[engine_work] Xu9j4 Mi-16 Rebuild

[petert 586]

Is there some trigonometry involved?

None. Just serious measuring.

 

Put one inlet valve in head, cyl #4, no spring, no retainer or collets.

 

Set piston #4 at TDC.

 

Carefully place head on block with gasket.

 

Torque down to 1st stage only.

 

Set up a dial indicator in line with the inlet valve.

 

Drop it on to the piston and measure the distance it falls.

 

From this total distance, subtract the lift @ TDC figure. The result is the distance between valve and piston at TDC. Note that it actually gets closer after TDC. So this is really a rough figure to get you in the zone.

[Anthony 1,003]

What sort of figure is sensible minimum for valve-piston clearance (ie what's the minimum figure once the cam lift @ TDC figure is deducted)?

 

~ 2mm / 0.080" rings a bell, but not sure if it needs to be a little more for hydraulics.

[petert 586]

0.080" is correct for a hydraulic inlet, although you'd want to be seeing 0.090" at TDC, as it will get approx 0.010" closer between 6-10 deg ATDC.

 

Thus for my Stage II inlet, you'd need to have 0.105" + 0.090" = 0.195" (total) at TDC for safe motoring

[kyepan 291]

so 0.254mm, cool we will check this.

[Anthony 1,003]

You having a maths fail again Justin? 0.195" is a whisker under 5mm

 

Calculation is the figure in inches multiplied by 2.54 which gives the figures in cm, and then multiply by 10 to give the figures in mm, like so:

 

0.195 x 2.54 = 0.4953cm

0.4953 x 10 = 4.953mm

Edited April 24, 2013 by Anthony

[kyepan 291]

Yep, failing you're calculation is correct

[kyepan 291]

Cometic MLS gaskets - seem to bring with them a great deal of debate about surface prep and sealant, either spray on copper or hylomar..

What are peoples experiences on here? I realise one person (who i can't remember who) was not happy, but others have been fine.

 

The gasket has a thin viton coating as standard... and specifies a 50ra surface (i don't know how smooth that actually is... )

 

Any thoughts?

 

and some head bolt stuff.

 

Another muddying-the-waters chunk from Engine-builders.com...



...

...
"Don’t go by what is in the ‘book’ (repair manuals) for clamping," Chris Brown, director of specialty products for ARP explains. "Who knows where those torque specs came from?" If you’re using specialty fasteners that have much higher strength than OE fasteners, then these torque specs will have no relevance. "These specs could have been lifted from an OEM bulletin somewhere," warns Brown. "And you’ll find out pretty quickly then, if you snap a bolt or stud, that it was wrong."
Most specialty bolt manufacturers provide detailed instructions with their kits explaining how to install, and torque their bolts, as well as what type of lubrication to use. Some even include charts showing how much clamping load to use.

Very few engine builders know how much clamping load they need, says Brown. In many cases, they’ll measure the clamp load by using torque values, and this, in turn, creates some confusion. “Say you torque a 3/16˝ bolt; you can torque it to 100 ft.lbs. if you don’t put any lubricant on it because it generates so much friction. But, if you put a dab of moly lube on the threads and under the head, you may only be able to torque it to 30 ft.lbs.," Brown explains.

Some of the confusion surrounding torque and preload comes from not knowing the difference between them. Torque is just the twisting force. It’s an index number and does not equal load. You also have to compensate for the friction coefficient of the oil. Therefore, torque values should be accompanied by the specified lubricant for the most consistent results.

Carroll Smith agrees that friction plays a vital role in achieving proper stretch and clamp load. And if you use a different lubricant than the one provided by the bolt manufacturer, Smith says, "good luck." It’s critical to use the correct lube because it was designed for the specific bolt and application in many cases, especially in high performance applications. Many high performance bolt manufacturers include the lube with the bolt kit when you buy them.
"Obviously, the more slippery the lube is, for the same amount of torque you’ll stretch the bolt further, and vice versa," says Smith. "Proper lubrication of head bolts doesn’t really matter as much in a vintage 289 Ford – but if you’re assembling a true high performance engine, you’ve got some real pressure inside of those cylinders.
"If you’re running a 13:1 compression engine at 9,000 rpms, you’re trying to lift those heads right out of there. If you’re running a 9:1 engine at 4,000 rpms, you can practically hold it on with nails! A little difference is huge; the devil is in the details," Smith quips.

"Thirty weight oil (a common bolt lubricant used in many rebuilding facilities) is a little more inconsistent because it goes away fairly quickly under extreme pressure applications, like high performance engines are,” says ARP’s Brown. A 7/16˝ head bolt can, for example, generate a clamping load around 14,000 lbs. – a significant amount of stress.

Ron Hukari, a racing engineer with SPS Technologies, says, "with sealing, a very important thing for guys who aren’t necessarily building engines for NASCAR or Formula One, is getting a good, consistent product and installing it correctly. Metallurgically the yield strength of the bolt needs to be consistent. If you have a problem with heat treating and don’t get enough yield strength, when you go to tighten to a certain torque, you’ll find the bolt doesn’t have the preload you think it does and you’ll have a leak."

There are several things that affect clamp load, according to George Lorimer, a former engineer with GM’s Powertrain Fastener Lab. In an article by Lorimer posted onwww.boltscience.com, he states that one of the problems with clamp load is: "the second you take your wrench off the tightened head, it starts to decrease." Furthermore he claims thathead bolt clamp loads can vary up to 40 percent when torque control is used. This "relaxation" effect can vary from bolt-to-bolt, thus the need for a proper tightening strategy.
Some of the factors that Lorimer says influences the relaxation effect are: Surface finish, Temperature - high and low, Type of joint: Gasketed (soft), Material of joint (hard or soft), Combination of metals (steel/iron vs. aluminum), Initial preload, Joint strength (spring rate), Bearing area under bolt head, Vibration, External loads to the joint.
Decreasing the variation of clamp load requires a good tightening strategy. One way that has proven effective is to "cycle" the fastener. Torque cycling bolts can reduce the relaxation effect by up to 50 percent or more.

DO THE TIGHTEN UP DANCE
Torque cycling – in essence, "breaking in" the stud or bolt – helps "ease" the threads. At the microscopic level, fasteners have peaks and valleys in the threads. Thus, when torquing, you have to overcome a certain amount of friction first.
According to the experts, new fasteners have a higher friction level because they have not been burnished. New bolts need to be seasoned with the threads it goes into. After this process, the grain will compress at the surface, which reduces friction. The proper torque cycling procedure is to tighten and loosen about five or six times, but only to 50 percent of the final torque value each time.
"You stabilize the friction coefficient after repeated tightenings," explains Brown. "This, correspondingly, increases the clamp load because the bolt or stud will stretch more. You’re overcoming less friction. More of your torque value is going into stretching the fastener, less into overcoming friction," ARP’s Brown explains.
legendary engine builder Joe Mondello of Mondello Technical School in Paso Robles, CA also points out a critical but often overlooked point: "Once you torque cycle a fastener, the nuts and washers must go back to the same stud because they will be married to that particular bolt or stud. When you go ahead and torque them down after following the recommended cycling procedures, you’ll be at about the fifth cycle, and you’ll be at the maximum clamp load and maximum distribution of the bolt or stud."

Torque-to-yield bolts in OE applications are usually only used in the most critical areas like heads, rods and mains, say these experts. For the manufacturers it comes down to a cost savings issue, but that’s not the case with racers because their cost is on a smaller scale. It is a way of wringing out every last bit of clamping load out of a relatively low strength bolt.
Torque-to-angle is a better method of tightening – it’s more accurate than straight torque. With straight torque, friction impedes consistent clamp load values. So you have to overcome a certain amount of friction in order to achieve load. "Friction is very hard to predict, too, even with special lubricants to try and control it," says Brown.
Brown believes that the inconsistency of straight torque is why torque-to-angle is a better method. "With torque-to-angle, you typically have very low torque values and then a rotation through a certain angle based on the helix or thread pitch to achieve a specific amount of load," he explains.
"With our fasteners, because the strength is much higher, the idea is that we select material that will generate the correct amount of clamping load at 75 percent of the yield strength of the fastener. With torque-to-yield you’re stretching it to the point just before it breaks." The advantage of very high strength specialty fasteners is that they reduce the chance of failure by not being as close to the limits of the material, say both Brown and Smith.

"With fasteners it’s a question of knowing just a little bit," says Carroll Smith. "You don’t have to know metallurgy, but you need to know the facts." Although it wouldn’t hurt to know the metallurgy, the important thing is to know how to get the best, most consistent clamp load.

Edited May 14, 2013 by kyepan

[kyepan 291]

http://forum.205gtidrivers.com/index.php?showtopic=122196&hl=cometic

 

i notice tom fenton recommends wellseal. Tom which bits do you paint it on?

[welshpug 1,657]

any metal to metal joint, like gti6 cam ladders, I would not use on steel gaskets however, they have a layer of sealant on them already, that's the black stuff as you mentioned above

 

why are you asking?

 

 

JUST BUILD THE BLADDY THING

 

 

 

Sandy may be able to illustrate the surface finishing quality, it is important for a steel gasket.

 

 

have you measured your clearances @ TDC yet?

Edited May 15, 2013 by welshpug

[kyepan 291]

i already asked sandy - he doesn't use them! that is telling in itself.

[welshpug 1,657]

The cometic ones specifically I take it you mean?

 

I know he does use standard Peugeot gaskets, most of the iron block ones are steel, alloy block fibre.

[Sandy 191]

Yes, I use OE gaskets on all my engines, never had an issue to date. Finish and trueness of the faces is important, I surface grind for ultimate precision. Liner protrusion equally important on alloy engines, including the liner seat condition.

[kyepan 291]

it lives

[kyepan 291]

Right, so, here's the proper update, it's a long story so i'll keep it reasonably brief.

 

I bought the cams from ant as a pair, who in turn got them from someone else, as a pair, it turns out they are a pair of cams, a pair of exhaust cams, we thought the inlet was an xu10 cam hence no distributor key way, neither of us knew!!

 

So muggins here sets about fitting the cams, here's just before i clamped them down.

 

Because I was using verniers, i had to set the rough initial position of the cams using some standard pulleys and the locking pins.

Then set the verniers to roughly the center of their travel and popped them on. Had i known what i knew now i would have noticed that the inlet cam was nearly 180 degrees out of phase, 90 deg after the inlet, rather than about 90 before it.

 

Here's an utterly cringeworthy self effacing twatograph I was going to put on facebook, it shows me being all cool in my dads hat timing up valves with a vernier.. what it actually portrays is me being a total numb nuts and bending some valves, well done larry, you twonk.

 

Got the belt on, got the verniers on, tensioned and turned over by hand about two pulls of the ratchet on the bottom pulley, so not very much, all of a sudden - PENGGGG sound.. not good.

Backed up went past again - PENGGGG.. double not good. Stop and scratch head...

 

After a while of thinking about sticky lifters like we had with the rebuild, i resolved to look at the cams again, with the pulleys off and to my.. mild horror, the inlet cam key way, was not where my current inlet key way was, infact it was where the exaust cam key way was, and hence discovered, it was in fact an exhaust, i had two arse hole cams, and no cock cam... and when you get two arse hole cams, valves get shat on.

 

Now, time for a bit of yeehaa,

 

 

I got the belt off, and looked at the keyway on the inlet cam, then at the exhaust i had on the inlet side, and managed to rotate the inlet it round to roughly where it should be, put the belt on, and then timed up both with the vernier.

 

Unbelievably, it ran, abet with a noticeably tappy head. took it up the road, and it was quite down on power, almost like the belt was on a tooth out, called a mate to come over with his compression tester.. three cylinders said yes..

 

one cylinder said no.. Does anyone have a match and some petrol please.

​

 

So, got on the phone to ant, he said don't drive it far, could last 50 miles, could last 500, took the car to kevs, who very kindly opened up for me on a sunday night, thanks Kev.. and went home to lick my wounds.

 

A few weeks later, I went up and took head off, noting the positions of the cams,

 

Clamped the liners down so they didn't move

 

ant and I inspected some valves, at least five were bent.

Ant very kindly dropped it to Gardias, who diagnosed a total of 8 bent valves, it had a skim (no skims left in that head), and i received a slapped wrist for not using enough coolant. There is always time for a cheeky vid of it with no exhaust on!

 

 

Another few weeks later, We went back to finish the job, new head gasket, new head set, new head bolts, skimmed head, cleaned up deck, back together,

Here's the head being rebuilt with the help of Ant on the spring compressors, because i'm a weakling and collets are a bitch.

Then to time it up... kev very kindly let us work late into the evening, despite having better things to do..

Day 2 or three... cams are being timed. Now, you remember the PENGGGG sound, half way though timing we were getting that again, you can imagine my horror...

 

 

A while later, anthony, yet again appeared to help, I was properly in a muddle, despite doing it before, lack of confidence i guess, he whacked some oil down the lifter bore, double checked nothing was likely to touch, turned it over a few times and the sound went away.

This is how they should look.

 

Cams timed to PeterT spec, and we were done. Only a trip to Sandy for mapping left to do.. or so i thought. The car sounded better, the head was near silent and you could hear a little grumbly induction grunt coming from behind the grill at the front, and a nice burble from the rear.. see vid below

 

Driving back into london, I got off the motorway and all of a sudden, massive misfire at anything above 1/4 throttle... hang on a minute. stop, change leads, still does it. I suspected coil pack, and was right, changed that (keep a spare in the boot) and boom, were on track.. here's a video of it prior to mapping

 

Cut forward another month, and i find myself cruising down the motorway to saltash, met with sandy and we got to mapping, not the most ideal day, as it was 25 degrees, but it had to be done. We discussed getting rid of the squeak by using the bypass bleed screws, which worked well, and Sandy said it actually made the map a bit smoother. He mapped it up to 7500, with a 7700 soft limit and hard shortly after, 7300 shift light. I need to get some on road videos, but have yet to give anyone a passenger ride (apart from sandy) But he was too busy checking the on road / in traffic characteristics and smoothing a couple of bits out. Sandy had to increase the mid range fuelling somewhat, mostly because of overlap.

 

here's a video on the rollers as Sandy dutifully works through some of the midrange high load sites, note the small flames being ejected from the exhaust, watch it squat..

 

We saw 185 ish at the wheels on the rollers (note they are uncalibrated) , an improvement on the 171 previously. Now it was a hotter day than last time it was mapped, and the car felt good and strong in the new upper revs, but not massivly quicker, during the drive home the temperature dropped, all cruising though. I stopped in swindon, and as is usual, handed Anthony the keys with a slightly devilish smile, knowing he needs more induction hammer in his life, he dutifully took it for a spin, but we were three up heading for harvester ribs and a well earned lemonade. So whilst it still went well more was yet to come. So a fresh tank of super, and swindon to london to go, air temp, probably 12 deg celcius.

 

Got to the on ramp for the M4, and nearly shat myself when it picked up from virtually no revs and sailed all the way to the flashy light shift point, then again in third... etc.. etc. It's as quick as my old 1 bar pulsar.. no doubt. Properly quick. Sails right over the top of the rev range, used to die past 6, now it just keeps going, and going...and the sound.. OH my the sound.

 

Anyway, i'll try to get down to surrey rolling road one saturday soon, for a quick power run to have a look at the curve, although would rather wait till its a tiny bit cooler temp wise. as the last time it was probably 16 deg to get a better back to back comparison. And i'll get some incar vids too.

 

Finally a few words of thanks, to Anthony, Batfink, Paul13, Tom (cheesegrater) who managed to do some tricky welding for me and Sandy Brown.

Edited July 11, 2013 by kyepan

[petert 586]

Sounds great. You've certainly been through the wringer on this one. Glad to hear it puts a smile on your face (and others).

[Willem_Jacobs 6 1 Cars]

Hey Justin,

 

First of all terrible to read you have accidentally gotten the timing all wrong...

 

I happen to have a PeterT regrind (exhaust)cam to replace the inlet cam on my S16 engine, do you happen to know exact what the difference in timing-key position is? I roughly estimate it to be +- 60... But if you happen to have measured the exact difference i could have a custom pulley made to match the original timing-holes...

[petert 586]

You really need to know what you're doing. Sometimes I wish I'd never released that information. I know of several engines that have gone bang. Not necessarily by the person doing the cam swap, but the next person who comes along to do some maintenance. The cost of inlet cam is peanuts compared to the cost of a rebuild.

[kyepan 291]

I did it by eye referring to the old inlet cams correct position, then dialled it in with a dial gauge, it's the only way to be sure you're lift atdc is accurate. You need a vernier pulley, you can't hope to get it accurate otherwise.

[Willem_Jacobs 6 1 Cars]

I have a vernier pulley, so no reason to be concerned about if i can get it dialled in correctly... It's just as Peter stated... I want it to be 'future maintenance' proof...

[kyepan 291]

a driveshaft inner cv has slightly died on the way from dalston to cornwall... place your bets about whether it makes it back without the help of the big yellow alcoholics anonymous van!

 

Clearly that much torque is too much for a set of 6 year old shafts.

[welshpug 1,657]

I dont think it os really, many pug diesels run mpre torque in heavier vehicles without issue.

[kyepan 291]

yer i know, i was saying that a bit tongue in cheek

[cheesegrater 43 1 Cars]

Join the elite driveshaft destruction club DDC for short.

[kyepan 291]

a quick update.

 

37L of mixed driving including a good deal of bwarpage - 260 miles- 270 miles every time i fill up it's about 37L

40L of motorway driving, (at reasonably pacey motorway speeds) and a trip into london at london speeds - 300 miles

 

I make that somewhere between 32-35mpg!

 

pretty darn economical map and efficient engine, i'd say with the new cams it's actually more economical on long runs, it just sits with virtually no throttle at all at motorway speeds feeling like it's just idling, when you push the loud pedal, it gets loud and fast rather like my old pulsar..

 

J

[welshpug 1,657]

Not bad at all, funny how a gti6 is more economical though, whilst producing similar figures.