blown ring and solutions?

[blazinfast]

im a "young'n" so dont verbally beat me just yet.

i have a 85 k5 that i think the rings have gone out on and since i will have to take the motor out to fix that anyway i was going to bore it out and try to get more power out of my engine. what would be a good course for me as an 18 year old to take with this engine?

"take it to the shop" isnt an option, dont have the money
only the machining would be done there

and its a 350, if you guys need more details let me know and ill try my best

 

[blazinfast]

is there another place this post should be?

or is it slow like this usually?

 

[readymix]

You only waited 28 minutes....


Have you done a compression test?
Leakdown?

It could be as simple as a valve issue.

 

[Pvt. Maggot]

You can pickup a 383 kit for about 800 bucks, I'd say go that route..get a manual and tear it down, make sure you bag and mark where everything came from. now go get some wrenching done.

 

[K5dreamer]

first thing is first, go to sears, napa, whatever, and get yourself a compression tester. Its a very easy test to do, especially on these trucks because the engine bay is so big. all you do is pull out the spark plugs and screw the compression tester into the hole, then crank the engine over a few times on each cylender to get a reading. they should be around 120-150psi and all very close to each other. if you get a random flyer thats at say, 80 psi, youve got a blown piston ring.

if youve never done any serious work like this, pulling and rebuilding the engine by yourself is a big step. do the compression test and make sure its actually nesseary.

just for fun, what makes you think the rings are blown???

 

[readymix]

K5dreamer, A reading of 80psi does not autimaticaly mean a blown ring. Could be a valve or gasket issue too.......

Leakdown test is also needed to properly diagnose.

 

[vortec]

find a wrecked gmt400 on ebay or junkyard and yank the engine with all its goodies attached. engine building is fun, but it's not always practical.

 

[W7NB]

i have a 85 k5 that i think the rings have gone out on and since i will have to take the motor out to fix that anyway i was going to bore it out and try to get more power out of my engine. what would be a good course for me as an 18 year old to take with this engine?

Boring an engine makes very little difference in power. You main gain a few cubic inches but compared to the original 350 inch displacement it's less then 2% for a .30 over. Boring is done to clean and true the cylinder walls for the new piston and rings.

The 383 is a great idea. I ran one in a jeep and plan to build a TPI 377 or 383 this summer for my blazer. The 383 is a 350 with the longer stroke of a small block 400 crankshaft, but uses the smaller bore of a 350 which avoids the heat/cracking problems the 400's had. Just to give you an Idea the only difference between a 377 and 383 is the bore - a 350 bored .30 over with a 400 crank is a 377 and bored .60 over is a 383. Thats all you gain - a whole 6 cubic inches, and the block is finished after that build, although some people will bore them beyond .60 over.

Building an engine requires a fair number of tools, measuring equipment and expertise. I have seen several people decide they would just "Build it myself" rather then pay for a shop to do it. By the time you by the tools, engine stand, books etc, pay to have the block cleaned and machined, have the heads done, and pick up all the parts you will need to do the build you will find that you spent very near the cost of a decent longblock from a reputable builder. And thats IF you block is rebuildable. And IF you don't mess up somthing critical and have to tear the motor down again.

The only time I find it worthwhile to build a motor myself is if I want to keep the vehicle original with matching #'s or if I want somthing non-stock and have to build it myself. On the other hand there is the pride in building it yourself.

Answer some questions for us. Why do you think it's got bad rings? Blowby could be a PCV valve issue. Is it burning oil? Noises? Some more info to work with would help.

 

[blazinfast]

well i think it is a blown ring because when it cranks up, it smokes like crazy out of both sides and the after its warm it lessens alot on one side. it still smokes like crazy from the right side though. it goes kinda away when driving, but i just assumed that was because im going too fast for smoke to collect and be visible.


it could also be a blown head gasket. im hoping that it is this

in any case i will pull the heads off and have them ported and maybe get a bout .005 shaved off the bottom to increase compression

 

[76zimmer]

well i think it is a blown ring because when it cranks up, it smokes like crazy out of both sides and the after its warm it lessens alot on one side. it still smokes like crazy from the right side though. it goes kinda away when driving, but i just assumed that was because im going too fast for smoke to collect and be visible.


it could also be a blown head gasket. im hoping that it is this

in any case i will pull the heads off and have them ported and maybe get a bout .005 shaved off the bottom to increase compression

Slow down a little here, do you want to cure this problem, or are you looking for a new engine.....you seem to want to jump into this with all 4 feet.

 

[Hogback Fabrication]

Just to give you an Idea the only difference between a 377 and 383 is the bore - a 350 bored .30 over with a 400 crank is a 377 and bored .60 over is a 383. Thats all you gain - a whole 6 cubic inches, and the block is finished after that build, although some people will bore them beyond .60 over.

4.030*4.030*(pi/4)*3.75*8 = 382.66 cubic inches

4.000*4.000*(pi/4)*3.75*8 = 376.98 cubic inches

A 377 is a stroker with the stock 4.000" bore, a 383 is .030" over.

 

[W7NB]

4.030*4.030*(pi/4)*3.75*8 = 382.66 cubic inches

4.000*4.000*(pi/4)*3.75*8 = 376.98 cubic inches

A 377 is a stroker with the stock 4.000" bore, a 383 is .030" over.

Yeah, bad math on my part. Still, what will 5.66 cubic inches yield in horsepower on a 35+ cubic inch motor?

76 zimmer just wants a bragging motor. Never mind the one he has might be fixable.

 

[blazinfast]

well i think i might just shave the heads alittle and get them ported and get some quick power

been researching and it seems like the way to go

 

[W7NB]

Shaving the heads increases compression which will increase power, but if you shave too much you will have to burn priemium to prevent knocking.

Also, porting will help airflow, but mainly at higher RPM. Figure out where you want your powerband to be before you decide how you want the motor built.

 

[blazinzuk]

Depends on your budget but if i was going to try for cheap power (a realitive term) I would get a basic rebuild kit for the 350 and spend money on vortec heads. There is only so much power you can build with stock heads. Engines have to breath. Look at the engine as a system. If you do that you will come out with a much better engine. You will probably need an aftermarket cam and aftermarket intake, a decent ignition, make sure your carb is in good working order, a set of headers and a good exhaust. These along with vortec heads will give you a surprising amount of power.

Anyone can rebuild a small block Chevy. The first motor I rebuilt I got a cheap torque wrench, some plastigage, some feeler gauges and I think that was about it. Obviously you will need basic handtools. Buy a book and read the whole thing before you start. A book will educate you about the machining process too so you know what you need.

 

[blazinfast]

well i know all the basics of an anegine and ive rebuilt little stuff like lawnmowers and the top end of my volkswagon, but i pulled the heads off and heres what i found:

the exhaust manifolds only had a gasket on one side

the gasket on the right head was destroyed

the pistons and rings are in amazing shape

found out i have an aftermarket intake, edelbrock

also i have a busted ball joint, which doesnt relate to the heads but it was good to find

thats about it, the heads are at the machine shop now, will keep you guys posted,