Spider improvement effort - Page 5 - Alfa Romeo Bulletin Board & Forums
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post #61 of 414 (permalink) Old 01-05-2010, 04:28 PM
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So what is the reason to put a Montreal engine when a V6 24V would provide the same if not better performance?

For me the only reason to install a Montreal engine is the possibility to exploit it's potential technically at least at the same level as in the modified Nord or V6 engines. What you are doing here with the Montreal engine is a bit more than a "cleaning". IMO you have to be a little more brave and make a deep modification of the engine, you know, ports, valves, CR, cams, ITB, ECU, in the fashion you use to do it with other engines...

Ah!! could you explain a bit that?: "...For those of you that think "3 angle" valve cuts are best you are way behind. You do NOT attempt to manage flow at such small radiuses and high speeds with "shapes"! Larger valves applied to such seats only add additional interference to fluid flow (air)..." because as far as I know, seen, tested, and simulate, 3 angle seats provide the best flow, especially at high speed flows (at low lifts, and at high rpm).

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- '90 2.0 Spider -- '93 164 QV -- '93 155 2.0 TS -- '02 156 2.5 V6 -- '?? FMG 3.8 Project
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post #62 of 414 (permalink) Old 01-05-2010, 04:45 PM
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This should be interesting.

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post #63 of 414 (permalink) Old 01-06-2010, 05:59 AM Thread Starter
Richard Jemison
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What???

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So what is the reason to put a Montreal engine when a V6 24V would provide the same if not better performance?
Why would I want a street ***** when I have a movie star?

As I said, this is a car built "my way" and this "way" with my cams & headwork, TBs increased to 40mm from 35mm, I will get in excess of 275 HP from a docile high torque motor that is veryUnique! I build V6 12V motors for daily use that make 275 HP. Why should I worry with the complications of the 24 V motor when the former is smaller, lighter, and FAR LESS COSTLY to build into a performance motor?
But who would choose a V6 over a Montreal V8???

Maybe you forget that there is more in building a "specialty" car than HP? You think?

As for the valve work question, I did explain the statement. Read it again.

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RJR Racing

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post #64 of 414 (permalink) Old 01-06-2010, 06:45 AM
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Dear Richard, I read it again. I suppose others did it as well.
The seats are 1mm, about .040 inch wide,-near the outer edge of the valve head. The outer portion of the inner surface of the valve head has been thinned toward?-to? the 30 degree seat.
Since "the motor is not being prepared for high performance" it seems excessive for street but why not have some fun?
Question; is such a narrow seat OK for a street car?Heat transfer and other considerations. Structurally, 1mm at the periphery of a thinned valve OK?
The theory to open the valve area to the max, and forget the "bending" seems clear.
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post #65 of 414 (permalink) Old 01-06-2010, 12:35 PM Thread Starter
Richard Jemison
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Seats

Seats as done are not "narrow". FYI .030 & .040 seats are adequately wide, & even narrower used on race heads.. These are .040 & .050 finished.
The valves are not "thin", just reshaped. And my VSK13 springs have adequate but not excessive seat pressures.

The wider the seat more likely debris can interfere with seating.
Here are pics of fully preped (ports opened & strightened, bowls deeper & widened around short guides & valves unshrouded) 3.0 V6 12V "L" heads built with 45 degree valves last week. Seats are more than adequate with valve seat width cut back to .040 since most likely when sold they will get used on street car looking for power. Stainless valves are not easy to "burn".
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post #66 of 414 (permalink) Old 01-06-2010, 12:51 PM
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About the engine selection criterion, OK, it's your car, money, and wishes, so nothing to more to say.

But as I see things, the reason why you have not installed bigger seats for the valves, is that seats are placed very close of the combustion chamber edge, and if you install bigger seats and bigger valves,you should shrink the valves on the combustion chamber, which is not good for flow, or maybe not feasible, so to increase flow you have "open" the valve throat area taking 2mm ID on the intake seat and 3mm ID on the exhaust one, so you have not enough material on the seats to apply a 3rd angle, that is the only reason to justify your 2 angle seats.

Think that what really matters is the HYDRAULIC DIAMETER of the seats, which is lower than the ID of the seats, the 3rd angle helps to adapt the flow direction between the valve seat and the valve, the same as intake bellmouths (air horns) geometry do with intake flow.

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- '90 2.0 Spider -- '93 164 QV -- '93 155 2.0 TS -- '02 156 2.5 V6 -- '?? FMG 3.8 Project
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post #67 of 414 (permalink) Old 01-06-2010, 02:38 PM Thread Starter
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valve seat design

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But as I see things, the reason why you have not installed bigger seats for the valves, is that seats are placed very close of the combustion chamber edge, and if you install bigger seats and bigger valves,you should shrink the valves on the combustion chamber, which is not good for flow, or maybe not feasible, so to increase flow you have "open" the valve throat area taking 2mm ID on the intake seat and 3mm ID on the exhaust one, so you have not enough material on the seats to apply a 3rd angle, that is the only reason to justify your 2 angle seats.

Think that what really matters is the HYDRAULIC DIAMETER of the seats, which is lower than the ID of the seats, the 3rd angle helps to adapt the flow direction between the valve seat and the valve, the same as intake bellmouths (air horns) geometry do with intake flow.
You are not correct. (and you write like an Engineer, so this is obviously a wasted post!) I have spent many years with my flow bench and building Alfa and other, engines.

The middle "angle" cut is unnecessary. You are not going to get air to follow a small radius at speeds and "opening" size is what counts. I have changed the seat from a 90 degree to 75 degree to get flow to the edge of the valve Can`t you get the concept here? Your example of Airhorns and valve seats don`t correlate! Why would I want 90 degree to 45 degree to 30 degree??

I would not put the 45 degree cut in there period after a full 75 degree reshaping!

Enough of this. If you had more hands on engine & head building experience this conversation would not be happening.

You do your heads with 3 angle cuts. I & other knowledgable builders do not!

Success with this design is well proven. You don`t need to do anything I do. Suit yourself. I do!

Richard Jemison
RJR Racing

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post #68 of 414 (permalink) Old 01-06-2010, 03:09 PM
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Thought it would be interesting.

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post #69 of 414 (permalink) Old 01-06-2010, 03:28 PM
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Rock on Richard. Fascinating project.

1975 Spider -- Long gone gateway drug
1983 Spider -- Dead: slowly parted-out on eBay
1974 Spider -- Sold, alas.
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post #70 of 414 (permalink) Old 01-06-2010, 04:49 PM
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Quote:
Originally Posted by Subtle View Post
Thought it would be interesting.
Lets go, but now I'm not sure if we are speaking about the same angles, for this reason I'm attaching a drawing with the angular dimensions you are using, at least as I understood, correct me if I'm wrong please.

Yes, I'm Engineer, I hope this will not be a problem, no?

I'm not saying your methods are wrong, just different, remember there is more than one way to skin a cat, but for your statements seems you are the only one who know how to do it (don't get it wrong, please )

Paco.
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post #71 of 414 (permalink) Old 01-06-2010, 05:02 PM
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It's OK Paco, I'm an engineer too and Richard tolerates me.

Ed Prytherch
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A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #72 of 414 (permalink) Old 01-06-2010, 05:25 PM
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Hey Richard,
Do you have a customer for those ported L heads?

Ed Prytherch
79 Spider
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76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #73 of 414 (permalink) Old 01-07-2010, 04:19 AM
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Great thread, can't wait to see more!
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post #74 of 414 (permalink) Old 01-07-2010, 11:05 AM
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Ported L heads? Hmmm......

1987 Milano Gold 3.2 24V + JK Cams
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post #75 of 414 (permalink) Old 01-07-2010, 12:01 PM Thread Starter
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Seats

Here`s a rough drawing (not to scale) done of my valve cuts drawn by Jeff Wey, another Engineer customer of mine. You can see the difference in this & the "3 angle drawing", although he is drawn to a 60 degree cut which is easier to find in day to day automotive machine shops.

Ed
No, not sold, I did 2 sets of "L" heads during the holidays. One for my motor and another to sell when assembled with cams/coated cam followers/springs etc so they are complete.
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