Valve sizes...

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calipornya
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Valve sizes...

Post by calipornya » Mon Mar 08, 2004 5:18 pm

Recommended valve sizes for a 1.9, running Web 86 cam, 0.035" deck height, 54cc combustion chambers, Weber 40's, SoCal climate? BTW, it's going in a 69' IRS Bug.


Thanks in advance.

MASSIVE TYPE IV
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Post by MASSIVE TYPE IV » Mon Mar 08, 2004 6:29 pm

42x36- No doubt.

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Alpine
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Post by Alpine » Mon Mar 08, 2004 8:47 pm

Here are a few pages from a good book that I just bought that cover choosing the correct valve sizes for a motor. My posting this info will probably upset some people so save the pics if you're interested as I will remove them in a few days.

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Wally
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Post by Wally » Tue Mar 09, 2004 2:20 pm

Hi Alpine,
Why should this book upset anybody? Although there are a lot of examples and they outline a good theory, I cant't see the relevence with our Under Head Cammed Type 4 heads.
IMHO, even s/body with only moderate type 4 building experience would give you better advise than these pages on valve size figures in a type 4 head...

Best regard,
Walter
T4T: Type 4 Turbo engine, under construction

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Alpine
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Post by Alpine » Tue Mar 09, 2004 2:28 pm

Well, on page 17 the author does list a Type IV dual carb 1.8 ...

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dstar5000
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Post by dstar5000 » Tue Mar 09, 2004 2:44 pm

Alpine wrote:Well, on page 17 the author does list a Type IV dual carb 1.8 ...
...valve sizes.

MOSt know THAT info already.....

I'm with Wally. We can't open the book,
so it ain't much of a help here.
8)

Don
‎"Let me say it as simply as I can: transparency and the rule of law will be the touchstones
of this presidency,".. Barack Obama January 21, 2009, 30 minutes before he signed the law
sealing all his personal information....

Bruce2
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Post by Bruce2 » Tue Mar 09, 2004 3:08 pm

Hmmm, that book recommends 44.5x38 valves for a 1.9 liter engine. Not what I would do.
Jason, what will you be using the engine for? True daily driver 10,000+ miles per year, or garage queen >1000 miles per year?
What cam, 86A, 86B, 86C? Any recommendations without knowing your cam are useless guesses.
.035" of deck height is not enough. The pistons will hit the head.

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Alpine
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Post by Alpine » Tue Mar 09, 2004 4:57 pm

Bruce2 wrote:Hmmm, that book recommends 44.5x38 valves for a 1.9 liter engine. Not what I would do.
How did you come up with those sizes? If it's from Table 2.1a, then those valve sizes are for "an engine in racing tune" and might well be appropriate. I forget what valve sizes Racer Chris has in his 1.8 but I think they are quite large.

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Post by MASSIVE TYPE IV » Tue Mar 09, 2004 5:08 pm

Chris' valves are limited by class rules...

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Alpine
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Post by Alpine » Tue Mar 09, 2004 5:14 pm

But they're big (for a 1.8L street engine), right?

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Alpine
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Post by Alpine » Tue Mar 09, 2004 5:18 pm

Oops, I was dead wrong. His valves are stock size.

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raygreenwood
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Post by raygreenwood » Tue Mar 09, 2004 7:22 pm

Actually, when looking at the CC size versus valve charts.....a 1.7L....which has appr. 419cc per cylinder.....he has listed ....basically 42 x 35.5. Sounds like 42 x 36 to me. Thats what I run and it makes a difference. Ray

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Post by MASSIVE TYPE IV » Tue Mar 09, 2004 7:49 pm

42x36 is *perfect* for most any combo that is a street car!

MattR
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Post by MattR » Tue Mar 09, 2004 11:20 pm

Whats the ideal for a 2.0 914 engine running a webcam 494 grind and 96mm p/c? This is for street driving and an occasional autox.

Guest

Post by Guest » Wed Mar 10, 2004 12:45 am

From the simulations that I have run using Peformance Trends' Engine Analyzer software, you don't gain anything in a ~ 2.0L motor using a radical cam (except maybe at the very top-end).

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