1974 Mark IV project

[klevins@gmail.com]

Bought this right after TG last year…1974, 43k miles, totally original. Had not driven much since 2005. Starting to work on the upgrades.

[1Bad55Chevy]

Holley EFI conversion with a rear mounted bypass regulator?

Any reason you mounted the fuel pump on the top half of the tank? Holley recommends mounting the fuel pump below the fuel tank so the fuel siphons out and flows freely to the pump when running. When it's mounted over the tank like that the pump is constantly straining to suck fuel up into it.

[klevins@gmail.com]

Holley EFI conversion with a rear mounted bypass regulator?

Any reason you mounted the fuel pump on the top half of the tank? Holley recommends mounting the fuel pump below the fuel tank so the fuel siphons out and flows freely to the pump when running. When it's mounted over the tank like that the pump is constantly straining to suck fuel up into it.

I had hoped to use an in-tank sender mounted pump but there's no off the shelf option, and the generic through the top Holley pump won't fit with limited clearance above the tank. I didn't want the plumbing to hang below the vehicle so I went with a pump mount height that's about half tank height. The actual vertical lift is ~2-3 inches with lowest fuel level, so I'm not too concerned about stressing the pump. At 1/2 tank or above the fuel will self syphon to the pump.

[1Bad55Chevy]

I am going to do the same conversion on my mark iii. The mark iii has a totally different tank that mounts vertical behind the rear axle so at a half tank it would be pulling like 10 inches or so. I found this article on Holley and I am going to do it like this.

https://www.holley.com/blog/post/how_to ... mp_module/

Idk if you have any drive time yet on it but you will love it. I did one on a square body chevy a few years back and the guy loved it. During the crazy Texas freeze of of 2021 my neighbor who owns the truck started it in his non heated/non insulated detatched garage when the wind chill was -22* and it cranked and idled! It was the most impressive thing I have seen out of any aftermarket fuel delivery system! Are you running your ignition system through the unit? That is something I have yet to try on one of these units.

[klevins@gmail.com]

I am going to do the same conversion on my mark iii. The mark iii has a totally different tank that mounts vertical behind the rear axle so at a half tank it would be pulling like 10 inches or so. I found this article on Holley and I am going to do it like this.

https://www.holley.com/blog/post/how_to ... mp_module/

Idk if you have any drive time yet on it but you will love it. I did one on a square body chevy a few years back and the guy loved it. During the crazy Texas freeze of of 2021 my neighbor who owns the truck started it in his non heated/non insulated detatched garage when the wind chill was -22* and it cranked and idled! It was the most impressive thing I have seen out of any aftermarket fuel delivery system! Are you running your ignition system through the unit? That is something I have yet to try on one of these units.

I actually had this link bookmarked. It’s a good approach, especially with the hydromat pickup. The challenge is if you look at their BOM they hacked 2 or 3 different EFI pump assemblies to put the whole thing together so it’s an expensive approach.

I have not fired up the motor on EFI yet. Just plumbed this yesterday. Will flush the original steel line today, add a second fine filter near the motor, then run it up for initial learning session. Then everything is coming out of the engine for a 2166 manifold, 3500 cam, new springs, lifters, straight up timing chain, valve seals and springs.

[1Bad55Chevy]

What cam are you looking at?

At first I thought you meant 3500+ RPM power range but that would be a little extreme lol. Sounds like a cool build.. post more pics we would all love to see it!

[klevins@gmail.com]

Let me rewind to the start…

Yup, that’s me. You’re probably wondering how I ended up in this situation. I blame BringATrailer.

[1Bad55Chevy]

What in the El Chapo is going on in that shop? Seems like a pretty big 1 car garage! Lol

[klevins@gmail.com]

Progress is slow.

[klevins@gmail.com]

Too tired to type almost hehe. Timing chain was original, quite worn but the polyamide gear was still intact thankfully. Replaced with a straight up timing double roller set. Left out the slinger per forum consensus but will remember to run a bead of silicone inside the spacer before I put the balancer back on. Getting the new timing cover pulled down to center the front seal was quite the job but got it done.

[klevins@gmail.com]

Trying to figure out whether to make something to block the exhaust port in the 2166 manifold or add some kind of valley pan…

[frasern]

The later type 460 intake gasket incorporates a valley pan, if your manifold has no heat shield, use this pan.
Personally, I like the fiber gaskets better than the steel ones, so I would consider cutting the sealing surface off, and using the early type gasket with the later pan. This was done in the '80s by speed boat builders, however, there may be a newer type of hybrid gasket which combines both, as there is for a cleveland.

[klevins@gmail.com]

The later type 460 intake gasket incorporates a valley pan, if your manifold has no heat shield, use this pan.
Personally, I like the fiber gaskets better than the steel ones, so I would consider cutting the sealing surface off, and using the early type gasket with the later pan. This was done in the '80s by speed boat builders, however, there may be a newer type of hybrid gasket which combines both, as there is for a cleveland.

Gotcha, what do you think of omitting the pan if I use a gasket which incorporates the crossover block? Basically I want to avoid oil coking on the bottom of the manifold vs other considerations.

[frasern]

The factory manifold used either a heat shield, or that gasket/pan for that very reason, but they were steel manifolds. Aluminum manifolds do tend to cook the oil a bit more. And I have never seen an aluminum 460 manifold with a built in heat shield, like the early factory ones did. I hate to compare different engines, but on my truck 400, I have had trouble getting the intake manifold to seal, so I am going to do the fiber gaskets and modified pan described above. (SP2P manifold)
As for blocking the passage, I can't really say, I've never blocked one.

[klevins@gmail.com]

The factory manifold used either a heat shield, or that gasket/pan for that very reason, but they were steel manifolds. Aluminum manifolds do tend to cook the oil a bit more. And I have never seen an aluminum 460 manifold with a built in heat shield, like the early factory ones did. I hate to compare different engines, but on my truck 400, I have had trouble getting the intake manifold to seal, so I am going to do the fiber gaskets and modified pan described above. (SP2P manifold)
As for blocking the passage, I can't really say, I've never blocked one.

Thanks for the input. After a little research I found that the Fel-pro MS96044 is a hybrid with integral steel pan and crossover block. Covers all the angles!