Continuing with Wilson's problematic 72 Skylark

Mark,

That was my thought too sir. Thats just one piston. Haven't pulled the rest yet.

My plan is to tear it completely down and take block/pistons to my machinist and see what, if anything is salvageable.

 

Gents,

Quick update.

So, I tore the rest of the motor down on Thursday evening. Its safe to say that she need a rebuild. Main bearings were not nice. Babbitt material missing on some and the thrust bearing had copper showing.

Rod bearings pretty much the same in terms of Babbitt missing. Cam bearings are cloudy and scuffed pretty bad.

Interesting thing is, the crank journals and cam journals didn't look bad at all. Still have a nice finish to them.

All 8 Cylinders have scuff marks on the bottom of cylinder (6 o'clock) with matching scuffing on piston skirt. the skirt material isn't smeared, just scuffed. Thinking this was all due to the coolant in the engine oil.

I am going to have my local machinist look at the block and see if it can be honed or if I am going to have to punch it out. The motor has already been punched out 40 over and mains were cut 20 under. Didn't look at rod bearings to see if or what they were cut to.

Assuming the block is ok and it can be salvaged, and if the motor needs punched, is it worth going to 60 over on these motors? I am just looking to put together a nice little street motor to cruise around...nothing neck snapping.

So, with that said, any tips I should do when getting this motor back and assembled? I've built turbo V6 motors and my share of Ford and Chevys, but this is 1st BBB Ive done and it seems like from what I read on here, they are a different animal.

Part of me just wants to find a motor that is already done and call it a day at this point.

Thanks for your input guys.

Chris

 

Great read! Thanks for sharing Larry. One would assume this block was sonic tested before it was built but one never knows.

If the block needed to be punched, my game plan to get the block "verified" was getting it tanked, magna-fluxed, and sonic tested.

Keep the good information coming!

Chris

 

If you plan on using the AutoTec pistons you can skip having the block bored and just have it honed the same to the next size that has decent rings available which would be 4.360" looks like there are 1/16", 1/16", 3/16" rings available for that size, instead of the slightly thicker 5/64", 5/64", 3/16" stock style rings. Even with the 1/16" thick rings only being 1/64" thinner, when you times that by 16(2 rings per piston) you get .250"(1/4") less friction per revolution which would free up more power that would be lost from frictional drag. There may even be better rings for that size available, I just did a quick summit search.

Also with the above mentioned pistons besides being able to order them with whatever bore diameter you want you can order them with whatever compression distance you want as well so you can skip having the deck milled to get to zero deck and be able to use the less expensive composite head gaskets.(around a $50 savings)

The AutoTec pistons have a quench pad on them so they're less detonation sensitive especially if they are setup to have .035" to .045" of quench.

Being able to skip having the block bored will cost around $100 less, being able to skip having the deck milled will be around $250 less. Skipping having the deck milled will save you from having to get custom length pushrods(around $150) so you'll be able to re-use the ones you have. Not milling the deck will also help maintain intake manifold to cylinder head alignment, saving the expense of corrective machining to either the intake or the head surface where they mate together.(around $200 of machining cost savings)

If you add up all the above machining and part costs saving you can get with using these pistons makes then virtuously free vs. using a cheaper inferior piston that needs all the bells and whistles machining to make them run right in your engine;


http://www.buyracingparts.com/pisto.../autotec-455-buick-forged-dished-pistons.html


GL









Derek

 

Sonic testing cast iron is questionable at best. It still requires visual confirmation and a skilled machinist's judgement. The transducers need to be modified to even work on bores vs. flat spots and there's lots of things they don't catch. That being said, I always use mine before taking on aggressive porting projects (backed up by drilling and pipe plugs), as well as any suspect blocks.
Just some non-confidence inspiring info intended to show that it isn't any sort of guarantee...merely a better guess than not doing it.

In every case I'd try to hone a block and fit a custom piston, offset bore when needed, or otherwise attempt to preserve wall thickness.

 

All very good information gents!

Well, I dropped off my block, crank, heads, and pistons to my machinist this morning.

Initial inspection from him made me happy.

Said the piston scoring isn't as bad as I thought. he has seen worse.

Cylinder bores look decent but he is going to verify that the machinist before didn't just bore out the cylinders to a standard 40 over and leave it at that; possibly resulting in the pistons being too tight in the bores.

He is also going to check the heads and make sure they aren't decked too much, but to also make sure they are square. Thinking chamber that was located on #6 piston has a exhaust valve issue which was causing the "put-put" I was getting at idle.

Also, with the heads possibly having a couple valve jobs on them throughout the years, his concern is that valve height is off from valve to valve. (probably the reason amongst other why this motor had adjustable pushrods)

My goal is to be able to order pushrods at a specific length and not have to adjust individually.

I will keep you guys posted but the engine project has officially begun.

Keep the insight coming! Definitely want to hear from the "Buick Gods"

Chris

 

Good luck, I have been following this thread for awhile. It is all worth it when it fires up and runs flawlessly, trust me....

 

Thanks John. I am definitely looking forward to it.

 

Good to hear you are making progress. My 73 is .040 w the forged speed pros 45 in the hole. 9.3 to 1 compression. Be careful and those adjustable push rods are a great asset to have. You might be best getting new valves and opening Sears as they are cut numerous times and the heights are all over. Need to true and clean up bowl area. That is where power is. I have seen worse scuffing and marks in all my dealership years rebuilding and engines run fine when not allowed to replace blocks because warranty crap. I made same mistake w my fuel pump. Went w rob mc now. Alls good. These old pump awAy. Might even go electric now w my trusty Mallory. Good luck. Get it done

 

My 455 broke a fuel pump lever this summer. The lever ended up scoring the camshaft and sending shrapnel throughout the engine, requiring a full rebuild. Thankfully, all of the non-wear parts were reusable (minus the cam, the crank needed polishing) and I finally have an engine that's running right again. Good luck with the rest of your build. It's annoying that something so small can cause so much of a hassle.

 

That's good you got it back together. Glad I updated my pump with rob mc tho I might pull to check. Easacky. Clem and assemble. Like I did I seen many a scratched cylinder. Hope your machinist agrees

 

Can't imagine any other machinists being OK with material embedding into a piston and tooling grooves into a cylinder.
The opinion will always stand due to A. the risk involved and potential for damage down the road and B. he can't assume that risk, esp. at the expense of hurting the business he promotes. Very counter-intuitive.
Will it run? Sure.
The consequences are on you, good or bad.
Glass beading, shot cleaning, magnetic crank inspection processes are not permitted at some shops for a reason. Worn particles are bad.

I'm definitely not disagreeing with the first hand experiences of service techs and mgrs, just pointing out that the machinist will likely have different prerogatives. Also, a performance engine will see much more abuse with rpm and power levels.

 

Update gents!

Motor is back and car is running. Just doing shakedown on the car the past few days.

I ended up installing a quick fuel carb instead of the q-jet. Throttle response and driveability are leaps and bounds better with quick fuel.

Only think I am monitoring is a slight pop in exhaust when car is at idle. Not sure what it is. Timing is @ 15 degrees at idle and mechanical advance is coming in at 31 degrees @ about 2500 Rpms.

Checked all 8 plugs and they are all light brown but plug on cylinder #4 has some oil on threads. Electrode doesn't seem to be affected.

Wondering if it may be running a little rich at idle but plugs aren't indicating that.

Also verified all corner sir bleeds on carb using vacuum gauge. Gauge indicates about 10-12 in.

Any thoughts?

Chris

 

Do yourself a huge favor. Instead of guessing and messing with tune after tune, install an O2 sensor/gauge. Then you'll know EXACTLY what the A/F ratio is. I use the Innovative Motorsports setup. Installed the gauge under the dash over by the glove box against the kick panel. Out of the way but easy to see when I need to.

 

Good idea Yardley. I think I am going to do that over the winter.