free hit
counters
What would you do? - Page 2 - Engine/Ancilliaries - The Lotus Forums Jump to content
Artie

What would you do?

Recommended Posts

Artie

I will assume for the minute the head is OK and you will have the nip checked. Do you have any pictures of the offending headgaskets. Where have they failed, is it the same place each time, what is the failure mode. You mention head bolts, have you checked the stretch against a new bolt. I havent checked if these are torque to yield, if they are and have been reused several times the clamp load may be inadequate. Are you using the correct fasteners to hold the head down. I have found cases on other engines where the under head profiles are different to spec and consequently give a different torque reading. This could result in the torques appearing to be to spec, but with insufficient stretch to give the required clamp loads. Also check the condition of the faces on the head where the bolt heads mate as that could also contribute to torque and hence clamp load issues. Also another thought, if you are running at this higher boost and the clamp loads are incorrect, that would be enough to give the headgasket issues. Other owners running lower boosts may have the same clamp loads but the lower cylinder pressures and temps they have may be insufficient to give the same issues.

By the way, the gear to measure the nip isnt too expensive and a useful addition to the toolbox as once you have it you will find other uses for it.

Hope this gives you ideas to think about

Regards

Ralph

Share this post


Link to post
Share on other sites
Upgrade today to remove Google ads and support TLF.

Any news yet Artie,

Or are you taking some time out to take a breather and sort the battle plan out mate!

Hope all goes well chap, regards danny

Share this post


Link to post
Share on other sites

Eric,

I can be first to tell you to be advised on using the Cometic. I tried it and the oil feed to the head leaked. The Cometic uses a copper sealing ring and the Lotus factory uses a rubber o-ring. I believe the Lotus one is made by Goetz.

Best,

Jeff

Share this post


Link to post
Share on other sites

Eric,

I can be first to tell you to be advised on using the Cometic. I tried it and the oil feed to the head leaked. The Cometic uses a copper sealing ring and the Lotus factory uses a rubber o-ring. I believe the Lotus one is made by Goetz.

Best,

Jeff

Thanks Jeff, glad to get another data point. I think the stock gasket is used in a variety of tunes which overall speaks well for its design and construction.

:cheers:

Eric

Share this post


Link to post
Share on other sites

Sorry Chaps for the lengthy delay. I have not yet pulled the engine from the Lotus. I cannot reach the bolts on my exhaust manifold completely in order to render an "in situ" extraction of the cylinder head. I will exhume the lunk hopefully in the near future. Track season starts in about 4 weeks and I have to still run another 1000 miles through my freshly built FD to have it broken in for track duty. I will keep everyone posted on my findings. The last head gasket failed at the 1 oclock position on cylinder 4 when facing the engine from the US drivers side. It was a very small pinhole failure. Water was being burned through the cylinder and out the exhaust. This time it is exhibiting the same exact symptoms. I have never built or disassembled a cylinder head, so I am not sure I am willing to take a stab at this as my "first attempt". As for head studs yielding, that is a concern that I have. The cylinder head has been off the engine 2 times since I have owned the car, once for the engine build 2 years ago, and once for the reinstallation of the new head gasket which was a stock goetze gasket from JAE. Now the head will come off again, so I have purchased a set of ARP head studs from JAE to factor in the possibility that the original head studs have yielded. I do know that the head had been rebuilt back in 1999 with new valves due to a cam belt failure according to service records I have from the PO. This means the head studs have been torqued 3 times at least. The cylinder liners are essentially brand new, they were stripped of their out of spec nikasil 2 years ago and completely re-nikasiled and then final diamond honed to match the JE forged aluminum pistons I bought also from JAE. I am told that the head gaskets aren't a failure prone area for these engines and my boost doesn't climb above 1.2 kg/Cm2. this isn't even 1.2 bar its about .4 psi less. Even if the head had been skimmed 2 times in it's life time, it wouldn't change the static compression by more than .25.

Artie

Share this post


Link to post
Share on other sites

Made some progress today on the removal. I have the front water lines, vacuum line, exhaust bracket and decklid to remove, then I can pull the engine out. I'll hopefully pull it out sometime this week. Once I get the engine over to the builder and have a status report of what we find. Hoping to have her back up and running by the end of April, in time for summer!

Artie

post-1055-0-38975200-1301260165_thumb.jp

Share this post


Link to post
Share on other sites

Okay, Okay! All the talk about 400 plus HP over in the chat room with Dave et al, I have gotten remotivated to pull the lunk out of my car again! Finally got the last bits off tonight and yanked the heap out! She sits anxiously in the back of my truck, ready to go back to the builder to re CHECK everything again to ensure they didn't miss something! I will be fitting a high tension timing belt this time and am having the water pump refurbed AGAIN, to ensure no leaks upon reinstallation! I hope to have a satisfactory report from the builder hopefully by weeks end to determine a possible cause for these repeated head gasket failures! Here are a few pics just to prove I have the engine out and ready to get cracking! :construction: Hopefully this will be the last extraction for a while!

Artie

EngineRandR.bmp

engineRandR2.bmp

engineRandR3.bmp

Share this post


Link to post
Share on other sites

I dunno, Artie. Those pics look photoshopped to me. I think you're just trying to keep up with Dave's thread. :sofa::lol:

Question: I just had a head gasket replaced on one of my cars (an "oldie-but-a-goodie" not listed in my avatar specs) with (I kid you not) 222,225 "chassis miles" on the clock from new, but with a replacement motor installed last year with about 160,000 miles on it when extracted for the transplant. The head was, of course, "skimmed" "milled" "machined" (whatever the correct term is) and a valve job done for good measure. I assumed that the machining of the head would have some sort of fractional effect on the original compression ratio (you allude to this above), and when I mentioned this to the mechanic he said that head gaskets come in various thicknesses to compensate for this. I had never heard of this before, so I'd like to ask you if Lotus (or whatever other aftermarket options exist) gives you a choice?

Best of luck in slewthing out the culprit in your ongoing issue.

Cheers

John

Share this post


Link to post
Share on other sites

The original head gasket was made obsolete by Lotus. The current Goetze composite gasket is .020" taller than the original. The maximum machinable limit for the 910 head is .018"...

So no problem there.

Share this post


Link to post
Share on other sites

I dunno, Artie. Those pics look photoshopped to me. I think you're just trying to keep up with Dave's thread.

Its not a competition on who's thread is best.....the more info that is put on the forum the more everyone understands whats going on and why....

I have followed this thread with interest, it makes a valid point on head gasket failure which my thread won't cover (hopefully)......

I will be covering cylinder alignment and nip later on which includes the head fitting... this may help Artie find the fault causing this repetitive problem..

Artie you say you use an engine builder, is it not possible to do it yourself, it will help keep control on the finer points which may otherwise be overlooked...

Dave

Share this post


Link to post
Share on other sites

John, HAHA! Good Show mate! I don't even have photoshop on my laptop! Anyway, cometic makes a multilayer steel gasket that is thicker than the stock gasket, but as I remember, maybe "trackmagic" has tried it on the G body car he has with an Stevens engine in it and it leaked at the oil passage....SO, I won't be trying that!

Dave,

Although I had considered taking the engine apart and inspecting it and checking everything myself, I am not that versed in engine building! I paid the shop a hefty sum to build the engine correctly and expect just that! The engine has not been assembled completely to my satisfaction, the head gasket should not be popping every 400 miles! I had hit 1.6 bar of boost on the original engine before the build on numerous occassions with the same ecm and turbo and injectors without failure over the course of 4 years and never popped a head gasket! The rebuild is plagued by this phenomenon, so I can only surmise one thing.....They missed something! That being said, I contacted them and we discussed it and they agreed to pull it apart, let me witness the measurements and proceed. If the nip or any other item is off due to their negligence, then the tidying up is on them! I know they know what they are doing, they just made a minor error, so I'll let them sort it out since I paid for it! I trust they will do the right thing! If this happens again, then perhaps I'll take it in my own hands and figure it out, but I'm not ready to do that at this point. I will keep you all posted on the findings, hopefully by the end of the week!

Artie

Share this post


Link to post
Share on other sites

Sounds fine Artie, if you paid good money you should have a good product......Did i read that you fitted new liners and pistons on last build , before the gaskets went .?

If so who kit did you use ? and what spec .? just searching for areas that may need checking....

Dave

Share this post


Link to post
Share on other sites

Dear Mr Artie, please to explain to dummy neophyte what is "nip?" Even the most excellent google machine search is very largely challenged to make to be a satisfaction answer.

Benificence be upon you in your quest to blockade the blowing gases.

Cheers

John

Share this post


Link to post
Share on other sites

It's what pesky fluffy dogs do ! :yes:

Actually it's the amount of "crush" educed on the cylinder liners, head gasket and head as you tighten it down, thereby being crucial to seal. :book:

Share this post


Link to post
Share on other sites

Thank you, Roger. :unworthy:

Share this post


Link to post
Share on other sites

Nip is the realtive height of the cylinder liners to the block top surface. I believe the spec is -.001" /+.003" and you want them to go from lowest to highest, not random up down up down.

Share this post


Link to post
Share on other sites

Just some searching thoughts Artie, The JAE piston crown design ..was it identical to the original and did you check the compression ratio ....also when the liners where removed where they marked for which order they were in to insure they went back the same way ....

Just small points but they can have an effect...

Dave

Share this post


Link to post
Share on other sites

Dave, this has always been one of those "great mysteries of life" to me, the "marking" of engine components to ensure that they go back in the exact position they were removed from. It generally makes sense to me, but.......

What if you needed to replace the liners with new ones? If they (the new liners) have never been installed before, how do you decide where (in what "order") to place them? If one is as good as the other, than why is it important to put "used" ones back in the same bore? Is it to maintain existing wear patterns, or what? As another example, when I had the valve job done, I noticed that each valve had been numbered so as to go back in its original matching cylinder position. But, as they were "lapped" to spec, why would this matter. Valve guide wear perhaps?

Thanks

John

Share this post


Link to post
Share on other sites

The main reason is compatibility. if a component has bedded in that position then it makes sense to leave it there...each component part is made to a tolerance, when an engine is first built they are usually taken into account...and discrepancies matched out ..ie...on the liners , the machining of the block on each pot should be spot on , however they are actually to a tolerance +or - a thou or two . when the liners are made the same applies. when you dry fit the liners initially you may find the nip up and down a bit... buy swapping the liners around you find that the pluses and the minuses balance out to within the overall excepted tolerances...... so if a liner is +2 thou and fitted into a pot also + 2 thou then it will sit 4 thou tall.. if the next pot is say -1 thou and the liner - 2 thou then that will sit 3 thou low ..they are 7 thou out .from each other ..and also out of spec with the block face ..!!!! swap the over and they will be 1 thou out.....within spec.... So marking them makes it a little easier on reassembly but you still need to check them..!!! .. The same applies to valve stems but not so important if mixed up....

When fitting new you start from scratch to match the fit....if you need to strip again when marked it saves matching up again....A 30 second procedure can save a lot of hassle...

Share this post


Link to post
Share on other sites

Dave,

If you aren't familiar with JAE, then consider them much like SWLC or another famous, reputable european/British Lotus specialist. They are very knowledgeable in all things Lotus, especially the Esprit and our variant. They have contracted JE pistons to make a forged piston that is to the Lotus specification! The Piston crown is not the exact same design, however it is designed to directly replace the Mahle pistons in compression ratio and size/shape. The pistons are also ceramic coated on top to enhance burn and also transfer less heat to the top of the pistons to prevent hot spots. Additionally, the liners were chemically stripped of the original nikasil in order to recoat in new nikasil so any form of marking would have been removed. Ideally, the liners are set back into their original positions, however, like new liners, the nikasil coating adds dimension, although fractionally so, it still alters the original size and therefore would require juggling around the liners from original position anyway. The reason to check the nip, is to ensure a proper linear crush of the head gasket across all 4 cylinders, so at that point you will align the newly coated cylinders according to spec and move them to the appropriate orientation to achieve the necessary specifications. I stopped by the shop yesterday to see any progress, but the guy building the engine was off, so I'm hoping some progress today! I will report any findings ASAP!

Artie

Share this post


Link to post
Share on other sites

Something to bear in mind when ceramic coating pistons; if less heat goes into the piston it expands less and will be 'looser' in the bore resulting in less piston ring control. The piston ring gaps are affected too.

I'm not suggesting this has anything to do with your failure Artie, merely that changing one thing often has a knock on effect.

Share this post


Link to post
Share on other sites

Arte

Another thing to check. I come across some engines the other day (not Lotus) where the block machining was incorrect. To be specific, the threads in the block for the head bolts didnt finish deep enough, consequently the bolts were cutting the last 2 threads so the torques seemed ok / a fraction high but the head gasket blew because the clampload was insufficient. You have said that the bolts have probably been reused and may have stretched, the head has been skimmed, etc. Check that there is enough thread engagement to cope with these changes (or the bolts are close to bottoming out) before you screw it back together.

Cheers

Ralph

Share this post


Link to post
Share on other sites

Derek,

you are confusing two separate phenomena occurring simultaneously. The ceramic coating is designed to deflect the "radiant" heat of the combustion to eliminate hot spots on the surface of the piston that can cause detonation. The thermal expansion of the pistons in the liner, although related to combustion, is more a factor of the engine overall temperature and it's expansion due to the heating of the aluminum it's made of. However, forged pistons are "forged" to help align the molecules of the metal in a uniform and much stronger arrangement, a nice secondary benefit is it also minimizes expansion and shrinking of the pistons in their bore and thus allows you to run a tighter tolerance between piston skirt and liner. And also the reason why I had the skirts coated with a moly coating to help with retaining oil to help lubricate the skirts that fit snugly in the bore(compared to "normal" engines). I assure you guys that I didn't just pick up a bunch of parts that weren't designed to be used together. I contacted John Welch, and several other very knowledgeable specialists on this build and partly the reason it has frustrated me so much! I have invested a lot of money in this engine and done everything to specification and "overbuilt" parts of it to ensure I don't need to do it again, but a head gasket failure is grounding the project! I will report on what the issue actually is, hopefully tomorrow, so lets wait and see instead of speculating on possible culprits. I PROMISE I did everything the correct way in selecting components, now, it is up to the builder to sort out any mismeasurement or accidental oversight. The engine is at the shop and I hope they will begin disassembly tomorrow.

Artie

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...