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Join Date: Dec 2001
Location: Cambridge, MA
Posts: 44,228
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Thoughts on these heads?
First let me say that I know nothing about rebuilding 911 motors. handy in other ways, but never tackled a motor. But I know folks who can help.
I've got my E down it's smallest components and am slowly rebuilding it. the motor has 107K on it and runs fine. Some day I'd love to have a 3.0 MFI motor done for it, but that day is far down the road. What can I do with a $7K parts budget (give or take to get the job done) to make my little 2.0 a real screamer. And if it can't be done, that's fine too. My interest was piqued with these heads. Would they work? what would you do with them? http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/377247-fs-1971-dated-twin-plug-heads-cams-cam-towers-1600-a.html#post3586346
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Tru6 Restoration & Design |
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11-13-2007, 02:27 PM
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Quote:
They sound a bit strange with the exhaust ports opened but not the intakes. That being said, with a 2.0 it's not clear to me that there's a whole lot to be "gained" by opening up the intake ports to 35 or 36 mm for street use -- the engines aren't that port constrained to begin with. Sure the 2.0S used 36 mm intake ports, but the 2.0S was also the peakiest of the early 911 street motors with it's peak HP at 6800 RPM and it's peak torque up at 5500 RPM -- an engine speed that most people only use on freeway entrance ramps. Even at 5500 RPM, the 2.0S had the slowest peak torque intake velocity of any street 911! Specifically addressing the heads in the other thread, they will lose exhaust scavenging as a result of the reduced exhaust velocity -- which can only be a bad thing in my book. They might be a good deal if you were to be building a 2.4 or 2.7 with S cams, since you'd only have to open up the intake ports rather then the exhausts. Aside from that, I don't think that these heads would be a really good fit for you. Most expensive option: If you're going to be rebuilding your motor for street use, I suggest getting some 84mm or 85 mm pistons and cylinders to bring the capacity up to 2.2 or a little more using your same heads. Keep the CR up around 9.5:1. You can keep everything else pretty much the same. If you wanted to you could drop in S (or similar) cams, but by keeping the ports a little on the smaller side you'll wind up with an engine with passable off cam performance, and S performance from 4000 RPM on up. You'd only be giving away a little to a real S from about 6500 to 7000 RPM. Just doing the case, P&C's and a rebuild kit and you'll be well north of $5000 already. Digging up some used 2.2/2.4 cylinders could save you some money. For this application even iron T pistons should be fine. Somewhat Cheaper Option: Keep your 2.0 cylinders, and replace the pistons with either S or JE pistons with S valve pockets and about a 9.5:1 CR. This is essentially what I have in my car, and you're welcome to stop by before Wednesday (I'm not working) to try a back-to-back comparison. You could also go one step further and put S (or similar) cams in at this stage. The results would be similar to the earlier option, but the smaller capacity means less torque. Cheapest Option: Just do a straight rebuild. To be honest, the big bucks are in the case refurb which is pretty much a given once you crack it open. Like I said, you're welcome to stop buy and try my car. I've also got my race engine going together on the stand, so you can check that out and some heads S and TK heads that I have to see what the difference is in the porting.
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John '69 911E "It's a poor craftsman who blames their tools" -- Unknown "Any suspension -- no matter how poorly designed -- can be made to work reasonably well if you just stop it from moving." -- Colin Chapman Last edited by jluetjen; 11-15-2007 at 12:15 PM.. |
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11-15-2007, 12:08 PM
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1969 Porsche 911E 2.0 E
