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Best flowing 3.6 litre heads.

Which 3.6 heads would flow the best on an engine with high CR and itb's? The 964 heads I have read flow extremely well after a port and polish even though the 993 heads have larger ports. If both went through the same polishing and port matching which would better suit and engine with about 11:1 CR with ITB's??
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Old 09-14-2004, 11:51 PM
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What size engine and what sort of rev range are you looking at? What sort of induction system? "Best" is a tough question to answer in isolation.
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Old 09-15-2004, 03:43 AM
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like I said, 3.6 litre engine with ITB's, independent throttle bodies. im guessing the revs could creep up into 8grand.
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Old 09-15-2004, 12:36 PM
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exactly what cams are you using? Port size is very sensitive. jluetjen was right, you aren't being specific enough.
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Last edited by KobaltBlau; 09-15-2004 at 02:25 PM..
Old 09-15-2004, 02:23 PM
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most likely GE 100 cams or possibly a custom grind very very close to the GE 100 grind. Ti valves, springs and retainers, supertec head studs, knife edged crank, boat tailed and shuffle pinned case, pauter Ti con rods, JE short skirt pistons and Steve Weiner's new ITB setup that he showed at the GAF.
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Old 09-15-2004, 04:59 PM
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I'm kind of waiting for SteveW or Henry from Supertec to weigh in here. I'm really out of my realm with the big engines and those guys seem to have done it all. It does look like you'll have a hard time pulling HP all the way up towards 8000 RPM while still maintaining a decent rev range given the 50 mm intake valve size of the M64/22 ROW 993 Carrera. The rest of the 3.6's all have smaller intake valves of 49 mm's. I'm guessing that the stock 43 mm intake ports are also going to be too small for that sort of engine speed. So you'd be looking at coming up with some larger valves in addition to doing some serious porting work on the heads. 7500 RPM seems like a more reasonable engine speed target. Even at that that speed you're also talking about a pretty steep 4300 fpm corrected piston speed, so as you mentioned competition rods and rod bolts will be needed.

This sounds like it is going to be a fairly significant development project trying to get a motor like that together, but it sounds like you're prepared to spend the bucks to do it. The guys you really need to listen to on this BBS would be Steve and Henry.
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Old 09-15-2004, 05:24 PM
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Yup, big bucks and lots of time are going into this. Still contemplating a TT setup as well ooooh even more money so I think that might (IS) be out haha. So Steve, Henry where are you guys???
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Old 09-16-2004, 05:47 PM
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Quote:
Originally posted by Porschekid962
most likely GE 100 cams or possibly a custom grind very very close to the GE 100 grind.
No street use at all then, I assume. What class are you racing in?
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Old 09-16-2004, 11:02 PM
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class is yet to be determined, havent added up all the other points on the car yet. something i wouldnt want to be in im sure haha. If not the GE 100 cam possibly the GE 60.
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Old 09-17-2004, 09:50 AM
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The GE100 cams with 100 degree lobe centers would limit the 3.6 with ITB. A cam with 106 lobe centers would be much better.

Most people design engines backwards. They collect a few parts and base the combination on "how much can I make with this stuff"
Usually I get called just as the engine is ready for assembly. The cam choice is then a compromise to suit the parts chosen.
The better way is to decide the RPM range and HP you need first.
Then design the intake, exhuast and cylinder heads to suit the rpm/hp choice.
The next decision would be displacement.
Now you can choose the camshaft. Basing your choice on the RPM band.
The final choice is compression ratio. If this is a track only car
and the upper rpm limit is close to or over 8000 rpms, 11-1 c/r seems low.
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Old 09-17-2004, 09:50 AM
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Wise words from John,...... Race engines are designed & configured according to the class you will run in. Durability and longevity are the next criteria to assess as everyone might not be able to afford a 400+ HP 3.6 that is a 25 hr engine,...

To answer your questions:

The 993 heads flow better than 964 heads but one would not see the difference until the 310 HP level and above.

Further, 993 RS heads (and intake valves) are better yet,......as are 3.8 RSR heads,...

As indicated, if this is to be a 3.6 race motor with the expectation of 340-380 HP, then you should start with 993 heads and have them flowed. There is room for improvement! Camshaft and compression choices will frame what kind of power you will end up with.

An engine such as this spins to 8K and there are many oiling modifications and hardware changes required for durability at those engine speeds.
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Old 09-17-2004, 10:07 AM
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Just to go back to a point that was touched upon, it's generally not a good investment to design and build a race engine and then look for a class -- because you'll wind up being uncompetitive in the most unlimited class. The best bet would be to pick the class that you are targetting and buy the rule book. Then read the rule book a few times and design an engine that will be maximized within the rules of the class desired. If you're lucky or clever, the engine will also be a good fit in a couple of other classes too.
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Old 09-17-2004, 11:18 AM
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I would add to Johns comments that you should also consider the entire car while you are at it. I have seen several cars that don't fit ANY class, so you end up in exibition class or none at all.

Last edited by snowman; 09-17-2004 at 12:33 PM..
Old 09-17-2004, 12:30 PM
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It sounds like this is more of an intellectual excercise than a real motor so the race class wouldn't be that critical.
-Chris
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Old 09-17-2004, 01:36 PM
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Oh dont worry chris this engine will be built. Sooner than later too. As soon as the new brakes go on the car I am going to begin piecing this engine together. It is going to end up going in my dad's car and then I get his three litre and get to pop that im my car, as soon as i buy it haha. I dont think he is going to race it very often, just wants the ultimate hot rod engine. After the 3.0 gets rebuilt it might end up going back into his car and then I get the 3.6.
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Old 09-17-2004, 03:26 PM
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Quote:
Originally posted by ChrisBennet
It sounds like this is more of an intellectual excercise than a real motor so the race class wouldn't be that critical.
-Chris
I agree, Chris. This was tounge in cheek:

Quote:
Originally posted by KobaltBlau
What class are you racing in?
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Old 09-19-2004, 09:07 AM
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