High Flow, Low Cost, 8V Cylinder Head Project
#136
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What I don't get with these head projects is why going to all the trouble with the head if these engines very rarely break the 600 whp barrier and 951 8V head with few modifications that OP did, is at 550whp at the moment.
What would be the reason for switching to 16v head on 3.0 build?
What would be the reason for switching to 16v head on 3.0 build?
#137
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What I don't get with these head projects is why going to all the trouble with the head if these engines very rarely break the 600 whp barrier and 951 8V head with few modifications that OP did, is at 550whp at the moment. What would be the reason for switching to 16v head on 3.0 build?
#138
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Are you sure it is stiffer? 16v is more complex structure and the more the head is complex the more it is prone to fractures.
Also 535whp is monumental for these engines, I don't know if I ever heard anybody succeed to produce reliable more regardless of head type.
Then there are non turbo exhaust valves that are a risk for catastrophic failure on high power turbo car + lack of 16V turbo pistons.
Considering all together I can not find a reason to switch to 16V. I can get 16V head for peanuts but I can not think of single real benefit that would be worth of extra complication.
Also 535whp is monumental for these engines, I don't know if I ever heard anybody succeed to produce reliable more regardless of head type.
Then there are non turbo exhaust valves that are a risk for catastrophic failure on high power turbo car + lack of 16V turbo pistons.
Considering all together I can not find a reason to switch to 16V. I can get 16V head for peanuts but I can not think of single real benefit that would be worth of extra complication.
#140
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Are you sure it is stiffer? 16v is more complex structure and the more the head is complex the more it is prone to fractures.
Also 535whp is monumental for these engines, I don't know if I ever heard anybody succeed to produce reliable more regardless of head type.
Then there are non turbo exhaust valves that are a risk for catastrophic failure on high power turbo car + lack of 16V turbo pistons.
Considering all together I can not find a reason to switch to 16V. I can get 16V head for peanuts but I can not think of single real benefit that would be worth of extra complication.
Also 535whp is monumental for these engines, I don't know if I ever heard anybody succeed to produce reliable more regardless of head type.
Then there are non turbo exhaust valves that are a risk for catastrophic failure on high power turbo car + lack of 16V turbo pistons.
Considering all together I can not find a reason to switch to 16V. I can get 16V head for peanuts but I can not think of single real benefit that would be worth of extra complication.
I think you're probably right in that there is little need to switch to a 16v...but I would preface that by saying 'for a roadcar'. For a track car, the 16v is definitely a better option for the facets mentioned. Some people have done this while retaining much of the stock running gear and had good results. Some have made more changes for hard core race cars. I think for 95% of us the 8v is totally fine for the street.
#141
Voith, can you mention at least one high HP 16V engine on here that has suffered catastrophic exhaust valve failure?
What extra complication are you talking about?
Don't you think that headaches related with head work, valves, cam, etc and the cost related is not an extra complication over a stock 16V head that will breathe better right away?
If you are able to properly read through the archives on here it should come to you that there is zero reason to prefer an 8V over a 16V when building a 3L turbo engine. You may as well purchase a Golf GTD.
What extra complication are you talking about?
Don't you think that headaches related with head work, valves, cam, etc and the cost related is not an extra complication over a stock 16V head that will breathe better right away?
If you are able to properly read through the archives on here it should come to you that there is zero reason to prefer an 8V over a 16V when building a 3L turbo engine. You may as well purchase a Golf GTD.
#142
Nordschleife Master
I did 514 rwhp at 1.1 bar of boost on pump gas using stock 968 head (stiffer springs) and stock 968 cams with Variocam. I guess that pretty much sums up the potential
For the block you either go Alusil or sleeve it. And there's the same options for 16v as for 8v excluding the odd Mahle 3.0l 8v batch that can be found from time to time. So it's not really a matter of less piston choices either. Sure, you need to adapt the headers and intake manifold. But considering you can leave the head and cams stock it can be done on a reasonable budget similar to a reasonable 8v route.
The low cost, high flow, 8v head in this thread is might impressive in terms of ROI. But I will never understand spending a huge amount of money on a 8v head.
For the block you either go Alusil or sleeve it. And there's the same options for 16v as for 8v excluding the odd Mahle 3.0l 8v batch that can be found from time to time. So it's not really a matter of less piston choices either. Sure, you need to adapt the headers and intake manifold. But considering you can leave the head and cams stock it can be done on a reasonable budget similar to a reasonable 8v route.
The low cost, high flow, 8v head in this thread is might impressive in terms of ROI. But I will never understand spending a huge amount of money on a 8v head.
#143
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Voith, can you mention at least one high HP 16V engine on here that has suffered catastrophic exhaust valve failure?
What extra complication are you talking about?
Don't you think that headaches related with head work, valves, cam, etc and the cost related is not an extra complication over a stock 16V head that will breathe better right away?
If you are able to properly read through the archives on here it should come to you that there is zero reason to prefer an 8V over a 16V when building a 3L turbo engine. You may as well purchase a Golf GTD.
What extra complication are you talking about?
Don't you think that headaches related with head work, valves, cam, etc and the cost related is not an extra complication over a stock 16V head that will breathe better right away?
If you are able to properly read through the archives on here it should come to you that there is zero reason to prefer an 8V over a 16V when building a 3L turbo engine. You may as well purchase a Golf GTD.
Ive been all smart with BMW 24V engine and its exhaust valves and I burned one valve in a way that its pieces fell in the combustion chamber, stuck between piston and cylinder and made catastrophe in my wallet. It is why all turbo cars have sodium or other means of cooling exhaust valves & seats, it is not there for nothing.
Also 16V turbo crowd is too small to draw any significant statistic from them. How many of 10 16V engines from the 3.0 list is still running?
By all means if money, expertise and learning trough failure is not a big problem, 16V is great, but since in most cases reliable 500~550whp is absolute ceiling for these engines, I do not see any benefit in all extra work and price involved.
It is also very strange JM built engines and US 944 GTR used 8V engines and not GTDs..
Last edited by Voith; 03-23-2015 at 11:17 AM.
#144
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Been a good read so far. I have a lot more learning to do.
Here's another topic to bring up. The topic of Stainless steel vs sodium filled valves. I have done some reading on Corvette/other forums and the topic seems to be split.
Sodium filled valves should be able to transfer more heat, but some seem concerned about the heat being transferred to the guides. Stainless steel seems to be a compromise of the pros and cons of the sodium filled.
My plan is to stick with the sodium filled 951 exhaust valves and go with the stainless Intakes sourced from SI, unsure the size just yet.
School me.
Here's another topic to bring up. The topic of Stainless steel vs sodium filled valves. I have done some reading on Corvette/other forums and the topic seems to be split.
Sodium filled valves should be able to transfer more heat, but some seem concerned about the heat being transferred to the guides. Stainless steel seems to be a compromise of the pros and cons of the sodium filled.
My plan is to stick with the sodium filled 951 exhaust valves and go with the stainless Intakes sourced from SI, unsure the size just yet.
School me.
#145
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Point of sodium valve is to get as much heat to guides as possible. That way seat area stays ~150°C cooler and that is a lot.
Last edited by Voith; 03-23-2015 at 11:20 AM.
#146
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I understand the theory. Heat at the guides, should transfer the heat to the water/oil passages, thus being cooled. As far as I understand it. I should say, the amount of heat transferring to the guides that may cause increased wear.
Doesn't seem like an issue as plenty of stock 951's are running around without guide problems. And sodium filled valves are usually the choice of high performance engines. The cheap price of the SI valves does make the SS valves something to consider. Wondering what cons the SS valves would have to performance.
Doesn't seem like an issue as plenty of stock 951's are running around without guide problems. And sodium filled valves are usually the choice of high performance engines. The cheap price of the SI valves does make the SS valves something to consider. Wondering what cons the SS valves would have to performance.
#147
In fact the folks who have built 16V engines have properly put a lot more attention to detail than some of the 8V folks who may have foolishly believed that building an 8V was going to be a lot easier/cheaper and have gone through issues along the way. At least with engines with a power output and durability worthy of a 3L capacity.
JME and others on here have built 16V engines as well, FYI.
The stock 16V outlet valves may not be sodium-filled, but to destroy them you will need to run your engine at WOT for several hours.
I am not saying it is useless to source sodium-filled exhaust valves, I am saying that staying 8V instead of going 16V for a 3L build because of the intake manifold and outlet valves is wrong.
Last edited by Thom; 03-24-2015 at 06:08 AM.
#148
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There are a lot more successful 944 8V race cars with recorded long life, than 16V.
Why mould and produce a new iteration of 8V head and spend hundred thousands of deutsche marks or $ if 16V was developed and was available at the time?
What is the reasoning for 8V with unlimited budget?
Why mould and produce a new iteration of 8V head and spend hundred thousands of deutsche marks or $ if 16V was developed and was available at the time?
What is the reasoning for 8V with unlimited budget?
#149
It's the proportion that matters, not the outright number.
The 944 GTR engines, which were an initiative from the US at a time when Porsche was not interested anymore in a full racing program with these cars, were running before the factory production 16V head was designed.
The 944 GTR engines, which were an initiative from the US at a time when Porsche was not interested anymore in a full racing program with these cars, were running before the factory production 16V head was designed.
Last edited by Thom; 03-24-2015 at 06:09 AM.
#150
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924 GTP = 1980 = 16V
944 GTR = 1987 = 2.5 litre, SOHC, turbocharged engine. It produces 650 h.p. at 1.8 bar. The aluminum liner-less block was specifically cast for the GTR. It has a 100 mm bore x 78.9 mm stroke.
http://motorsportsmarket.com/pages_n...il.asp?car=131
944 GTR = 1987 = 2.5 litre, SOHC, turbocharged engine. It produces 650 h.p. at 1.8 bar. The aluminum liner-less block was specifically cast for the GTR. It has a 100 mm bore x 78.9 mm stroke.
http://motorsportsmarket.com/pages_n...il.asp?car=131