Sunday moring I started my 283, and went to a show about 15 miles away. About 1/2 way there it developed a miss. At the show I pulled a couple of plugs to check fouling, but they were Ok.
On the way home the miss got worse, to the point where it as running terrible.
I did a cylinder check when I got home and found that every other cylinder was not firing. 1,4,6 & 7. That normally indicates a bad carb circuit.
To make a long story short, I pulled the covers, beleiving I had a valve porblem, and sure enough I had a broken intake valve spring on number 6 cylinder. All the four cylinders had oil on them.
I replaced the spring and numbers 6 and 7 fire, but numbers 1 and 4 are not firing.
Prior to the broken spring, the engine ran flawless. There is only 500 miles on a complete rebuild, everthing new in the valve train. The engine has never been over reved, and on that day, it never went above 3000 RPM.
I will take a compression this weekend.
What stumps me is the fact that the cyinder with the broken spring is firing and the other two are not.
Any ideas?
Some of the quick things I have done, new plugs, switched plugs from a good cylinder, tried two new wires, no vacuum leaks, sprayed carb cleaner into each carb barrel, no effect.

 

I have read what you have said and something does not add up here.the entire side of the motor is not fireing.I would think a wind check should be first.Is this a entire rebuild or just the top side ? Also was it a stock rebuild or has it been enhanced ? and 500 miles is nothing did you do a wind test prior to these problems.I am sorry I cant help you but good luck

 

can you help me out?? waht is a wind check?? ihave not heard the term before. :confused:

 

for a cly not to fire you need,no fuel,no spark or no compression or a combo of these. :chevy

 

I'll take a WILD GUESS.
There is not enough info, and no prize :jester

Plugged jet/circuit, 1/2 ran lean, overheated those 4 cyl. spring(s) failed, maybe pistons too.
Did not boil over because other 1/2 was OK and radiator managed to dissapate heat.

:confused: just a WILD GUESS :smash:


[Modified by Matt Gruber, 1:11 PM 7/17/2002]

 

Ih2lose, What is a wind test? It wasn't the entire one side, it was every other cylinder in the firing order.
Matt, thet is the first thing I suspected. That is why I squrited some carb cleaner into each of the front barrels of the card. It made no difference.

I am going to check it out this weekend and will let you know of my findings. It is too darn hot here right now. We have the three H's.
Hot, hazy and humid.:mad

 

Do you have a dual-point distributor? If one set of points closes up or goes south, you could have the same symptoms, as the points are an offset parallel circuit - would also screw up your timing.

 

Well I went out tonight and did a compression check and number 4 cylinder was zero.
I pulled the cover and it also had a broken valve spring.
It is odd that they are next to one another and stradle the exhaust cross over. The heat riser has been eleminated, so I doubt that it is heat related.
The temperature never went above 205. I used an IR gun. The RPM was never over 5000.
I checked for coil bind and at max lift, I had over .060" between the coils.
I am using Sealed Power VS-677 stock springs.
Any ideas? :confused:

 

This is all very strange. I feel for you. getting a new engine is suppossed to be a good experience, one more thing out of the way! Keep us posted what you find.

 

Try a cylinder leak down test (pressurize cyl through spark plug hole with both valves closed) and see where the air goes. Could be bad valve, valve seat popped out (if it has inserts), or piston failure. The leak down test will tell you. :smash:


[Modified by K2, 5:35 PM 7/18/2002]

 

plaidside
if the valves were snug, they may now be stuck open.

today my 72 wouldn't idle smooth; i put on my o2 gauge, rght side off the scale lean. Took bowl off; blew air thru all, did not see any dirt; put it back on, idle screws now 1 tun, was 2.5 turns. smooth again 550 rpm in drive.
if you had a lean main jet circuit & tight valves, R.I.P. :nono: