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Bailey's single build thread


Bailey.

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Right guys, got a bit of shit news, a few weeks ago I did a compression test and read within 5 psi of Each other around 165 in all cylinders! So today my leakdown tester arrived so I gave it a blast!

 

Results as follows-

 

1-20%

2-60%

3-0%

4-60%

5-17%

6-65%

 

2 and 4 are leaking into the inlet side form sure and 6 is leaking into the exhaust, oviously the the valves arnt seating properly!!

Where do I go from here?? Head off and new valves fitted??

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this was my thoughts, all were tested twice too, especially no,2 as i thought i was doing something wrong after good results for no.1!!! up in arms a bit now! just feel like selling the bloody thing......

 

 

If you are prepared to give up this easy before you have even started the conversion or confirmed there is anything wrong for sure, i suggest you dont go single, its not something to be done on a budget.

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It was more thoughts in my head than an actual plan tbh! Just shocked me as the car runs like an abseloute dream and doesnt smoke etc, took me totally by suprise.

Thing is whats a pro gunna tell me? "yes there is an issue somewhere, we will have to remove the head to find it!!!" I think i may try the comp test again as i did do it about a month ago, i cant see anything changing in that short amount of time????

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It was more thoughts in my head than an actual plan tbh! Just shocked me as the car runs like an abseloute dream and doesnt smoke etc, took me totally by suprise.

Thing is whats a pro gunna tell me? "yes there is an issue somewhere, we will have to remove the head to find it!!!" I think i may try the comp test again as i did do it about a month ago, i cant see anything changing in that short amount of time????

 

 

 

Im no engine builder/mechanic but as far as i see it if compression tests are good then leak down tests should also be good, i dont see how its possible to have good compression test results and bad leak down results, but now i read you did the compression test a month ago something could have worn in that time i guess, if you dont want to take the car to a pro and are happy your results are correct then its strip down and rebuild time i guess.

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If anyone is considering pushing up power levels its a fundamental that the head comes off , leakdowns,compression checks are just a band aid guide - THE HEAD MUST COME OFF !!!

Its the heart of the engine where all the action is taking place ,having unknown internals here , then any bolt on power can cause a failure , its either known good by inspection or a lottery

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If anyone is considering pushing up power levels its a fundamental that the head comes off , leakdowns,compression checks are just a band aid guide - THE HEAD MUST COME OFF !!!

Its the heart of the engine where all the action is taking place ,having unknown internals here , then any bolt on power can cause a failure , its either known good by inspection or a lottery

 

I know where your coming from but most if not all tuners unless have head work done do not remove head when going single! But I will be, don't worry;-(

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I know where your coming from but most if not all tuners unless have head work done do not remove head when going single! But I will be, don't worry;-(

 

I think you will find that is customer cost driven ,and not the tuners advice !!, you know that you are going to make more power,more boost,more chance of detonation ,why spend out on the finest ecu and mapping only to det because of carbon build up on the piston ?

Not only that it ensures that a new gasket is fitted and the head is true (you dont know how many overheats the previous owner had ) it also allows inspection of the valves and seats , checking the valve guides and new seals (they will probably be close to worn anyway) ,

You can also inspect the bores and pistons (decoke and polish if necessary) , tank clean the head and ensure water passages are not furred up .

you can also inspect the head for any hotspots or imbalances in fuelling (different colours on the valves ) and hairline cracks , tracking ,water leaks,gas leaks , and generally clean up the head .

if you were feeling a bit flush then get the head ported and polished and cc,d as well as relapping /renewing valves and checked over by a head specialist -

All in all why wouldnt you take the head off - to save money -lol - could cost you a LOT more later on .

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After speaking to a head specialist a friend uses for head rebuilds etc, he seems to think it's quite possible to have good comp results and not so good leakdown test results if some of the valves arnt seating properly, so hopefully just remove the head, have the valves reseated and off we go again! It would be a good time to have an inspection of the rest of the motor when it's all apart! So I'm a bit happier today! If I talk about selling again, mods you have my blessing to remove me from the forum,'lol! On we go!!

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Could be the valves not seating, we had this on a race engine last year. Compression was spot on across the board but bad leakdown results, took the head off and it needed all of the valve seats recut and the valves reseating, put it back together and perfect. You can test the inlet valve seal by removing the throttle body and the exhaust valve seal by removing the exhaust manifold and listening to see where its leaking from. If its not that then it could be piston ring leakage, hopefully its the head.

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I always check all unknown heads for hardness, as a matter of course. Overheating if it's serious, will soften the alloy and the head will never be as reliable as one that's never been overheated. I have also save myself a lot of grief, not to say money, by checking used heads before purchase. It's stuff like that which can make the difference between a reliable big power build and one that will have you tearing your hair out and wishing you'd never started it. I vacuum test all valves to be sure their seats are perfect before the head goes back on.

If a heads been overheated and warped it's almost certainly only fit for floatation tests as the cam bearings will no longer be in a straight line, but banana shaped. Cams don't like being forced into anything other than a straight line :) I am afraid all that sort of stuff puts the price up, but experience has taught me that getting involved in cut price jobs is just not worth it, as no one goes away satisfied, long term.

Edited by Chris Wilson (see edit history)
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