45 DCOEs - Too big? Too small?

[jacob80]

Hey guys,

 

About two years ago, we picked up a set up triple Webers 45 series from MSA, but I really have no insight as to what 45 is really the measure of (jet?). At any rate, I've decided my next build is going to be utilizing these triple webers, but I'm not sure if they're the right size.

 

Also, I haven't decided whether or not an L28 or L24 block would be better suited for these carbs. I have an E31 head with an MSA Schneider stage 2 cam on the head, but I've heard bad things about that specific cam.

 

Any help, or links, are appreciated.

 

Thank you!

[JMortensen]

45mm is the size of the hole coming OUT of the carb body. The cam is too small, both blocks will work but the L28 will give more power due to bigger displacement.

[jacob80]

Is essence, my ultimate goal is 200whp with a triple Weber configuration.

 

I haven't searched extensively yet, but is there a good (common) cam size that works well with the 45mm DCOEs, E31 head, and L28 block?

 

I am also unaware as to what my compression ratio be. I don't not plan on running anything above 9.7:1 as per Braap's suggestion in another thread.

[kamikaZeS30]

You need an aggressive cam to get the most out of those Webers. I had a set of Webers on my L28, they ran okay, but I don't think my cam was aggressive enough.

 

Be careful with the auxiliary venturis when you're installing them, make sure those set screws are tight!

[goodoldjam]

Should be 10:1 with flattops.

My dad's L28 is probably about that high and he never had any issues running on premium. Thicker gasket if you want to go lower.

Edited September 24, 2010 by goodoldjam

[JMortensen]

Should be 10:1 with flattops.

My dad's L28 is probably about that high and he never had any issues running on premium. Thicker gasket if you want to go lower.

I would take issue with the thicker gasket to lower compression idea. If you do a thicker gasket you'll likely remove all the quench and even though the compression is down it may be more detonation prone. I would say if you're in doubt about running on pump gas, get a bigger cam. A bigger cam will run less dynamic compression and can make a higher compression motor work without pinging.

[jacob80]

I, too, see the thicker gasket as a band aid fix.

 

Whatever gets me here should work:

 

 

[BluDestiny]

I believe josh817 did extensive research on how to get to ^^^^that^^^^

 

http://forums.hybridz.org/index.php/topic/90037-japanese-na-l6-400hp-how-they-do-it-pictures-ive-found-etc-not-56k-safe/page__p__854228__hl__%2Bjapanese+%2B400hp+%2Bna__fromsearch__1#entry854228

[z-ya]

Your goals are achievable with the parts you have. It's all in the tune. I've been running a 180WHP track car for a few years now with a mild cam and 10:1 CR. Rock solid.

 

Nice video BTW...

[Bahraini240z]

Your goals are achievable with the parts you have. It's all in the tune. I've been running a 180WHP track car for a few years now with a mild cam and 10:1 CR. Rock solid.

 

Nice video BTW...

Using 45 triples?

[z-ya]

Using 45 triples?

 

No, EFI.

[SHO-Z]

By a comparison the 4 cylinder BMW 1800 TI/SA had dual 45mm Webers, 10.5 compression and produced 180 hp. This was in the 60s so the BMW engineers at that time thought 45mm per cylinder and 450 CC.

[josh817]

The green car is running 50 or 55mm carbies. Probably Solex. You can get away with 45's and they won't be "too much", since you can choke them down substantially. If you used a small cam, I'd sell the 45's and invest in 40's so you have some extra cash. If you find yourself using like a 34-36mm choke in a 45mm carb then I would get down to a 40mm carb body. I bet the increased velocity would help the torque at the lower end, with a smaller cam.

 

Curious about the dynamic compression ratio since I'm building another motor also! I assume lower RPM's work fine and its not until higher RPM's that you would ping, as your compression raises from valve events, and ignition timing increasing?

 

Edited September 28, 2010 by josh817