Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks



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Morten Offline OP
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Next problem (not the last) with the parts I received back is piston deck height/clearance.
As you can see in pictures piston is slightly over block surface, measurement is in mm.

What is minimum deck height/clearance?
Can I get that by machining pistons lower, or is that a nogo?

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Last edited by Morten; 10/09/22 12:55 PM.
Filling Station - Chevrolet & GMC Reproduction Parts


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If it we mine I would leave the pistos as -is, The head gasket will take care of that problem.


Gene Schneider
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I agree with Gene.
The head gasket is thick enough to provide the clearance you need.


Ole S Olson
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Morten Offline OP
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Thanks, that`s good news.
I was aware that gasket would give clearance, but thought I would risk some kind of performance issues, because of change in compression ratio.

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The higher compression would be a plus.

Boring out the cylinder walls also will raise the compression ratio.


Gene Schneider
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Agreed.
Valve and seat grinding (without installing new seats) will set the valves a little lower in the head and reduce the compression ratio slightly.
So, you are probably actually just gaining back what was lost.

You'll be fine. :-)


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Morten Offline OP
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Block is newly bored for +.060 pistons, and if above head with cracks can`t be saved, next head will only get seats grinded, and not replaced.

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That would be the course of action I would choose as well.

In fact, I DID choose to do the same thing.

The shop I took my head to tried to talk me into installing hardened seats. I refused, and I'm glad I did.


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The hard seats are unnecessary and grinding the seats into the head can weaken the area and encourage cracking.
Valve spring shims (under the springs) should be used to make up forrthe increse of the deeper valve seats.


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I agree that installing hardened seats can create more problems than it solves. One thing that I have learned from this forum is that we are not building 50,000+ mile vehicles. I doubt if valve seat recession due to the lack of lead in the gas will ever be an issue for you.

Gene's suggestion to install shims under the valve springs is a good one. You also might want to have the shop grind a small amount of material off the tip if the valve stem. Then is will be at the original height where it contacts the rocker arm.

Now might be a good time to have the rocker arms faced if there are grooves worn in the tip.


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Regular grade of gas did not have lead in the 1930s1940s and 1950s.
Lead wAS ADDED TO PREMIUM GRade at that time to raise the octane
which makes the gas burn slower and prevent pre-ignition knocking.


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I`m now in the process of adjusting the connecting rod bearings.
Engine shop made my used crank and bearings fit, and checked the were not out of round.
I felt a few were a tad to loose, as I could move bearing sideways by hand.
I have then adjusted the bearings with some 0,002 shims instaed of their thicker shims.
I feel they are now adjusted correctly according to manual, but when all 6 is adjusted this close, I can`t turn engine by hand, but if I use a short wrench on harmonic balancer I can turn it pretty easily.

I have only crank, connecting rods, pistons mounted, so no lifters or head (compression).
Cylinders are also rebored, so new pistons.
What is best to an overhault engine, a little loose connecting rods, or an engine that is a bit hard to turn?

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The new pistons and rings on honed cylinders present more resistance than when the engine is broken in. It should be a bit hard to turn. Will get harder when the valve train is installed. Once the pistons smooth out the walls and seat the rings it will get easier to turn.

If you can lightly tap the rods side to side they are good. Pushing by hand is too loose prior to break-in.


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I wonder if you have the main bearings a little tight. I would loosen the main bearing caps slightly and try to turn the engine. Then start tightening one at a time and try to turn the crank each time.

Chipper is correct that the method to check rod clearances is a light tap side to side.


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I agree on the rods, they will loosen with a little running.
With the mains the crank shaft should turn freely with the rods disconnected as the mains take forever to loosen with just running. Thats where you get the turning over difficult when hot problem.


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The main bearings are adjusted correctly, it`s when I adjust the connecting rods it gets a little harder to turn for each bearing I adjust.

You have confirmed what I expected (hoped), but I got a little worried when I thought about the parts not yet installed, that will also make it a little harder to turn.
When I turn it with the wrench, it feels correct and even all way around, so I`ll continue the assamble.

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Sounds exactly right to me!


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I agree. Having rebuilt several early 6 cyl engines they are very difficult to get to turn over by hand or hand crank. The starters will often turn them over fast enough to fire even on 6 volts. Occasionally I have used a 12 volt battery on initial starts. After a few starts they loosen enough to start fairly readily.


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I once had Dad step on the starter while I helped out with the crank. :-)
It Worked!


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I had to resort to pulling one with another vehicle. Put in high gear was enough to get the engine rotating. After less than 1/4 mile it was running at a high idle speed. Think getting enough gas to carburetor was part of the delay in it running.


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lol i just went through this scenario less than a year ago, pretty much same discussion as this on here.
ended up using my riding mower 12v in parallel with my 6v optima to get it to spin enough to start. after a few start cycles it would spin up on its own with just the 6v and the more i run it and drive it the better it gets :)


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Morten Offline OP
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Thanks all, I can see I`m in good position to just carry on.

It takes a while before I can do the first startup, but I have planned to prime entire oilsystem by rotating oilpump with my electric drill until I have a nice flow.
But regarding the binding at first startup, which option is the best?

1. Assemble complete engine, start it up and let it loosen up by running. This will give best oilflow, but hard to turnover until it starts.

2. Assemble complete engine, remove spark plugs (to reduse compression), turnover engine with starter, until starter gets hot, and repeat process. Reduced oilflow so engine might get hot and poorly oiled.

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I would spin it over with the stsrter with the plugs removed for about 30 seconds and then install the plugs and get it running AT A FAST IDLE.... DO NOT idle at a low speed. You want a higher speed yo get the oil sllnging around.
f it turns over too slow you can jump it with a 12 volt battery or booster for a short time.


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Do not use the starter method (method #2)

First, it won't significantly loosen up your new engine.

Second, if you do it enough to actually loosen up your engine, you will have worn out your starter.

Third, you won't be throwing ANY oil up on the cylinder walls or the camshaft lobes and lifters.

Also, sliding surfaces require some speed to actually float on a film of lubricating oil.
(Think about even water being thick enough to lubricate your slipping foot in the shower... once it gets moving.)

PS
Obviously I agree fully with Gene.
I was still typing when he beat me to it. :-)

PPS
Also, the first fill of oil should be a light oil.
Something like a 0w-20 would be nearly ideal.
And watch your temperature gauge!

Last edited by Stovblt; 02/13/23 04:32 PM.

Ole S Olson
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The heat riser on manifold was frozen by rust, I`ve now got it loose, but want to lock it in closed position, as I will only use my car in the summer, and I previosly had problems with boiling petrol in carburator.
I don`t have the outside arm, so can`t check position on the arm.

Is position in picture the closed position, where I can lock it, to get the least heat to carburator?

Picture is borrowed from here: Heat riser overhaul kit

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Last edited by Morten; 03/24/23 04:46 PM.
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