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Discussion Starter #1
re: Rebuilt (top) of SBC

I rebuilt the top part of a SBC from the head gasket up, but not the camshaft...just lifters..I have set the timing and it turns over but will not start, I have check the spark plug gaps, and everything else I can think of.

History: When I open the top of this motor it had the passages block or partially blocked, yet it was driving, at some point someone had to keep tuning it to compensate for these restriction and one of those must have been the 2 barrel carburetor, this is an assumption.

*Is it necessary to readjust the carburetor for the newly rebuilt motor, now that the passage are free to breath?, I smell rich gas (raw) as it cranks over, I checked the plugs and at least one is getting soak with fuel.

thanks, Nacho65SS
 

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Ignacio the first thing to address is that you can not put new flat tappet lifters onto an old flat tappet cam. If you bought a new set of hydraulic rollers with after market tie bars instead of the factory wish bone retainers and spider spring that is OK; but flat tappets cams will go flat in a heart beat, filling your motor with metal shavings as it does so.

Second question: What did you do to the passages to make them breathe easier?

Most people with this era car swap out the two barrel cast iron intake manifold for an aluminum square bore four barrel intake, and then they add their personal favorite brand of 600 to 650 cfm four barrel carburetor out of the box. They maybe might swap out the tired old points inductive system for a newer capacitive discharge HEI distributor and an aftermarket ignition box (the Delco-Remy ignition box used on the Corvette is actually a poorly disguised MSD AL6 system painted blue), but most settle for just the elimination of points going with a small cap HEI off of a Camaro or pick-up truck that reuses the factory coil.

Add to that possibly a set of block hugger headers, or a set of long tube headers and a true dual exhaust. And at this point the only thing missing is a bottom of the page flat tappet hydraulic cam from Comp or Crane for that thumping idle sound every one who doesn't know why it sounds like that craves.

If your were depressed about the sudden demise of your old rich uncle who left you a sizeable bequest of cash (as opposed to a box full of old GM stock certificates), then you might have tried to console yourself by buying a new set of aluminum aftermarket heads (usually way to big for your needs).

But I am at a loss of what you did to improve or remove your perceived obstruction.

Big Dave
 

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Discussion Starter #3
intake manifold water passages were blocked at the openings, with a hole smaller than a dime, but my question is, would that have made someone tweek the settings on the fuel air mixture on the carburetor, such that now it is out of wack and burning rich fuel, do I need to draw it back...as far as the lifters, I replaced them with exactly what I took out of it (the motor)..
 

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Discussion Starter #4
I'll going to inspect the cam lobes, but they're probably done for, I'm going to change out the cam and lifters and will also check the timing chain...goging
 

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All flat tappet cams cost more than a roller cam. This is because you have to add up the cost of motor oil to put in the car. Motor oil that still has the correct level of sacrificial zinc and phosphate metals in the oil to prevent wear of metal on metal parts (such as your lifter body rubbing against the cam lobe) costs nine dollars a quart. I'm talking about Joe Gibbs racing oil or Brad-Pitt motor oil (formerly known as Kendall GT motor oil). Both of these blends use Pennsylvania crude stock and brew it just like they did when your car was new.

Modern motor oil hasn't had but a trace of the metals in the oil (known as DZZP) ever since midnight December 31, 2001. Starting in January 2002 all metal was removed from the motor oil because all cars that had been made in the past 25 years have had roller tappets that do not need high zinc or phosphate content to survive (they still wear out without the zinc, just not as fast as a flat tappet does without the zinc). This was done to protect the catalytic converter your car doesn't have from metal contamination that would render the catalytic converter useless if zinc or phosphate got into the exhaust as blow by gasses.

Even with Zinc in the oil you have to put a flat tappet lifter back on the exact same lobe you took it off of as they wear into each other. That is to say a flat tappet lifter isn't flat on the bottom but curved slightly by wear. This is all part of the break in procedure and why the motors are all started at the factory and the oil changed before they where delivered to the dealership when they were originally built. This removed all of the metal that came from those to parts wearing away against each other to form that rounded bottom.

It is that curved surface that holds the cam in place. It explains why a roller cam requires a cam button to hold the roller cam in place (people that had flat tappet cams bought and installed a cam button because their heroes race car had one; so it must make your car go faster if it has one, but that isn't why their hero had a cam button in his motor).

The problem with trying to run an old engine built back in the sixties today is that not only has corrosion eaten up the cars but gas isn't gas anymore (they where designed to run on at least 96 octane leaded fuel, not 87 octane alcohol and gas) and the motor oils back then where designed to protect the engine against wear not to protect the air quality.

Finally if your block is so full of scale that the coolant passages are clogged, then it will be a perpetual problem trying to keep it from over heating. That block has to be baked in an oven for 12 hours at 650 degrees to get rid of all of that crud that is inside of it and to prevent any further rusting. You can not use water as coolant. You need water pump lubricant and an anti-corrosion chemical that is added to all antifreeze to prevent that from happening again. You need to run a 50/50 mix of antifreeze to distilled water as a coolant.

Big Dave
 

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Ignacio, if it ran before you tore it down, I would check to make sure you're getting spark, double check that your distributor is positioned correctly, and maybe take close look at your carb to see if dirt or something is messing with the needle seat and/or float level that would cause the flooding.
 

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Well in your last video you have an almost dead battery. The motor should be spinning faster than that. You could have your timing installed 180 degrees out. So that you are firing compression stroke on cylinder number 6 instead of number 1. I've made that mistake before where the motor moved after I pulled the distributor.

Big Dave
 

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Discussion Starter #9
Dave I set the Damper marking to ZERO then pulled the #1 spark plug and carefully stuck a screw driver and the top of the piston was right there...with the Dizzy cap off I point the firing point at cyl 1, it seated all the way flat, then aligned the cap with cable 1 in line....that should have got me to fire even a rough start...I'm scratching my head, I know without actually being in front of it is hard for you to say, I think I will drain the new oil and put the expensive zinc stuff to give myself a chance at saving the camshaft which now does not appear to be flat....thx
 

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Dave I set the Damper marking to ZERO then pulled the #1 spark plug and carefully stuck a screw driver and the top of the piston was right there...with the Dizzy cap off I point the firing point at cyl 1, it seated all the way flat, then aligned the cap with cable 1 in line....that should have got me to fire even a rough start...I'm scratching my head, I know without actually being in front of it is hard for you to say, I think I will drain the new oil and put the expensive zinc stuff to give myself a chance at saving the camshaft which now does not appear to be flat....thx

Piston comes to Top Dead Center twice in a complete four cycle series. It is at TDC ready to fire on the top of the compression stroke and at the top of the exhaust stroke. If your piston is on the exhaust stroke tae the distributor out and turn it around 180 degrees so that the rotor point as number six and after charging your battery up again see if that makes a difference.

Big Dave
 

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Discussion Starter #13
ok thanks Dave I see the error I am making setting the timing, I should put my finger and wait for it to be blown out from the compression stroke....go got it...will use the additive.
 

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Discussion Starter #16
update I tested for spark and I have sparks on all 8, since I can smell gas I know I have some gas, I'm now doing a compression test, so far I found that 1 and 2 had zero compression, when I did the wet test on 1 it shot to 90, 3 and 4 dry were 60 and wet 90...so I will do them all and see where I am in the big picture...any thoughts are well received...thx
 

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Well new they were 120 psi across the board with each hole having 8.5:1 compression on a cranking test (dynamic). Static the pistons were 10.25:1 flat tops, but you don't get that much because the intake valve closes several degrees after BDC.

Zero means you have a holed or otherwise broken piston which I am sure you would have noticed with heads off. So I am going with valves are all lashed too tight keeping the valves off the seat.

Big Dave

Big Dave
 

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Discussion Starter #18
So one side done(left), cyl 3 has zero dry and zero wet...has to be the valve are not seating, how can I check for bent valves?
Dave do you have a good source for procedure on lash adjustment, I am not confident with what I have read or seen thus far, there are differences of opinion...thx
 

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Discussion Starter #19
ok I think I' sure I found the culprit, on cyl's 1 and 2 with the rockers off the Springs are not in tension they are loose and even rotate fairly easily by hand, are exuast and intake spring different heights, I may have mixed them up thinking they were all the same...
 

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Springs are all the same height. Obviously they shouldn't be loose, as you risk dropping a valve into the engine if the valve stem retainer locks let go (and they will without a force applied to hold them in place).

I have never encountered what you are describing on any Chevy engine, no matter how many miles it had racked up. Something is seriously wrong with the valve train if that is the case.

Big Dave
 
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