78 620, L20B foreign matter in combustion chamber.

[wayno]

It seems like it would have been easier to tap the hole for the PCV rather than make a plate.

[Atikin9000]

It seems like it would have been easier to tap the hole for the PCV rather than make a plate.

Might still do that but just tapping into something that’s not an $8 flat bar of aluminum just worries me, I just don’t want to find another intake if something goes wrong, waste of time or not I have a plate now.

[Stoffregen Motorsports]

Might still do that but just tapping into something that’s not an $8 flat bar of aluminum just worries me, I just don’t want to find another intake if something goes wrong, waste of time or not I have a plate now.

I get it.

 

Plate looks good, and I'm glad you were able to get those studs out.

[datzenmike]

Started with '79 620 intake. There are several but generally the same. It has the PCV valve and vacuum fitting sharing the same hole on top. The two EGR openings become one below it on the inside of the intake.
 

 

 Top is vacuum supply hole. Bottom would be the EGR but now is the PCV.

 

 

Cleaned out the carbon from the plugged EGR holes, tapped the rear one to take the PCV valve. Filled the other with JB weld. And tapped the top one for the vacuum supply fitting. Angle grinder to smooth and round off the corners...

 

When done it looks somewhat like the L16/18 intake but larger diameter runners for the larger L20B. I also port matched it to the head.

 
 
 
.

[Stoffregen Motorsports]

I've never done a long term fix with JB weld, at least not like that. I wonder if cracks or separation will occur over time.

[datzenmike]

On an intake? It's doubtful. It's good to over 500F. It's air cooled... :lol: you can hold the intake with your hand. Might heat soak but what? 200F.... maybe. It isn't threaded or holding a fastener although I think it can with good results.

[Atikin9000]

 

What about this bolt, circled.

 

Really tempted to just screw the pcv into that.

 

 

iirc those go all the way through.

 

 

Also just out of curiosity what’s the second flange for? (in the middle)

[datzenmike]

That bolt was just used as a plug. The L20B I got it off was being used on a 4 speed in reverse to power a VW trans axle in a tracked off road crawler. Didn't have a vacuum booster so... plugged.
 
I guess you could but it was designed to feed all cylinders equally. Those rear cylinders would be running ever so slightly leaner because of the air sucked in.
 
 

Also just out of curiosity what’s the second flange for? (in the middle)

The fitting with the hose connections? A vacuum source for the charcoal canister and vacuum source for the ATC (air temperature control) on the snorkel on the air filter. The ATC mixes exhaust manifold heated air with cold air to warm and maintain at about 100F. Engine runs more efficiently when the air used is always the same temp and it prevents carb icing in the winter cold.

[hang_510]

I've never done a long term fix with JB weld, at least not like that.

I know someone that used JB weld in a stripped sparkplug hole, and he tapped it with the plug.

L16 and he said it worked until the HG blew. Probably never removed the plug until then.

[Atikin9000]

Noticed today that the head came back with out the two most out exhaust studs, I’ll call and see if he still has them, on the off chance that he doesn’t what are my options.

 

 

I put the studs I took out from the intake in the said holes for reference. I’d say use those but they are a bit short on the end that goes into the head, that and they get super tight a half turn in and I don’t want to strip the threads.

[flatcat19]

I think they're bolts that go there...?

 

 

The studs are used for the fat washers that hold down both the intake and exhaust.

Outer most mounting holes only hold the exhaust manifold.

[Atikin9000]

I think they're bolts that go there...?

 

 

The studs are used for the fat washers that hold down both the intake and exhaust.

Outer most mounting holes only hold the exhaust manifold.

 

 

They’re studs, threads are clean but nothing seems to want to really screw in there.

 

[Atikin9000]

Looks like the studs that I took out of the intake will work for the exhaust, flipped them around as the photo shows the head befor took it in to the machine shop.

[datzenmike]

The four along the bottom are bolts. One stud at each end on the top holds the exhaust in place. The bottom bolts have a cone shaped thick washer that clamps both exhaust and intake down.

 

I would guess you could exchange them for studs.

 

BTW the cone washer goes on like this...

 

bolt head (( threads

[Atikin9000]

The four along the bottom are bolts. One stud at each end on the top holds the exhaust in place. The bottom bolts have a cone shaped thick washer that clamps both exhaust and intake down.

The ones that holds the exhaust in place were missing and the intake studs ended up working

[datzenmike]

Yes the outside end ones. I suppose you could use studs for the others if they aren't too long. They are a bitch to get at and tighten.

[Atikin9000]

Yes the outside end ones. I suppose you could use studs for the others if they aren't too long. They are a bitch to get at and tighten.

Look good enough?

 

 

[wayno]

You will not know till you put it together, to me the stud looks too long, but when I go out to the shed and look at a head I have that one looks long also, but I pulled that head and it wasn't too long.

I look at studs this way, if I strip the threads out of a head tightening it with a bolt, instead of getting a longer bolt I use a stud and bottom it out in the head(it is there forever), then I use a washer/nut from then on, but if all the holes had studs, you likely would never have an issue with that gasket as you can tighten the nuts holding the intake/exhaust more using studs.

[Atikin9000]

You will not know till you put it together, to me the stud looks too long, but when I go out to the shed and look at a head I have that one looks long also, but I pulled that head and it wasn't too long.

I look at studs this way, if I strip the threads out of a head tightening it with a bolt, instead of getting a longer bolt I use a stud and bottom it out in the head(it is there forever), then I use a washer/nut from then on, but if all the holes had studs, you likely would never have an issue with that gasket as you can tighten the nuts holding the intake/exhaust more using studs.

 

Studs from the intake were too long, mocked up the exhaust manifold and there was a good 2”.

 

I got one of these to replace a lower bolt that was missing.

 

[wayno]

Like I said, it is way easier to strip aluminum threads out of the aluminum head using a bolt, you cannot tighten them as hard as you can, while you can tighten a nut on a stud way tighter, that is why they likely came from the factory with studs on the ends at the very least.

I have seen heads with studs in every intake/exhaust hole.

[datzenmike]

Maybe flip those studs over so you won't run out of threads tightening the nut down or shorter ones..

[Crashtd420]

Like I said, it is way easier to strip aluminum threads out of the aluminum head using a bolt, you cannot tighten them as hard as you can, while you can tighten a nut on a stud way tighter, that is why they likely came from the factory with studs on the ends at the very least.

I have seen heads with studs in every intake/exhaust hole.

I did just that on my head.... I liked it because like you said you can bottom out the stud.... if bolt is too long it can bottom out and things won't be tight.... to short and you could pull the threads right out of the head....

You should be able measure the manifold thickness, the amount of threads the head has, washer and nut, to determine a good stud length...

[Stoffregen Motorsports]

I did just that on my head.... I liked it because like you said you can bottom out the stud.... if bolt is too long it can bottom out and things won't be tight.... to short and you could pull the threads right out of the head....

You should be able measure the manifold thickness, the amount of threads the head has, washer and nut, to determine a good stud length...

Studs are the best for this application for that very reason. Those threads in the head casting are super easy to strip.

 

Length falls into that category that our forefathers described as "self evident".

[Atikin9000]

 

What’s considered clean for mating?

 

This is where I’m at right now.

[wayno]

You should be able to see your reflection. :lol: :lol: :lol:

 

Not really, if you can run your had over it and have it feel smooth then your likely alright, but you have to be honest with yourself,

if you think you felt anything then your not done yet.