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javabug
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« on: November 30, 2011, 04:01:29 am » |
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Running DRLA 48 Tri-Jets on my 2110cc, which work great—BUT—I am probably right on the border where 45s or 48s would work for me. For the sake of discussion and my curiosity:
What kind of difference would 45 DRLAs make compared to the 48s on my particular combo?
Specs:
90.5x82
Web86b
9.5:1 compression
40x35.5 heads ported by K-Roc
CB 1.4 rockers
1.625" merged with dual quiets
009/points/blue coil
Carbs:
65 idle/155 main/180 air/75 accels/36mm venturis
I'm really just thinking out loud for now, but have wondered about this for a while. Let's discuss.
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Mike H.
Sven was right.
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Rennsurfer
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« Reply #1 on: November 30, 2011, 05:51:06 am » |
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The 45 DRLA carbs will flow more c.f.m. than the 48 IDAs. Someone had to say it.
Carry on.
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"You can only scramble an egg so many ways."
~Sarge
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TexasTom
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« Reply #2 on: November 30, 2011, 05:58:30 am » |
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Pay attention FRED!
He's running 48 Dells now ...
I'd bet it would be even more smooth of a drive. Seems almost a shame to neck those beasts all the way down to 36 vents. But if they work, enjoy!
Why go changing everything and mess it all up??? LOL!
.02
TxT
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Work, work, WORK!
Modesty accepted here ...
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Rennsurfer
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« Reply #3 on: November 30, 2011, 06:47:13 am » |
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Pay attention FRED!
He's running 48 Dells now ... Hey, Tom... YOU pay attention! READ MY POST.
Friggin' Texans.
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"You can only scramble an egg so many ways."
~Sarge
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javabug
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« Reply #4 on: November 30, 2011, 14:21:04 pm » |
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I'd bet it would be even more smooth of a drive. Seems almost a shame to neck those beasts all the way down to 36 vents. But if they work, enjoy!
Why go changing everything and mess it all up??? LOL!
Do you think cranking the vents way down on these could make them hard to tune on transition? I have a stumble upon depressing the pedal at cruising speed that is the LAST obstacle in tuning that I can't seem to overcome. Before and after that spot it runs freakin' great. |
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Mike H.
Sven was right.
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TexasTom
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« Reply #5 on: November 30, 2011, 17:14:08 pm » |
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Where's the ignition timing?
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Work, work, WORK!
Modesty accepted here ...
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javabug
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« Reply #6 on: November 30, 2011, 17:52:02 pm » |
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32° total. Tried both stock 009 curve and modified, with about 17° of initial.
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Mike H.
Sven was right.
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TexasTom
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« Reply #7 on: November 30, 2011, 18:32:35 pm » |
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What's the rpm at cruising speed? My gut says it's a bit lean ... ? As for the vents, it may not be absolutely optimal but it should easily be tunable. Not like you're at any extremes ...  |
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Work, work, WORK!
Modesty accepted here ...
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javabug
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« Reply #8 on: November 30, 2011, 18:42:25 pm » |
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About 3400rpm is "highway" speed. I have had the lean thought, including not enough from the accel pumps at that spot? The only time I got it completely smooth was when I jetted it real rich throughout. Nice and smooth, but soggy.
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Mike H.
Sven was right.
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Brandon Sinclair
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« Reply #9 on: November 30, 2011, 19:39:17 pm » |
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Go up on your airs to 190s or 200s-the larger airs let more air in the emulsion tubes and allow the gas to work its way up to and into the carb easier and this makes the mains come on soonerin the transition.
You should also double check your float levels-you can make the mains come on sooner if the float level is higher, but I would work with the airs first.
FYI-your accel jets seem huge, but the rest seem to be in the ball park so I would leave it where it is-no need to make it rich and soggy.
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« Last Edit: November 30, 2011, 20:06:59 pm by Brandon Sinclair »
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javabug
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« Reply #10 on: November 30, 2011, 20:48:31 pm » |
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Thanks Brandon. I have been going back and forth between the 180s and 200s. I can't say one feels better than the other. Anyhow, thanks for the input Tom and Brandon. Any more thoughts on the 45 vs. 48 discussion? Really curious as to the differences, since I could probably go either way. Wasn't looking to start a "fix my problem" thread, although I do appreciate the help, as mentioned.  |
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Mike H.
Sven was right.
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Mike Maize
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« Reply #11 on: December 01, 2011, 01:39:10 am » |
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I would rather go to bigger heads than smaller carbs... |
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Zach Gomulka
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« Reply #12 on: December 01, 2011, 01:45:14 am » |
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Your heads and CC's aren't HUGE, so I'd say the 45's are right on. Didn't they come with a 38mm venturi though?
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Born in the '80s, stuck in the '70s.
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javabug
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« Reply #13 on: December 01, 2011, 02:34:52 am » |
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I would rather go to bigger heads than smaller carbs... Your head is big enough now. |
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Mike H.
Sven was right.
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javabug
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« Reply #14 on: December 01, 2011, 02:37:21 am » |
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Your heads and CC's aren't HUGE, so I'd say the 45's are right on. Didn't they come with a 38mm venturi though?
I think a 38 vent would still be acceptable in this case. |
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Mike H.
Sven was right.
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Mike Maize
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« Reply #15 on: December 01, 2011, 02:39:32 am » |
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I would rather go to bigger heads than smaller carbs... Your head is big enough now. Full of big brains....  |
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javabug
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« Reply #16 on: December 05, 2011, 16:39:44 pm » |
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Where's Mr. Torben A? I'd love for him to add his input and critique my engine.
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Mike H.
Sven was right.
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Torben Alstrup
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« Reply #17 on: December 07, 2011, 00:41:01 am » |
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Hello I didnt follow the thread, but got paged that I was asked for, beleive it or not. In your case the difference would be next to none. - MAYBE - a hairswith better bottom end response with the 45´s. - Your intake valve size is 40 mm. Even a good port on top of that size valve with the cam and lift rarely yield more than about 43 hp per port. On top of that the carbs have been choked down to 36 mm venturies, most likely to improve lower end throttle response. If it runs perfect leave it as is, or sell the tri jets to me and get a set of 45´s T |
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« Last Edit: December 07, 2011, 00:44:22 am by Torben Alstrup »
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javabug
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« Reply #18 on: December 07, 2011, 13:12:50 pm » |
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Thanks Torben. Sorry for the page.  The venturis are indeed small for improving the low-end response. |
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Mike H.
Sven was right.
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Torben Alstrup
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« Reply #19 on: December 07, 2011, 13:27:30 pm » |
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No problem mate.
T
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