Motor Refresh Options

[swissarmychainsaw]

Here's the short version:
1973 Suburban 350/350 4x4

Considering motor upgrading. Refresh, crate, or newer engine?





Here's the detailed version:

Stock 350 ( I think )

• - Unknown miles
• - Rochester Quadrajet
• - Headers
• - The box of parts I inherited seems to show that it might have had a cam/lifter swap at some time
• - Runs good and is reliable as anything
• - I have not even tuned it up

Goal:

- Reliable
- Decent Power
- Decent MPG
- Simple ( so I can do all the work myself )
- Pollute less

Problems I would like to address:

- Feels low on power.
- Burns oil ( about a quart per 1,000 miles? or about 4 gas stops, not necessarily empty to full )
- Exhaust Stinks ( like you can’t leave the rear window down due to exhaust fumes )
- 8 mpg ( indicated, but I’m not sure I trust my speedo, it could even be less! )

What I love About this Thing:

- Rock Solid reliability
- Simple
- Stock ( no guessing what part’s going to work )

Solutions I have thought about:

• Crate Style Motor, essentially replacing what I have with a “new” one.
  
  - Pro
  - New is good
  - Con
  - Expensive?
  - Not great power

• Freshening up the Stocker; here I’m talking about buying a kit from Summit and putting on “Ram’s Horn” manifolds.
  - Con:
  - Might take a while
  - Relatively expensive ( $2400 )
  - What about Pistons and Rings?
  - Pro:
  - Keeps it simple
  - Do all the work myself

• Dropping a Newer (Vortec) Motor in it ( 5.3/6.0/7.4 )
  - Con:
  - Electronic Control = complexity ( beyond my skill set? )
  - You drop the motor in and it does not run, then what?
  - This seems like the most complicated option, from selecting the engine to figuring out the electronics
  - Pro:
  - better gas mileage and power
  - Probably the cheapest bang for buck

[enaberif]

Rebuilds are almost the cost of a new crate. You could check a couple of the bearing races for the crank and cylinder walls and it might just need a refresh.

[Dead Parrot]

Assuming this is going to be a normal daily driver, my vote is for a basic crate motor. Might consider a cam swap as well. Don't remember the cam number, there are several threads on topic. Probably has the shortest vehicle down time.

Consider swapping the 3 speed TH350 for a newer 4 speed w/overdrive. You can do both swaps at the same time.

If this one still has point ignition, add an HEI while you are at it.

On the oil issue, how new are the valve cover gaskets? I replaced my 15+ year old gaskets and my add a quart every 1000 miles turned into still full after 1000 miles.

[rich weyand]

Originally Posted by Dead Parrot

Assuming this is going to be a normal daily driver, my vote is for a basic crate motor. Might consider a cam swap as well. Don't remember the cam number, there are several threads on topic. Probably has the shortest vehicle down time.

Consider swapping the 3 speed TH350 for a newer 4 speed w/overdrive. You can do both swaps at the same time.

If this one still has point ignition, add an HEI while you are at it.

On the oil issue, how new are the valve cover gaskets? I replaced my 15+ year old gaskets and my add a quart every 1000 miles turned into still full after 1000 miles.

Note that if you swap the TH350 out for a 700R4 or 4L60(E), you have extra screwing around to do because you are a 4x4 and have to deal with the transfer case connection.

[rich weyand]

Get this:
http://www.jegs.com/i/GM+Performance...FYU6aQodRoQNVA

Put this in it before you even spin it up. Then you don't need to replace the lifters.
http://www.jegs.com/i/COMP+Cams/249/12-235-2/10002/-1

Definitely go to an HEI distributor. Get one with stock mechanical and advance curves or you will be messing with those dam adjustable things forever. Others can recommend one here. I never had to do that.

Put good wires on it.
http://www.jegs.com/i/Taylor/895/74206/10002/-1

Put headers on it.
http://www.jegs.com/i/Hooker+Headers/520/2453/10002/-1

Refresh the Qjet. Get the correct rebuild kit for your model. Folks here can help with that. Get this book, too.
http://www.jegs.com/i/SA+Design/840/SA113/10002/-1

[swissarmychainsaw]

@rich weyand
Any reason not to go for this one?
http://www.jegs.com/i/Chevrolet-Perf...99529/10002/-1
Chevrolet Performance 12499529 - Chevrolet Performance 350ci/290HP Engine & Package
It's 100 HP more for less than $500; and I have a line on one NIB locally for $1500!

Originally Posted by rich weyand

Get this:
http://www.jegs.com/i/GM+Performance...FYU6aQodRoQNVA

Put this in it before you even spin it up. Then you don't need to replace the lifters.
http://www.jegs.com/i/COMP+Cams/249/12-235-2/10002/-1

Definitely go to an HEI distributor. Get one with stock mechanical and advance curves or you will be messing with those dam adjustable things forever. Others can recommend one here. I never had to do that.

Put good wires on it.
http://www.jegs.com/i/Taylor/895/74206/10002/-1

Put headers on it.
http://www.jegs.com/i/Hooker+Headers/520/2453/10002/-1

Refresh the Qjet. Get the correct rebuild kit for your model. Folks here can help with that. Get this book, too.
http://www.jegs.com/i/SA+Design/840/SA113/10002/-1

[andrewmp6]

If he swaps to a 700r4 he can use a np208 from a 81-87 but will have to change both driveshafts and the trans crossmember if i remember right.If it was me i would look at a bare basic crate 350 you don't need nothing fast and it will bolt right in.

[6cylinderstepside]

If you want simple, stay with the 100% same set up and yank the old engine, have it rebuilt, and put it right back in, or do a crate engine. Changing from headers to manifolds won't address anything you are concerned about. Tranny stuff is great info but not really what you are talking about. If it runs good now, a rebuild is a good option because there's nothing busted inside. Almost the same as a crate is still $300 you might want to leave in your pocket. The one change to your existing set up I would agree with is HEI if you are not already there. Otherwise if it ain't broke, rebuild it and keep running that rock solid configuration you already have.

[rich weyand]

It's worse than the 350/260hp base crate engine. The cam is out of a 300hp high-compression 350 from the 1960s, and is ill-suited to a low-compression configuration. Basically, that cam completely kills the low end. It's great for 50-90 shots out on the two-lane, but you have to get out and push to get it off the line. There just isn't enough static compression to take the hit on dynamic compression you get from that cam timing.

Better is to take the base 350/260 for 1500 and re-cam it, or get that 350/290 for 1500 and re-cam it.

For the record, I had a base 350 in my truck, replaced it with the 350/290, and then re-cammed that, so I have driven all three in the same truck. So I know how all three drive, and, yes, I spent $500 more for that engine, and then spent another $1100 having it re-cammed once installed.

[americanmusc1e]

Here is a middle option..

Try to find a 96-up vortec 350 crate motor. decent bump in power and efficiency vs the old-style 76cc heads. You will need a different intake, flywheel/flexplate, and valve covers, but the increase in torque and hp is noticeable. Plus the roller lifters do much better on modern oil and they don't leak oil near as bad as the old-school SBCs.