Mental help needed, please.

[Kalums]

Ok, I'm having straight forward decision making "funk" for lack of a better term. I need you all to help. Not so short back story: I've got a 1971 GMC K2500/flatbed, with a 350/ TH350/ NP205, Dana 70 dually rear-end, Dana 44 front 4.10 gears( Un-confirmed, that is what the "tag" on both axles says). I've already done a complete tune up(plugs, wires, cap, rotor, new HEI innerds, including weights and springs) rebuilt the Edelbrock 1406 that came with it and completely rebuilt the fuel system(tank, sending unit, fuel filter, fuel pump, fuel line to the carb) I've also replaced the starter and flex plate (both were missing teeth).I've also replaced mounts/lights/ and other aesthetic parts. .. At this point I'm getting frustrated... It will not time correctly or run smooth. I've tried finding TDC using a piston stop and it is way off(yes I rotated it by hand both directions and then found the middle) it will not stay "timed" I set it 12 dgrs advanced, shut of the truck, come back 10 mins later and it is "out" by 2 dgrs(either direction). There is also noticeable slop when turning the crank by hand to when the rotor actually starts turning. This to me tells me my chain/gears are toast and at some point I've developed a tick/tap in the driver's side of the engine that sound suspiciously like a lifter/valve/rocker or similar on #7.
**At this point I'm at a cross-roads.**
1) Do I continue to patch this possibly original ( I think the heads were replaced at some point) 53 year old engine "because it runs"?
OR
2) Swap in a Factory GM long block "TBI" 350 crate motor that has been sitting in the crate since 2017?

Any and all advice is welcome/appreciated.

[Getter-Done]

I would say swap it out.

You will be time and money ahead.

[Kalums]

Originally Posted by Getter-Done

I would say swap it out.

You will be time and money ahead.

This is actually the direction I'm leaning. I feel like I just need more experienced opinions than my own... Or put another way, "I value others (with more experience in this type of matter) opinions."

[wwboater]

Swap it and get it on the road to enjoy. If it is the original engine you will still have it and you can take your time tearing it down and really seeing what you have.

[Kalums]

Originally Posted by wwboater

Swap it and get it on the road to enjoy. If it is the original engine you will still have it and you can take your time tearing it down and really seeing what you have.

Valid point, thank you. I could tear it down and take my time rebuilding it the way I want for long term replacement... My wife is gonna laugh at me... I swore "no leftovers" ��

[geezer#99]

Tell us more about this tbi crate motor.
What’s the specs on it?

I’d keep plugging along.
You’ve got a running motor to learn stuff from.

[weq92f]

.

Crate motor.

-Kevin

[jabborabbo]

Originally Posted by wwboater

Swap it and get it on the road to enjoy. If it is the original engine you will still have it and you can take your time tearing it down and really seeing what you have.

This ^^^^^^^^^^^^^^

['68OrangeSunshine]

You already have a Crate Motor. Use it.

[Rust_never_sleeps]

It's your hobby. Spend your time, money and mental energy(aka "spoons") where you find them to be rewarding

[jerry moss]

since the truck isn't original and unmolested I say do the crate motor and be driving it in a day or so. save your old one and build it up as time and $$$$ allow.

[jerry moss]

since the truck isn't original and unmolested I say do the crate motor and be driving it in a day or so. save your old one and build it up as time and $$$$ allow.

[Kalums]

Originally Posted by geezer#99

Tell us more about this tbi crate motor.
What’s the specs on it?

I’d keep plugging along.
You’ve got a running motor to learn stuff from.

It is a standard 350 crate motor (long block) from GM "designed for 87-95 TBI Gen 1 vehicles" which I think just means it is a standard 350 with TBI heads.

[geezer#99]

How complete is it?
Does it have a distributor, intake, roller or flat tappet cam, fuel pump push rod, etc.
Bunch of things you gotta know before swapping.

[Kalums]

Originally Posted by geezer#99

How complete is it?
Does it have a distributor, intake, roller or flat tappet cam, fuel pump push rod, etc.
Bunch of things you gotta know before swapping.

After "googling" the part # you know as much as I do. Jegs has a "spec" sheet on the GM part # and so do a few other sites... One says it's a 2 bolt main replacement, another says it is a 4 bolt main. One says 195hp, another says 210hp. You get where I'm going with this. I personally have no clue, I haven't cracked the crate yet it is still in the plastic. It does look to have mounting holes for a mechanical pump... But no "hole" for the armature. It did come with a newer style (90s) distributor, external coil HEI type. That and a new water pump both in AcDelco and "GM" boxes separately. The water pump also has a AcDelco thermostat in side the pump box, but I believe that was put there by a human. I don't think it was a "GM combo pack".

[geezer#99]

What I’m angling towards is it might not be an easy swap.
You’ll need an electric fuel pump with a bypass regulator and fuel return line. Specs show a flat tappet cam. The distributor that came with it will have the right gear on it. Of course you’ll need to do a normal cam break in. And a pre-lube. Also possibly a different flex plate. And the water pump is likely a long one which requires different pullies.
All kinds of things to consider.

[Kalums]

Originally Posted by geezer#99

What I’m angling towards is it might not be an easy swap.
You’ll need an electric fuel pump with a bypass regulator and fuel return line. Specs show a flat tappet cam. The distributor that came with it will have the right gear on it. Of course you’ll need to do a normal cam break in. And a pre-lube. Also possibly a different flex plate. And the water pump is likely a long one which requires different pullies.
All kinds of things to consider.

Not trying g to be confrontational or argue, just trying to learn... Why would I need an electric fuel pump? I was actually just reading on how to "cut/bore" a hole for the armature on a mechanical in that "K" block. Also if I did get an electric pump how would I run a return line? My tank is in the cab and I see no viable way for a return line to be routed as my tank doesn't have ECC.

[geezer#99]

There you go, drill a hole, use a mechanical pump. Problem solved.
I did consider that but there are a couple pitfalls. A jig isn’t cheap. What rod to use that’s compatible with the cam lobe. Does the cam have a fuel pump lobe. Some don’t.

You don’t absolutely need to have a return line. Pump’s can burn out faster if you don’t.
I’m just trying to point out all the little things that can turn your weekend engine swap into your truck sitting idle for 6 months.

[67 twins]

Originally Posted by geezer#99

There you go, drill a hole, use a mechanical pump. Problem solved.
I did consider that but there are a couple pitfalls. A jig isn’t cheap. What rod to use that’s compatible with the cam lobe. Does the cam have a fuel pump lobe. Some don’t.

You don’t absolutely need to have a return line. Pump’s can burn out faster if you don’t.
I’m just trying to point out all the little things that can turn your weekend engine swap into your truck sitting idle for 6 months.

This is good advice, because unless the engine is a direct swap for what you already have in there you are always going to run into something.

[Dashman]

You could change the manifold on the TBI engine and use a carburetor with an electric pump with no return line. It would be basically the same setup you have now, and the only additional electrical item to add is a relay from the switched source for the pump and choke. Otherwise, I believe there would be some sensors to add along with a computer.

Once you go that full TBI swap route, there would be no sense in going back to a carburetor because of all the other stuff you'd be removing.

I think it's a matter of change to TBI now, or just enough to keep it going reliably. Invest a lot of time and effort now, or just enough until a later date of your choosing. I would choose a carbureted engine swap, with minimal time spent on it, and get to using the truck soon.

[Kalums]

Originally Posted by Dashman

You could change the manifold on the TBI engine and use a carburetor with an electric pump with no return line. It would be basically the same setup you have now, and the only additional electrical item to add is a relay from the switched source for the pump and choke. Otherwise, I believe there would be some sensors to add along with a computer.

Once you go that full TBI swap route, there would be no sense in going back to a carburetor because of all the other stuff you'd be removing.

I think it's a matter of change to TBI now, or just enough to keep it going reliably. Invest a lot of time and effort now, or just enough until a later date of your choosing. I would choose a carbureted engine swap, with minimal time spent on it, and get to using the truck soon.

Don't get me wrong absolutely nothing wrong with TBI... I just have no desire to go that direction right now👍

[Kalums]

Originally Posted by geezer#99

There you go, drill a hole, use a mechanical pump. Problem solved.
I did consider that but there are a couple pitfalls. A jig isn’t cheap. What rod to use that’s compatible with the cam lobe. Does the cam have a fuel pump lobe. Some don’t.

You don’t absolutely need to have a return line. Pump’s can burn out faster if you don’t.
I’m just trying to point out all the little things that can turn your weekend engine swap into your truck sitting idle for 6 months.

Besides pulling the timing cover and the cam out is there any way to know if the cam has that lobe?

[geezer#99]

You might get lucky seeing thru a drainback hole or pull the pan and look upwards.

I’m starting to think your best bet is sell the crate and buy a motor more suitable. One with a mechanical pump and a roller cam.

['68OrangeSunshine]

Originally Posted by geezer#99

You might get lucky seeing thru a drainback hole or pull the pan and look upwards.

I’m starting to think your best bet is sell the crate and buy a motor more suitable. One with a mechanical pump and a roller cam.

I'll back Geezer on that. Vintage correct Crate Motors are available.

[Kalums]

Originally Posted by geezer#99

You might get lucky seeing thru a drainback hole or pull the pan and look upwards.

I’m starting to think your best bet is sell the crate and buy a motor more suitable. One with a mechanical pump and a roller cam.

I did a deep dive... And you guys are correct. I'm pretty sure the correct answer is sell the crate motor and get a "period correct" motor. It will be infinitely easier on my self and sanity in the long run. Thank you all for the suggestions and help. Now to wait... Cause I know I won't get msrp for this crate engine but I'm not giving it away either. You guys know. 👍