Spark Plugs What is wrong?

[53chevyforever]

Okay...just bought the truck...running this way...compression test already done
and is good...I have had all ac plugs and made no difference...both carbs run
perfect on my other truck...1406 stock eddy and stock600 holley.
The cam already in engine...214 at .050 and 456 lift. One is a new msd street fire and the other hei is good I know runs perfect..been carrying as a spare...fires right up and idles well..its mid range and low on power almost like a wire is off...but not quite. Really does not smoke. Throttle response is good...fuel pump has 5 pounds of pressure. So you tell me?

[demian5]

Originally Posted by 53chevyforever

Okay...just bought the truck...running this way...compression test already done
and is good...I have had all ac plugs and made no difference...both carbs run
perfect on my other truck...1406 stock eddy and stock600 holley.
The cam already in engine...214 at .050 and 456 lift. One is a new msd street fire and the other hei is good I know runs perfect..been carrying as a spare...fires right up and idles well..its mid range and low on power almost like a wire is off...but not quite. Really does not smoke. Throttle response is good...fuel pump has 5 pounds of pressure. So you tell me?

Sounds mechanical:
That vacuum is quite low like a tired motor. Did vacuum gauge needle bounce or move while truck was running?
Do a leak down test to rule out rings seats, etc on those cycls. The autolite tells me that cylinder has had issues for a while and its not carb related.

Anything else is purely speculation and the lack of wanting to do any diagnosing.

https://mobiloil.com/en/article/car-...-leakdown-test

[B. W.]

Originally Posted by 53chevyforever

Okay...just bought the truck...running this way...compression test already done
and is good...I have had all ac plugs and made no difference...both carbs run
perfect on my other truck...1406 stock eddy and stock600 holley.
The cam already in engine...214 at .050 and 456 lift. One is a new msd street fire and the other hei is good I know runs perfect..been carrying as a spare...fires right up and idles well..its mid range and low on power almost like a wire is off...but not quite. Really does not smoke. Throttle response is good...fuel pump has 5 pounds of pressure. So you tell me?

OK, so you know what is good, you can eliminate those. It narrows it down to a timing issue or a mechanical issue. Do what Geezer said: bump up your initial timing (I'd dial in as much as you can, if it begins to "hard start", back it off a little. Also confirm your timing mark.

If it has run like this since you bought it then you are chasing someone else's rabbit. There is a possibility that the cam was installed out of time. What heads are on it? If the heads have dual springs I have seen one spring break & the engine runs fine but doesn't run well up top. (the remaining spring keeps the valve operating & quiet, but "floats" at higher RPMs)

I'm hoping it's a simple timing issue, sure you are too!

[53chevyforever]

Well today I noticed the water down just a little in the radiator...so added some...let it warm and open the thermostat...guess what big bubbles
in the flowing water....never stopped doing the bubbles....it has turn down
tailpipes so I couldn't see the exhaust.

[greasemonkey]

Originally Posted by 53chevyforever

Well today I noticed the water down just a little in the radiator...so added some...let it warm and open the thermostat...guess what big bubbles
in the flowing water....never stopped doing the bubbles....it has turn down
tailpipes so I couldn't see the exhaust.

Sounds like you know what this means...sorry man. Maybe it'll be the gasket between 4 and 6 like Aussie speculated. Not a terrible job to do.

[snipescastle2]

You can confirm the presence of combustion gases by having a shop place their emissions analyzer sniffer above the filler neck, if "HC" readings go up, bingo!
Not all head gaskets leak coolant into the oil, some leak into the intake passages. I'm surprised this engine isn't running hot....if you cannot maintain system pressure in the radiator, the boiling point of the coolant goes way up, placing a vacuum on water does just the opposite, lowers the boiling point.
That's why you keep a pressure cap on the radiator. 15-16 psi is normal, should raise the boiling point to 230-240 degrees.something like that.
You haven't noticed any unusual smoke/steam coming out from behind when you accelerate have you?
Hope it's an easy fix, I'd be looking for cracks in between the combustion chambers or maybe it's just a gasket issue.
Hth,
Ben