Looking for suggestions or opinions on my '71 C/10

[caboverjunkie]

Hey all, I am a proud owner of a '71 C/10 and as I'm sure all of you know, they never are really "finished". I've built and installed a small-block 406 with a Saginaw 4-speed with the 3-ring (3.50 first gear) input shaft. I'm pretty sure I'm gonna have to replace the pressure plate and clutch and main bearings due to a vibration I have and it seems to be affecting the oil pressure by putting excess wear on the bearings. Domino effect I guess. I 've changed over to AMSOIL 20W-50 oil. When the engine is cold to warm, the oil pressure is fine, but when everything is hot, if it idles at 20 lbs. I'm lucky, sometimes less if it's a hot day out. The pressure was better when the engine was new, but it has less than 10k mi. on it now. The wide-ratio trans. works great with the 12-bolt 3.07 rear. My dilemma is, I don't know if I should go with a Posi, Limited-slip, or one of those Powertrax lockers. They all seem to be a good idea, but which would be the best? The truck is, well was now, kinda a daily driver, with a little "playing" from time to time. Nothing major, just "blow the soot out" every now and then, you know. The truck is nowhere near perfect, but after all, this is my first build, and I want to try to do it right. Any help at all will be greatly appreciated.

[Old Yeller 1970]

Originally Posted by caboverjunkie

I'm pretty sure I'm gonna have to replace the pressure plate and clutch and main bearings due to a vibration I have and it seems to be affecting the oil pressure by putting excess wear on the bearings.

Are you certain you have a 400 flywheel on it? Because 350's are internally ballanced and 400's are externally ballanced if you have a 350 flywheel on a 400 you will have a definite vibration. I once had a hotrod 62 Impala with a 400 and a vibration that turned out to be this problem.

[Shaky]

Old Yeller gave a good suggestion.

I have a '66 C10 with a 3.27 first gear Richmond 5-speed and a 3.07 12-bolt. I used an Auburn cone-clutch posi. Seems to work good. If you have a healthy motor it might be better to go with a clutch-pack type.

[Sinister]

20 lbs of oil pressure at hot idle doesn't sound bad to me.

[caboverjunkie]

Well, I thought about that too. Since I bought it second-hand and barely used, I called Centerforce to verify the part # and they said it was indeed the correct one. I was thinking maybe it could be the pressure plate since it is a "rebuilt" unit. I don't have a clue about how to go about checking the balance on the pressure plate. I thought $125.00 was a great price for the plate and disc, but now I'm thinking it may be biting me in the butt.

[caboverjunkie]

The 406 I built is an early '71 (3951511) .030 over 4-bolt main with flat-top pistons. Due to funds running low, I had to re-use the stock 400 heads, (3973493), big chambers, 76cc, I think, 1.94 and 1.50 valves. We had to cut the heads .020 just to get them flat. I rebuilt the heads with stainless valves, and used 1.5 roller rockers with a .480 lift, .230 dur. cam. On top of that I used a high-rise Hurricane intake with a 750cfm double-pumper Demon carb. It does pretty good, I guess with only 350 hp and 450 lb. ft. (400s always were a good torque motor). If I drive it like I've got some sense it will do an average 14mpg. Not too bad for an old junkyard motor.

[Old Yeller 1970]

Originally Posted by caboverjunkie

I don't have a clue about how to go about checking the balance on the pressure plate.

I would pull the transmission off and run the engine with the pressure plate still bolted on, just to verify the vibration is still there (I assume you feel it when you are in park, as well as on the road). Then I'd pull the pressure plate off and run it again and see if you still have the vibration or not. If it disappears it's probably the pressure plate. If it's still there, I'd pull the flywheel off and have it inspected by Centerforce or put on another one. If it only vibrates when you're on the road, you likely have a warped drive shaft.