L31 Extreme Budget Build

[L31MaxExpress]

I have had a very minor vibration in this that was getting much worse with the torque converter bolted up. Well I feel dumb at this moment.

Completely missed that the TCI flexplate I had and used is for an internally balanced 1-piece rear seal engine. I did not even realize that was a thing and somehow completely missed the missing counterweight when I threw it on before dropping the engine in. Here I was about to rotate the torque converter and noticed it was missing the counter weight. Good thing I have a spare SBC 4L80E flexplate hanging on the wall that matches the TH400s 11.5" converter bolt circle. Missing counterweight will cause a vibration all right and it gets 10x worse with the converter bolted up.

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[L31MaxExpress]

Finished swapping the flexplate a little while ago. Engine is silky smooth now, only took a couple of hours to change out. I supported the engine oil pan with a floor jack. Used a piece of plywood on it to give it more surface area to protect the pan. I removed the carrier bearing mounting bolts to get me some room to move the transmission back. Then removed 4 of the bellhousing bolts, ran in 4" long bolts in their place. Then removed the transmission mount bolt and the other 2 bellhousing bolts and slid the transmission back. Plenty of room to work in the resulting gap without having to fight removing cooler lines, shift linkage, speedo cable, the crossmember, the driveshaft and actually having to pull the heavy TH400.

 

[Scooterwrench]

Then removed 4 of the bellhousing bolts, ran in 4" long bolts in their place.

Yeah,I've used that trick many times. I'm surprised the driveshaft had enough swing to pull it back that far. I don't remember ever getting that lucky. Your engine has two piece rear seal?

 

[Erik the Awful]

I only use V bands now that I’ve tried them. Not just any V bands these ones lock in positively and no leaks. I’m currently using 2.5, 3.5 and 5” V bands from them on turbo applications.

One important tip on V-band clamps. Once you have them in place snug them up and then take your smallest hammer and tap around the outside of the band to settle it onto the flanges. Then final tighten. If you don't do that the clamp will be tighter on the bolt side than the other side. The aviation industry uses V-band clamps on bleed air hoses, and if we didn't tap around the flange before final tightening it was a QA fail.

I will say that welding the flange to the header makes that style suck A LOT less.

Yup. A few weeks ago I welded the driver side flange on WCJr, but I did it so I could cut away the top of the flange because it kept hitting the shift linkage.

So where's $2000 in machine work coming from then?

From @Sean Buick 76's thread.

 

[L31MaxExpress]

Yeah,I've used that trick many times. I'm surprised the driveshaft had enough swing to pull it back that far. I don't remember ever getting that lucky. Your engine has two piece rear seal?

It is a two piece driveshaft, I pulled the carrier bearing mounting bolts and it became real floppy.

I have a 1-piece rear seal engine and that TCI flexplate is for a 1-piece rear seal engine, except for one that has been completely internally balanced.

 

[Scooterwrench]

It is a two piece driveshaft,

Yeah,I gathered that!

I have a 1-piece rear seal engine and that TCI flexplate is for a 1-piece rear seal engine, except for one that has been completely internally balanced.

When did GM start externally balancing small blocks? I know the 400 was externally balanced but didn't know they did it to 350's. I remember a guy brought me a truck that he had replaced the 400 with a 350 and used the 400 flexplate. It literally shook the rear view mirror off and cracked the windshield.

 

[L31MaxExpress]

Yeah,I gathered that!

When did GM start externally balancing small blocks? I know the 400 was externally balanced but didn't know they did it to 350's. I remember a guy brought me a truck that he had replaced the 400 with a 350 and used the 400 flexplate. It literally shook the rear view mirror off and cracked the windshield.

In 1986 when they went 1 piece rear seal. Even the 4.3L is externally balanced in the rear.

 

[L31MaxExpress]

Drove it around for a couple hours today. Got warm this afternoon here. With the ac on and the added engine and engine compartment heat it was a little more doggy than it was last night in the 40ish degree air. Only ran up about 58-59% injector duty cycle. Every engine I have ever had hates heat, lol. Still though I was playing around and figured out how to launch it best. I can launch it pretty hard now without a smoke show. Bring it up on the converter, walk it out and give it full throttle. 0-60 was about 6 seconds even heat soaked with the ac on. I screen captured it this time and it recorded the engine audio in the background. This little 350 is pretty mean to pull around a G20 van like that with a TH400 and a 3.08 gear. The stock TBI small block air cleaner, paper element and small block intake ducting is causing a substantial vacuum at higher rpm in the intake but keeping the intake air cooler is probably worth it compared to more, hotter air. I love the old induction noise through the engine cover of these old G-vans, it is really noticeable even with the stock air cleaner and ducting.

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[L31MaxExpress]

I also set the cruise at 65 mph rolling down the highway in minimal traffic, took my foot off of the pedal and it held ~65 mph beautifully. Will be nice to have on the long drives for the Power Tour.

 

[Scooterwrench]

The stock TBI small block air cleaner, paper element and small block intake ducting is causing a substantial vacuum at higher rpm in the intake but keeping the intake air cooler is probably worth it compared to more, hotter air. I love the old induction noise through the engine cover of these old G-vans, it is really noticeable even with the stock air cleaner and ducting.

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Cotton gauze filter?