The picture of the cylider did not came in my previous post.
Hopefully it will this time.
Dimensins
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by racehead-1 » Wed Oct 14, 2009 8:13 am
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by jakesportingservice » Wed Oct 14, 2009 5:09 pm
Just a quick thought can the exhaust port handle that big of
a valve with out getting into water ?
My thought is with the smaller valve the port might be more
efficient than with the larger valve . JMO
Jake
a valve with out getting into water ?
My thought is with the smaller valve the port might be more
efficient than with the larger valve . JMO
Jake
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by racehead-1 » Wed Oct 14, 2009 6:47 pm
No problem regarding the wall thickness of the port and also the seat for a valve seat insert of 32 milimeters.
Jake explain why the smaller valve should be more efficient.
The exhaust is the pressure side. The ratio of the intake valve to the exhaust is 70%. From what I know it is to get the exhaust gases as fast as possible so there is not too much exhaust gases to delute the fresh upcoming air mixture.
Jake explain why the smaller valve should be more efficient.
The exhaust is the pressure side. The ratio of the intake valve to the exhaust is 70%. From what I know it is to get the exhaust gases as fast as possible so there is not too much exhaust gases to delute the fresh upcoming air mixture.
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by jakesportingservice » Wed Oct 14, 2009 9:01 pm
Is this engine naturally aspirated or is using a power additive?
This will make a difference in the answer to your Question.
Jake
This will make a difference in the answer to your Question.
Jake
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by racehead-1 » Thu Oct 15, 2009 3:40 am
This engine is naturally aspirated and is not using a power additive. When you say power additive you mean a NOS system?
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by coulterracn » Thu Oct 15, 2009 5:16 am
Turbo or super charger, etc...
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by jakesportingservice » Thu Oct 15, 2009 3:30 pm
ok now that i know that it is naturally aspirated i will say that a smaller exhaust port can work better than a large one in the way that it can have more velocity and with that the port will be able to in effect keep the flow moving in the correct direction .
What i normally use for an exhaust port is around 88% to 90% of the valve size for the throat and make the port expand around the guide around .200 thousands larger than the throat .
The exit of port needs to be larger than the valve size is what i have found to work for the heads i work on. The exit normally for me is not round it is more rectangular with a very large radius seems to work .
I'll see if can get a couple of pics to show you.
Jake
What i normally use for an exhaust port is around 88% to 90% of the valve size for the throat and make the port expand around the guide around .200 thousands larger than the throat .
The exit of port needs to be larger than the valve size is what i have found to work for the heads i work on. The exit normally for me is not round it is more rectangular with a very large radius seems to work .
I'll see if can get a couple of pics to show you.
Jake
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by racehead-1 » Thu Oct 15, 2009 5:04 pm
[color=#000000]Exhaust velocity is not everythhing, if you don
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by racehead-1 » Thu Oct 15, 2009 5:10 pm
[color=#000000]Exhaust velocity is not everythhing, if you don
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by jakesportingservice » Thu Oct 15, 2009 11:31 pm
Hello I've looked at the photos and it looks to me that the valves are close to the edge of the combustion chambers .
With that how much room is there to the edge of the bore from the valve ? Are the valve canted at all ?
If they are not and there is not much room to the bore i would try and stray away from adding the larger valve as it would be trying to shroud the valve more than i would want it to be .
The answer to how much % on the intake throat is usually around 86% to 90% depending on if the head is a street car or a all out competition engine if it is run on the street i would stay towards the smaller % so the engine still has good throttle response in the lower rpm range.
I've seen some vanes in floors of some heads before and i also am not sure why they put them in. With your head i would try to staighten the runner of the port and widen the short turn with out lowering it as much as you can as it looks like there is not much of a turn there as it is . try to shape the vane on the floor and make it aim at the center of the port exit .
Work the guide narrowing it and make it profiled to the port so it is more streamlined and aerodynamic. Since your ports are already round i would stay with that as it is .
The port exit looks as if it is large enough with the size valve that is in the head now but you can make it a bit larger and shape it more round if you prefer to make it look better and remove casting lines .
With that how much room is there to the edge of the bore from the valve ? Are the valve canted at all ?
If they are not and there is not much room to the bore i would try and stray away from adding the larger valve as it would be trying to shroud the valve more than i would want it to be .
The answer to how much % on the intake throat is usually around 86% to 90% depending on if the head is a street car or a all out competition engine if it is run on the street i would stay towards the smaller % so the engine still has good throttle response in the lower rpm range.
I've seen some vanes in floors of some heads before and i also am not sure why they put them in. With your head i would try to staighten the runner of the port and widen the short turn with out lowering it as much as you can as it looks like there is not much of a turn there as it is . try to shape the vane on the floor and make it aim at the center of the port exit .
Work the guide narrowing it and make it profiled to the port so it is more streamlined and aerodynamic. Since your ports are already round i would stay with that as it is .
The port exit looks as if it is large enough with the size valve that is in the head now but you can make it a bit larger and shape it more round if you prefer to make it look better and remove casting lines .
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by racehead-1 » Tue Oct 20, 2009 2:59 pm
[color=#000000]Yes, the valves are close to the edge of the bore. The size of the valve could be incresead not to my desired 31mm but to 30mm. The 45
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by larrycavan » Wed Oct 21, 2009 5:43 am
Regarding the exh port exit size being smaller than the exhaust header pipe:
That is the accepted standard method to help fight reversion. However, I've seen exhaust ports that were matched to the header pipe and there was no visible signs of reversion in the intake ports.
Most recently on a factory 4 valve head [Suzuki].
IMO, reversion is more profoundly affected by system lengths, cam lobe profile and lobe centerlines.
That doesn't mean to ignore the advantage that an anti reversion ridge at the port exit could provide. It only means that the ridge, in some engines, seems to be less of a contributor to the anti reversion affect.
It is, as it always is, the correct parts combo that tends to have the greatest affect.
I've seen hemi chamber head with the ridge that had noticable level of reversion. I've seen pentroof chambers with and without the ridge that showed no signs of reversion in the intake runners.
We can't always have the system lengths we desire to use on a particular engine. In such cases, the seemingly safe bet is to leave the ridge.
JMO
Larry C
That is the accepted standard method to help fight reversion. However, I've seen exhaust ports that were matched to the header pipe and there was no visible signs of reversion in the intake ports.
Most recently on a factory 4 valve head [Suzuki].
IMO, reversion is more profoundly affected by system lengths, cam lobe profile and lobe centerlines.
That doesn't mean to ignore the advantage that an anti reversion ridge at the port exit could provide. It only means that the ridge, in some engines, seems to be less of a contributor to the anti reversion affect.
It is, as it always is, the correct parts combo that tends to have the greatest affect.
I've seen hemi chamber head with the ridge that had noticable level of reversion. I've seen pentroof chambers with and without the ridge that showed no signs of reversion in the intake runners.
We can't always have the system lengths we desire to use on a particular engine. In such cases, the seemingly safe bet is to leave the ridge.
JMO
Larry C
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