Cosworth pistons major problem!!!!
Apr 16, 2009, 04:11 AM
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Cosworth pistons major problem!!!!
Hello,
A week ago we tried to rebuilt an Evo IX motor that had Cosworth pistons and Cosworth rods.
The Cosworth built motor was having only 5000 miles.
The main problem was that this Evo was needing 1lt of oil (15W-50 Cosworth recommendation) every 600 daily driven miles!!!!
We thought that the problem was on the piston rings.
Everything was ok on the rings and the rings gap... the magor problems was on the pistons and the piston clearance from the cylinder wall!!!
We measure them (Cosworth forge pistons PA2689 standard 85mm) and the following numbers came on....
Piston 1:84.40mm diameter on the top 84.81mm diameter on the end of the bottom
Piston 2:84.40mm diameter on the top 84.87mm diameter on the end of the bottom
Piston 3:84.40mm diameter on the top 84.83mm diameter on the end of the bottom
Piston 4:84.40mm diameter on the top 84.87mm diameter on the end of the bottom
The pistons are smaller than it should be after 5000 miles only!!!!
I am not sure if the pistons was smaller when we bought them or they got smaller afterwards.
That is the reason of the oil problem !!!
Huge piston to cylinder gap!
The problem is on all 3 Evo's that we used Cosworth pistons PA2689 !!!!
The green coating is ok.
Also now you have to use a hummer the get the pins out of the pistons!!!
I am trying to find out the Cosworth pistons diameter specifications for these pistons.
I contact already and email Cosworth USA and Cosworth UK.
I am waiting for the specs.
I am wondering right now which one (Buschur,AMS,anyone else) have std bore forged pistons with zero deck height and ofset pins for Evo IX.
We need to change the Cosworth's.
A week ago we tried to rebuilt an Evo IX motor that had Cosworth pistons and Cosworth rods.
The Cosworth built motor was having only 5000 miles.
The main problem was that this Evo was needing 1lt of oil (15W-50 Cosworth recommendation) every 600 daily driven miles!!!!
We thought that the problem was on the piston rings.
Everything was ok on the rings and the rings gap... the magor problems was on the pistons and the piston clearance from the cylinder wall!!!
We measure them (Cosworth forge pistons PA2689 standard 85mm) and the following numbers came on....
Piston 1:84.40mm diameter on the top 84.81mm diameter on the end of the bottom
Piston 2:84.40mm diameter on the top 84.87mm diameter on the end of the bottom
Piston 3:84.40mm diameter on the top 84.83mm diameter on the end of the bottom
Piston 4:84.40mm diameter on the top 84.87mm diameter on the end of the bottom
The pistons are smaller than it should be after 5000 miles only!!!!
I am not sure if the pistons was smaller when we bought them or they got smaller afterwards.
That is the reason of the oil problem !!!
Huge piston to cylinder gap!
The problem is on all 3 Evo's that we used Cosworth pistons PA2689 !!!!
The green coating is ok.
Also now you have to use a hummer the get the pins out of the pistons!!!
I am trying to find out the Cosworth pistons diameter specifications for these pistons.
I contact already and email Cosworth USA and Cosworth UK.
I am waiting for the specs.
I am wondering right now which one (Buschur,AMS,anyone else) have std bore forged pistons with zero deck height and ofset pins for Evo IX.
We need to change the Cosworth's.
Apr 16, 2009, 05:44 PM
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A few points
From my experience Cosworth Pistons are of the highest quality you can purchase and they are made in the same UK facility as where the Champ, CART and F1 pistons are made
The uniformity between pistons and finish and the design is simply of the best possible quality
Secondly, a piston is properly measured at approx 10 - 15 mm from the botttom of the skirt on the side.
The critical measurement on a piston is the piston to wall clearence which is supposed to be in the range of .0029 to .0035 on a typical street car - (more for heavy boost or nos applications). The way the measurement is made is by using a bore dial gauge to measure the bores and also checking the roundness and top to bottom eveness of the bores then measure the piston with a quality micrometer and subtract the difference.
The final dimension to check - especially for oil consumption is the ring gaps and oil control rings.
I would be very suprized to see any Cosworth engine product having any problems what so ever. Simply put the Cosworth stuff is the best you can buy - period.
I am a Master Distributor for Cosworth and will be happy to answer ant tech questions you have.
BTW did you do a leak down and compression test prior to disasembly?
Al
From my experience Cosworth Pistons are of the highest quality you can purchase and they are made in the same UK facility as where the Champ, CART and F1 pistons are made
The uniformity between pistons and finish and the design is simply of the best possible quality
Secondly, a piston is properly measured at approx 10 - 15 mm from the botttom of the skirt on the side.
The critical measurement on a piston is the piston to wall clearence which is supposed to be in the range of .0029 to .0035 on a typical street car - (more for heavy boost or nos applications). The way the measurement is made is by using a bore dial gauge to measure the bores and also checking the roundness and top to bottom eveness of the bores then measure the piston with a quality micrometer and subtract the difference.
The final dimension to check - especially for oil consumption is the ring gaps and oil control rings.
I would be very suprized to see any Cosworth engine product having any problems what so ever. Simply put the Cosworth stuff is the best you can buy - period.
I am a Master Distributor for Cosworth and will be happy to answer ant tech questions you have.
BTW did you do a leak down and compression test prior to disasembly?
Al
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Apr 16, 2009, 09:52 PM
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BTW - just thinking about your post, if you needed to remove the wrist pin with a hammer - no doubt your tuning resulted in detonation and either bent the wrist pin / piston or both.
I have seen cars with huge power running the Cosworth pitsons and writs pins and never saw any of them bend or become stuck in the piston.
Al
I have seen cars with huge power running the Cosworth pitsons and writs pins and never saw any of them bend or become stuck in the piston.
Al
Apr 17, 2009, 01:33 AM
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konstantinos i bought a cosworth shortblock and i have the information sheet that comes with it. it lists piston to cylinder clearance and ring end gaps from the top and 2nd ring. send me a pm if you need the info.
Something else this shortblock came with + 0.5 mm overbore pistons. I asked cosworth why they list it as 85 mm and they told me that they buy new shortblocks but some of them simply dont have the right piston to cylinder clearance and they need to be honed for larger pistons. so maybe your problem is there.
Something else this shortblock came with + 0.5 mm overbore pistons. I asked cosworth why they list it as 85 mm and they told me that they buy new shortblocks but some of them simply dont have the right piston to cylinder clearance and they need to be honed for larger pistons. so maybe your problem is there.
Last edited by DimitrisIX; Apr 17, 2009 at 01:37 AM.
Apr 17, 2009, 06:25 AM
#10
Hello,
A week ago we tried to rebuilt an Evo IX motor that had Cosworth pistons and Cosworth rods.
The Cosworth built motor was having only 5000 miles.
The main problem was that this Evo was needing 1lt of oil (15W-50 Cosworth recommendation) every 600 daily driven miles!!!!
We thought that the problem was on the piston rings.
Everything was ok on the rings and the rings gap... the magor problems was on the pistons and the piston clearance from the cylinder wall!!!
We measure them (Cosworth forge pistons PA2689 standard 85mm) and the following numbers came on....
Piston 1:84.40mm diameter on the top 84.81mm diameter on the end of the bottom
Piston 2:84.40mm diameter on the top 84.87mm diameter on the end of the bottom
Piston 3:84.40mm diameter on the top 84.83mm diameter on the end of the bottom
Piston 4:84.40mm diameter on the top 84.87mm diameter on the end of the bottom
The pistons are smaller than it should be after 5000 miles only!!!!
I am not sure if the pistons was smaller when we bought them or they got smaller afterwards.
That is the reason of the oil problem !!!
Huge piston to cylinder gap!
The problem is on all 3 Evo's that we used Cosworth pistons PA2689 !!!!
The green coating is ok.
Also now you have to use a hummer the get the pins out of the pistons!!!
I am trying to find out the Cosworth pistons diameter specifications for these pistons.
I contact already and email Cosworth USA and Cosworth UK.
I am waiting for the specs.
I am wondering right now which one (Buschur,AMS,anyone else) have std bore forged pistons with zero deck height and ofset pins for Evo IX.
We need to change the Cosworth's.
A week ago we tried to rebuilt an Evo IX motor that had Cosworth pistons and Cosworth rods.
The Cosworth built motor was having only 5000 miles.
The main problem was that this Evo was needing 1lt of oil (15W-50 Cosworth recommendation) every 600 daily driven miles!!!!
We thought that the problem was on the piston rings.
Everything was ok on the rings and the rings gap... the magor problems was on the pistons and the piston clearance from the cylinder wall!!!
We measure them (Cosworth forge pistons PA2689 standard 85mm) and the following numbers came on....
Piston 1:84.40mm diameter on the top 84.81mm diameter on the end of the bottom
Piston 2:84.40mm diameter on the top 84.87mm diameter on the end of the bottom
Piston 3:84.40mm diameter on the top 84.83mm diameter on the end of the bottom
Piston 4:84.40mm diameter on the top 84.87mm diameter on the end of the bottom
The pistons are smaller than it should be after 5000 miles only!!!!
I am not sure if the pistons was smaller when we bought them or they got smaller afterwards.
That is the reason of the oil problem !!!
Huge piston to cylinder gap!
The problem is on all 3 Evo's that we used Cosworth pistons PA2689 !!!!
The green coating is ok.
Also now you have to use a hummer the get the pins out of the pistons!!!
I am trying to find out the Cosworth pistons diameter specifications for these pistons.
I contact already and email Cosworth USA and Cosworth UK.
I am waiting for the specs.
I am wondering right now which one (Buschur,AMS,anyone else) have std bore forged pistons with zero deck height and ofset pins for Evo IX.
We need to change the Cosworth's.
post pictures of the pistons if you want better answers. that will tell us way more than your measurements given
Last edited by 94AWDcoupe; Apr 17, 2009 at 06:28 AM.
Apr 17, 2009, 06:55 AM
#11
A few points
From my experience Cosworth Pistons are of the highest quality you can purchase and they are made in the same UK facility as where the Champ, CART and F1 pistons are made
The uniformity between pistons and finish and the design is simply of the best possible quality
Secondly, a piston is properly measured at approx 10 - 15 mm from the botttom of the skirt on the side.
The critical measurement on a piston is the piston to wall clearence which is supposed to be in the range of .0029 to .0035 on a typical street car - (more for heavy boost or nos applications). The way the measurement is made is by using a bore dial gauge to measure the bores and also checking the roundness and top to bottom eveness of the bores then measure the piston with a quality micrometer and subtract the difference.
The final dimension to check - especially for oil consumption is the ring gaps and oil control rings.
I would be very suprized to see any Cosworth engine product having any problems what so ever. Simply put the Cosworth stuff is the best you can buy - period.
I am a Master Distributor for Cosworth and will be happy to answer ant tech questions you have.
BTW did you do a leak down and compression test prior to disasembly?
Al
From my experience Cosworth Pistons are of the highest quality you can purchase and they are made in the same UK facility as where the Champ, CART and F1 pistons are made
The uniformity between pistons and finish and the design is simply of the best possible quality
Secondly, a piston is properly measured at approx 10 - 15 mm from the botttom of the skirt on the side.
The critical measurement on a piston is the piston to wall clearence which is supposed to be in the range of .0029 to .0035 on a typical street car - (more for heavy boost or nos applications). The way the measurement is made is by using a bore dial gauge to measure the bores and also checking the roundness and top to bottom eveness of the bores then measure the piston with a quality micrometer and subtract the difference.
The final dimension to check - especially for oil consumption is the ring gaps and oil control rings.
I would be very suprized to see any Cosworth engine product having any problems what so ever. Simply put the Cosworth stuff is the best you can buy - period.
I am a Master Distributor for Cosworth and will be happy to answer ant tech questions you have.
BTW did you do a leak down and compression test prior to disasembly?
Al
Apr 20, 2009, 11:23 AM
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Apr 20, 2009, 11:27 AM
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BTW - just thinking about your post, if you needed to remove the wrist pin with a hammer - no doubt your tuning resulted in detonation and either bent the wrist pin / piston or both.
I have seen cars with huge power running the Cosworth pitsons and writs pins and never saw any of them bend or become stuck in the piston.
Al
I have seen cars with huge power running the Cosworth pitsons and writs pins and never saw any of them bend or become stuck in the piston.
Al
Apr 20, 2009, 11:29 AM
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konstantinos i bought a cosworth shortblock and i have the information sheet that comes with it. it lists piston to cylinder clearance and ring end gaps from the top and 2nd ring. send me a pm if you need the info.
Something else this shortblock came with + 0.5 mm overbore pistons. I asked cosworth why they list it as 85 mm and they told me that they buy new shortblocks but some of them simply dont have the right piston to cylinder clearance and they need to be honed for larger pistons. so maybe your problem is there.
Something else this shortblock came with + 0.5 mm overbore pistons. I asked cosworth why they list it as 85 mm and they told me that they buy new shortblocks but some of them simply dont have the right piston to cylinder clearance and they need to be honed for larger pistons. so maybe your problem is there.