Ok, where can I get the lowdown on the quirks of the different cam types as far as engine building goes?

By "type" I mean solid, hydraulic, roller, etc

 

http://www.competitioncams.com/catalog/

Study it from cover to cover

 

thanks. one more question. could you explain how to ID a cam type by looking at the pushrods? I'm wondering in case it gives me clues as to why the engine I picked up is fubared, so that I don't make the same mistakes that fubared it when I rebuild (I didn't build the engine, it was apparently like that when I got it. the guy lied through his teeth as to its "running well")

 

Can't really do that... push rods don't change according to cam type.... the only thing that changes is their length. Stock SBC push rods for flat tappet cams (hyd or solid) are 7.800", compared to 7.300" for factory roller cams.

What's actually wrong with this engine?

 

Well......dropped in an HEI distributor (didn't have one when I got it)....anyway, turned the engine to TDC on the #1 cyl., checked the rotor and put the cap and wires on.....turned it over and it backfired a few times, flames out the carb and all that fun stuff :P

turned the cap slightly to retard a bit, and it did it again. then I checked the position of the rotor compared to the timing mark on the balancer......TOTALLY different positioning......so either the timing chain is shot, or the gear on the cam that drives the distributor is.......plus I'm not sure what the valve lash is supposed to be set to (rockers weren't tightened down, the guy had been getting ready to put Vortec heads on it and changed his mind, went with a brand new crate Vortec engine instead)

 

Or you put the distibutor in phased wrong.

 

Sounds like the distributor is off by a tooth or two...

 

"phased wrong"?

and no, I checked the position of the timing mark on the harmonic balancer and compared it to the rotor position both times I checked it. When I did, it looked like the position of the two were completely unrelated to each other

 

Before you go any further, go back to Engines 101. Think about the basics of how an engine works.

There are 2 instances of #1 TDC for each complete revolution of the rotor. The engine will do exactly as you described if you have it set on the wrong one.

Remember how a 4-stroke engine works: if you look at one complete cylinder cycle, it take 2 complete crank revolutions, but only one cam (and distributor) revolution. Starting at #1 firing, the #1 piston is at TDC of course; but so is another one — the one 4 cylinders away from it in the firing order, #6. So, #1 fires; the crank turns; ½ crank revolution later, the piston is at BDC, at the end of the "power" stroke for #1. The #1 exhaust valve begins to open. The crank continues to turn. As the crank turns, the piston moves back up, and presently reaches #1 TDC again.... and reaches #6 TDC as well. As it nears TDC on this "exhaust" stroke for #1, the #1 exhaust valve begins to close; just as it reaches #1 TDC the #1 intake valve begins to open. And #6, which is also at TDC at this time, fires. At this point, the crank has made one complete revolution, the timing mark is back up, and the rotor is now pointing somewhere completely else from the #1 contact in the cap.... it's pointing at #6. The crank continues to rotate; the #1 piston descends in the bore with the intake valve open, filling the #1 cyl with new air/fuel mixture. Meanwhile #6 is in the "power" stroke, with its piston also descending in its bore. The #1 piston reaches the bottom, the intake valve closes, the piston once again moves up in the "compression" stroke, and when it nears TDC this second time, it fires.

The 2 instances of TDC are identical as far as the crank, pistons, timing mark, etc. are concerned. That means, you can't tell which one of those 2 instances of TDC is #1 firing just by looking at the timing mark. In order to correctly time the distributor to match the valve action you have to know where the cam is. Since the cam is the thing that determines when compression occurs instead of exhaust as the piston is moving up, by way of operating the valves, you have to find compression on the #1 cyl.

Remove the #1 spark plug. Have somebody bump the engine over in very small increments while you put your finger over the plug hole. Presently you will feel compression. Have them continue to bump it over slowly from the point at which you feel compression until the timing mark approaches line-up; that's #1 firing.

Try that. Flames shooting out of the carb = distributor 180° "out of phase", which sends the spark to #1 while the #1 intake valve is open. What would you expect to occur if you ignite a cyl while its intake valve is open? Does that match your description of what's happening, or what?

 

d'oh! had to think about it for a bit, but I think you might be right. I'll have to give it a try.......

 

ok. no more backfires out the carb.....but still won't fire up.....

 

woot! :hail: :hail: :hail:

hasn't fired up yet, but got it popping.......

either bad gas or LG4 exhaust on an engine far too powerful to survive the restriction is all that's left to play with besides setting timing.....gonna pull the manifolds and mount my Hedman shorties this weekend. hopefully that'll do it