SBC 350 diagnosis

[RWBeringer4x4]

Hey Mark, I thought I'd pick your brain on this... I can buy a '72 350 out of a C10 that has 72k miles on it for a reasonable price. If I put my RV cam in it with a SP-2P-2 manifold and either the newer 1406 Exelbrock or stock Quadrajet... how will off idle torque be?

I believe I've been running 10:1 compression and the 72 is likely around 8.5:1. I don't want to be disappointed in how it works. Thoughts anyone?

I've got a good Wolverine Blue Racer RV cam from about 1997 before Crane bought them out... I've never been unhappy, and I don't care about hot rod performance... it's a tractor after all. I'd be disappointed if I
Saw a dramatic decrease in fuel economy... but hp doesn't matter.

I'm about to start on my second 70s motor and I'm just as interested as ever.

As for how fast... the last motor easily hit 95 mph and I decided that was too fast for a 40 and I didn't care to find out it's top speed.

I'm not Mark, and I wish I could answer the off-idle torque question, but:

The setup you had was a high compression, bigger displacement version of my own. My 283 SBC/RV Cam/SP2P/Quadrajet was running about 8.5-9:1 compression. It was not, by any means, a power house, but it was sufficient to move the truck around. I had belt alignment issues so I wouldn't push it past about 3300 RPM, which was sufficient to get the truck to ~70mph on 31's, so spooling it up over 4000RPM would have taken me up into the 80's or low 90's most likely. (I never tried, I also determined that anything over about 65 is too fast for a cruiser).

Keep in mind that an SP2P is an intake that was built solely for fuel economy. It's got tiny runners which gives it great throttle response but it is in no means a "performance adder" over even a stock chevy intake. It falls flat on its face at about 4500rpm - can't flow any more air. I like it, and it was a great match for a 283. I will be transferring it to my 350 unless I decide to go with a later-model one-piece main seal style.

I know I mentioned it to you previously - but I think this setup was getting ~13-14mpg highway. Getting 17mpg in a brick-shaped object in a mildly built engine is impressive. Especially when I know your truck's tub is actually so thick it could protect you from small-arms fire.

 

[65swb45]

I've only pulled the heads and cam.


Going this route will have my truck up and running in a week vs 6 months to a year. I'll either keep it or take my time to rebuild my previous motor and then sell it off.

Done is good. I've got the really nice F that came out of the Karma Cruiser and is waiting three years now for me to reinstall the crank. Then I've got a nice F.5 I picked up from @matzell a few years back just waiting for the head to go back on and some new gaskets.

But chances are, if one of my rigs goes down, I will throw in the 2F I picked up from @RustyNailJustin , just because it will get my truck going in two weeks.

Spare time is a scarce commodity.

 

[gator25]

If I was going to take it off road and want some fuel economy I'd use a Quadrajet. I like Holleys, Edelbrooks, and Quadrajets just depends on your going to do with it. For what you want I think the Quadrajet will probably suite you best. Others may not agree.

 

[bikersmurf]

For off road I've loved the Q-Jets I've had. They've all been well worn though.

The almost brand new Edelbrock 1406 I was given idled so much smoother even at 500 rpm. It was tuned for a mildly built 350 at sea level... which I happen to live very near to.

I'll have to evaluate the Q-Jet that's on the new motor and determine if it's leaky and worn out. In its favor, it's coming on a one owner 350 not from some gear heads junk pile.

I've bought the motor and I'll pick it up tomorrow. When I clean the 45 years of filth off of the motor, I'll have a better idea. On the plus side, there's a thick oil film covering most of it so it shouldn't be to oxidized.

I'm not sure why people don't clean their engine compartments. I've lined up a hoist and an engine stand, and it'll get some paint, gaskets, seals, an intake, and a cam before it goes in.

 

[RWBeringer4x4]

Again - it's too bad you're not closer - I've got a bunch of Chevy orange paint I won't be using since the 283 is kaput but I suspect that shipping to Canada would negate any savings...

 

[bikersmurf]

If I'm ever down your way, I'll bring you some of our best local beer to trade you for it. At $10 a can, shipping it wouldn't be worthwhile.

Done with less effort is especially important when pretending I can still use my hands can cost me a weeks worth of functionality for an hour or so of work.

I've been teaching a friend to fix his car, and in return he's helping with the things I can't/shouldn't do.

 

[bikersmurf]

I figured out why the noise sounds like it is coming from the top end of this motor... Any guesses?







Answer:
The number 8 flattop piston is kissing the bottom of the head on every 2nd stroke. There is an ever so faint outline of the combustion chamber on the top of the piston. As the Rod/Bearing was getting worse, the piston was starting to hit the head harder and harder.

 

[waiting for time]

I figured out why the noise sounds like it is coming from the top end of this motor... Any guesses?







Answer:
The number 8 flattop piston is kissing the bottom of the head on every 2nd stroke. There is an ever so faint outline of the combustion chamber on the top of the piston. As the Rod/Bearing was getting worse, the piston was starting to hit the head harder and harder.

Did you take he piston out yet?

 

[bikersmurf]

Nope... there's about 1/8" of play in it. Shifted priority to putting the new motor in. The pan will come off after to see if it's a rod, bearing, or bolt... at this point it doesn't really matter other than its value as a core.

 

[65swb45]

I figured out why the noise sounds like it is coming from the top end of this motor... Any guesses?







Answer:
The number 8 flattop piston is kissing the bottom of the head on every 2nd stroke. There is an ever so faint outline of the combustion chamber on the top of the piston. As the Rod/Bearing was getting worse, the piston was starting to hit the head harder and harder.

IOW, your head reads like a cheap detective novel. Or did you need a magnifying glass, like Sherlock Holmes?

 

[bikersmurf]

No magnifying glass needed.

If you realize what you're looking at. I didn't at first.