Inliners International Forums General Discussion Engines A little tech help

Does anyone know the crank to cam centerline distances for the Chevy 6's and the Ford 240/300 sixes? I'm trying to figure out a way to raise the cam in a GMC 302.

Thanks, Armond

The Chevy 6 engines(194-292) cam to crank centerline is 4.4125"/4.4145". Not sure about the Ford 240/300's.

Doesn't the center line in the 216-261 Chevy 6, 151-181 GM 4, and 228-302 GMC have to be the same because they all use the same timing gears?

I think they are the same on those engines. I believe he is looking into offsetting the cam/crank centerline in the block by the difference in the diameter sizes of the later 6 cylinder cam. Or maybe just a better timing set option.

You got it, if the ford gears are larger, I can off set bore the cam bearings in the Jimmy block (higher) and run larger cam bearings as well as, hopefully, not have to notch the cam.

240/300: 4.804".

Have at it.

Oh, I left out the 194-292, same gear sets as the rest. though some have different stock part numbers. So Ford? That's a pretty big move. What's the plan? Just to clear the rods?

Stroker cranks or aftermarket big meaty billet rods will cause the rod bolts to hit the camshaft as they swing around. Notching the cam core is one way to get around this. Moving the cam out of the way is a better way. That will also make it possible to use a cam core of a much larger diameter, thus stiffening an inherently weak link in a hi-revving engine.

4.8! Holy smokes that would push my cam up over a half inch! Even a 61mm bearing wouldn't compensate for that much. I guess it's back to the scratch board. Thank you all for your input. Any ideas would be welcome. Armond

Maybe you could find a motor that already has a 4.804 C-C distance, hint, hint.

...And graft your head onto it.

If only the SCTA/BNI folks could be talked into it! I'm afraid the mighty Ford 12 port doesn't qualify as a vintage engine in their eyes. It would be better to go the other way and graft a race ford head onto the Jimmy and run in the XXO class! Except the bore spacing is too close.

I always thought it was "convenient" that a Ford missed their cutoff date for being considered vintage by a year.

They do get an entire class unto themselves with the XF but that flathead V-8's and where's the fun in that!

There are some crafty rule makers in on some of that. Cover your butt guys. For a while some older cars didn't have to meet new tech but that has changed now. The Ford guys thought they had the flathead 4 classes sewed up until the Dodge Boys & Rich Fox showed up. I wanted to run my 413 Dodge Flathead 6 but it is too big for the vintage classes.

You could always block off 2 cylinders and create one big a$$ 4 cylinder. Kinda' like those guys that run a V8 block with one whole bank blocked off to make a 4 cylinder.

I could run 3 and use the other 3 as a supercharger. The CI limit is 375. I could destroke it to that but it's too much work.

Yeah, even with just 3 cylinder its bigger than most 4 cylinders.

I think an L6 running 4 cylinders will break something in a few minutes.

Examining a few diagrams, I doubt if you can get more than 1/4" increase in cam bushing OD (not enough wall thickness), which will only move the cam itself up by 1/8". It's got to help, but it's a huge amount of work for not much extra room. It might help to offset it laterally - like Chevy did to the 250.

You don't need to match the timing gear C-C distance if you use:
1. an idler gear (and a reverse cam)
2. chain drive (and a reverse cam)
3. a much smaller diameter timing set and 2 idler gears (with the original cam)

Panic, the GMC engines, especially the late military blocks like I have, have much more meat around the cam bearings. My idea was to offset bore the cam bearings to use 55mm cam bearing. These have an OD of 2.3" and by re-cutting the bores with this new diameter on the bottom edge of the old first cam bearing the cam will move up .150. This gives the same crank to cam center distance as a SBC (opens up many options). True, not much but I'm also destokeing with a 228 crank. With both in place and steel rods the cam should be plenty stiff, no notches, with a 55mm bearing size, allowing me to use some of the better grinds.

Well with that attitude it will!

I'm guessing the harmonic balancer would be one of the first pieces to go.

I wasn't really serious when I said that.

Why not? Nothing wrong with blazing trails, right?

I'm sure there have been more unorthodox things done before that we've never heard about though.

I once ran an Iron Duke for 60 miles on 3 cylinders. The fourth had a 1" diameter hole blown through the top of the piston.

...it blew a little smoke... Had to stop every 10 miles to fill it up with oil. The oil pump pick up kept the chunks out of the engine and the only damage was the piston. Had the heads re-worked for good measure but didn't touch the bottom end other than the cleaning out the oil pan and replacing the pick up.

OK I'm in on this one.

Once had a Slant Six that started burning oil really bad. No $ to fix, so I ended up pulling the pushrods on two cylinders. Ran it as a 4 cylinder for the next year or so.

I think it would be interesting to know how many things like this worked after being told they wouldn't!

Ran my Geo on 3 cylinders for 5 years, ran great.

I did the same thing on a 327 V8. Pulled 2 pushrods on 1 cylinder. The valve guide had broke, allowing the valve to really move. Drove it for a full summer.

Yeah but GM forgot to put the 4th one in at the factory so that doesn't count.

When I was a kid and my family was making one of our Pilgrimages to visit my grandparents in California from Texas our '41 Dodge was in the process of throwing a rod near Seligman, Arizona. By the side of the road my dad pulled the pan, dropped that rod by removing the wrist pin. He shoved the piston back to the top and drove to Hackberry before he found someone that would rent him shop space and tools to fix it "good enough" to get us to Pittsburg, California. He spent much of his vacation rebuilding the bottom end of that engine in my grandparent's driveway without pulling it out of the car. I once heard my dad tell a doubtful customer who ask if he could fix their car, "If Henry Ford can build 'em surely to God I can fix 'em". And he could!

I've heard a similar story that in the Depression guys would just torch off the bad rod beam and reassemble the engine down a cylinder. Desperate people do desperate things.

In Hackberry he pulled all the plugs to get rig of compression. Hooked up to the guy's battery charger and used the starter to turn the engine over while he used emery cloth to smooth the rod journal. He fitted an off the shelf bearing the best he could and replaced the rod. Running on all six again it did not knock all the way to California. On one of the Nevada/Texas trips my son and I made in his college days we located the ruins of that Gas station garage on the hill just east of what is left of Hackberry. Every road trip is and adventure.

Clever solution. Great memories I'm sure. And memories is what keeps those who've left us alive in our hearts. Now we all know your dad a little.