you are right he tried a bigger one and it gain about 10 hp more. but this is the carb I have so I'm good with it. not worth buying one right now.
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340 dyno chart thoughts
- Thread starter fez440
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Well, A bigger carb would be nice but that isn't what has me saying "Hummmm" because if that dip in the torque line, which, IMO, comes in late. HP tops out a hair early. May be due to the smaller carb.
Oh! I would not call the LD-340 on that engine as "Under manifold" hindrance.
Oh! I would not call the LD-340 on that engine as "Under manifold" hindrance.
harrisonm
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Bigger carb and an Eddy Air Gap would be huge. The one possible weak link is the heads. I am not familiar woth those heads. Is anyone else? I'm just thinking that IF they look pretty but don't flow as well as 340 X heads, that will be hurting also.
yellow rose
Overnight Sensation
I don't like your cam. You could have used the 284/.484 106 LSA MoPar cam and had the same vacuum at idle and picked up power everywhere.
RustyRatRod just posted three great links in the I don't understand cams thread. I suggest you read those threads. They have every good info.
Also, can you post the BSFC, BSAC and BMEP numbers. Can't tell much more with just the numbers you posted.
BTW, if you blow a head gasket on the dyno by pulling the engine down, the dyno operator has issues. I'm not a big fan of pulling them down farther than actual bottom of engine RPM range, but these guys are correct. He should have pulled it down to 2500.
RustyRatRod just posted three great links in the I don't understand cams thread. I suggest you read those threads. They have every good info.
Also, can you post the BSFC, BSAC and BMEP numbers. Can't tell much more with just the numbers you posted.
BTW, if you blow a head gasket on the dyno by pulling the engine down, the dyno operator has issues. I'm not a big fan of pulling them down farther than actual bottom of engine RPM range, but these guys are correct. He should have pulled it down to 2500.
j par
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frosty_the_punk
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There's literally no chance in hell a 241/241 with 106 LSA is going to have the same vacuum at idle as a 231/231 with a 110 LSA.. He'd be looking at a loss of 3" vacuum at idle MINIMUM. You need to stop.
OP, I don't know what's going on with your torque curve, but it shouldn't dip like that between 3500 and 4500 RPM. the peak should be right where the dip is.. and a higher figure. I firmly believe 480lb/ft should be within reach!
IMO It should look more like the attached file.
NOTE: the light blue curve is a proposed spark curve with a multiplication factor of 10, So if it reads 350 @ 5400RPM it means 35 degrees advance @ 5400RPM. This is just a guideline, or an example of an optimised ignition advance curve for an imaginary engine of similar specification to yours, SO DO NOT REPLICATE THIS CURVE EXACTLY. but if your spark curve is deviating from this by a large amount (say 20%) in the mid range where you have your dip, it may indicate that your ignition/spark curve needs some tuning attention to remove the dip.
The low end of this spark curve, under 1800RPM should also probably be disregarded, too. Since this is an example of a full throttle pull at maximum load. (an unrealistic scenario for an engine speed that low in your application)
Yawn... and you build your engines,your way... Just ,my opine.... He has plenty of mechanical compression,to pull a .484 Purple shaft...(have you run one,properly tuned?), good cylinder heads(Edelbrocks,are.. enhhh,o.t.b....) need real cam timing,to run....There are several ways,to get there.... I would use a cam,instead of expensive head porting....
frosty_the_punk
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I agree it could be run, I Never said he didn't have enough compression, did I?
What I DID say is there's no way those two cams are going to have the same idle vacuum.
Either cam could be run, but whatever you gain at the top you're gonna lose something similar at the bottom.
Saying you can run 10 degrees more duration on both lobes while narrowing the lobe separation by 4 degrees won't have a negative effect on idle quality and low speed drivability is patently false and misleading. There will be a sacrifice and it will be both measurable and noticeable.
Whether that is a worth while sacrifice is a matter of personal taste.
OP wants a cam with a strong vacuum signal for his power brakes and that's that's what he has got. It's also pretty healthy in it's own right for a mild 340 build. I see nothing wrong with it and the hp gains from changing it out are going to be marginal anyhow.
You mentioned that "good heads" need "real cam timing". Are you referring to high flowing cylinder heads and long duration cams?
If anything it is low flowing cylinder heads which "need" more cam as they are starving the engine for air.
High flowing heads need a cam with high lift to be used to their full potential, but ultimately are comparatively less dependant on high duration specs to make power.
This is why modern engines with roller cams and high flowing heads make 400+hp with ultra smooth idle and perfect street manners. Great heads, Lots of lift and little duration cut on wide lobe separation.
I'm no expert but I think the cam sounded like a good choice just based on what comps website states about it. I am enjoying hearing everyone thoughts on the build.
could there be a bit of discrepancy in the numbers just based on the fact that he started at 3500 instead of a lower rpm? based on what he told me about all the numbers the combo is pretty good for a street engine and doesn't sacrifice anything. good vacuum. good idle.
could there be a bit of discrepancy in the numbers just based on the fact that he started at 3500 instead of a lower rpm? based on what he told me about all the numbers the combo is pretty good for a street engine and doesn't sacrifice anything. good vacuum. good idle.
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roccodart440
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That engine looks like a fun engine in a street car especially given the broad torque and quality idle. Those characteristics make for a fun and enjoyable ride on the street.
If it's a fresh engine broke in and dyno tuned, I'd run it and enjoy it for a season. If you are looking for more than next season make a cam change or try a few other things.
I like this cam if it were mine and wanted hyd cam with a little more power while retaining the style engine you've put together. I.e broad torque and friendly idle. Crane 694561 with a 1:6 rocker.
If it's a fresh engine broke in and dyno tuned, I'd run it and enjoy it for a season. If you are looking for more than next season make a cam change or try a few other things.
I like this cam if it were mine and wanted hyd cam with a little more power while retaining the style engine you've put together. I.e broad torque and friendly idle. Crane 694561 with a 1:6 rocker.
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roccodart440
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breaking them in on a dyno is the best and the safest IMO. You walk away with a turn key engine that has a decent base tune.
Yes thats reason I got it done. to get it tuned right and not have to worry plus if something went wrong it would have been covered. plus it was great to see it running !
My 2 cents for what it's worth............
Street only car.........it will be fun to drive any where you want to go when you want to go..........strong torque curve low in the rpm band says rear tire life may be a problem
Good luck and have fun!
moper
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What actual cam is in it? Did I miss that or did you omit that info?
RAMM
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I would agree with the above statement. Looking at the data I see an undercarbed, overcammed, low compression engine IMHO. Would love to see what a compression test reading would be.
If the OP is happy though just run it as is--it will be just fine I'm sure. J.Rob
roccodart440
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MOPAROFFICIAL
Oogliboogli
The timing.
Better chamber with a good dynamic should not want 37 degrees or even 35...Problem IS he only has around 155 ish cranking dynamic with that int close @ 66.
This thread though, I must has say again has me laughing at the responses up until the bsfc came out on paper, then it was " should be a great street motor" "it will still run 12's" lmao.... and the last but not least......the head flow numbers, the real reason...
they did about nothing to them that was good for what this guy is doing. The motor is still decent...but one of two if not both things could been done to give this guy bang for his buck, and that is...
THE CAM LIFT IS **** FOR THOSE HEADS, MORE LIFT!
THOSE HEADS ARE DOWN 20 CFM FROM .200-.400FROM WHERE THEY SHOULD BE WHOEVER DID THEM DIDN'T GIVE A ****.
A lot of people were counting on or assuming they flowed well, well they do...above .500! OR OUT OF THE CAM RANGE...So start adding the number by 2 from .380 lift and it all becomes clearer.
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MOPAROFFICIAL
Oogliboogli
On average you can use the .100 less than actual lift x 2 flow numbers and come real close, on average ve stuff that is.
Heads as is- actual .525-.550 lift around a similar @.050 dur would bring you into the land of 400hp.
those .100-.400 numbers should look more like this .
.100-73
.200-141
.300 -at least 195+
.400-245
Heads as is- actual .525-.550 lift around a similar @.050 dur would bring you into the land of 400hp.
those .100-.400 numbers should look more like this .
.100-73
.200-141
.300 -at least 195+
.400-245
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