75 620 L20b engine issues Please read!

[HntnFsh]

New guy here and hoping for some insight from you guys. Ive done searches on here and did a lot of reading. Also searched all over the internet. I know I'm a newbie and I understand that has a lot of bearing on forums. I have belonged to a couple Hunting and Fishing forums for a long time and Always try to help others whenever I can. I am hoping that you will understand, and not just help me, but read this story, and more importantly help my Dad.

 

Heres my story. Its long, but very important to me.

 

My dad will turn 93 next January. He has a 1975 620 with a dump bed that he bought about 15 years ago. This is a truck that a relative bought brand new. He couldnt remember if it was bought with the dump bed, or if the dump bed was installed right after they bought. Anyhow. He always wanted this truck. The original owner passed away and Dad stumbled across the truck sitting with a bad motor. Several years ago he had the motor rebuilt. It sat for about 5 years but he would go out and turn it over by hand regularly to keep the bearings etc lubricated. About 6 or 7 years ago, while he was snowbirdiing in Arizona I pulled the truck down to my shop and dropped a 5 speed tranny and the rebuilt motor in it. Then parked it at his house for a surprise. Dad has tinkered with it over the years trying to make it look better etc. He drove it a little but I would be surprised if he had 1000 miles on the engine.

 

Awhile back he took a small load of metal to the scrap yard. While there he raised the bed to dump it and left the power switch on. It ran the battery dead. The guys at the yard push started it for him and when it started, it backfired and blew the muffler off. I put a momentary switch on it to eliminate that problem.

 

Now for the real problem. It started running like crap. Loud knock etc shortly after. I checked it out the other day. No compression in 2&4. First thought was jumped time, but that was dead on. Pulled the valve cover and saw all of the rocker arm were off the valve guides on 2&4. On 2 the keepers came off the valve stem and the spring retainer and keepers and valve seal were scattered around in the head. I got a bore scope and could see dents in the piston and a chunk of metal in the #1 cylinder. I am tthinking the huge explosion may have done this damage. Do you think thats possible? I also pulled all the main and rod caps. The crank and bearings look fantastic. 

 

I knew it was bad so I spent a ton of time searching the internet and wrecking yards etc for a running motor. By sheer luck I found what I think will be a good runner. My sisters and I all pitched in and bought it for him for fathers day. I wouldnt be surprised if the person I bought the motor from is a member on here. Great guy with lots of knowledge. I'll probably be hitting him up for more advice but dont want to be a pain either so am trying to get as much of this as I can figured out.

 

Heres where I could really use some help if any of you are so inclined. The motor I want to put in does not have an intake etc. I planned on using the intake and carb off of my dads motor.

When I got his motor out yesterday I pulled the manifolds off and laid it on the floor. The EGR housing is rotted out bad. Most of the bottom is gone. I dont think I will be able to find a replacement. I am wondering if I am best off to pull the EGR off and put on a blocker plate or use JB weld and modify the manifold. Or just find a Weber conversion kit? My other option is to just put the manifold back on the way it is and run it. I'm sure its been rotted out for a long time and ran well. Ive also read a few posts on here from guys that arent real fond of the Weber conversion. so now I am pretty torn on what to do. If I do a blocker plate etc. Then I will need help figuring out vacuum hoses etc. 

 

Heres is my main goal and it may affect the type of advice you may have for me. Dad has been slowing down noticeably the last few months. He had a stroke while in Arizona last summer and has made an incredible recovery with only a little slurred speech and droop on one side of his face. Hes also going in, in a few weeks to get some major skin cancer removed from his face. My goal is to get this truck running as soon as I can so he can putt around in it and tinker on it for as long as he can. I just dont want him to have to look at that truck and see it just sitting there not running. He was ecstatic when we kicked in for the motor and started the process of getting it going again. It was all a surprise to him. I want him to be able to enjoy that truck for as long as he can. It is definitely his pride and joy. As a side note I saw him use a walking stick the other day when we went and picked up the motor. First time ever! I was surprised. He broke his femur about 10 years ago and has a steel rod from his knee to his hip. Ive never heard him complain in my life about being in pain.

 

Any how, I am wondering if any of you were in my shoes what option would be the most logical, quickest , easiest way to get that truck up and running again. I am actually considering just putting the old manifold , carb etc. back on and calling it good. At least it will be running. But I also dont want to take the chance on doing damage to the motor. Would I? Also, whatever direction you point me, I will probably need some advice on the proper way of getting back together to get the engine to run right.

 

I downloaded some pictures I wanted to share with you but dont know how to do it on this forum. I have a picture of the truck, the manifold with the egr valve, and the head with a broken valve flipped 180 degrees and wedged into the where the valve seat would be. But I also have a picture of the valve seat popped out, broken and twisted like a pretzel.

Thank you for taking the time to read my long winded posted. with probably too much info!😄

 

I would really appreciate any advice you may be willing to share with me. Thank you for taking the time to read my plea for help!

HntnFsh

 

 

 

 

[Ooph!]

You will need to use a photo hosting site like Imgur for the first few posts, there is a minimum amount of posts you need to have before the system will let you upload directly to Ratsun.

Edited June 19, 2023 by Ooph!

[HntnFsh]

Thank you. I will see what I can figure out.

[datzenmike]

The EGR manifold is solid aluminum, it won't 'rot out' though the steel fittings might look rough. If you mean the pipe from the exhaust to the EGR manifold... that's very possible. Really need a picture. I would just leave the hose off the EGR disabling it. If the pipe I mentioned is leaking exhaust, just seal it off. Maybe cut and fill the end with JB weld or remove and put a pipe plug in the hole.

 

The problem with a block off plate is you will lose the function of the PCV valve and at all costs that should be kept functional. The PCV valve mounts onto the EGR manifold.

[HntnFsh]

Thank you datzenmike. I found a parts diagram and the correct part I'm thinking of is the EGR passage. I believe it is aluminum and the whole bottom is gone. I'm trying to figure out a way to post pics. I think I actually found a new old stock passage that might work.

 

Let me see if I can get some pics up!

[HntnFsh]

Ok, maybe I can get some pics up now!

 

http://

[HntnFsh]

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[HntnFsh]

I found this EGR passage that I think I can make work. Its missing the spot where what I think is the egr hose goes into it. But maybe I can drill and tap it, or vent it somewhere else.

https://autopartsobsolete.com/cart.php?m=product_detail&p=20537&referralId=

[Ooph!]

I dont see the part in question from the link, I'd place a wanted ad in the classified section.

You are in Ohio do they have smog inspections on cars that old?

 

[HntnFsh]

I ordered the part so I think they took the picture and posting down. It looks the same as the one on the engine, but doesnt look like it has the spot for the big gray hose.

 

I am in Washington. No emissions.

[HntnFsh]

Actually, from what I remember looking at the picture in the ad. I'm pretty sure it had a small nipple. Maybe 1/4" ish in size coming out where the big gray hose is at.

[Stoffregen Motorsports]

Nice little truck. Looks like one of the old soft valve seats fell out, causing the engine failure. That could also happen with the new engine if it has the old soft seats in it.

 

Keep in mind that these engines (and the trucks they are bolted to) are strong and reliable if they are put together and maintained properly. Many new parts makers only make junk and you'll be fighting that along the way. Starters, alternators, water pumps, gaskets, fuel pumps, master and slave cylinders, etc. are examples of some of the worst offenders these days. I've learned over the years that it's always best to rebuild or have rebuilt, your stock original parts instead of replacing them with aftermarket junk.

 

93 and still driving? That's great. Hopefully you get this truck back on it's feet so he can enjoy it for a while longer.

[datzenmike]

 

Plug the end of the pipe from the exhaust manifold to seal it.

Disconnect the small hose to the EGR to prevent it working and away you go. The EGR isn't working properly now anyway if outside air is getting in when the EGR valve opens it's letting oxygen in making the mixture too lean. This may have contributed to the engine eating a valve?

[HntnFsh]

Wow! Thanks for the info. I appreciate it. I was just putting the manifolds on and snapped a stud. Was going to head to town and get a couple. I'll pick up some plugs too!

[HntnFsh]

Just wanted to give you all an update, although it isnt much of one. My back has been a mess, so I havent got much done on the swap. Found a few stripped boly holes that I fixed, swapped over a few parts. I took the little adapter off between the EGR housing and the tube that goes into the manifold and took it to work and welded it shut. Tried a  local shops and couldnt find a plug so welding was quick and easy. I'm hoping to get everything swapped over that I need to and have the motor ready to drop in probably Sunday. Goal is to have the truck sitting in dads driveway early next week.

[datzenmike]

Sounds good. I've never seen an EGR manifold so eroded. (exhaust gasses are quite corrosive and usually that S pipe rots away) The system is supposed to work using only inert exhaust which has almost no free oxygen in it. EGR adds a small amount of exhaust to take up space in the combustion chamber which lowers the temperature. It's not on at idle nor at full throttle so it doesn't affect performance but if there is a hole in the system oxygen can get in. This would leak outside air into the intake and lean out the mixture at part throttle. Yes.. seal everything up air tight.

[HntnFsh]

Made some headway today. I dont know why, but I really struggled getting the motor in and lined up today. Guess being mid 60s makes a lot of things harder than they used to be. I'm not liking crawling around on cement floors and trying to be a contortionist as much as I used to. Thankfully I had the wife helping out with running the hoist while I worked the jack under the tranny and lined stuff up. Downhill slide now. Really looking forward to getting everything hooked up and firing her up.

Grand daughters graduation tomorrow, then if I dont hit the Columbia to try to catch a chinook Sunday, I'll try to finish up. If not early next week should get it done!

 

[HntnFsh]

I was able to get quite a bit done today. I think I can have the truck running and ready for a test drive tomorrow after work. I do have a few question for you though.

 

1. The distributor for the new motor has electronic ignition. The old one has points and condenser. I thought about keeping the new one with electronic ignition. Can I just hook up the red to + and black to - on the coil or am I needing more parts. If I need more and just run the old points and condenser distributor I think I should be able to just pop out the electronic distributor on the motor and pop in the exchange distributor in the exact same spot. In the picture you will see the electronic distributor without the cap on.

 

2. The original heat control valve in the manifold is still there. I have a feeling it may have been froze shut. It may have contributed to the engine issues. I sprayed it with Kroil a few times worked it by hand quite a bit. It seems to be free and working smooth. should I just leave it as is, or am I better off finding a way to keep it in the open position all of the time?

 

3. The hose on top of the egr valve will be disconnected. Are there any other hoses that you can see in the pictures that I should eliminate? I assume anywhere I disconnect a hose on the hard hoses I am going to have to cap them off?

 

4. I noticed the new motor had an intake and exhaust manifold that had smaller openings than the ports on the heads. I am assuming these are off of a L16 or L18. Wouldnt the restricted intake and exhaust airflow cause performance issues? Or is it not an issue with these motors.

 

Here are some more pictures so you can see what I have going on.

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[HntnFsh]

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[HntnFsh]

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[HntnFsh]

Sorry for the duplicate and upside down pictures.

Pretty excited about being so close to getting this done and making the delivery!

 

I think I will bring the old head with the valve stuck in the opening to work and run it through the solvent tank and clean it up good and hang it on the wall of my shop. Looks like a good conversation piece!😄

[datzenmike]

1/ That's a remote igniter EI and needs the electronic box that's usually located inside the cab. I doubt you have it so run your points distributor for now. There is a way to use an HEI module from an old GM distributor if there is no box available and in addition you need an EI coil. The points one won't do. This can all be addressed at a later time.

 

2/ The heat riser valve should have a bi-metallic spring on it that lightly holds it closed. Exhaust heats it and it unwinds and opens the valve. Check it's closed when cold but open when engine is hot. If it is just check it's still working every now and then. Lube and move it to keep it loose.

 

3/

 

The EGR hose is already disconnected. Everything looks fine don't mess with the hoses.

 

4/ Don't worry about the port diameters. It's all good.

 

 

The new engine head ID us cast into the bottom edge between plugs 1 and 2. I'm assuming by the EI remote igniter distributor it's a W58? Can you check?

[HntnFsh]

Went out and looked. The head on the replacement motor is a U67. My guess is that the previous owner put the older manifolds on to eliminate emissions junk. From the video I saw of it running I am sure it also had a weber carb. Heres a picture of the manifolds that were put on the head.

 

Datzenmike,

you are very valuable wealth of information. I know I have said it before, but I am going to say it again. Thank you for taking the time and effort to share that skill and knowledge. Its no small task, and I really do appreciate it!

 

I mainly mentioned the manifolds out of curiosity.  It just seems like it would be a hindrance to set up a motor that way. But maybe its ok on these.

In the picture you can see there was a pretty good restriction on intake and exhaust. I think the manifolds I am running are the right fit and will work just fine.

http://

[Stoffregen Motorsports]

What's the casting number on the intake manifold? A46? Looks like and early (desirable) intake.

 

The round port exhaust manifold is not worth using, unless you have a round port head.

[datzenmike]

'75-'77 L20Bs used a U67 head and intake and exhaust manifolds that were co-joined so the hot exhaust could warm the intake. The heat riser valve would shut this heat off (sort of) when warmed up but usually the spring rotted off or the valve rusted open/shut or in any position making it useless. This was a bad design unless only driving in the winter.

 

'78-'80 L20Bs used the much better L16/18 earlier design where coolant passed from the W58 head into ports under the runners and out near the front of the base of the carburetor and was plumbed into the thermostat by-pass system. This system would actually draw away exhaust radiated heat on torridly hot weather days.

 

My '76 L20B was co-joined. I drilled two 3/8 holes in the U67 head and used a '79 intake with the coolant passages and an L16 exhaust manifold.

 

I lost track of what parts were swapped.