Has anybody seen this months Hemmings Muscle Machines? In the mag, there is an article about a Gold '65 GTO "Bobcat". I guess it was the Pontiac equivalent of a Yenko (well, kinda ;) ). Anyway, the article gives a run down about tricks the Royal Pontiac mechanics used for extracting every last bit of power out of the 421. Some of the tricks are obvious, one isnt.

I guess that they would cut (leave?) the washers off of the gasketed spark plugs so the spark plug tips stuck farther into the combustion chamber. The mag says that it reduced the chamber by 1cc or so, raising the compression. Is this for real :confused: ? I was wondering if it was due to the way the Pontiac head was designed? Ive never seen Pontiac heads off of a car (couldnt see the chamber)- Only Chevrolet graemlins/thumbsup.gif . Lots of knowledgeable engine people here, so I thought I might ask. Kind of a cool super tuning trick if it actually does work smile.gif

yeah, 1cc would raise the compression ratio- but by not enough to make much of a difference.
but i bet leaving the washer out would project the plug farther into the chamber- like an extended tip spark plug. that might be worth a few ponies.

Yes, one of Royal Pontiac's Bobcat tune jobs done to one of the first GTO advertising cars was what made it a "ringer" and run like a bat!!

I think it still holds a factory record as being about the quickest there was back then? And this was like in '64!!

Check some old mag. write-ups on it if anybody can find the old articles..

pdq67

That and having 421 cubes instead of 389 according to one story.

Couple of other tricks Pontiac did. They produced the factory drag cars with "swiss cheesed" frames, no insulation, equipment delete package.

... or window mechanisms. They had a strap to hold the window in place or lower it. Must have been some light cars. :D

Steve

I remember seeing the Swiss cheese cars and the strap pull windows on American Musclecar when the Pontiac drag cars were on there- that was pretty cool.

This spark plug trick kind of caught my attention, as I started to wonder if you could do that on a Chevy (Small block mostly, I guess- Most BBC were tapered seatS anyway, right?).

The plugs look like they are in a weird (vs. Chevy) position on a Pontiac, BUT you would think that both plug HOLES would be exactly the same if they used the same plugs.

I was intrigued by this, because my 350 has 441 heads on it, and when I bought it, it had Autolite 25's in it- which are tapered seat plugs. My version (1969) 441 calls for gasketed plugs, yet it ran just fine, (it actually seemed a little "tighter") with the tapered plugs! They stick out at least 1/8 or so more into the combustion chamber. After I read that spark plug trick in HMM this month, I was wondering if the previous owner was on to something that I should have kept doing :confused: . Seems like a quick and dirty way to gain some power, and every little bit helps!

I'd be more likely to believe that indexing the plug so the ground strap isn't in the way of the flame front would do more good than just leaving off the washers to "increase compression".

I don't think that leaving the spark plug gaskets off would make any difference at all in the engine's performance. Even a 1cc reduction in chamber volume will not add to the compression ratio appreciably - not even enough to measure. Plus, I think that the estimation of the gasket being equal to 1cc in volume is very exaggerated.
Consider this: a U.S. quarter (twenty-five cent piece) is equivalent in volume to 1cc. A spark plug gasket would not amount to the same volume as a quarter.