Jump to content

4.3L w/ blow-by???


zeitgeist57

Recommended Posts

Ever since I bought my truck, the engine barely runs at startup. When it gets warm, it runs much better, but bogs and hesitiates really badly when I push on the gas.

 

Well, I thought (hoped) that it was just bad valve seals, but tonight I connected my air-compressor to the #1 cylinder on the 4.3L through the spark-plug hole, and all I get was hissing in the engine block :(:(:( For that cylinder, I removed both rockers so the valves SHOULD be fully seated, but I couldn't even compress the spring to remove the valve retainers; there just wasn't enough cylinder pressure to hold up the valves.

 

The odometer has 67k on it, but it was a Ohio Highway truck and it looked to have led a HARD life...should I now assume that the engine has 167 or 267k miles on it and it's now time for a rebuild/new motor? I ran compression checks before (probably incorrectly) and got 130-140 after 2 or 3 engine revolutions.

Link to comment
Share on other sites

1st make sure the piston is all the way to the top of the cylinder you can check by putting a smallish srewdriver in the plug hole and rotating the motor untill the screwdriver no longer rises.

 

2nd if you don't have a fairly large compressor it may not be able to pump enough air to hold the valves up if it still won't use the rope trick I can come by and help you one night this week if you want, scince I need to stop by anyway lemme know

Link to comment
Share on other sites

Originally posted by GAS,GRASS,OR,ASS:

1st make sure the piston is all the way to the top of the cylinder you can check by putting a smallish srewdriver in the plug hole and rotating the motor untill the screwdriver no longer rises.

 

2nd if you don't have a fairly large compressor it may not be able to pump enough air to hold the valves up if it still won't use the rope trick I can come by and help you one night this week if you want, scince I need to stop by anyway lemme know

Dave, ya gotz PM'ed! smile.gif
Link to comment
Share on other sites

Originally posted by copperhead:

the engine in his truck now is carbed, so no need for one with a computer. If the engine is hosed, a 350 is easy enough to find, and just as easy to drop in.

Well, other than notching the frame a bit. But I fully agree if the motor needs any money into it, just swap in a 350; definately worth it. If I had the cash, my Blazer would probably have a 350 in it, but since there's no way I'd go carbed on my Blazer, the cost/labor would definately be higher.
Link to comment
Share on other sites

quote:

Originally posted by Nitrousbird:

Well, other than notching the frame a bit.

 

quote:

Originally posted by Copperhead:

Why would the frame need notched?

 

It doesn't. The frame rails were the same between V6 and V8 models. The small block bolts in with no frame modifications. The worst part of the swap is moving the trans crossmember back the correct distance (depending on choice of trans) and having a driveshaft fabbed.

Link to comment
Share on other sites

Guest nevarmore
Originally posted by Jr.:

... and having a driveshaft fabbed.

The 350 swap is so common that you probably won't even have to do that. Just hit up a truck performance dealer and they'll prolly have it all in stock ready to ship.
Link to comment
Share on other sites

Vince, wouldn't he be able to use the original tranny? A 4.3 and a 350 share motor mounts and bellhousings, correct? I don't believe that Clay is trying to get a whole lot of power out of it, he's using it primarily to haul stuff, so I wouldn't be too worried about killing that 3 speed.
Link to comment
Share on other sites

Originally posted by copperhead:

Vince, wouldn't he be able to use the original tranny? A 4.3 and a 350 share motor mounts and bellhousings, correct? I don't believe that Clay is trying to get a whole lot of power out of it, he's using it primarily to haul stuff, so I wouldn't be too worried about killing that 3 speed.

Yes, but the V8 swap shoves the tail of the tranny like an inch and a half one way or another (I think backward), requiring an altered driveshaft.

 

I did this swap in a long bed / ext cab, and the PITA was that the truck used 2 driveshafts with a carrier bearing. We had to have the front shaft custom made and balanced. Not a big deal though, less than $100 at the local joint and clutch shop. I'm sure there's a website detailing this, let me see if I can find one.

Link to comment
Share on other sites

Thanks, everyone!

 

Dave (Gas,grass,and waaaaay too long of a name) is gonna help me a little with the 4.3L after Xmas. Mike is right: I AM looking to keep my 3speed (or swap in another manual transmission if necessary). Vince is also right: the truck has a [rusty] two-piece driveshaft with a [rusty] carrier bearing connecting the two halves just about two feet back from the cab on the frame.

 

I'd like to stay carb'ed...the less complex the better! If this bish can't start in the winter, then phuck it...I'll drive the Passat or Maxima smile.gif If a 350 won't bolt up to my 3-speed, OR I need a new flywheel, then I need to take a long, hard look at cost and difficulty of installation with hand tools. EVERYONE: If you're going yarding, I'm always interested in what you find. Blackstang's dad has a pretty good 350 on an engine stand in his garage that I might take if a 4.3L rebuild will cost anywhere near $400.

Link to comment
Share on other sites

The 3 speed is a decent transmission, assuming you don't powershift. A friend of mine went through at least ten of them in his truck in about a 4 year span, each one breaking on a powershift (he did it a lot). He was able to pick then up extremely cheap though, no one seems to want a manual tranny with only 3 gears. It got to the point where he was able to rebuild them with spare parts from the other ones. He had a somewhat built up 305 in it, he was guessing it was around 300 horse.

 

Your truck being a fullsize, I would assume that you shouldn't have to modify anything to drop in a SBC, but I could always be wrong. I didn't even realize that they put the two-piece driveshaft into those trucks. If you could find a single piece that would fit your long-bed for cheap, I would suggest jumping on it.

 

I priced a rebuild kit for a 4.3 a while back, I think I was looking at a Summit catalog at the time. $250 for the hypeructectic (sp?) kit. A new carb and manifold would really help out that 4.3 you have, if you decide to keep it. It would keep it running better, longer, and would also open it up a good bit, which is never a downside when you a trying to push that big truck with only a V6.

 

I'm going to Marietta sometime today, so I can look around for whatever you want me to. PM me with a list of whatever parts you want me to look for, and your phone number if you would like me to help you out this week, as I'll be down there until sunday.

Link to comment
Share on other sites

Originally posted by Jr.:

quote:

Originally posted by Nitrousbird:

Well, other than notching the frame a bit.

 

quote:

Originally posted by Copperhead:

Why would the frame need notched?

 

It doesn't. The frame rails were the same between V6 and V8 models. The small block bolts in with no frame modifications. The worst part of the swap is moving the trans crossmember back the correct distance (depending on choice of trans) and having a driveshaft fabbed.

I thought he has an S-truck, not a full size.
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...