Lotus Elan

coolant leaks - new head gasket

PostPost by: cbguerrajr » Sat May 13, 2017 7:06 pm

need help with suggestions / ideas from the usual experts, please.

assembling rebuilt engine (83.5mm, new pistons, head and block skimmed, new ARP head bolts, etc). head gasket from Ray.
After torquing the head down, added coolant and a leak was immediately seen from head gasket on exhaust side, near #1 1nd #2. i thought the front edge of head gasket might have hung up on top of the timing chain cover gasket. Engine never started.
removed head, examined everything and found nothing amiss, so carefully re-positioned the gaskets and re-torqued the head back on (63psi). added coolant and the leak re-appeared, same place but slower
removed head again and took a bunch of measurements of the head gasket, measurements shown on the attached photo.

So here's the puzzle: after removing the head gasket, and measuring the metal seals for the cylinders, it became evident that all the rings had compressed unevenly . in each case, the side near the carbs was thinner than the exhaust side (one side of the rings compressed more than the opposite side, or were uneven to begin with?). so on the exhaust side there isn't enough pressure on the fiber part of the gasket to seal around the water passages
after compression, the fiber section was uniform at 1.1 mm all the way around. but the metal rings were not. a ridge was easily felt between the metal ring and the adjacent fibrous area on the exhaust side, but on the carb side the two felt the same thickness...

so what could cause that?? a defective head gasket? I ordered a new different head gasket, this one from Ajusa. But I'm uncomfortable not having a good explanation as to what went wrong.

Has anybody used RTV form-a-gasket instead of the cork+steel gasket between the head and the timing chain case? I'm thinking of trying that, to make sure that all the available pressure is applied on the HG, and not on the front gasket.
help?!

Carlos G.
Attachments
head-gasket-leak-copy.jpg and
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PostPost by: promotor » Sat May 13, 2017 7:30 pm

Are the ARP bolts, or stud and nuts? Perhaps if they are bolts they are bottoming and not allowing full crush of the head gasket? It's even possible with stud and nuts that the nut has reached the end of the stud thread before crushing the head gasket.
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PostPost by: cbguerrajr » Sat May 13, 2017 8:09 pm

thanks, I had thought of that possibility and checked it out. ARP bolts have 4.3" usable area after bottoming out the threads, and the head is about 4.6" tall where the bolt holes are. so there should be about 0.3" left before that could become a problem
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PostPost by: mark030358 » Sat May 13, 2017 8:41 pm

Hi,
Dirty thread in the block, clean them out. I'm assuming head and block is flat.

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PostPost by: cbguerrajr » Sat May 13, 2017 10:30 pm

thanks for the suggestion, mark
head and block recently machined flat.
block thoroughly cleaned at same time. with head off, bolts can easily be turned with fingers to the end of the threads. also, why would the threads be dirty only on the exhaust side of the block?
baffling

carlos
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PostPost by: 2cams70 » Sun May 14, 2017 1:10 am

Did you use ARP lube on the bolts? Also what washers did you use? Standard or the round ones that come with the ARP bolts?
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PostPost by: rgh0 » Sun May 14, 2017 1:20 am

You need to achieve around 30% compression on a fibre head gasket to get it to seal. Measure the gasket thickness uncompressed and then measure the gap between the head and block once its torqued up to ensure you have even compression all around.

It is hard to tell how much compression you got with a removed gasket as there will always be some spring back of gasket thickness once its removed.

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PostPost by: cbguerrajr » Sun May 14, 2017 1:49 am

thank you both
i used the washers that came with the ARP bolts, chamfer facing up and used their lube on the threads and between bolt head and washer.
I'll measure the new gasket before installing it and I'll try to measure the gap between head and block after torquing, although that sounds difficult to do with the engine in the car. hmmm.
how safe is it to go over 65psi torque with an old head and new bolts?

Carlos
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PostPost by: rgh0 » Sun May 14, 2017 2:25 am

The ARP bolts will take a higher torque, say to 75 ft-lbs max appears to be safe. I prefer to use the studs when going to the higher torque, as your turning a finer thread on the top of the stud rather than the course thread in the block and you get a higher stud loading at the same torque as a result.

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PostPost by: 2cams70 » Sun May 14, 2017 2:51 am

Check that the round ARP washers aren't hanging up on any of the cam bearing blocks. That's why two of the OE washers have squared off edges to allow clearance. You may have to grind two of the ARP washers similarly.

Personally I'm not too keen on using higher than standard torque figures. Something else is wrong if it doesn't seal. Ford designed the threads in the block to withstand a certain tension - any more and you risk distortion of the deck face and bore (but that's just my opinion - don't have any evidence !).
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PostPost by: rgh0 » Sun May 14, 2017 2:59 am

I have found that higher bolt tensions are required to keep the head gasket sealed with high revving, high HP, high compression race engines. They should not really be needed with a standard road engine using an original style gasket or fibre gasket.

The fibre gaskets i use come with a "silver paint" sealant on the surface which probably helps with sealing the water passages.

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PostPost by: promotor » Sun May 14, 2017 7:17 am

Are you using a genuine Lotus block or a crossflow block, and do you have cylinder liners fitted?
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PostPost by: cbguerrajr » Sun May 14, 2017 1:36 pm

thanks again. i think 2cam70 is getting warm. i had to grind flats on two of the washers as he said, but i still wasn't happy with the closeness to the cam towers, especially when they tended to spin while torquing. also, the exhaust cam positioner or guide (next to #1) was fouling, Not only the washer needed a flat but the base of the bolt head was against that spinning "disk". So i had to grind a small amount to reduce the diameter of the base of the head bolt. the base of the head of the ARP bolt is much larger than the OEM bolt, almost same size as washers. And if I recall, in other locations, the washers might have been touching the cam towers too, might have been on the exhaust side... definitely will look at all that again. it could explain why the torque applied did not result in enough pressure on the gasket. damn. the guy who rebuilt the head had to line bore the cam journals because they weren't true and in order to keep the bearings standard size, he cut down the base of the cam towers slightly. that might have changed the geometry causing the interference with the washers now (?)
I agree to keep the torque at 65psi. the engine block is of unknown origin, as the original engine was blown decades ago, it has no liners and the casting was ground off where the number would be. but above the motor mount under the carbs this was stamped : LP-6178-LBA and somewhere else T1.

you guys have been very helpful with suggestions and insight, giving me some things to work on.

Carlos
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PostPost by: alan.barker » Fri May 19, 2017 8:58 am

Have the shanks of the ARP bolts got a good clearance with the holes in the Head.
When the top of the Block was surfaced is it square to the Cylinder bores. Maybe the Block is a 1600 Block that has had a lot of metal machined off (topped)to reduce the height to the TC height.
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PostPost by: billwill » Fri May 19, 2017 4:32 pm

One thing not mentioned, because it might be toooo obvious, but you did do up the bolts in the recommended sequence did you not?

Doing up all the carb side before the exhaust side might produce those symptoms.
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