Two questions on 63 L84:

[Michael G.]

Anybody know the torque spec for the nuts that hold the FI plenum to the base plate?

Also, anyone got a good pic of a 63 stab bar and attachings?

Thanks, Mike

[Michael H.]

Re: Two questions on 63 L84:

Anybody know the torque spec for the nuts that hold the FI plenum to the base plate?

Also, anyone got a good pic of a 63 stab bar and attachings?

Thanks, Mike

The only spec I ever found for those nuts was 25-35 lbs in. (that's INCH, not foot) I know that sounds a litte light but 25-35 foot lbs sounds way to heavy. (that's how we break the legs of the plenum)

I don't think it was ever published in the service manual. The spec actually comes from the 63 AIM but it's difficult to understand.

[Michael G.]

Re: Two questions on 63 L84:

Thanks Michael, That's kind of an odd spec for a 3/8's inch attachment. With virtually no bolt stretch and that gasket under there, the clamp load will disappear almost immediately. These will be hand-tight before I ever start the car.

Mike

[Michael H.]

Re: Two questions on 63 L84:

Thanks Michael, That's kind of an odd spec for a 3/8's inch attachment. With virtually no bolt stretch and that gasket under there, the clamp load will disappear almost immediately. These will be hand-tight before I ever start the car.

Mike

Yup, I agree. It sounds weird but that's the only spec I've ever seen in any GM paperwork. That's the number I've used for decades without issues. I usually tighten these nuts as tight as I can using a 1/4" ratchet.

There had to be an actual torque spec that Flint used when they installed the unit on the engine but we may never find out what it is.

I've sure seen a lot of plenums with broken legs from over tightening.

Another bolt that I've never seen the torque specs for is the 63-65 FI top cover bolt. I even talked to one of the guys at Rochester decades ago about this and he said "as tight as you can make them using a 1/4" nut driver. He had no torque specs for this bolt.

[Michael G.]

Re: Two questions on 63 L84:

If it's worked for you, I'll get out the 1/4 in ratchet and give it a shot. Wish me luck....

Now if I can just figure out how to get ANY tool on the passenger side front plenum leg rear-most nut....

Thanks, Mike

[Mike M.]

Re: Two questions on 63 L84:

I used a Universal Joint socket with two different length extensions that worked.
HanD

[Michael H.]

Re: Two questions on 63 L84:

If it's worked for you, I'll get out the 1/4 in ratchet and give it a shot. Wish me luck....

Now if I can just figure out how to get ANY tool on the passenger side front plenum leg rear-most nut....

Thanks, Mike

I think that one requires a 1/4" drive 9/16" socket and extension?? I seem to remember that this combo will slide straight down from the top??

There's another nut that requires a 1/4" drive 9/16" flex socket with extension.

[Michael G.]

Re: Two questions on 63 L84:

A 9/16 socket with a separate universal was too long, but I think the 9/16 flex socket and some extensions might work. I don't have one, so , I'll give it a try tomorrow.

Hey, about that stab bar - I'm trying to figure out if it is supposed to be essentially straight or curved at the center-line of the vehicle. Can you guys tell me?

Thanks, Mike

[John H.]

Re: Two questions on 63 L84:

Hey, about that stab bar - I'm trying to figure out if it is supposed to be essentially straight or curved at the center-line of the vehicle. Can you guys tell me?

Thanks, Mike

Mike -

The center 18" or so of the bar is perfectly straight in the front view; it curves up about 3/16" just inboard of where it enters the bushing in the frame bracket. Except for VERY early 63's, all '63-'67 small-blocks used the same 3/4" front stabilizer bar.

[Stuart F.]

Re: Two questions on 63 L84:

Michael H.;

When you say (quote) using a 1/4" nut driver, to me that implies a screw driver handle and not a ratchet where you can certainly gain a lot more leverage. What sat you?

Stu Fox

[Michael H.]

Re: Two questions on 63 L84:

Michael H.;

When you say (quote) using a 1/4" nut driver, to me that implies a screw driver handle and not a ratchet where you can certainly gain a lot more leverage. What sat you?

Stu Fox

Yes, exactly. Like a screw driver with a socket at the end. The recommendation for the 1/4" nut driver came right from Rochester decades ago. I don't remember who I talked to now but he was there during the days of the 63-65 FI units.

I've seen a lot of FI top covers that were cracked around the bolt holes from over tightening.

[Michael G.]

Re: Two questions on 63 L84:

I used a small torque wrench to tighten the ones I could reach to 30 in-lbs and estimated the others, based on feel. Given that the torque spec will result in virtually no clamp-load, I'm sure that it doesn't really matter if I'm that accurate with the tightening. This joint must work without clamp-load, but, after many years of delevoping tightening specs for GM, I have no clue how this one doesn't leak. I didn't put permatex on the gasket surface, but I'm beginning to wonder if I should have used it here.

Regarding the stab bar: Mine's slightly bent up in the middle, who knows how that happened, I'd hate to think what kind of load might have been applied, and how, and when. Looks like I'd better find another bar.

Thanks, Mike

[Michael H.]

Re: Two questions on 63 L84:

I used a small torque wrench to tighten the ones I could reach to 30 in-lbs and estimated the others, based on feel. Given that the torque spec will result in virtually no clamp-load, I'm sure that it doesn't really matter if I'm that accurate with the tightening.

I found another source for the torque specs on plenum to adapter nuts. It's the 63 AIM. At start of 63 production, the acclerator return spring and bracket were added at the St Louis plant so the part and torque specs on the nut that retains the bracket were in the AIM. (sect L84, sheet 3)

The parts/numbers were removed from the sheet on 5/5/63 because the engines were then shipped from Flint with the spring and bracket already installed. The spring/bracket part numbers (items 2 & 3) were removed from the parts list but the torque symbol and spec (2) is still in the list in the lower left corner of the page. 25-35 Lbs In.

I dunno. It definitely sounds weak but I sure wouldn't try 25-35 Ft Lbs.

Those numbers may have worked in Ft Lbs for the 57-62 FI units because they had a much taller/stronger plenum leg than 63-65.

[Stuart F.]

Re: Two questions on 63 L84:

On the F.I. Plenum, correct me if I'm wrong, but the plenum only handles air being drawn in by the engine at say up to 20"hg. I doubt that a minor leak would complicate the performance in this area. Probably the only fuel the joints would see would be vapors from hic ups. I realize there are certain sensor functions involved and even vacuum taps, but all in all, I can't see the sealing joints coming under any great stress from pressures or vacuums.

Stu Fox