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78 620, L20B foreign matter in combustion chamber.


Atikin9000

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I always stick a screwdriver in the spark plug hole if the timing marker is dirty or so messed up I cannot read it, once I find TDC I look at the notch on the crank pulley and note position on the timing plate, I have one where it is the second pointer, that one sticks out slightly farther than the others on the timing plate, but all the others I have it is the first pointer.

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That's a pretty fatalistic approach to one of the most important aspects of engine tuning. I want my timing pointers to be exact.

 

There is more involved to this than just setting it to the recommended degree of advance, I am burning crap regular in my work truck, I have it set at 2 degrees before TDC and it barely knocks/pings sometimes, not enough to worry about, but the 520 I have at 8/10 degrees before TDC and it runs fine also, but I burn premium non-ethanol fuel in that one, it's hard to call what is exact when there are so many variables.

But when you are talking about setting the cam timing, there is only one way to get it right, it has to be at TDC, otherwise one is just guessing, and guessing will get you in all sorts of trouble sooner or later, likely sooner.

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I was doing the same mod to my '74 umpteen years back, pulled the EGR lump off there and was gonna make up a nice new PVC mount, block off plate etc..........noticed then that the truck throttle cable mounts to that EGR plate so no go. I ended up welding those two passages shut in the manifold and lopping off the entire EGR portion of that intake (hangs off the front of the intake...ugly)

You could also use a 521 cable mount which bolts on two of the carb mounts.

--Ray

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That's a pretty fatalistic approach to one of the most important aspects of engine tuning. I want my timing pointers to be exact.

 

In almost every case this will be close enough right from the factory. Even it perfect, you may end up finding that at your altitude it needs tweaking a couple more degrees advance anyway to get the most out of your gas. I'm literally at sea level so probably less than what's indicated. I have no idea what my timing is but it is where it runs the best. . 

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I have never used anything other than a tap to chase my threads, but I am very careful about stuff like that, I don't just stick the tap in a drill and go for it, I do it by hand a quarter turn at a time, but I have only done it on a couple blocks, I only chase them if I cannot thread the bolts in with my fingers.

I have never chased a nut or bolt before, I just wire wheel the bolts, and nuts get thrown away if they get buggered up.

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I use taps. But it's not really what you should do.

 

 

You'll either do a really good job. Or a really bad one. Like really, really bad.

 

 

10x1.5

8x1.25

6x1.0

 

 

Get a set of tap sockets. You will find your tap tool likes to be in the way of progress.

 

Fill the grooves of the tap with grease to catch all your debris. Clean, and repeat many times.

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You guys think it will be ok to chase the block and head studs with these? I thought it was alright until some one mentioned that it’s to sharp and to use a “thread chaser” bit.

 

WOWNNAQ.jpg

Yes don't tap.... taps are ment to cut threads.... get a long enough bolt doesn't matter what grade.... cut a long notch along the threads.... you can use some grease to catch the shit in the hole but that notch will act like a thread chaser and not damage the treads.....

Look up home made thread chaser....

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3dnAhuU.jpg

I've put together blocks and heads without doing anything before. It's unlikely you will have a problem as long as the bolt threads down in and pushes any crap ahead of it. It would need to be full of gasket material to bottom out first but it is prudent to blow them out with compressed air at least. I have lots of old head bolts so I just grind one lengthwise, grease it to catch any debris and carefully turn them in. Like wayno, turn in back off turn in back off and work your way to the bottom.

 

A tap would work also for a one time use but you really need a bottoming tap to get the threads all the way down to the depth the bolt will go. Yours is tapered, might reach.

 

138475.jpg

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There's no issue with using a tap in cast steel.  I'd use a thread chaser in the head however.  The pedestal bolts are a bit more "dainty" and often need to be heli-coiled if you get too aggressive with them.  

 

Mike - the problem with your home made thread chase is that any debris you clean out has nowhere to go but to get pushed back into the threads again.  The cavity you ground away looks like it'll be riding on the threads, or very very close to them.  The flutes on a thread chaser are much deeper, and typically there are 4 like the tap photo above.  This set is cheap enough:

http://www.amazon.com/Lang-Tools-2584-15-Piece-Restorer/dp/B000XJ48V0/ref=pd_cp_469_1?_encoding=UTF8&psc=1&refRID=V6TTQ51KV4A0QQHK44TV

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This one was for the thermostat housing and much smaller. It removed quite a bit of duff but not on just one try. I kept going till the grease came back clean. For the head bolt I slit it lengthwise on two sides with a cutting wheel. The only thing it collected  was a black powder, probably the graphite on the gasket? 

 

Then I put it away for next time somewhere where I will find it.... and then can't find it and make another. I probably have 3 now.... somewhere.

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I've used the same set of thread chasers for years - back when Sears sold the same set that Snap-On puts their name on now.  What's great is that you can use them with drill and drive them in quickly and remove them quickly.  Much stronger than most bolts you would use.  I suspect the ones I posted above are made by the same company as the kit I use.  

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I should of noticed this earlier but while I was cleaning the head studs I discovered this guy, I’m leaning towards not reusing this, any suggestion on replacing?

APR studs are about $130, just seeing if there’s any other options.

 

jvPbgDX.jpg

 

 

Other question is, which way do these washer for the head studs go?

 

t2iIL5r.jpg

 

One end is a bit rounded.

 

ivlxSna.jpg

 

One is flat.

 

When I took these off they were all miss matched, some had the flat part facing the head some had the rounded part facing downward. What is the correct position.

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I guess I just always put the rounded side up, it looks weird the other way.

Check to see if any of your wrecking yards have a Datsun with an L block in it and go get a few headbolts.

I like the stud kits myself, but I am building a high compression engine and have a couple LZ23 engines that take modified head gaskets, I like the stud kits for them.

Search around for the headbolt and if you cannot find what you need PM me, Farmer also lives down there in that area, maybe he has what you need in the nuts and bolts bucket.

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