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Porting the 907 head  Rating:  Rating
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 Posted: 02-07-2010 05:06 pm
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roverman
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Hi, any suggestions or personal experiance with this head. I've been told 305 cfm./28" @ .45"lift on intake side, Anybody? I will be using I.R. with port injection/possible slide plate.  Thanks, roverman.

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 Posted: 04-02-2010 12:20 pm
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907heaven
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I've done quite  alot of work on these heads - will you be keeping standard valve sizes or going larger?  At 10" water (sorry that is what my flowbench runs at) you can see about 170cfm with standard valves, 180cfm with +1mm valves and 190cfm with +2mm valves.   Regards GARRY

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 Posted: 04-03-2010 12:42 am
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roverman
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Garry, Thanks for response, 2mm os. on valves. I'll look-up the conversion factor to 28". How was flow, under the curve ? Have you flowed/ported the Zeus head ? I am considering. Try not to chirp, like "others" in this forum, but their going on a Rover V8. Unless I stumble on a suitable 90 deg. V8 firing order,(LS ?), I'll need to make cams. Wierd/forbidden, subjects like this, are discussed shamelessly, over at "British V8 Forum", roverman.

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 Posted: 04-03-2010 10:01 am
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907heaven
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I've heard of people threatening to do this conversion; I once supplied a guy a couple of heads to try it but never heard the outcome, I would imagine though that you would have a very wide V8 - maybe hard to fit in an engine bay?

I've ported several Zeus heads; they are a nice head "as cast", and are better formed in terms of internal cooling passages - supposedly having 30% more cooling capacity.  Bear in mind also that the Zeus head has a bigger chamber - 42cc versus the 36-38cc of the earlier heads.   Do you have two zeus heads?  They are much rarer than the early heads.  Ultimately in terms of airflow you can achieve just as much from the early heads; you just have a bit more grinding to do. 

The flow under the curve is excellent - a match for much more modern heads. Obviously you'll appreciate that describing port shapes is virtually impossible; but as a general guide - try and work with the existing port shape; they have a slight curve in plan view; which many people try to straighten out; in my experience with poorer results than working with the basic shape.   If you need some 38mm valves let me know - I keep them on the shelf.

Can't you get a flat plane crank and run the engine like a pair of siamesed 4 cylinders?  I know it wouldn't sound as nice; but Ferrari manage to make that firing order sound OK - I also hear that flat plane cranks produce more HP?

There are quite a few Jensen Healey's in the UK running around with Rovers in them; maybe 4 Jensen Healey cam covers under the bonnet (hood) wouldn't look so out of place?  After all the 907 was always built as half of a V8 engine; the prototype V8's made good power - they just couldn't get a cam belt to stay on them.  Are the bore centres on the rover the same - the Lotus is 4.25".  I would be interested to hear how you get on.  Good luck.

GARRY

 

Last edited on 04-03-2010 10:02 am by 907heaven

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 Posted: 04-07-2010 08:55 am
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subwoofer
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At the other end of the porting spectrum: How much improvement can be expected from a simple "gasket match" porting on the early (before, say, 1980) heads? Not removing any material further in than about 1" from the gasket face, the point just being to remove any steps in the cross section.

--
Joachim

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 Posted: 04-07-2010 11:37 am
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907 heaven
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 I don't ever really do so little work as that, so can't honestly say, but what I can say though is that in terms of "bang for buck" - you need to be working at the valve end of the port.  The shape of the valve head, valve seat and short side turn of the port influeneces flow more than anything else.  Many people look at a head without the valves in and forget that the biggest restriction is the valve itself - "porting" is perhaps not the best term to use - since the actual port is not really that much of a restriction - of course it can be improved; but the part of the port that really matters is the 3/4" immediately before the valve.

Matching the port and the intake manifold is good practice and won't hurt, but I would really not expect to see a significant gain in airflow to be honest.

My advice would be to just simply smooth out the lumps and bumps on the short side turn of the port (don't go wild), put a 30 degree back cut above the seat (on the valve) and cut a 3 angle valve seat on the intake port.  Trying to describe porting is very difficult; but what I've described above will get you a reasonable improvement without a lot of work.

Regards 

GARRY

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