Xu9J4 Springs, Seat Pressures & Noisy Head

[Kane 34]

Since completing the rebuild of my Mi16 I've run into a number or problems which I am attempting to track down by process or elimination. The issue I'm on now is a fairly ticky top end which is present regardless of engine speed. List of things I'm going to check over include:

 

Cracked exhaust manifold

Lifter issues

Worn cam nose

Injectors

 

When i sent the head of for the first round of works i had a 3 angle cut carried out on the valve seats although only to find out after i had reassembled everything and got the engine running that the exhaust guides were out of tolerance. So back off with the head and another cut to the valve seats was done.

 

Engine is back together and I've just driven it roughly 50 miles to my new house. Absolutely no running issues during the drive, varying load in all gears. The engine feels like it is loosening up well (approx. 1500 miles since first build). Unfortunately though i still have this ticking noise.

 

I refreshed the lifters as per PeterT's website originally and when i had to strip down the head again checked to see if any were sticking. None of the lifters appeared to be sticking although IIRC there was one which didn't seem to have filled, or at least fully. I stripped it down checked it internally and there didn't seem to be any issues. So reassembled and put back in.

 

First question, can lifters fail so that they don't fill even after a substantial run of the Engine?

 

My next potential issue is seat pressures. As the seats have been recut twice and the fact the springs will not be providing as much pressure as originally fitted, Do you think this could be a contributing factor to the noise I'm experiencing. I aim to check clearances and re-shim the head to bring them back into to spec, if required, but wondered if anyone had experienced a noisy top end because of this issue previously?

 

Is there anything else i should be checking for (head related) while i have it off?

 

Thanks in advance.

 

Kane

[jackherer 543]

List of things I'm going to check over include:

 

Cracked exhaust manifold

Do you have the standard '8 branch' manifold? If so definitely check that before you spend too long thinking about what it could be, I've got a pile of them in my garage and loads of them have got cracked welds but they aren't as immediately obvious as they are on an 8v mani, you need to have it off the car so you can hold it at various angles and shine lamps into it before you'll see some of them.

[Kane 34]

It is an 8 branch yes and thinking about the state of the engine itself when i stripped it down i wouldn't be surprised if it was cracked. I have however listened to the cam area with a screwdriver and i have a feeling its a mechanical tick. The engine will be coming out as i plan on respraying the whole shell so will check the manifold then. Absolutely hate trying to remove it when the head is on the engine in the car!

 

Do injectors quieten down if i was to have them cleaned? Alternatively is there a recommended set of injectors i could source as a replacement? Engine is a standard rebuilt xu9j4, block decked to up compression to approx. 10.8:1

 

Oh and I'll be sourcing a 6 inlet setup also to solve my throttle issue

Edited January 28, 2016 by Kane

[kyepan 291]

firstly well done on the rebuild!

 

couple of thoughts for you

 

Were the valves checked for straightness during the build? as a slightly bent valve (not perceptable by eye) will result in a ticky top end. Did you have any events during the build where a valve could have got dinked or clipped... I know this because i dinked a valve (or nine) when installing some cams on my Mi and it got decidedly ticky.

 

If the answer is no to all of that.. then an idea.. I also reconditioned a set of lifters as per peter t.. and fluffed it right up, and had the opposite problem, too much oil in them and the valves wouldn't close. If you think the lifters are not pumping up, then my vote is get a set of original peugeot lifters and put them in without reconditioning (or at least without draining and refilling) and see if it quietens down. The after market lifters are terrible quality don't even touch them.

 

Granted you've got to whip the cams out to do this, but it only takes a day to do (less if you're on it, and if you have standard cams / pullies) and you know your way around just fine.

 

Again! well done on the build!

 

Cheers

J

[kyepan 291]

An additional thought, if you've had the valve seats recut, the engineer should have also back cut the valves down to make sure they are the same installed height. If this hasn't happened you'd have less valve clearance so that won't make it tappy.. but still worth checking.

 

I also shimmed under the springs for some reason, recommended by the engineer, i can't remember why, it might have been for valve seat pressure.

Edited January 29, 2016 by kyepan

[Kane 34]

Yeah, during the second strip down/inspection it was found that 2 valves were ever so slightly bent so they have been replaced with new. I can't remember exactly if he had also back cut the valves but i guess it will be confirmed when i check clearances.

 

I had read up on your experiences with aftermarket lifters, and others who have encountered similar problems so will avoid at all cost.

 

Thats my plan behind the shimming, to bring the seat pressures back into check if required. I think that is one of the last items in the head that hasn't been considered as a problem, oh and still the possibility of a lifter not filling although i think i might have an idea on how I will check that next.

 

Plan is it run the engine up to temperature and shut down then whip off the cam cover. Using a solid item, maybe block of timber or similar try and depress the lifters one by one. If none of them move then it is likely something else causing the noise as that would indicate that the lifters are full and operating as normal. Does this sound like it may prove useful?

[petert 586]

If you've cut the seats/valves, you'll need a minimum of two standard shims under each spring to get the seat pressure correct. Aim for 80lbs min. It's doubtful that it's the reason for the tick however. Perhaps there is insufficient pre-load on the lifter? There needs to be a minimum of 0.040". Standard is approx. 0.065". Swap/change the lifters and see what happens.

[welshpug 1,657]

There should in theory be more preload on the lifters with re-cut valves.

 

if base circle of the cam is smaller to get around clearance of peak lift issues that could cause it especially if a regrind.

 

I have come across tired lifters in a gti6, possibly could have been revived but we had a donor head to take a cleaned up unit from.

[Kane 34]

What's the procedure for checking lifter preload? Can't find any useful info online

 

Both cams are standard Welshpug so not likely that issue?

[petert 586]

The lifter needs to be depressed by the base circle of the cam a minimum of 0.040" when then caps are torqued down. Given the cams are standard, I'd start swapping lifters. I was chasing a tick over the weekend. It turned out to be the plug lead, not fully pressed on to the plug!

[Kane 34]

Thanks for the advice Pete just a couple more questions for you. What are the typical causes for insufficient preload on the lifter? I guess the dressing of the lifter face could result in less preload if too much was removed, I did however make sure that I didn't spend too long refacing as per your website. IIRC there were 2 buckets I had to replace as there were signs of excessive wear.

 

Next one..

 

When measuring preload is it a case of setting a dial gauge on the lifter without the cam installed. Drop in the cam, torque down the caps and then take the measurement ensuring the cam base circle is centered over the bucket? The problem i forsee here is space, I'm not sure there's much room on the lifter to locate the dial guage and not accidentally knock it while I'm fitting the cam.

 

Thanks again for all your help.

[petert 586]

You would have been lucky to take a quarter to half a thou off the bucket. Neglible really.

 

Measuring preload is tough. You can't use a straight edge across the cam bearing journals because they're all different diameters. You need to measure the plunge as you screw down the caps. An externally mounted dial indicator is best but a simple reference down the bucket bore will suffice. You're only looking for 1-1.5mm. The exact number isn't critical.

[Kane 34]

Thanks again Peter.

 

Back onto seat pressures for a minute. When restoring the installed heights of valve springs is it recommended to replace the existing shim for an alternative single shim or would fitting multiple shims under the valve spring be OK.

 

I wouldn't imagine there would be any major issue fitting multiple shims providing they were of the same material but thought I'd ask the question just in case.

[petert 586]

The problem with too many shims is heat transfer, or lack of. Two is fine and I did three once.

[SweetBadger 94]

 

You can get 1mm shims from Pug, they are from the TU 8v engine part number 095131. I used these on my recent MI head rebuild and they are the same diameter as the MI shims.

 

Not sure on availability though as my local dealer could only get me 8 of them; I used the 1mm shims on the exhaust valve springs and doubled up the MI ones on the inlets.

 

The part number for the Mi16 spring washer (0.55mm thick) is 095312