Engine builders question

[Mikie711]

This is to do with bearing clearances. Specifically big end bearing clearances. Rover manual states, for oe rods and crank obviously, that the service limit for big end clearance is 0.025mm - 0.049mm. So I have a brand spanking new, never been used rover crank with "A" grade big end journals (type B crank BTW) which all measure between 48.00 and 48.02mm. Rods are THS single tang steel and there ID is between 51.62 and 51.68mm, slightly less than what Arrow list for the same type rod on their site. Bearings are Vandervell heavy duty, VP2's to you and me and are 1.82 to 1.86mm thick. So you would expect bearing clearance to be quite tight. But no, much to my dismay on measuring them with good old Plasta gauge I get clearances on all journals of 0.063mm (2.5 thou for those from the old school).
Now, to muddy the waters, so to speak, I read an article about a guy building a vintage Elan lotus twin cam engine using the very same bearings and he had his crank machined to give a clearance of 0.025" as I quote " to improve oil flow across the bearing in a high revving application".
My question to the collective wisdom that is SE, as I know a few of you out there have built, been involved with building, heard of someone building a race engine, is should I
1. try different bearings in an attempt to get he clearance down within spec, bearing in mind (no pun intended) that only the crank is oe.
2. Stop worrying it'll be fine.
3. Go for over sized VP2 and re-grind the brand new crank to get the correct clearance. (more bloody money)
4. Just fit OE bearings and hope the handle the extra revs (north of 8500) which I have been told they won't, again by QED.
There might be another option in that Vandervell used to make 0.001" over sized bearings for racing for this very reason. The fly in the ointment is that the Rover bearings are no longer made, they are special order according to QED. Going to phone Vandervell tomorrow and see what they say.
FYI this is only the dry build of the bottom end to check everything fits OK before it all goes for balancing once I start the proper build I will document it on here as it's a bit different from Steve's

If you got this far then well done as I have just re-read it all and it does go on a bit sorry.

Mike

[robin]

Mike,

No direct experience, but the numbers don't add up (as you no doubt know!).

ID of 51.62 - 2x bearing thickness of 1.86 (=3.72) leaves 47.90
ID of 51.68 - 2x bearing thickness of 1.82 (=3.64) leaves 48.04

That would give a range of clearances 48.04 - 48.00 = 0.04 at one end and 47.90 - 48.02 = -0.12

So at it's loosest it would be in spec (less than 2 thou) and at it's tightest it wouldn't really fit.

So is it to do with the surfaces not being parallel perhaps?

Cheers,
Robin

[Mikie711]

What I think we are looking at is bearing crush. The ID's is the only part that I'm not confident about as they were measured using a bore gauge/micrometer and a vernier caliper. Both gave the same reading with the bolts torqued. Spoke with Dave Andrews and he recons the extra 1/2 thou will be OK, I mean it is half the thickness of a nats bollock. Just weird the way it all changes when bolted together. Wish I hadn't bothered checking it now, ignorance is bliss and all that.
Anyway thanks Robin, kinda thought it would be you that replied. Going to go with the VP2's and see how the fair once it's running, which should be December sometime if I ever get my head back from Mr Farby!!.

Mike

PS more questions likely to follow as I come across them.

[Rich H]

Slap it all together and forget about it... (Please bear in mind I work mostly on 1980's Porsche 924s!)

I would imagine it would only be an issue if your oil pump was pap and couldn't keep the oil pressure up given it'll be flowing more through the bearing.

I take it the plastigauge was new?

[robin]

I assume you mean Rog? He's Fabry not Farby - though I might start calling him Mr. Farby just to wind him up

Rog is a top bloke and his results speak for themselves, but he does take on too much work, so you kind of have to factor in the extra weeks and months waiting for your head to come back. He responds to gentle encouragement though, so keep nagging You'll be pleased with the result I'm sure!

Cheers,
Robin

[Andy G]

could be wrong but i think his current lead times are a bit shorter

[Mikie711]

Probably would be if I wasn't waiting for my new cams to arrive so I can send them down to him, the head needs a bit of modifying to make these fit what with 12mm of lift an all

Rich, brand new oil pump, modified as per Dave Andrews page so should be up to the job. Can't find anybody with an uprated one although the later ones are supposed to be better. Probably fretting over nothing but thought it was better to check. And the plasta gauge was about 6 months old but should be OK as it doesn't come with a use by date.

[Mikie711]

Did my main bearings today as follows, read codes off block and crank, which were 21211 for the block and AAAA for the crank. This gave me all blue main bearings, 2 plain 3 grooved, in the block and a red, blue, red, blue, blue mix in the ladder.
Assembled the bottom end with oil rail and plasta gauged the bearings. As I have a spare head bolted that on for good measure. Stripped it all down and measured the clearance. All were hovering around 0.038mm. Number 5 journal was closer to 0.050mm so as I had a spare red bearing I swapped it in place of the plain blue in the ladder. Sorted.
Bottom end ready to go. Can't wait to get my head back.

One thing that came to light doing all this is if you are working out what bearings to order use the rover handbook for the engine. I used QED's web page that give the info on which bearings to use depending on the codes on the engine but it's backwards!!. All because I couldn't find my copy of the engine manual, you live and learn.

Mike

Next job: check valve to piston clearance. (once I get the head back)

[robin]

high lift/duration + big valves = better be careful on timing and clearances

IIRC <2mm clearance at TDC with standard valves. If you have the time to do it, I might consider assembling head with no valve springs, and only one piston's worth of valves actually populated - I guess you can hold them in with a couple of tie wraps or similar. Torque head down on old head gasket and then rotate engine to TDC (assuming you started with it at 90deg) - then see just how far you can move the valves ... don't forget to put engine back to 90deg and clamp valves to head, before removing the head again

It's well worth doing, because with that type of cam and engine, I assume you're going to be looking for a lot of overlap, and you cannot have that without clearance, but you don't want to be overly conservative either, or you're missing out on power generating opportunities

Don't forget to allow a few thou for heat expansion and rod elasticity

Let us know what you find - it's all good data for the memory banks

Cheers,
Robin

[Mikie711]

Was planning on doing it with only the middle springs in and dial indicator.
Plasta gauge the valve pockets in the pistons with 2 different thicknesses.
install cams retarded
Engine to TDC
set dial indicator on valve cap
bring cam to full lift on vernier (assuming it doesn't touch before full lift in which case I will no how much short I am)
remove head and check clearance
Need to check with Dave the minimum clearance required but I think the pistons I have are from the later omega batch and they are supposed to have deeper pockets. Still going to check all 4 pistons with all 16 valves just in case.
With this much lift I really have no option but to check the whole lot. If one is even slightly tight it could spell disaster on overrun if not before.

[robin]

More professional than my approach.

You won't reach full lift at TDC I believe ... the clearance is more like 2mm not 12mm ... even with deeper piston pockets ... however, even the wildest overlap settings wouldn't call for full lift on either valve at TDC (unless you're planning on 100,000 RPM!).

I'm guessing you won't be looking for more than 150 thou at TDC on either valve, no?

Cheers,
Robin

[Mikie711]

When I said bring cam to full lift, I meant its lift at TDC. Not sure how much clearance is acceptable, think Dave mentioned 200 thou but need to check that before I start. Not to bothered if it is tight as everything has to go for balancing before final assembly so getting the pistons machined will just be one more job.

Mike

edit: just checked the piper spec sheet for the cam inlet is 3.63mm and ex is 3.05mm lift at TDC. Full lift is 12.22mm and 12.17mm in/ex at 104 deg ATDC for the inlet and 108deg BTDC for the exhaust.

[robin]

So less than 150 thou then, but only just high rev limit required - cannot wait to see dyno results - should be a monster if you've got the components to go with the cams

Cheers, Robin

[Mikie711]

Quick run down of engine spec so far:
Sabre Heads ported and modified VVC head (original valve size)
Piper cams solid followers, blanking kit and double springs
Verniers
QED 42mm DTH Throttle bodies with 110mm trumpets (might end up being 40mm depending on air box)
Pico 330cc injectors
Alloy fuel rail and adjustable pressure regulator (may need a secondary in-line fuel pump)
Brand new Rover crank
Fedral Mogul liners
THS Steel rods
Omega forged pistons
Flowed and ported oil pump
Lightened flywheel
AP racing 250bhp clutch
Piper timing belt
Payen BW750 double pinned silcon head gasket (D. Andrews recommendation)
janspeed 40mm 4-2-1 manifold and system. (This might get changed as it may have unequal primary lengths)
Xoomspeed Xoombox data logging, launch and traction control
Emerald ECU
PLX wideband lambda (this thing is the dogs danglies, so easy to install)
VP-2 bearings.
Lotus sport oil cooler
probably a bernard scouse airbox
All new temp and pressure sensors to included oil temp and pressure senders for data logger.
Converted to twin coil ignition.
Balanced and if required piston pocket machining by Agra Engineering.
Not been a cheap 6 months getting all the parts together. The good thing is there is a wealth of information out there for the Rover K, it's really a question of how deep are your pockets.
Hopefully once all bolted together it will produce good power but retain usable torque and not be to peaky.
Some details to iron out like weather to install and thermostat to control oil temp or not, be difficult as I am not using a sandwich plate rather a new oil filter housing. Wiring in the data logger/launch/traction control is taking so thinking about and is hard finding the right connectors to plug into rather than splice the engine loom. Also haven't decided on which thermostat to go for, weather standard PRT, elise parts, QED or PTP kits. Not sure but hink they are all pretty much a muchness so be down to price/looks at the end of the day.

Now on the hunt for a cheap standard Toyota 2ZZ-GE engine and start all over again

[robin]

Hi Mike, as you no doubt know, the deeper the air box the more power you'll make - Skeggsie's race car had an airbox that reached most of the way through the boot (it was making a lot of power - 260 or so IIRC).

What they did find is that uneven length trumpets improves power - the middle two are a different length from the outer two - cannot remember which way around, but I suspect it was the outers that were shorter than the inners ...


Cheers,
Robin