Jerry, Scott is right. The webers are an expensive do nothing unless you
take steps to utilise their potential. An increase in CR, free flow
exhaust,headers and a street cam first. Even then, a pair of HS6 SU's are
cheaper and easier to tune"
----------
> From: Scott W. Paisley <scotty@csn.net>
> To: Gerald F. Doherty <gdoherty@sprynet.com>
> Cc: triumphs@autox.team.net
> Subject: Re: Living with Webers (long)
> Date: Saturday, April 26, 1997 10:08 AM
>
> Jerry wrote:
>
> > I'm contemplating an engine rebuild for my 73 TR6. I asked me
> mechanic
> > for suggestions on increasing the horses. He strongly urges
> installation
> > of triple Webers...
>
> Hi Jerry,
>
> Triple webers in your case, is not the approach I would take. That
> would be the last modification to make. There are several other
> things I'd suggest you do first, especially since you are thinking
> about doing a rebuild anyway. Be warned, if you do a complete
> rebuild, you are looking at approx $1500 without modifications,
> assuming you do both the upper and lower portions of the engine. While
> it's true that the webers will supply more fuel, without other
> modifications to the engine, I think a weber setup would not be a good
> use of resources. (IMO) As for modifications I'd suggest this line of
> defense.
>
> Compression. You car being a 1973 has a CR of 7.75:1. Previous years
> had 8.5:1 The 8.5 heads were 3.460 inches thick. To go to 9:1 you need
> to mill your head down to a thickness of 3.43 inches thick. This is a
> significant amount of milling as your head is likely to be 3.5 inches
> thick already. 3.43 is an estimate, but should be darn close to 9:1.
> You can go higher, but this is a nice number as you shouldn't have to
> modify pushrods (I think), and can run on normal pump gas. You
> *might* have to modify the chambers in the head slightly, but this can
> be done with a dremel tool and is quite simple. I don't think this
> will be necessary though. In your shoes I would mill to 3.43 or 3.44
> inches. This will give you a significant boost of power. Don't do
> this without rebuilding the low end, as the extra compression will
> play havoc on tired rings.
>
> Cam: You should replace your stock cam with something that has a bit
> more lift. If you ever add the webers, this will take great advantage
> of their ability to flow fuel. You can always add those later, and
> these mods will complement the webers. I've done quite a bit of
> homework on cams, and here are a few I like:
>
> IO IC EO EC DUR DUR LIFT RPM RANGE COMMENTS
>
> 10 50 50 10 240 240 .220 ? stock in early engines
> 18 58 58 18 256 256 .240 2000-5000 stock (1973 on?)
>
> 22 63 63 22 265 265 .280 ? Zimmerman, $45,
> noted to have good torque
> 28 57 69 16 265 265 .280 Zimmerman Advanced 6 degrees
>
> 30 56 74 28 266 282 .288 2200-5200 Road 83 (Moss Motorsports)
> 37 63 74 28 280 282 .288 2500-6000 Fast Road 83 (Moss Motorsports)
>
> 31 71 71 31 282 282 .285 3500-5500 S2 Cam, $135 from TSI, This is
> a very common modification,
> noted to
> be difficult under low RPM
> 29 69 69 29 278 278 .281 2500-6000 Isky Z19, $98
>
> The Zimmerman cam is from a local machine shop I use here in Denver.
> This cam has a little more duration and overlap than stock, but
> significant more lift. This should help the car breath, but still
> have a good idle. Many people use the S2 cam, as it was a British
> Leyland cam. I know a few people who have run this cam, and while it
> gives good HP on the higher RPMs, it *can* be difficult to get the
> idle down, and I wanted my car to idle nice, with good power on the
> lower RPMs.
>
> I really like the Isky Z19 cam. It's very much like the S2, but has 4
> degrees less duration and overlap, and a little less lift. Note that
> it has an advertised RPM range which is much lower than the S2. I
> think it would be a good compromise if your trying to get the absolute
> most out of your street car. That's not what I'm doing, so I went
> with a milder cam grind. (from Zimmerman)
>
> Now that we have better breathing we *should* (but don't have to) do
> something to help take advantage of the cam. Port matching is one of
> the best things to do WRT that, and port polishing and opening should
> be left for race cars, IMO. Port matching will greatly improve flow
> and isn't that difficult if you have a die grinder. A free flow
> exhaust will help too, but I run a stock exhaust as I like to run my
> car on long trips, and a sport exhaust can get tiring. The exhaust
> ports on my manifold didn't match up at all.
>
> These are the simple things you can do to the head. Raise the
> compression, new cam, port match. Milling will cost around $60-$100,
> cam should be around $75-$100 if you can regrind your existing cam,
> and port matching is free. :-)
>
> On the low end, you should balance the engine, and replace and machine
> everything that moves. Have the Big ends on the connecting rods
> redone. Machine the crank if necessary. Balance the pistons,
> connecting rods.
>
> I should add that I'm currently making these mods to my engine as I
> write this! Once I have the car on the road, and see how it runs,
> I might make a few changes to what I've written here, but I think
> things should turn out pretty close. My Compression Ratio is 9.5:1
> and I think I'll have to use shorter pushrods. I'll let the list
> know how it all turns out.
>
> Much of this is detailed in the Triumph Competition Prep Manual.
> It's very good reading, and can be had from most any TR place.
> I got mine from TRF.
>
> Cheers,
>
> -Scott Paisley
> '75 TR6
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