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Would like some feedback. Recently finished the head and will start putting the car back together by the beginning of next week. Anyway tell me what you think :)











 

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Nice and clean... What did you get the work done? if you don't mind me asking how much did it cost.... Im thinking about having mine done too...
 

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I can't tell a whole lot from the photos, but I would have shortened the valve guide and tapered it in the direction of the intake flow. Shortening valve guides has proven to be safe, durability wise, and it removes a bit of flow restriction.

Also, that port divider wall between the valves seems to have been flattened instead of knife-edged. I would expect that to hinder flow significantly.

Steve Hayes
 

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The flattened port divided looks to be on the exhaust side with the flow going the other way. Still not ideal for flow but probably a good idea to have some meat in there with the high temps.
 

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"edited"

(in reference to the intake side)
you dont want a knife edged divider. you want a blunter divider so there is a bit of preload (preload meaning cushion that acts as a "ball bearing for the air to roll off of") on the air. the air should split into each port (not drag along the walls of each port which is what happens when you knife edge the divider). Further knife edged metal is more likely to break when under constant heat cycling and increases the possibility of stress risers; the soft aluminum is less prone to have this happen but it can still occur.
 

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Have you seen Supra heads crack with knife-edged dividers? The few I've seen have NOT cracked. Have you seen Supras with the port work you described make more power than knife-edged ports? All of the worked heads that I've seen from proven race-engine head shops were knife-edged. What are you basing your statements on?

Also, what do you mean by "preload on the air"? That term makes no sense to me, particularly in the context at hand. You mentioned "split into each port" when in fact we are talking about the exhaust port, where the gas will be MERGING into one port, not splitting. I would expect the blunt area cause turbulence and hinder flow, but without testing I couldn't say for sure. However, the fact that the proven head shops do not do it that way should tell us something.


jltcat said:
you dont want a knife edged divider. you want a blunter divider so there is a bit of preload on the air. the air should split into each port (not drag along the walls of each port which is what happens when you knife edge the divider). Further knife edged metal is more likely to break when under constant heat cycling and increases the possibility of stress risers.
 

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Another question I'd ask is, What is the total cross-sectional area of the two exhaust ports (prior to merging), compared to the cross-sectional area of the port just after merging (just after the blunt divider wall), compared to the cross-sectional area of the port exiting the head? From the looks of it, there is a relatively large "chamber" just beyond the divider wall, then it necks down again for the port exit. If so, I would think that small-large-small configuration would hurt flow. I'd love to see this head compared to both a stock head and a more conventionally ported head on a flow bench.

Another question is, Who designed the port configuration on this head? For example, I know the guy who designed the port configuration on the Garage Advance head (he has years of experience on top fuel bikes and other forced induction applications) and the SHP (Peter Blach) head (he has years of experience on forced induction Porsches). Both of those heads have yielded excellent results on Supras, yet neither of those guys use the configuration seen here. Therefore, I wonder where this one came from and what the performance results will be.
 

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Looks like someone didn't get quite what they expected...?
 

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knife edging the exhaust isnt that important when talking about a Supra head. The knife edging as far as increasing runner volume or balancing the runners has its advantages but as far as making it knifed edged for the sake of making an edge wont do a lot considering the (small large small) runner. There is back pressure caused by these exhaust restrictions where the exhaust is waiting to be put through the turbo system which will pretty much garentee that there will be no turbulence caused by the small amount of material in the divider.

The amount of heat generated by that side of the engine makes the knife edging very prone to stress risers. The metalergy in the supra head varies substantially due to the nature of castings. the various metals used to form the alloys have different weights and since formed on earth under the influence of gravity the heavier metals have a tendancy to settle to the bottom of the liquid melt therefore causing minor variations from head to head making spots on the head harder/softer more heat effected or less heat effected so the castings resistance to heat risers or cracking is different from head to head.

A standard flow bench is a great device except it measures flow relative to the atmosphere and cannot simulate a turbocharged engine. Its a straight through flow meter. Unless the shop that you are using has their flow bench set up with the turbo you are using you cant generate an accurate measurement of flow.
 
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