Regarding the piston taper, it is also the hottest part of the piston when the engine is running so it expands more than the rest of it. It is easy for people to forget that the pistons heat faster than the block or liners. Insufficient clearance can kill an engine very quickly.

I`m no engine builder, But that was very educational watching the valve guides been done. Great vid.

The valve guide process is pretty neat, thanks for showing us.

Excellent episode. I can imagine the kind of language if one of those ball bearings bounced away! I haven't seen anyone else explain the piston taper so well. Nice job.

Interesting the bit that you thought was a waste of your time was actually really eye opening, 😂 the things we take for granted, amazing!!

Yay... I remember at 30, my 9yro brother teaching me stuff. Never be too proud to learn.

Very neat air tool for making sure your reamer is perfectly aligned with the axis of the valve and for sizing the valve guide lines. It's stuff like that which makes going to a shop like yours absolutely essential. Anything less is a hopeless bodge.

Today's video is very educational. I didn't no about the piston being tapered and interested about valve guides . Top channel.

Hi power 3sgte, nice. Best engine ever developed! Auto machinist from NZ.

a most eloquent explanation, easily understood by the novice and expert alike. loved it. making something that is complicated simple and straightforward.

Thanks for the teaching on the piston issue. I’m not @n engine builder just diy and was told many many years ago that’s how to determine bore wear. I know better now. Thanks again. 😊

Control bearing balls @ +/-2% were always expensive, but I didn't realise they had become so much more expensive. Wowzer. Great video as always Lee.

I get the same phone call at least once a week, especially when someone is using a 2618 alloy piston. They freak out! lol. And on the carbide balls for the K-liners, I use a large round magnet tray under the guide to catch the ball. I got tired of chasing the damn things around the shop lol. Awesome Video!

That was interesting about tapered pistons, you could do with a tips video to help home builders, reffer them to it which will aid thier rebuild information is always good from the professional rebuilders, may also cut down on the phone calls or emails. Brilliant site Regards Mick.

Thank you for a good lesson God bless from South Africa

Excellent breakdown. Detailed and to the point.

I've just finished rebuilding my first engine (wasn't intending to, just sort of full into it) and took away all sorts of interesting info from the machine shop that bored the block and reground the crank. But then I'm always willing to learn from people with practical experience!

20 years ago I was rebuilding a CB250RSA Honda motorcycle and was having the cylinder barrel re-bored to suit a Genuine Honda +.050 piston. The engineer doing the job asked me what clearance do Honda recommend. We were both surprised with the genuine workshop manual (not Haynes) which quoted 1 Thou of an inch. When bored the piston without rings would not drop of it's own volition, it had to be gently pushed. Over the following years Honda were proved right, the engine did not seize, burn oil and reformed faultlessly. After a history of British and Italian bikes where 3 to 4 thou was 'normal', this 1 thou was an eye-opener. Love your postings.

Brilliant Video Lee and Co.

Guess I'm VERY old school. Last time I checked piston fit I was still putting it in the bore alongside a feeler gauge.

Well done. Good clip. I started as a Mechanic in NZ back in 1971 when we were thrashing Humber 80's and Angle-Boxes. 3500 revs and you're starting to break centre main bearing caps. Would go to another donor engine and take the cap from that and, Voila, back on the road. The earliest high performance engine that I personally saw, was the Coventry Climax, originally a Firepump engine which before FVA's and BDA's revving to 6,000, would rev in excess of 8-8500 revs, in the fifties and were used in the much maligned Hillman Imp and I think the Cooper Climax. This was in the time when they just started Cam Grinding pistons. The most fascinating engine I have seen was a Marine Crossley. Probably about 300 revs maxs maybe a bit more, as a motor on old Ferryboats, replacing steam engines. Me and the Engineer used to sit in the bilges with targets set up by the prop shaft shooting slug pistols at targets, to pass the trip and wait for the Skip' to call for reverse. The engineer would walk over to the massive engine that was moving visibly, not just in the mounts but the parts seemed only loosely bolted together, head bolts bubbling and all the engine dancing. He would stop the engine and move a lever that pulled the cam in or out or introduced an idler and the engine would then run in reverse. Huge coarse prop. No gearbox. A clonkity, clonkity, clonkity, probably now only a memory. Like a big slow Gardner.

The fact they aren't checking piston to cylinder clearance before building the engine, tells us everything we need to know!

Very educational, good tip about the piston gap, thank you

I remember hearing about "Piston rock" because of thermals ages ago. I remember hearing old saying "If you're running "X fordge pistons" in "blah Blah" you may hear a little piston rock, You gotta let it warm up before you beat the shit out of it

Great info and knowledge on this channel.

Sound advice for those who want to rebuild their engines. I've known for years that pistons are tapered. I used to do engine reco/rebuild work for a living myself.

I use liners in everything. I did a single head for a stockcar part way through the season with bronze liners, the other had mint guides since they had been already done with cast guides, so the owner didn't want them touched. At the end of the season, we checked the engine over, and the cast exhaust guides were worn out with some wear on the intakes; the liners were still perfect. I have never taken apart an American pushrod engine that didn't have the exhaust guides worn out. I have seen them with so much wear that the valve was hitting the side of the chamber. lol The worst actually had exhaust gasses blow past the stem when adjusting rocker clearance. Centre valves on small block Chevs are the worst.

These vids are gold, Cheers Lee 👍

Nice video Lee 👍👍

Great machinist bravo Adam Brooklyn nyc

Cheers Lee one of your better videos although they’re all pretty good. Pistons are ground oval as well as tapered. See you soon.

The valve guide replace ment looks like a great idea, i guess you can save all those pinto and cross flow heads

The test fit of the valve into a he finished guide, maybe I’m weird, but that was a beautiful thing.

Exactly why I watch the channel to learn! Building a 3.2 VR6 ironically - would love to see more content / detail on that build. That head also seemed to have been gas flowed?

I never knew you could do that with valve guides, very interesting.

Good work!

Clever valve guide repair system, nice.

I've built a couple of engines, i'm no mechanical engineer, just a car mechanic/MOT tester but even i know there is running clearance and the pistons usually rock over to an angle as the "Thrust up" the bore.

Very interesting. Thankyou.

Pistons are wave ground to a barrel form in the vertical and cam form in the horizontal very lightly , imperceptible to the naked eye. The ring lands are generally 0.25 mm (010" - sometimes more ) less in diameter than the nominal skirt diameter . The grinding method produces the skirt finish to hold lubrication that if studied carefully with a magnifying glass appears as shallow waves .This combination of forms ensures a minimum skirt contact with the bore , but ensures sufficient lubrication to enter between the skirt and cylinder bore to float the piston .The vast majority of heat generated in the combustion chamber is carried away through the rings and therefore the most critical area in piston design and suitable alloys are chosen to maintain the set minimum clearance between the steel rings and their grooves . Excessive clearance in the ring grooves leads to flutter resulting in excessive heat generation , poor heat transfer and eventual failure . What appears to be excessive clearance between the installed piston and its bore is what the piston manufacturer has designed in to help the piston survive . The skirt clearance is what the piston manufacturer has calculated to allow for differential expansion between the piston alloy and cylinder bore material . This can range from 0 where both coated aluminium alloy are used for both piston and cylinder ( the extreme found in F1 engines which lock up when cold) to 004 -005 " / inch of bore in a low silicon alloy piston ( non eutectic ) in a cast iron cylinder. The metallurgy of a 2T piston enables it to suffer large temperature gradients across the whole of the piston not seen in a 4T cylinder .due to its porting arrangement.

I've always sent the block and pistons together to get the proper fit and balance.

Nice , never got to rebuild engines but have a Chevy 350 I'm going to do .

Love watching your videos Lee!! Too bad the Home Engine builders who perceive clearance issues are not familiar with engine dynamics or thermal metallic activity on an engine. Oh well. They might learn one day.

Oil pump and balance shaft shaft combined is very common on modern 4 and 3 cylinders, main reason being cost and packaging.

Of course clearance is proportional to the size of the object. .003" is a lot when dealing with a shaft that may only be .200" or so in diameter. I enjoyed the comment about home engine builders 'not knowing what they don't know'. It's the Dunning Kruger effect.

When you are tapping the calibrated ball down the guide, try putting one of these magnetic component dishes underneath, lined with a sheet of paper towel to slightly cushion it.

Not an Engine enthusiast, but this is all interesting stuff ... especially with theory & demo both presented. One question: I wondered why you didn't remove the bottom excess of the injector lining before pushing the ball-bearing through ... as to my lack of experience, that would seem to avoid any deformity occurring when doing it as a secondary process ... as that way you can guarantee that the ball-bearing is the 'final-cut' ... I'll do my best to understand any answers to this ... Thanks.

As you were talking about bikes, only 4ST have tapered pistons, but 2ST still don't.

Tapered, barrelled and oval. Pistons really are a complex shape to make sure that they come true when up to temperature.

One good idea out of a thousand sounds about right

I have had some engines fitted with the thin-wall inserts, and been VERY happy with the results, but while i knew the theory, I hadn't the full story on using them - cool and interesting! Uh, no, that was ballocks about the piston and rings - VERY surprised you said that rubbish! a/ as others have siad, the additional clearance towards the top is because there is greater thermal expansion as the crown runs a LOT hotter - and it's why higher power engines are recommended to run an additional thou' or two, to allow for the higher temperatures. b/ the piston rings are fitted with a rear spacing, partly to allow gas behind them for better ring seal - when pushed back into the piston grooves they will sit back from the piston face. in practice, they're skimming the cylinder wall and floating within the groove as the piston moves slightly around TDC and BDC.

as below when on operating temp the piston would be cylindric. When going to Tractor puling you should listening to a pro-stock. You could hear the pistons tumbling in the block when cold.

Skirting (😂) around the startlingly shallow height of modern pistons that will clearly accentuate the 'rocking,' piston ring gap is an obvious further check issue before reassembling. I learned from dieselpumpuk recently that high performance engines should also use a deliberately wider ring gap to allow for increased expansion at higher operating temperatures.

Thermal expansion. Doesn't matter who makes it, they all have to make things with this in mind.

Interesting 🤔 🧐 I didn’t know that about modern pistons. It’s decades since I rebuilt an engine. In the ‘old’ days the pistons were linear throughout their length.

There's two machine shops around where I live, the owners are brothers and they compete to see who can charge the most to fuck up your engines or heads. So when I stopped having machine work done to heads or blocks I started having better rebuilds and better engines.... it's weird how machine shops can destroy mechanics reputations in a given area

Pistons with such short skirt hight will Rock even more than old long skirt ones, as far as I can remember pistons were always tapered and oval before slipper pistons came along.

I learnt something 😊

All great you're doing the sleeve, but what about those seats? I'm looking at burn pitting all over the place. I've had more issues burning seats than bending valves in high output engines, especially when mitro-methane or Alcohol is added to the fuel. Normal for me is a 3 face grind on the valves, a 2 face grind on the seats, and then either bore/sleeve OR bore and install oversize shaft valves.

the hottest part of any piston is around the exhaust port and this should have the most clearance, no piston is perfectly round, and rough surfaces are best to carry oil.

Only reaming (! sounds naughty) I've done is bronze outer bearing on classic Mini rear suspension trailing arms. There's a needle on the inner. Pump that grease in buddy.

Also, they are not looking at the piston to cylinder clearance when hot. Aluminium alloy has a greater coefficient of expansion than Cast Iron or Nickel Steel ( liner) Another thing to take on board, is that some pistons are also oval when cold and become round due to controlled expansion, as they heat up. The modern shorter, slipper pistons will rock more than those with a longer skirt. It's an education just to take a modern piston and measure it in both axes, it's not just the ring belt that is different! Great videos, I wish I had some of your kit when I was building engines 50 years ago!

Interesting. My old pistons had a rock and it had me concerned but think it was just ring and bore wear now......

Here in USA my machine shop won't bore engine without new piston on hand

Regarding the valve guides why not measure them before fitting ? Dosnt a new guide conform to OEM dimensions and tolerances. I have fitted k- line liners a long while ago but have no idea of how long the might last what say you

I don't personally like setting a bore gauge in a micrometer I preferably use a setting ring which is a luxury if only measuring a few different cylinders

A bulb is something you put in the ground to grow. A lamp goes in a light 😊.

I would imagine that you would have to be careful not to let the sizing ball be too much warmer or colder than the head and guide, ideally the same temp? With that very close tolerance, the size could be negatively affected?

Engine builders know best listen to them

I can't believe people could be so uninformed regarding piston taper! The oldest engine I've rebuilt was a 1937 Villiers junior, and that had a tapered piston! I had to turn a piston down from +60 to +20 to fit the bore, which was unworn. No problem for my old Smart and Brown.

I am nearing the end of my working life now and I can't remember ever coming across a parallel aluminium piston, I may be wrong but I think the cast iron pistons used in the old 27hp Bedford engines might not have been tapered, so when is modern

Hi Lee, where to start 🤣 Hmmm why is there a ridge at the top of the cylinder, and how come the ring area doesn't have much wear. It's funny, I learned this when I was 11yr old from my shop teacher and my best friends Dad, you would think someone in their 20s, 30s, etc would read a book, yeah I said it read a stinking book. Anyway, a good teaching moment. Your guide reconditioning system is really nice with the pneumatic lock, I have seen systems that use a mini flex hone for final sizing. The VW 2L tdi engines have a horrible time with valve guides, in fact VW only sells heads and not the guides, and the aftermarket guides are worse than the factory, so anyway Deutschland Uber Alles Blue Mule NC USA

Back in my youth when I was fooling around with MGs, I noticed the clearance when I rocked a piston...it never bothered me because I understood the rings would take up the slack, not to mention a cam ground piston was slightly ovoid to allow for heat expansion. Those customer complaints just tell me that a little knowledge on their part is a dangerous thing!

Maybe include a paper with a diagram explaining it. Give it to them when they drop off the engine and when they take it home.

Is "thou" 0,001mm?

Sleeved valve guides? This is a new one for me. Different. Bronze indium(?) something guides on AEG-163 classic Mini Cooper S, had fun and games with them. Had a couple with cracks inlet to exhaust valve seats. Only good as doorstops when that happens. But the later last castings were better. 12G940 much better too with slightly smaller exhaust valves, MG1300 mark 2 heads the tops.

A little knowledge is a dangerous thing.

I think that nose cone on the track car would look awesome in carbon fibre effect

Tight guides in a performance engine will cause sticking valves. Loose is fast.

Interesting the easy way is too check the ring gaps if they are wrong you will be I know how to biuld an engine too

You didn't mention the difference between stock and forged pistons. Forged pistons require more than stock clearances so of course they're going to move side to side. That's because of the material used, they expand more and once up to temp should end up the same.

Piston skirt length is amazingly short these days, short buckets. Reduced power losses from friction I St. Assumption take it, or is that f'ked up thinking again? 🤪

This channel should be called The Whinging Pom

Either you need a policy of doing m/c block WITH pistons & rods installed, or make it very clear on the invoice where your liability ends.

At 13:30 The main reason why there is a taper on pistons is because there is more metal at the top. This expands due to heat more. At running temperature they should be parallel. Engineers know things.

How are those BB's for sizing the bronze valve guides any different material or tolerance than every day BB's, I think I'd sooner a regular BB was used and replaced often rather than silly £ BB supplied with kit; unless someone can tell me different?.

If you are going to have machining work done don't complain about the results if you can't measure what you got and your new parts to check it's all going to work together. If you don't have the measuring equipment have it done by the machine shop ( cheaper than another rebuild) or don't do it yourself.

The best example I can think of a tight fit engine is a full on f1 or other high output engine. Everything is so tight cold that you have to warm the block up before starting. You don't want your average built engine like this as most poeple dont even properly warm up their engine before romping on it anyhow.

@ 4:10 In the US we just call them air hammers ( you know from " jack hammers " but with air instead of electric that you jack a plug in an outlet 😄)

whats the update on the ford/volvo engine ?

Re. The "you've overboard it", if the to and fro wastes enough time to warrant it, perhaps consider adding a summary of your explanation to the invoice or delivery note?

Quite right about the clearance, piston to bore . Talking of bore(ing) , these adverts are getting beyond now , constantly butting in, and not even subjects that are relevant. 🤯

What's happened to old Heath Robinson he hasn't been mentioned for a while 😉 was hoping to see the ford/volvo engine being stripped hopefully next time

Called piston fit.

Always a problem when your.doing half the job and leaving the build to amateurs with little or no basic engineering knowledge. The guide inserts never knew this system existed a god send for th ultra rare stuff . The run through was a little hectic to try and fully understand but i got the gist of it in the end . Must be proven to be reliable and trouble free i guess but looked like a very thin walled split bushing guide and would have been concerned about it moving or dropping out if i didnt know they were proved anin use

Electric motors are so wonderful.

nice to hear imperial ,like steak and lea perrin sauce

It is a very crazy design with a balance shaft before the oil pump. There will be unnecessary breakdowns and the going gets tough. I think there are those who remove the balance shaft.

Differential heat expansion anyone?

There's a lot of unhappy customers at Barum.