>/hmmm.gif[/img] [img]<<GRAEMLIN_URL>>/grin.gif[/img]

[StriperSS]

And so it begins..........................
another epic thread, and I was in at the start of this one! [img]<<GRAEMLIN_URL>>/laugh.gif[/img]

[Alss]

love those cars..cool thread Steve .... [img]<<GRAEMLIN_URL>>/beers.gif[/img] ..again