putting a GMC 6 into a 1947 plymouth. it's a bit heavier then the old flatty so the pan hits the tie rods, my options are to raise the motor (pain in the YNW) or lower the pitman arm. Since I am good at welding I have the idea to cut the pitman arm, & lower the part of it that attaches to the tire rods by welding a vertical piece of 1/2 inch steel bar to the cut pieces (kind of like creating a dropped spindle), this would lower the tire rods. BUT would it mess with the geo. of the steering system? That's my question... I've welded cast material successfully before so that's not a issue with me. Thx. in advance.
go for it....a Hemi on one car and a Chevy on another car transplants didn't work with the modified drop steering....but maybe yours will....
Yes it will mess with the steering geometry. I am not sure why the engine being heavier would change the clearance as the center link on the steering that the tie rods attach to is not affected by the ride height of the chassis. Only the outer end of the tie rod will move up relative to the frame as the chassis moves down. Roo
While im not sure how the weight of the engine would effect this, cutting and welding forged pitman arms always gives me the creeps. as much as Im willing to cut something apart, I don't mess around with them, too much chance of something going wrong and too many horror stories to ignore. Since you are just getting the engine in place, I would think it would be a lot more efficient to change the mountings, add spacers, etc, for it now and not have to worry about a critical steering component being compromised and possibly failing down the line, as well as not having to correct the steering from what is changed from modifying the pitman arm.
I totally agree. That sort of thinking is straight out of the R-rod encyclopaedia. Without searching, maybe a dropped pitman arm is available for your application.
Steering components are forged, not cast. Yes, it will Fuck Up the steering geometry. Nobody can figure out why the engine weight created a clearance problem. Take that as a clue.
Raise the engine. I would think a GMC 6 would not be a good fit in that engine compartment as they are rather small in ‘40s Plymouths.
Actually, a 331-392 Hemi fits rather well in there. Wide, but otherwise, compact. Is the Jimmie going in for shock value? 1. Notch the pan. 2. Raise the Jimmie. Don't weld main steering components, especially on the South end of the worm!
I guess I should have been more precise. The length of the engine compartment is short. I know from putting a 318 in one the firewall has to be dinged a little to move the engine back to allow the pan to clear the tie rod. I imagine a GMC is a lot longer and will require firewall mods to fit well. The dropped tie rod modifications were not done on the idler or pitman arm in “traditional” days and usually resulted in limited steering.
If you lower the pitman ,I assume you are also lowering the idler on the other side as well [ dropping the whole drag link ] If you do this you will also need to bend and lower the steering arms to correct bump steer issues you will create. Google image "Bump Steer Geometry" You'll understand. You can get this close enough with a string line and draw crosses on the ball joints.
I can garentee you any pan you are using can be cut which is what I would do. Up near the front it only needs to clear the con rods and once your clear the tie rod slant it back on a 45* angle. It can also be flat. The pickup is in the rear. A pan gasket is all you need and if it wasn't glued on both sides u won't need it. Only some rtv in the corners.
You say cast? I am thinking pitman arms are forged? If the arm is indeed forged, it could be safely welded by a competent craftsman using proper beveling and compatable metals and welding techniques. It would then need to be dye pen or xray tested to insure weld integrity. Welding cast steering components is something quite different, and I would not be inclined to do so.
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