Extent of rebuilding an engine

Do you want a reliable rebuild, or a cheap one? If you want a cheap one , second hand.
What are you after, standard rebuild or better performance or all out power?

All my rebuilds are strip, clean, measure then decide what I'm wanting to achieve and if I afford it.
Most people will tell you that no lip means you don't need a rebore, you need to measure the ovality and taper in the bore before you can make any good decisions as to where to go with this.
That's were a good shop for your machining will be the deciding factor, if it 's got an oval or tapered bore, rebore is the only way to go.
You can use most bolts/studs/nuts but always replace all head studs.
Bearing are cheap replace them
Rods, again what are your goals? if standard then "most "factory rods are good enough, again get them checked.
The heart of the engine, the oil pump, again these are cheap insurance, replace them
Reuse rings? if your that broke don't bother doing anything, get a second hand engine

Cars are the same, but because the stakes are lower than with aircraft, it's acceptable often to just run things until they stop working properly. If you want to do things properly you would still check tolerances on everything.

I replace rings, bearings if they are worn, I've not replaced them on one motor I did, but my engine builder friend pointed out they had no wear at all.

I use genuine head gaskets and front and rear mains seals.

The stress on tolerances is not that high with a Volvo motor, the cranks are already well balanced on a b230 for instance. The pistons if they are the same type (a-e) balance within a gram or too. But the different sizes are different weights. Which makes it fun to get them all even as most b230 use two different sizes of pistons.

I measure the bores and generally if there is cross hatching on the bores all the way around, they measure up pretty evenly, definitely not enough to be an issue. Even with a slightly worn bore on the thrust side but no where else that is usually only 0.02mm out from the other sides. I use a bottle brush style hone tool. The other style is not as effective and not used by engine builders to my knowledge.

Over thinking an engine rebuild is what kills things I've found.

If you send off to a machine shop, they can cc the head and Pistons and get your total compression, the squish is an important factor for an engine build even with stock parts on a Volvo motor. The stock elring is about 1.2mm compressed. The latest motor I've built is at 0.95mm squish and 8.9:1 c.r. For a turbo motor from a non turbo b230fb with 531 head.

The oil pump was measured and replaced due to wear, and I had to go up a size on one piston. I reused 13mm rods also. The rods and Pistons are very durable and unless they are worn out you generally don't touch them. Other you move onto another block

Head bolts are not torque to yield so can be re used when they are measured for stretch.

The crank did not need to be touched, the crank on these motors are very good and aren't soft like old Australian motors that get ground down on a first rebuild. They also suck for balance unlike the b230.

For a home build, rings and bearings and shave the block and head and reassemble is good, to get the tooling needed for a low power rebuild with stock parts is overkill. If you did plan to go for over 300hp at the wheels. Then h beams and forged pistons and having the engine shop balance everything is worth it vs the cost of buying ask the tools needed still.

I was told by a few people to never reuse rings or big end bearings.

If it's something I'm going to keep for a long time, or a competition engine, these are my minimum mandatory requirements:

Reusing bearings? Never.

Reusing nuts/bolts/studs? Depends which ones. On a redblock, flywheel bolts, head bolts, and any bolts placed under significant stress or load are replaced. Nyloc nuts are replaced. Fasteners not subject to significant loads aren't (e.g. sump pan bolts, etc). Exhaust manifold nuts replaced with VW copper nuts.

Reusing pistons? Depends if a rebore is required, or if there is damage, or the design is crap, then yes. Rings are always replaced. If a rebore is required, new CP pistons and matching rods sourced from JVAB are used, with the nice thick gudgeon pins.

Reusing rods? 9mm rods are never reused. If the bore is okay meaning the pistons are being reused, the replacement 13mm rods are crack tested and shot peened by a shop that is certified for doing aircraft work, not a hot rod shop. Even new rods are crack tested, and shot peened if okay.

Reusing oil pumps? Depends on the age and mileage. If it's a young, high volume Penta / turbo version, measure it according to the book, and give it a new ball and relief spring if the gears are in spec. If it's old or a little one, it gets a brand new Melling M181. In all cases, it gets the iPD drive collar and Penta-spec oil pipe seals when being replaced.

Reusing piston rings? Never.

Reusing other things that you have forgotten? Sorry, my psychic powers don't work. :) But let's guess and talk about other components.

Reuse crankshaft? Generally. It is sent for shot peening though if it passes crack testing. If it shows signs of problems, it's replaced by a Penta crank which is also tested and treated the same way. Then it's linished, and finally balanced with the whole reciprocating assembly including the flywheel.

Camshaft on OHC engines? The cam is checked for wear and replaced only if it's worn, or if it's already planned to be replaced by a better profile.

Camshaft on OHV engines? The cam is generally replaced because it's likely to be worn, and in old-timer engines because there are better profiles available. New lifters are always used with a new cam. Cam bearings are replaced.

Pushrods / rockers on OHV engines? Pushrods are reused if they're straight. Rockers are shot peened. The rocker shaft is examined for wear and straightness. If rules / budget allow for competition engine, go roller rockers.

DOHC tappets? Replaced with new ones. Old ones are disposed of; I do not take risks with interference engines.

Cylinder block? It is decked, line bored, hot tanked, and flushed at absolute minimum.

Welsh plugs / freeze plugs? Replaced with brand new ones.

Felt seals on OHV engines? Replaced with neoprene seals. Prayers and gentlemen's agreements work better at retaining oil in an engine than felt seals.

Cylinder head and valves? The head is crack tested, tested for flatness, bigger valves are installed if required along with the 5 angle valve seat machining and lapping. Old valve springs are replaced. Old or not are tested regardless for equal pressures. Valve stems and guides are checked for wear and the stem seals are replaced of course. Retainers are checked for wear. Chambers are cc'ed, and ports are matched to manifolds and equally to each other.

Timing belt? Replaced with best quality available.

Timing belt tensioners? Replaced with new ones; No exceptions. Old ones are put in the emergency spares pile if SOHC, or disposed of if DOHC.

Water pump? Replaced with brand new Hepu pump. No exceptions. If a Hepu is on the engine, it goes into emergency spares; if anything else, it is disposed of.

Engine sensors? Replaced if old or if the sensor is known for failure; retained if new and age is known.

Crank pulley / harmonic balancer as applicable? Replaced if old and if the type is subject to fatigue; otherwise clean an re-use.


Expensive? Yeah. Overkill? Maybe, but a redblock engine done this way will go, keep going, and survive almost anything, as long as it's maintained, kept oiled and coolant-ed and otherwise maintained, and not abused too crazily.

'Do it once and do it properly' is a mantra which pleases me. That way, since I'm in my twilight years, it will never need to be done again in my lifetime.

jlfents;122119 wroteHowever, I want to go deeper and know why things wear - specifically to a block.

Sure.

How much does one thermal cycle affect a block? Not as much as many heat cycles. See answer below.


How much does numerous thermal cycles affect a block? Old engine blocks tend to better and stronger than new ones, because of the heat cycle process. It was said that years ago, BMW used to used old road car engine blocks for their 1200BHP F1 turbo engines, because the number of heat cycles had settled the metal and so the blocks were less likely to crack.

At what point does a block deform and warp? Usually when a conrod goes through it. :D Seriously though, Volvo cast iron redblocks are not prone to warping as such; however, the blocks do deform at very high RPM, causing them to spit out welsh plugs. It's the alloy heads, rather than the blocks, that tend to warp after they've overheated or when a head gasket has blown.

What causes a block to go out of tolerance? With a redblock? Damage, basically, caused by abuse and lack of basic maintenance.

From what I gather, not always do the journals in the block need to be corrected in terms of alignment? If so, then providing good maintenance and no overheating has taken place then shouldn't the alignment and straighness never go out of whack? The journal alignment doesn't tend to go off, it tends to be a product of the quality of the original manufacture, and what kind of tolerances the maker was prepared let slip through to the showroom. If the alignment is found to be off, it means it wasn't ever that good. Volvo blocks tend to be okay in this respect, but a line boring by a competent machine shop never does any harm. Doing that simply removes the manufacturing tolerances and puts it back to the blueprint spec.

And similiarly, how does the deck flatness change? It doesn't change, either, unless the block is damaged. However, the deck heights of Volvo redblocks hasn't ever been that brilliant out of the box. Sure, they've flat, but the deck heights aren't consistent with the blueprints. This is one area where the competent machine shop can make serious improvements.

Happy to be professionally corrected on any of the above; I am just an enthusiast with big ears and gray hair.

Yes you are talking massive overkill bgzm, no need for shot peening a crank or line boring these motors. Especially on a stock rebuild.

Theory gets in the way of reality I find. Much like the asking about thermal cycles etc, basically of its overheated a heck of a lot in an na application, sure it will be cactus, move on. If the bores aren't worn, then the chance of anything else being wrong is very low.

Vee_Que;122013 wrote
the cranks are already well balanced on a b230 for instance.

Have you ever heard of anyone grinding a crank so its perfectly symmetrical.... which would make it perfectly balanced?

Would they do this is a racing engine?

How would it be perfectly balanced? The counter weights are there for a reason... When they are cut down they aren't removed either, but the engine will be faster to rev and have no engine braking power. They can't be removed due to the design of cranks in general.

Cranks are cast. So they are not perfect. "symmetrical" doesnt mean grinding of the counter weights. I meant putting the crank into a CNC machine of some kind and making the weights exactly the same shape and size and thickness.

Each counter weight would be perfectly identical. Since its impossible as far as i know, to determine how much each counter-weight weighs, grinding each counterweight to the exact same size, might make sure that each counterweight is the same shape and weight.

The shape of the counter weight also determines its balancing.

Casts are only accurate to a certain degree. I was wondering if anyone had "balanced" a crank to such a precise degree.

Canoe, yes you are correct in your description. There are always slight density and shape difference in the crank. For previous projects we have reshaped a V8 rolls crank casting as you described. In other work we have remanufactured complete replacement cranks by CNC machining from modern steel billet.

Both process are pretty expensive and you would want to have a good reason to need such a precise crank. Standard dynamic balancing should be fine, as used in most cars on the road.

Isn't crank balancing also about matching the mass of the counterweights to the mass of the reciprocating assembly (piston, rings, rod)? At a guess you would measure the crank's own CG by spinning it unloaded on a machine and measuring deflection at each bearing surface.

1971_144GL;122253 wroteCanoe, yes you are correct in your description. There are always slight density and shape difference in the crank. For previous projects we have reshaped a V8 rolls crank casting as you described. In other work we have remanufactured complete replacement cranks by CNC machining from modern steel billet..

Hi There,
so what was the results in doing as you described?
Were you able to tell that such a finely balanced crank made any difference?
How could even tell that it did?
The only way i can make a comparison is a wheel/tyre needing balancing. It takes more energy to spin a non balanced wheel.
With a crank, it would take more energy to make it spin...and effect the pistons. It might be microscopically "out", but it adds up.
Also as a theory about this, it would take longer to rev up.

You also point out, that there are variations to the density of materials in each counterweight.
How could you measure that...and make allowance for it?

So would be interested is anything that was the outcome of doing this.
Thanks

Vee_Que;122156 wroteYes you are talking massive overkill bgzm, no need for shot peening a crank or line boring these motors. Especially on a stock rebuild.

Yeah, well, my toys aren't rebuilt as stock, so... there's that. :) And by the time I get to the ones I'm tinkering with, they've been 'round the block a few times, like, a half meg or so, give or take, so they're pretty bloddy tired by then. I'd like my engines to outlive me, no matter how much snot I give them while I can.

jamesinc;122263 wroteIsn't crank balancing also about matching the mass of the counterweights to the mass of the reciprocating assembly (piston, rings, rod)? At a guess you would measure the crank's own CG by spinning it unloaded on a machine and measuring deflection at each bearing surface.

This method is how I've briefly seen engine internals being dynamically balanced by the late Stan Sainty many many years ago, back in the mid 1980s. A friend was getting an 1800cc Gemini engine built over there and while we were there checking on the progress of the build, he had the crank on the balancing machine. It wasn't long after that engine was done that Sainty engines began to dominate the drag racing scene.

All of this theory sounds great but at the end of the day not many people here have access to the tools and knowledge being talked about.

On all the engines I've put together (3) ive just torn them down, cleaned everything really well, checked for wear and replaced as needed and go go go. Both of my redblocks ive built have driven and survived just fine. They are just tractor motors.

If you are building something that will be spinning to the moon and back then by all means get it pro built but at that point you probably arent the home garage mechanic and if you are you probably have access to the machinery and knowledge.

Dont over-complicate this. Tear the motor down, clean it, replace all the bearings and the rings. If the pistons look bad then get new ones and have the cylinders bored and honed to suit. Slap on a seal and gasket kit and go go go. Quit analysing everything and get your car on the road. You could just as easily pro build a motor and blow it up the same as a quick build.

jamesinc;122263 wroteIsn't crank balancing also about matching the mass of the counterweights to the mass of the reciprocating assembly (piston, rings, rod)? At a guess you would measure the crank's own CG by spinning it unloaded on a machine and measuring deflection at each bearing surface.

Yes, if you fit lighter pistons and rods this is what you do to balance them out, take steel off evenly. V engines need to be balanced with simulated weights because of the fact you have two rods and Pistons on one counter weight section. A straight 4, 6 or 8 does not need that. It's an automatic tale an engine builder will tell you to make money.

Otherwise knife edging cranks is done on a street engine reduce the mass, I'm conjunction with lightening the rods and Pistons.

My balancer only does these sorts of jobs and as I said, he spins the b230 crank up and they are not out of balance to itself, no vibration. But when you put a flywheel on and front pulley they do become unbalanced.

If you were to go further and to the effort of reducing the weight of a crank by 50% you're not going to know each individual throw is going to be even, only the total mass when spun up. And then you have a big heavy flywheel on the back of the engine as well as the front crank pulley. And the stock pistons and rods or even aftermarket performance ones. Lighter is not always better though as you will lose all low down torque and need to rev the engine to get off the line and to keep an engine at cruising speed is a lot harder. Just like in grand tourismo when you go for the stage 3 lightened motor, it's sometimes slower, and in real life, weaker. It's not needed on a street engine.

http://www.hotrod.com/articles/ctrp-0410-crankshaft-developments-race-engine/

Usually they are rebuilt because most guys run turbo motors, and they are worn, so you rebuild another motor without the wear and put new rings in and turbo pistons or upgraded rods and Pistons which come from yoshifab.com as the easiest source. John v is impossible to get onto I find. That is my reason to do motors for people and myself.