So, I am at about 4,000 miles now on the rebuilt 3.4... Used breakin oil for the cam breakin first two 20 minute runs at 1500 to 2500 rpm.. Changed out for fresh breakin oil and ran that for the first 1,000 miles.. Changed oil to non-synthetic oil... So, that's now 3,000 miles on the non-synthetic for the total of 4,000 miles..

Its running just a little rough.. Changed out a couple of vacuum lines as the vacuum dropped from 15 right after the rebuild to 12.. That brought it back almost to 15... Pulled the plugs and checked gaps, all at 050... Ran a compression check..

1 -- 150
3 -- 150
5 -- 110
2 -- 145
4 -- 145
6 -- 145

So, looks like number 5 didn't seat very well.. Put a little oil into the cylinder and it came up to 150... Seems to hold compression though either with or without adding oil to the cylinder...

I should add that it hasn't used any oil in 3,000 miles and the oil is perfectly clean....

Should I go back to breakin oil for a while to see if 5 will seat better or go on to synthetic oil at this point?? Also, does that vacuum look right at 15?? It is rock steady at 15...

 

Improper valve clearance (valves set "too tight") can be a cause of low compression as well . Are you 100% certain you don't have #5's valves a bit too tight ? (not enough clearance) ?

 

what he said reset the valves and see what happens , if that dont help go out and beat on it a lil bit , the increased cyl presures will help seat the rings.

im a firm beliver in not babying an engine for the first 500-1k miles, first thing i do with my turbo engines after cam breaking is go out and give it a couple full boost runs, on an n/a engine getting on the throttle hard in short bursts helps seat the rings

 

Based upon what I remember for testing, if valves are leaking valves then the compression won't ratchet up with cranking.. So, if it ratchets up but not all the way, then adding oil to the cylinder will cause it to go to normal if the rings are not seated..

I am pretty certain that I set all the valves the same but guess that might be worth the check... Not sure when I will be able to get to that... Living in Denver and it is my snow car so hard to find a nice gap in the weather to pull it into the garage (my 2010 does not do snow).....

 

^^^ THIS, a thousand times THIS! ^^^

I have never gone easy on any engine or clutch I have installed, and have never ever ever had an issue.

I'm a firm believer in breaking parts in the way they will be driven. In most cases where someone has broken in something taking it easy they tend to have issues when they start beating on it.

I also agree, check the easy stuff, valve lash, vacuum leaks, etc.

I also have never used break-in oil, don't believe in it. The closest I've used is regular dino oil for break in and the first 200 or miles then switched to synthetic. The only reason I used dino oil for the break in and first 200 or so miles is because I'm cheap and didn't want to use synthetic for that.

 

^^^I drive my stuff like I stole it while breaking it in.

 

Same here. Last year after my rebuild I was easy on it for about 10 minuets then got on it like I stole it I just kept the boost very very very low for a little while. Never had a issue with rings seating...exc.

 

i just gotta ask real quick is the 3.4 swap easy enough to do at home ?

 

Yes.

 

Yes, it is but...... A couple of things to think about... I completely rebuilt the replacement 3.4 before installing it... Follow the tech notes on the swap in the sticky... Take special notice of the distributor/oil pump shaft and the need to change to 3.4L injectors... I had those rebuilt too before installing them.... Also, take note of the need to use spark plugs for the 3.4L rather than the ones for the 3.1L... Now for a few other things....

1) My engine cherry picker wouldn't reach in far enough to pull the engine. You either have to take the nose off or use a gantry crane which is what I did.. Bought one at Harbor Freight...

2) Read my struggles with the anti knock sensor.. On mine (92) the knock sensor when installed interfered with the start solenoid so I had to install a 45 degree pipe fitting.. I mentioned the part numbers for fittings in my thread... I used the galvanized steel pipe one...

3) Good time to change motor mounts (mine had 450,000 miles on them).. But, a pain to do even with the engine out.. I had some help and used a coil spring compressor and disconnected the lower control arm to get at the nuts on the inside of the k member..

4) Break in.. Make sure you use good breakin oil only... Have an extra fan ready to feed air in the front as soon as it gets hot... Mine got very hot on first run... Make sure you have the timing set close before you attempt first start and make sure the timing light is ready and can quickly set it fairly close before full breakin.. Don't take to long.. First 20 minutes at 1500 to 2200 RPM.. Then shut down and let it cool... Second run 20 minutes at 1500 to 2200 RPM.. On both runs, vary the RPM up and down in the range every couple of minutes.. Shut down, let it cool, change to fresh breakin oil and change the filter.. Fine tune the timing... Then, if you want, drive it like you stole it for 500 miles and change the oil and filter again.. Put in NON-synthetic oil for anther 5,000 miles, then go to whatever you want.... Might be overkill but I am conservative....

 

In all of my (flat tappet) engines I have only ever done a single 20 minute break in, varying RPM from 2000 to 5000 RPM, not letting it settle at any one RPM for more than a few seconds, for at least the first 5 minutes or so. I use the cheapest oil I can find, because well, I'm only using it to wash out the assembly lube. I then go straight to Synthetic if I planned on running synthetic in that engine (some I did not). Never had an issue. I have occasionally ran cheap dino oil again after the initial 20 minute break in but only for about 100 miles or so if I feel that not all of the assembly lube has been washed out.

My roller engines I usually just put in some cheap oil, and drive it around for a couple days and then switch to synthetic, without the 20 minute break in. The break in is for the flat tappet cam wear in. First fire up on my roller engines I will usually let it run for about 5 minutes to get some temperature in it and check for leaks, but I do not run it as a break in period, just to check systems.

In either scenario I change the filter with the first oil change, or when switching between dino and synthetic oil.

 

Yup, have heard of doing that as well... I did a lot reading and talked with the shop that honed the cylinders to compare all notes and suggestions... I had also put in a new crank, new cam, new lifters, new pushrods, new rings, new rod bearings, new main bearings, etc.. So, a lot of new parts wearing in generating a lot of heat and potential for wear in metal in the oil on first runs.. The best way I found to avoid glazing the cylinder walls was the use of breakin oil followed by non-synthetic... Synthetic is too slippery so the cylinder walls can have a tendency to not wear in properly against the rings so the seating isn't quite as good... The key is to keep the cylinder head pressure up hence the ramping up to whatever high RPM you chose... That helps push the rings out to get better seating and fit against the cylinder walls as it breaks in....

Again, educate yourself and make your informed decision as to how you would like to do it since there are a ton of factors influencing breakin.. I chose the method above for my engine.. I ended up with all cylinders near 150 on compression except one.. I still haven't rechecked it but I have been driving it hard for the last 5,000 miles.. I am about ready to switch to synthetic once I check that cylinder again... By the way, it uses zero oil so nothing is bypassing the rings at this point...

 

The engine has 105xxx still do rebuild ?? And what is the hardest thing I will probably run into?

 

As for the mileage on the engine and a rebuild question.. My original factory 3.1L gave up at 135,000 but I think that was a special case.. That one was replaced by a GM rebuilt crate engine that ended up with and extremely worn cam, gears and chain at on 60,000 to the point the valves were almost not opening. Not sure they changed those on the GM rebuild. So, I changed those out and it went the rest of the way to 450,000. Really depends upon the engine and its history.. My doner 3.4L had in the neighborhood of 100,000 so not wanting to do this job again for a very long time and not knowing its full history, I decided to go the full rebuild route plus way easier to do now than later since the engine was out on an engine stand.. Take your time and you won't have any problems or oil leaks because you can take your time to do it right...

I wouldn't say there are really hard things to run into with the swap.. The biggest issue is getting your head around the stickies on the swap, that is, what to keep what to swap.. I mentioned above a couple of quirks.. Another was that the assembly manuals call for an oil o ring under the rear main cap at the oil pump shaft. After taking mine back off after it was assembled (late discovery of the note), I found out that only some engines had that for a short period of time and Chev discontinued it as it really didn't do anything. You will need to get creative and find something that will work to drive the rear main seal into place.. That takes a special tool.. Also discussed somewhere here is the proper setting of the valve lash... Manual says 1 1/2 turns, some say 3/4 turn, and some say 1/2 turn... I think I ended up with 1 turn and no problems..

Mostly read up on all the notes, ask questions along the way.. An extra recommendation since I did the swap and promptly took the car from sea level in Seattle to 5,000 feet in Denver. Air draw is slightly higher with the 3.4 than the 3.1. That doesn't make much difference at sea level but when I got to Denver, power was suffering. I swapped out my air intake from the 3.1L to one from a Camaro with the dual snorkel that runs over the radiator and has two air filters. I think that is from either the 305 or the 350 V8 car. Performance improved noticeably and include a 4mpg gain. Others have increased air flow by installing after market cold air intakes or simply cutting the snorkel off the 3.1 air cleaner.. Don't forget that whatever you do, you have to maintain the AIT sensor in the cold air intake.. In my case, I moved it from the 3.1L air cleaner to a bung fitting on the side of the GM dual snorkel intake.. That required an extension cable which I made by buying connectors so I wouldn't have to cut my original harness. I have part numbers for those if you or somebody needs them...

 

One additional note, I just noticed that your car is an 89 2.8L. I still think it is straight forward but there are one or two other things to do because you are going from a 2.8 instead of a 3.1 that are described in the swap stickies... Moving from the 2.8 to 3.4 you will notice much more performance increase than I did and I am happy with the 3.1 to 3.4 increase.. Your choice of cam if you rebuild totally will have an impact of course so I had a thread on here talking about cam's and performance with the cam change included with the 3.4 swap.. Make sure you study that as well...