Modern pistons for old engines

[Reidar]

Some time ago a fellow car enthusiast posted some pictures of a piston and conrod that csught my attention. It is from the earliest “new Mini” called the R50(w10 engine) and is 77mm and only 24,9mm compression height. pin is 19mm.
The conrod is 131,5mm. Interrestingly the minis crankshaft have 44mm conrod journals just like Renaults Cleon/Sierra engine.
Both pistons(Mahle) and conrods is light and piston rings are thin. They are flat top without cutouts for the valves. Not sure if there is material to cut sutch.

This piston and connecting rod combination is a bit short for my C2J Superfive engine but I have played with the idea of fitting a Brazilian CHT crankshaft.
Theese were derived from the Ford Corcel engine from the late sixties. The Corcel were developed by the Brazilians in colaboration with Renault and is technically similar to R12.

The CHT1600(1540cc) had 77mm boring and 83,5mm throw, and increase of 6,5mm over any Cleon produced by French Renault. To pompensatete they have about 3mm lower pistons.

This Mini piston and conrod combination put in an othervice standard renault C2J engine will place the top of the pistons 9,1mm down the bore from original. Probably not a good idea.
If one used the CHT1600 crank the piston tops would still be 5,85 lower in the bores. The longer throw would compensate the compression to some degree but not good for squish.
Would it be possible to deck the block by 5-6mm without running into serious problems?

I have not studied the lower capacity Cleon engines. For what I know theese Mini parts would be good candidates for those..

I have been looking for some longer rods and came to think of a low capacity CHT engine. It has 138mm connecting rods. I asked a Brazilian CHT expert and he confirmed that he used theese conrods on the CHT1600 together with some GM pistons allmost identical to the Mini ones.
Getting anything from Brazil is a hazzle but hopefully there is a set on the way soon.

The CHT1.0 conrods have 20mm pin hole witch means some sort of bush is needed to fit the Mini piston with 19mm pin. Both are originally interference fit in the cronrods. I understand drilling up to fit a bronce bush and make the pins fully floating is the most common solution. But I cant see s good solution how to lock the pins in the pistons. No circlip grooves and little support in the pistons for teflon plugs.

 

[PeterT]

Why not buy off-the-shelf forged pistons from CP-Carrillo (SC7515) and get custom made rods from Argo, Morpeth, NSW? I've had two sets made now. They're nothing short of spectacular.

 

[Reidar]

Why not buy a brand new car from the showroom?

I have allways been more attracted to the idea of finding solution adapting standard and used parts instead of buying fancy custom ones.

My results might have been higher if I bought special parts. It might even have turned out cheaper. But it just don’t appeal to me.

 

[schlitzaugen]

Hehehehe. You are a man after my own heart. Check out Uncle Tony's Garage on Utube, you might like it. He knows how to do it on a shoestring.

Peter likes to build performance engines that is why his advice is often point and shoot.

Frans from SA/NZ (you know him) is a combination of you two. He uses stuff already available and builds amazing engines with it.

 

[PeterT]

@Reidar, I admire your philosophy, but in my experience, it rarely works out that way.

Pistons
In my experience with PSA engines, the pistons rarely wear out. The bores and rings wear instead. A less fastidious engine builder would hone the bores and fit new rings. The honing process would typically remove 1 thou in diameter, which would increase the ring gap by 3 thou. People rarely make the effort to source ungapped rings and buy off-the-shelf, pre-gapped rings. The result is excessive blow-by and rattling at startup. Whilst this might be acceptable for a track car, it's not for a street registered restoration. The cost of replacement oem rings is well on way to 0.5mm oversize pistons, which include new rings in their price. Correctly bored and honed, along with correctly gapped rings, the new pistons provide an "as new" condition.

Rods
2nd hand rods are also a false economy. Again, a less fastidious engine builder would fit bearings and go again, fingers crossed and hope for the best. However, the cost of closing and honing the big ends and fitting new rod bolts, is again well on the way to the cost of new rods.
I've built some beautiful engines using standard rods, but always recondition the rods as part of the process. A custom rod also easily fixes your rod length problem.

Just my 2 cents.

 

[Reidar]

@schlitzhaugen: Thanks for your friendly comments. Frans threads have indeed been me favourites in here. And I have noticed that he also use more fancy parts from time to time.

@PeterT: Thanks for your constructive input. If one were to build a good engine in a resonable amount of time I’m absolutely with you. Especially if it were build for a customer or to use in racing.

 

[RINGER]

We often used more modern designed pistons in very old engines, to get reduced weight, better fitting clearances, & also often trimmed semi finished pistons to fit.
Many were interchangeable & gudgeon to crown was important as was skirt length or cut out.
Be aware current off the shelf piston rings meant to fit numerous applications often are gaped well above .003"per " of diameter (not desirable) whereas new rings always had to be filed to get .003" per " of diameter.
Also any used con rod should always have the big end resized - costs peanuts in the scheme of building a good long life engine. JG.

 

[Reidar]

Thanks both RINGER and PeterT for the heads up regarding the pregaped rings. Will try to get ungaped chrome moly ones.

The need to resize conrod big ends were new to me.
Unless I’m getting ripped off there will soon be a set og unused 138mm CHT1,0 conrods on their way from Brazil.

I desided for some slightly different pistons from the supercharged Mini. Mainly because they have 21mm interference fit pins. Easier to ream drill/ream up to press fit then to drill up to 22mm, bush down to 19mm fully floating with no good way to lock them.

 

[RINGER]

From a used engine the con rod big end is always slightly oval. This is from running up & down ~ stopping & starting.
That means when you fit a new set of slipper bearings to a used con rod there is not enough 'bearing crush'.
Insufficient or none can eventually cause spun big end shells & ruined crank ~ perhaps a thrown rod!
Stretched bolts & Resizing Con Rod Big Ends:

This is not my art ~ Bearing crush:

This bearing crush also gives good what is called 'shellback contact' for good heat transfer.
Pulling old bearings & seeing splotches of shiny & dull @ the back of the shell means it was not getting such contact.

 

[Greenpeace]

I might be just lucky.

Had an old 318 Valiant motor for many years. All stock internals, which at the time were 35 years old. Fitted bigger second hand valves out of a 360, big solid cam that I bought second hand off a mate, second hand 340 valve springs (from the same mate). Second hand extractors, intake and carby. Flycut the pistons in situ using an old head fitted with bigger Chevy valves that I cut angled teeth into. Bolt it down with an old gasket, stick an O-ring on the valve stem, set up the required gap between the O-ring and the top of the valve guide, chuck on the drill and start cutting till the O-ring touches the guide. The flycuts turned out as good as any milling machine. Knock the pistons out, quick hone, fit moly rings, new big end shells and timing chain (mains were fine) back together, throw it in a 2 ton Rambler and hit the road.
Had the car for 7 years, used to regularly spin it to 7500 rpm, ran 12.8/9s at 108/110 MPH like clockwork.

I've built plenty of Holden, Chev, Ford and Chrysler V8s and sixes, all for my own vehicles (as well as the odd 4 cylinder), with much the same approach as above (swap meets were the source of many used parts). Always built for performance, I've only ever rebored 2 engines (out of dozens) same with cranks, only had a couple reground, never had rods resized other than a 302 to 351 crank kit I once bought came with resized 351 rods. All these engines were built to rev to 2 to 3K past the stock red line, which I regularly did.
Engine failures? Other than the odd head gasket, a grand total of zero. I broke some rings in a Chrysler motor once, but that was my fault for getting a bit too ambitious with the nitrous oxide jetting.

I've supercharged several of the above builds as well, with no failures. I always fit a high volume oil pump, so long as you have good oil pressure the bearings should never touch the crank.
Some of these engines needed minor mods to either improve the oil return back to the sump or reduce the oil supply to the top end. SB Chevs and Ford Clevelands are well known for filling the top end with oil at high revs (thus emptying the sump) as the stock circulation system is not designed for these engine speeds. The end result of course is a spun bearing or thrown rod.

I might have to buy a lotto ticket.

 

[RINGER]

You will also break top rings should the ring ridge, if there is one, is not removed, when new rings are fitted.
Anyone can do whatever they like/wish, but licensed repairers [or otherwise, doing work for customers] can't afford come backs or re-do's plus some of us were taught & taught others how to do these type things properly, thus ONCE.

 

[Greenpeace]

You will also break top rings should the ring ridge, if there is one, is not removed, when new rings are fitted.
Anyone can do whatever they like/wish, but licensed repairers [or otherwise, doing work for customers] can't afford come backs or re-do's plus some of us were taught & taught others how to do these type things properly, thus ONCE.

I have a ridge remover when required, you normally work this out when removing the piston/ring assembly.
My father was a mechanic back when mechanics fixed everything, not a just bolt on on a new part.
I was a sponge in my youth and my father taught me to how to rebuild everything "the right way".

I have 2 nephews who are licensed mechanics, one in his late 20s and the other in his late 30s.
One works on cars and really has little mechanical knowledge, he changes oils/filters and bolts on new bits as required. The other works on trucks and has a pretty good grasp on things.
Mind you you they both think a carburettor and a set of points are some kind of sorcery.

As licensed mechanics to doing it properly and ONCE?? I work on my own vehicles for a reason.

My wife on the other hand has had new cars from various manufacturers over the years and thus has them serviced at the dealers.
I check them over every time she gets home after a "service". I could write a book about the things I have found, done, not done, shouldn't have been done as well as left undone.

 

[RINGER]

I agree with most of what has been said.
Apprentice 1962 & taught by WW2 blokes who kept em going with no spares
Taught us what they had learned.
1970's WA TAFE taught in a similar way starting with hand tool skills

1990 Regional NSW TAFE not even a lathe in training area. No hand skills or tool type use taught by modules on Computer screen.

Diagnostics (a properly 'experienced' and mechanics primarily learned skill) no longer exists without some programme. PAID FOR!

We reap what we sow!

 

[PeterT]

 

[Greenpeace]

Although it's easy to poke fun at the conversation the facts are we live in a sad world where tradesmen are taught less and less. Add to that the don't give two f#cks attitude that many have and it's hard to justify handing over $100 plus per hour for their services.

Mechanics, panel beaters, plumbers, electricians, builders, etc etc just want to get the job done as fast and as easy as possible so they can get paid as fast as possible.

When I raised my house I had to get the electricity meter box moved, the sparky I hired was an old guy recommended by a friend. My mate warned me not to swear around him as he was "very religious". All the main feed had to be replaced because the original electrician had used under spec wiring. The wiring behind and inside the meter box looked like a bowl of spaghetti. The "very religious" sparky swore like a trooper that day. Mind you his workmanship was impeccable.

The plumber I hired to do the ensuite work actually got the the shits when I called him to come back. I didn't think I was being unreasonable as he had used the hot water line to supply the toilet cistern. The concrete cutting work he did for the pipes under the existing slab didn't include replacing the termite protection. I found this out a couple of years later when the new ensuite got eaten out.

Panel beaters, I'm no panel beater but I now do my own work due to the endless disappointments I've paid for in the past. I can accept my own average job (that I don't have to pay for), but find it hard to hand over my hard earned to a "professional" that has lower standards than myself. Problem now is there is a yawning gap between the panel bolteronerers and the guys that have real repair and paint skills. A mate just got an old Buick painted by one of the latter. It was a pretty straiģht car to start with he just didn't like the colour, removed and replaced all the chrome himself. Got a flawless two tone black/silver paint job, but $30K???

Auto electricians? Most of them just want to replace the odd alternator and starter and maybe wire up a trailer plug or a set of spotlights on a "tough" day. I've ended up completely rewiring a couple of my own cars simply because I can't find an auto electrician that's remotely interested. "They don't make looms for that", "lot of hours in that", "try so and so" etc etc.

Any wonder there's a Bunnings on every f#cking corner.

 

[Reidar]

I came across a set of pistons from the compressor fed W11. They are slightly higher at 26,25mm but have 0,5mm dish. Top land is 4mm. Not mutch but they might be possible to machine down a mm or so if needed. The benefit is that they have 21mm fully floating pins with circlips.

I’m a bit worried though. Theese pistons with the 138mm Brasilian conrods and the Brasilian stroker (83,5mm) crank will have its crown 2mm higher in the bore than in a stock C2J engine. The C2J is 77mm stroke and have 37,5mm compression height piston like most 1,4L cleon engines but I do not remember how high they were at TDC. Hopefully a slight skim and/or a thicker gasket(1,9mm) will sort that out if they are a bit high.

 

[Wildebeest]

I agree with most of what has been said.
Apprentice 1962 & taught by WW2 blokes who kept em going with no spares
Taught us what they had learned.
1970's WA TAFE taught in a similar way starting with hand tool skills

1990 Regional NSW TAFE not even a lathe in training area. No hand skills or tool type use taught by modules on Computer screen.

Diagnostics (a properly 'experienced' and mechanics primarily learned skill) no longer exists without some programme. PAID FOR!

We reap what we sow!

Ringer,
Some time back now I would have a short session with my allotted apprenti following their tech day. I would ask, so what did they try to teach you today?
As the time went by I noticed that some things weren't being taught. Very little major component overhauls carried out. Simple things also, an instance was when the head kept falling off his hammer ! I showed him how to secure it by simple 'bumping' the handle on the bench. He was impressed, thought I was the new Messiah.

 

[driven]

Need to go Greener with the Bush Mechanic
All this steel is creating climate change.
Let's go Wooden Pistons instead DIY Piston

 

[Armidillo]

Need to go Greener with the Bush Mechanic
All this steel is creating climate change.
Let's go Wooden Pistons instead DIY Piston

Mallee roots? Huon Pine? We've got pretty good Ironbark up this way that might worth trying, although could be a tad heavy!

I wonder could you ceramic coat them?

 

[RINGER]

You may laugh but in the old days leather was often used in place of a worn out babbit bearing. Pulled down engines & seen.