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hks manifold cracked -split in weird place !


supra matt

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Well i had a exhaust blow though i had done the turbo gasket but left it as was taking the car off the road for a over haule but when i took it all apart i found this :blink:

 

now i did have it warped and was wondering if it's cos this bit was not warped that well (bit loose and some air gaps) so did this area get to hot ?

 

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Some people say that wrapping itself can cause this by promoting heat spots in areas where the wrapping cannot touch the surface like that section. It's a possible cause but not sure how likely.

 

The crack is on one of the most stressed areas of the manifold, so there's a few more likely causes:

 

1) Welding defect/poor workmanship

2) (If you have no decent flexi sections) the exhuast has taken a heavy knock and put too much strain on the manifold

3) Too much weight on top and/or insuffcient bracing

 

Pain it the ass though and not really salvagable :(

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o well looks like ill just have to make up some proper braces for it to take the stress out if it . would i be better to get it ceramic coated rather then re wrap it?

 

Do you have a decent sized flexi section on the DP and MP already? If not then that should be a priority above expensive coating options. I'd still wager it will crack again before too long.

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It's differential expansion of the runners, unsupported weight hanging off the runners and general build quality. The crack is now contaminated and unlikely to weld repair satisfactorily. I would think long and hard as to the pros and cons of cast iron versus cheap tubular manifolds before making a decision. A proper tubular manifold will have either slip joints, bellow sections or be made of Inconel, and the turbo and wastegate will both be fully supported separately from the manifold, and the downpipe will be separated, load wise, from the rest of the exhaust. 99% of aftermarket tubular ones fail to address most if not all of these points in order to provide a product the market will be able to afford. Some people get away with it, but if the car is a hard driven daily driver I would look at a cast iron manifold for longevity.

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Chris you say cheap but this manifold was over £1000 pound when new although i did not pay that i thought they were meant to be very well built ?

They seemed a lot better put together than the BL/SP type that 90% of the Supra community use, I did a thread comparing mine when I got it to my old manifold, everything about it seemed quality.

 

See here http://www.mkivsupra.net/vbb/showthread.php?t=188037

Edited by jevansio (see edit history)
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They all look OK, but 99% are fundamentally flawed in that they just hang the turbo and wastegate off the pipework, and they have no expansion joints or bellows. Porsche tried using a tubular manifold on the 944 turbo models, as the lay down engine required a long and complex manifold to package a turbo when they decided to market a blown version. They had endless trouble with it with umpteen revisions, and a new one is eye wateringly expensive. They got it right in the end. Does the turbo hang off the pipework? No. Does it have expansion bellows? Yes. Does it crack? Yes, but only after serious mileage.

 

Anyone who was / is into the Sierra Cosworth engine will know the fun Ford, with all THEIR resources, had with cracked and damaged turbo systems. They used a friction damped mount, which again was revised several times. And they were running a cast manifold.... ;)

 

I could find another 8 to 10 % mid to top range power on my RB26 engine by running a single turbo on a tubular manifold, at similar boost, but no way will I move away from the stock Ni-Resist cast manifolds. A porting of them is as far as I will go. I want to drive the thing, not mend it!

 

I did take the plunge due to there being no real alternative, and have a proper tubular manifold made for my 4A-GE turbo race engine. It wasn't cheap at about 4 times the HKS manifold....

 

http://www.gatesgarth.com/4age/primary/primary.html

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I think Arnout's (fine) manifold was a modded replica of some US one, he addressed the rather small wastegate port and improved the wastegate bolt pattern.

 

BTW I collect HKS cast iron RB25 and RB26 manifolds, so if anyone sees any for sale I'd be interested, they make a great and reliable cheap conversion.

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  • 1 month later...

Arnouts mani was a revised turbonetics mani.

I think Arnout's (fine) manifold was a modded replica of some US one, he addressed the rather small wastegate port and improved the wastegate bolt pattern.

 

BTW I collect HKS cast iron RB25 and RB26 manifolds, so if anyone sees any for sale I'd be interested, they make a great and reliable cheap conversion.

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