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TR6 TR6 Cylinder Head Questions
- Thread starter glemon
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bobh
Jedi Warrior
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Don,
I found the email from Chris (Feb 2006). This was his response;
"We have 219016 heads used for ÂŁ60. It would be costly to send to USA because of the weight. If you are lucky, you may find a 219019 head in the USA, which is a lower compression export version of the 219016 Chris"
I also found Chris' reply to my email asking the folowing questions;
1) What is the advantage or disadvantage of the smaller exhaust valve in the later US heads?
2) Same question regarding the "recessed" block.
Answers;
"The smaller exhaust valve is good for at least 200 bhp, the head is less likely to crack, the smaller exhaust valve alows a larger inlet, there will be less lost of incoming mixture on overlap with the smaller exhaust valve.
The 32mm valve is too big. our flow bench man reckons 31.25mm is optimum for the port, but still no gain for road use over the 30.3 If You have a recessed block, you shoud use the 'AK280' gasket to suit Chris"
On the subject of larger exhaust valves. Back in the day (the early 70s) I owned a 1971 TR6. The head had the old style inlet spacing and the Log type intake referred to earlier in this post. When I removed the head for some work. I found a crack between the intake valve and the exhaust valve on one cylinder. I suppose this head had the larger exhaust valves. I didn't know about the different heads back then. The area between valves was very small. I suspect this is the potential problem Chris referred to in his response to question 1.
Another thing to consider when choosing a head for the project.
In one of his articles Chris mentioned increasing the quench area or maybe he called it Squish area. I believe he was referring to the recessed block. Kas talkes about Zero Decking the block. I think both of them are talking about the same thing. Removing material to allow the piston to come closer to the combustion chamber on the compression stroke. The area of the combustion chamber opposite the valves and the rising piston will squish the mixture and push it into the recess around the valves. This is to get rid of the "pinking".
Decking the block increases the CR. All of the material removed from the block and head need to be considered when calculating the new CR. I seem to remember someone commenting that 9.5:1 is about the highest CR you would want for the street?
Someone else with more experience in this area may want to comment on this.
Bobh
I found the email from Chris (Feb 2006). This was his response;
"We have 219016 heads used for ÂŁ60. It would be costly to send to USA because of the weight. If you are lucky, you may find a 219019 head in the USA, which is a lower compression export version of the 219016 Chris"
I also found Chris' reply to my email asking the folowing questions;
1) What is the advantage or disadvantage of the smaller exhaust valve in the later US heads?
2) Same question regarding the "recessed" block.
Answers;
"The smaller exhaust valve is good for at least 200 bhp, the head is less likely to crack, the smaller exhaust valve alows a larger inlet, there will be less lost of incoming mixture on overlap with the smaller exhaust valve.
The 32mm valve is too big. our flow bench man reckons 31.25mm is optimum for the port, but still no gain for road use over the 30.3 If You have a recessed block, you shoud use the 'AK280' gasket to suit Chris"
On the subject of larger exhaust valves. Back in the day (the early 70s) I owned a 1971 TR6. The head had the old style inlet spacing and the Log type intake referred to earlier in this post. When I removed the head for some work. I found a crack between the intake valve and the exhaust valve on one cylinder. I suppose this head had the larger exhaust valves. I didn't know about the different heads back then. The area between valves was very small. I suspect this is the potential problem Chris referred to in his response to question 1.
Another thing to consider when choosing a head for the project.
In one of his articles Chris mentioned increasing the quench area or maybe he called it Squish area. I believe he was referring to the recessed block. Kas talkes about Zero Decking the block. I think both of them are talking about the same thing. Removing material to allow the piston to come closer to the combustion chamber on the compression stroke. The area of the combustion chamber opposite the valves and the rising piston will squish the mixture and push it into the recess around the valves. This is to get rid of the "pinking".
Decking the block increases the CR. All of the material removed from the block and head need to be considered when calculating the new CR. I seem to remember someone commenting that 9.5:1 is about the highest CR you would want for the street?
Someone else with more experience in this area may want to comment on this.
Bobh
justin_mercier
Jedi Warrior
Offline
You can do 10:1 without early detonation if you're using 93 octane pump gas. If you go to zero-deck the block, as my engine is, you also need to shave the pistons too. Modern BMW roadster engines have a 12:1 compression ratio and require you to use 93 octane in the car. I believe they also have knock detectors and other modern conveniences as well to prevent early detonation.
OP
glemon
Yoda
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Thanks Bobh, that's the information I was looking for on the valves, so I will go with the newer head, the newer intake manifold, some porting and port matching, and maybe 9.75 or 9.80 to 1 on the compression, and maybe a header as well, as long as I am trying to help the breathing capacity/efficiency.
OP
glemon
Yoda
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Cool, haven't bought one yet, curious about the results of the testing, have also been curious about the early single pipe manifold versus the later dual pipe, I calculated that the later dual outlet manifold has considerably more flow capacity, but don't know if that translates into street horsepower, I know the Kastner book says one big pipe is better than the dual exhaust, at least for racing.
Brosky
Great Pumpkin
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Don is correct, it is on my ten item list for spring that keeps growing. Mine started as a restoration project for my website (https://www.74tr6.com/exhaustmanifold.htm) and then it came out so well, that I decided to install it. But just prior to that, I spoke to the owner of the ceramic coating shop that did the manifold for me and he is well know for building Corvette engines as well as doing all of the ceramic coatings on the headers and side pipes of every Factory Five Cobra. We were talking about the manifold and he was admiring the design prior to coating and he asked me what I had on the car. I told him that I had Jet Hot coated headers, which he said was a good product but then he said, with a manifold like this, and all of the mods to your engine, you are foolish to go to headers. This manifold is as well designed as any Corvette manifold out there and Chevy does NOT recommend headers on any of the late model Corvette's unless you are full bore racing.
I also did not like the fact that the only way to remove the stock started was to pull the headers back, so off they will come and I will install the new hi-torque starter that has been on my bench for three years. And I do have it machined and tapped for my O2 sensor so I can keep my wide band Air Fuel Ratio Meter working. Picks are all on the link above.
I also did not like the fact that the only way to remove the stock started was to pull the headers back, so off they will come and I will install the new hi-torque starter that has been on my bench for three years. And I do have it machined and tapped for my O2 sensor so I can keep my wide band Air Fuel Ratio Meter working. Picks are all on the link above.
Brosky
Great Pumpkin
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Late manifold, dual pipe. Pictures are complete from start to finish on this link: https://www.74tr6.com/exhaustmanifold.htm
Simon TR4a
Jedi Knight
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Great looking manifold! I also liked the look of the Pacesetter header.
I used to have a TR6 but about 12 years ago upgraded(?) to a TR4a, so don't claim an intimate knowledge of the TR6 head.
My recollection is that the bridge between the valves is susceptible to cracking and this is a limiting factor in valve size. Because the TR6 is a 2 litre engine with a stroker crank the valves are marginal. Like the TR4 head, I think material can be removed to reduce shrouding, particularly of the intake valves.
I am curious about the idea of putting GT6 heads on a TR6, how do you deal with the 25% greater capacity? This would put an 8:1 head up to 10:1 unless the combustion chamber is carved out or a thicker gasket used.
I used to have a TR6 but about 12 years ago upgraded(?) to a TR4a, so don't claim an intimate knowledge of the TR6 head.
My recollection is that the bridge between the valves is susceptible to cracking and this is a limiting factor in valve size. Because the TR6 is a 2 litre engine with a stroker crank the valves are marginal. Like the TR4 head, I think material can be removed to reduce shrouding, particularly of the intake valves.
I am curious about the idea of putting GT6 heads on a TR6, how do you deal with the 25% greater capacity? This would put an 8:1 head up to 10:1 unless the combustion chamber is carved out or a thicker gasket used.