testing a used enigne - out of the car? long post

[aribert]

Long post - please bear with me.

I have had some bad "small 6" engine karma in the recent past. After rebuilding my 170 at 125K miles (.030 bores, .010 rods and mains) and doing a quickie re-ring/brgs at about 220K miles (I was installing a Clifford cam any way), at 248K miles I decided to pull the engine so that I could base/clear the engine compartment while I was respraying the rest of the car. Since the engine was out I decided to spendt some coin and had it bored .040 over/ crank reground, head milled (agressively, to what I thought would be 9.3:1), custom headers & dynamic balancing. Engine sounded sweet during break-in until at 190 miles of break-in the engine began to seize while on the freeway. Pistons had seriously expanded in the bores - the skirts were galled and blue in color (I had never seen aluminum turn blue before. Thinking that there must have been a tolerance issue that I did not catch on assembly, I got a 200 core, bored it .020 over, but reused my existing head, carb and timing set. The second time I went easier on break-in and had the same piston expanding issue at 293 miles (and several galled, blue piston skirts again). THird engine (still reusing the head, carb and timing set) was a quick and dirty re-ring (all the tolerances were right at the high limit) and I payed extra attention when I finally got on the freeway with it (by now I could hear the subtle engine laboring sound (not knocking) at higher rpm. Coasted down and stayed off of the freeway (and under 55 mph for the duration of that engine (about 2500 miles, it started to have piston slap noises and I partked the car). I have now pissed away about $3500 between all 3 engines.

So now all I want to do in the short run is to drop in a running 200, using it as is with the carb that comes on it, etc, and drive the car while I sort out the issues in my existing engine. I really hate the thought of pulling the engine again - every time I end up chipping more paint in hte engine compartment.

200s are not that common in my neck of the woods any more (Detroit area). I found a dual bolt pattern 200 a couple of months ago and bought it. Engine has less than 1 hr of run time in the past 5+ years and the seller of the engine did not pay attention to if the engine smoked - he was focused on driving the garage queen a couple of milse from where it was stored to his garage with semi-funtional brakes. Cylinder bores look shiney but the engine had several oily spark plugs.

What are the odds that the oilyness is valve guides? Is it worth my time to build a leak down tester (I have about half of the parts needed on hand but very limited time). So far I have taken my compression tester apart and used pieces of it to pressure each cylinder to about 40 psi and trying to listen for differences in the amount of air escaping. Once I gather the rest of the 3.03 trans conversion parts, I will be able to crank the engine on the ground to do compression test. Once the engine is in the car, pulling the head for a rebuild (and getting hardened seats and bronze valve guides) is not that big of a deal. Reringing the engine in the car is a less desireable thought. What would you do? Money and free time are both in limited supply this year.

 

[BUZZ]

Since your going to pull it later and go back in with built motor I think all I'd do is replace the valve seals, look for any other leaks and stick it in. As you stated you don't have a lot of free time and if your like me the second you pull the head you'll start tearing the rest apart for a full rebuild.

 

[addo]

What was going on with the bore and hone? Your situation sounds like a complete case of the machinist dropping the ball.

I was looking at a small four the other weeks where the pistons had turned blue and metal transfer commenced. That was chronic overheating; the idiot managed a classic line "I was just trying to get to..." (It's the just that screws people every time!)

FWIW, torque plate honing and hypereutectic pistons will be your best bet. You could also look at a reground cam and resurfaced original lifters next "upgrade". This will give you a good quality of distributor drive helix, and known good metallurgy in the cam and lifters.

Cheers, Adam.

 

[350kmileford]

I had two different, well-known machine shops laugh to my face when I asked if they could torque hone an inline 6 engine.

 

[addo]

I think that says a lot about them. None positive!

 

[Bort62]

I would like to know who is doing the final assembly on your engines ? The fact that you had the same issue twice (or maybe 3 times) suggests that the common denominator is doing something fundamentally wrong.

As far as your question - I would just do the valve guide seals and throw it in.

 

[jamyers]

I had two different, well-known but still half-a$$ed machine shops laugh to my face when I asked if they could torque hone an inline 6 engine.

Fixed that for ya.

 

[aribert]

Thanks for the replys - stem seals it will be.

Final asm was done by me - and this was not my first rebuild (but it was my first failure(s) at rebuilding engines). I had strongly suspected that the first failure was indead a machine shop bore tolerance issue. I had used the same (one man) machine shop for about half a dozen prior engine rebuilds. That machinist would not bore a block until he had the pistons in order to mic them. Second rebuild was machined at a different shop - and I was much more particular in measuring the bores prior to assembly. And the 3rd, the quick and dirty rering was at the very high limit for bore tolerance.

When I pull the 3rd engine, and do a post mortem, I should know for sure. Since there are several common parts between all three engines, I strongly suspect that is where my problems lie. Either I screwed up in my calculations/measurements on CR (I was intending on 9.3:1, never heard pinging, used only premium after the first engine failure) or the timing chain set had TDC marked in the wrong place or the carb was too lean (but the plugs were sooty looking and my fuel mileage was down about 30% compared to before I decided to rebuild an engine that did not really need it yet.

I did not intent to do anything exotic to my Falcon engine - I did all the same things to my Triumph 6 cyl and except for a blown head gasket after 65K miles and a couple of cam lobes that were beginning to pit (I was not in tune to the ZDDP reduction in gas engine oils) I have had no issues and I ride the Triumph harder than I do the Falcon.