L31 Distributor Cap

[L31MaxExpress]

So I found a cap that is not Chinese in origin. Hopefully it will hold up compared to the cheap garbage coming in from elsewhere. Merc cap vs the Delco garbage cap. The Merc cap seems to have heavier, thicker plastic than the GM garbage. This appears to be a clone of the old GM Marine cap and rotor that was discontinued and replaced with the aluminum terminal unit years ago. I know the GM aluminum terminal cap is lucky to last a season in a marine environment where the brass terminal unit goes much longer.

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[L31MaxExpress]

I swapped the cap and rotor and discovered that it was not the only source of my #4 misfire. I find it very odd though, that with a substantial misfire history and current misfire counts, the only time this has ever thrown a misfire code is when a plug wire burned on the header previously. I feel dumb admitting this, but I finally performed a running valve adjustment. Most of the poly locks turned right at 2 times before the rockers started tapping. #4 Intake was closer to 3 turns. After I started backing off on that poly nut the engine instantly smoothed out. I must have missed zero lash a bit on that rocker arm when I set them. If anyone read my marine intake swap thread where I had to pull the heads off, I had cranked these down 2 full turns to increase the preload as Holdener had done in his LS pushrod test. I backed the rockers off to 1.25 turns. That adjustment may sound like a lot, but remember this has really long travel LS7 lifters in it. They spec around 0.080" preload and with only 1/2 turn they tend to have morning sickness. The 383 definitely idles more smoothly and seems snappier off-idle with small bump of throttle. I did not snap it very hard though, because I did not want to sling hot oil everywhere.

For some reason the microphone on my phone picks up the valvetrain sound at like 2x the actual volume.

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I am going to unbolt the ac compressor bracket tomorrow and do a running adjustment on the driverside as well.

 

[SNCTMPL]

That is fun to watch, I always get a kick out of seeing the insides in action.

I like that the directed oiling of the rocker arms keeps the oil from splashing everywhere. Glad you found the cause of the misfire.

 

[L31MaxExpress]

That is fun to watch, I always get a kick out of seeing the insides in action.

I like that the directed oiling of the rocker arms keeps the oil from splashing everywhere. Glad you found the cause of the misfire.

I too find watching mechanical stuff functioning fascinating.

 

[SNCTMPL]

I picked up the D.U.I. tbi distributor from Summit the other day for my son’s truck, and the cap on it is very nice. The plastic is thick and it has brass terminals as well. The whole distributor is really nice. It’s made in Memphis, although I don’t know where all the components come from.

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[L31MaxExpress]

I picked up the D.U.I. tbi distributor from Summit the other day for my son’s truck, and the cap on it is very nice. The plastic is thick and it has brass terminals as well. The whole distributor is really nice. It’s made in Memphis, although I don’t know where all the components come from.

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I have had great luck with their distributors, coils and modules myself, just not the Vortec cap and rotor. Also their wires tend to fall apart at the crimps.

 

[SNCTMPL]

I went with their distributor and coil, but these 8.5mm wires from Summit.

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[L31MaxExpress]

Now that is out of the way. About to finish the Kodiak K&N based intake setup and will be adding a functional WRX STI hood scoop to force air into that K&N air box sealed to the hood. These 160-200*F IATS are getting ridiculous. I saw this 96-02 van body built with a Duramax/Allison/SAS/03+frame and front-end with the newer clip buildup a while back and I will be duplicating the hood scoop, except using the taller WRX version. My scoop will actually be sealed to the hood with a cutout over the air box though, where he cut a hole the size of the scoop and just dumps air under the hood, mine will actually be directed to the K&N air box. The airbox and filter setup are massive and I think the tall WRX scoop will be just the thing to cram cooler outside air toward the 383.

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[L31MaxExpress]

Just finished adjusting the driverside bank. The LS7 lifters are the quietest they have been at ~0.083" preload which is what 1-1/4 turn calculates to with a 3/8-24 rocker stud and 1.6 rocker. Engine definitely runs more responsively, smoother and quieter now. It also idles almost stock like smooth now, my guess is it will run a lot better on the road.

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[L31MaxExpress]

Exhaust note is much cleaner now too. I find it interesting that while the engine runs smoother, the exhaust sounds choppier.

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