2010-2011 sti HEAD FAULT
10 October 2011, 09:34 PM
#4
Engine Specialist
I'm not sure I understand what you mean? Someone has told you that even if you forge your engine you cannot do more than 360bhp based on the fact there is a fault with the heads?
Or are you saying there is a fault with your head gaskets? Sloppy pistons?
I'm a little confused! Or I need a drink!
Graham
Or are you saying there is a fault with your head gaskets? Sloppy pistons?
I'm a little confused! Or I need a drink!
Graham
10 October 2011, 09:45 PM
#5
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what i was told was the pistons dont fit well and can overtime wear into the head gasket causing it to fail (thats what the man said and i live near tewksbury)
so i take it this is the first any one has ever mentioned anything
can some one advise
so i take it this is the first any one has ever mentioned anything
can some one advise
10 October 2011, 10:18 PM
#6
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We have built a good number of late 2.5 engines now with over 450 bhp. The heads and gaskets aren't at fault. The pistons are the Achilles heel, and replacing them makes at least 400 bhp safe. We invariably go for rods as well, and have done with.
The primary issue has been the choice of piston, which has a weakness of the ring lands, causing break up and ring failure.
The primary issue has been the choice of piston, which has a weakness of the ring lands, causing break up and ring failure.
Last edited by Alan Jeffery; 10 October 2011 at 10:21 PM.
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10 October 2011, 10:29 PM
#8
Engine Specialist
We have built a good number of late 2.5 engines now with over 450 bhp. The heads and gaskets aren't at fault. The pistons are the Achilles heel, and replacing them makes at least 400 bhp safe. We invariably go for rods as well, and have done with.
The primary issue has been the choice of piston, which has a weakness of the ring lands, causing break up and ring failure.
The primary issue has been the choice of piston, which has a weakness of the ring lands, causing break up and ring failure.
Graham
Last edited by EngineMapper @ Group B Motorsport; 10 October 2011 at 10:32 PM.
10 October 2011, 10:30 PM
#9
I know of quite a few 2.5 with forged engines that have gone pop including fully forged Cosworth blocks all because there based on the 2.5l engine.
Cosworth had loads of CS400 and tried to sell them overseas and wouldn't warrant the engines........that says a lot.
Cosworth had loads of CS400 and tried to sell them overseas and wouldn't warrant the engines........that says a lot.
11 October 2011, 08:02 AM
#10
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It was thought early 2010 that it was likely that the heads on Hatches would struggle to flow enough to make more than mid 400's, so I had mine cnc machined/flowed/hand finished. As it happens that was not needed as many std heads are making mid-high 400's easily and some over 500, as Alan J has proved.
Perhaps its the myth that heads do not flow well that the person was refering to ??
Perhaps its the myth that heads do not flow well that the person was refering to ??
11 October 2011, 12:02 PM
#11
It was thought early 2010 that it was likely that the heads on Hatches would struggle to flow enough to make more than mid 400's, so I had mine cnc machined/flowed/hand finished. As it happens that was not needed as many std heads are making mid-high 400's easily and some over 500, as Alan J has proved.
Perhaps its the myth that heads do not flow well that the person was refering to ??
Perhaps its the myth that heads do not flow well that the person was refering to ??
11 October 2011, 01:22 PM
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So the conclusion is .... NOT TRUE !
It seems that low 400's is considered very safe (with forged pistons + rods etc.)
And that 500 + is deemed an engine that will need tlc + 'refreshing' every once in a while. (High boost may be something to avoid.)
So anything inbetween 400 - 500 'should be OK' ... with supporting mods...
The 2.5 unit is good but not unbreakable. Alan Jeffrey is the man to talk to.
Ring him - he's v friendly and 'knows his stuff' having rebuilt many new cars (including mine).
As for many forged 2.5 units going ping... are these in 'new cars' Immy ?
I've not heard / neither read of any 'new cars' with forged rebuilds blowing...
I do think there is a difference in dropping in forged pistons tho - and doing it properly with a strip down, bore, hone, etc etc.
Some engines are modified and then some are built...
Go well
A
Last edited by Apostle; 11 October 2011 at 06:18 PM. Reason: spleling
11 October 2011, 01:27 PM
#14
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It can't be denied that there is a grain of truth there, although there are also cases of human spontaneous combustion. Personally, I worry just as much about that possibility as I do about forged 2.5 engines we've built.
11 October 2011, 04:46 PM
#16
Am just going of members experiences of here. Apparently down to dogey cosworth head gaskets. Plus theres been a few type 25's with the Cosworth engines go pop and having spoke to Ian a while back he said it's all down to the 2.5 block.
Immy
Immy
11 October 2011, 07:21 PM
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I heard the suggestion/rumour about the heads not flowing well at over 450BHP from a couple of respected sources and talked to AlanJ who said it wouldn't hurt to do it and he recommended Ric Woods who did the cnc machining, flowing and hand finishing, with flow measurement and print out for about £1300.
I thought it probably helps produce a given power/torque at less boost, so I reckon with less boost there'll be a bit less stress on the engine !!
I reckon mine doing 460BHP at only 1.3 bar has got to help reliability.
Last edited by StanS; 11 October 2011 at 07:27 PM.
11 October 2011, 09:17 PM
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Well better save me pennies then and go for a very safe 400bhp with forged pistons and a shiny head
i quite new to this but there is a lot of help and advice
Many Thanks
Truck on
i quite new to this but there is a lot of help and advice
Many Thanks
Truck on
11 October 2011, 09:46 PM
#19
My 2008 sti with forged 2.5 also built by enginetuner has now been running at over 450bhp for over a year now, nearly 10000 miles done. And has had bursts at 495bhp with methanol.
Unfortunately I had to go back there today to get a repair
.......
a broken rusty exhaust clamp of all things
Any excuse for a trip to plymouth
Unfortunately I had to go back there today to get a repair
.......a broken rusty exhaust clamp of all things
Any excuse for a trip to plymouth
