73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: Tire Burner on March 27, 2007, 10:13:00 am
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I have recently Upgraded my Engine. I'm getting some REALLY bad gas mileage as stated in the Topic. Is this Normal for my Setup or is there some other problem at work here? My Engine Runs Beautifully and the first thing that happened to me after Installing the New Intake and Carburetor was to get a Ticket. Here's what my Engine has:
350 Chevy 4 Bolt Bored .060
Flat Top Hyper Pistons (10:1)
Nodular Iron Crank (Std/Std)
4130 Rods with ARP Bolts
Lunati Cam Single Profile
218 Duration at .050 and .458 Lift
Stock 882 Heads (My Next Upgrade)
1.6:1 Roller Rockers (Brings me to .488 Lift)
Weiand X-CELerator Intake Manifold
Barry Grant Road Demon Jr 725 Carburetor.
TH400 Transmission with a 2600 Stall Torque Converter.
My Goal was to make an Engine that Obviously had Performance, but was completely Steetable.
My Old Setup was an Edelbrock Torker II Intake with an Edelbrock Performer 1406 Carburetor. With my New Setup, I installed the Plenum Divider. Once it was all together i noticed ALOT of added Power. If felt like the Engine wanted to Leap out of the Truck.
Soon i will Change the Rear End from it's Current 2.73 to a 3.73. It already has some good Acceleration, but i could stand some more Neck Snap.
My Main Problems now are Gas mileage and Keeping my foot out of it when i'm supposed to.
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Your intake manifold, carb, converter & rocker ratio are a horrible combination for any decent fuel economy.
A dual plane intake manifold, quadrajet, 1.5:1 rocker arm ration and a lesser stall rating on your torque converter will drastically improve your mileage. Your engine combo is all about top end power and that's not what you need for the street.
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Yeah, I guess you're right. I was hoping i could have performance and not have it drink too much gas. Silly Pipe Dreams i guess. I was thinking maybe 12 to 15 MPG, but not 7 MPG. I guess it comes down to a simple Choice....... Either have the Performance and get Crappy Gas Mileage, or Have a Practical Economical Dependable Truck. I feel that i've missed alot of my Childhood. I never really had anything performance in my life. My First 3 Cars were all Volkswagens. Granted you can make a Volkswagen into a Hotrod, but i never did. This is my Second Childhood at 37. I guess i'll keep it the way it is for a while. Maybe i'll drive the Regular Car half the time to offset the price. I suppose i could have actually chosen a CAR to HotRod instead of a truck............
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You can definitely have both..it's just that the combination of parts that you have added are a little less than optimum
lose that weiand intake and get you a performer RPM airgap,tune the carb properly and 10 to 12 should be within easy reach in my opinion..
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Those recommendations will still give you plenty of more useable streetable power. You need torque not top end power. You'll love a dual plane intake's throttle response over your combo now better anyway
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actually, The Intake that i have is Dual Plane AND single plane. There's a Divider that they include with the Intake and i have it installed for just that reason. My Previous Intake was a Single Plane (Elebrock Torker II) I have noticed alot of Low end power increase with the new intake, but are you guys saying that an intake with a Permanent Dual Plane will give me EVEN MORE Low end? If that's what you're saying, i will probably look into getting that.
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A divider is not what makes it dual or single plane. A dual plane intake actually has one chamber that feeds 4 cylinders. 2 on the left bank and 2 on the right bank. The other chamber does the exact opposite. If I get a chance I'll post a nice picture that will help you see it better
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Hey, sounds like a mean ride, but if your mileage is a primary concern, think about your proposed 2.73 to 3.73 rear end swap. That's going to give you a 25-30% increase in rpms at cruising speed.
I've been thinking about going to 3.73 to improve mileage, but that's because I'm running 4.10s now.
It sucks making the performance v. mileage decision, if you finda way to do both, let me know! Good luck
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Hmm, I knew there was a reason i came here for my answers. You're right, that IS alot differant from using a Divider in a Single Plane Intake Manifold. I will have to try a Dual Plane. Have to stay with my Current Setup for a Little while though. Now that i have Experiance in Intalling an Intake, It shouldn't be too hard to Make that change for Comparison Reasons. If i used a Carb Spacer, would that work against the Low End Power of the Intake? I've been told that the Rise of the Intake improves performance, but all of the Dual planes that i've seen are low.
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Sometimes a spacer will offer a very small gain,usually in the higher RPM range,not much use on the street though..If you do decide to try a spacer after you switch to a true dual plane intake,make sure it is divided also,or has 4 individual bores thru it,not one big open hole..the open kind tend to hurt your torque,which is what your trying to improve..also don't go over 1" if you need one at all..some engines respond well to spacers,some don't..either way,it won't make enough difference that you'll be able to tell short of a chassis dyno.. take a look at the Performer RPM Airgap,it's not a short intake by any stretch,although slightly shorter than that weiand single plane.. this intake is designed after the LT1 intake that came on the 370hp/350 from 1970..one of the best small block intakes ever made..
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That is exactly the one i was looking at is a Matter of fact. I was just wondering if that would be a good choice and now i have my answer. Thanks, i'll try that in a Month or so. I'm having a Situation right now with my Motor Mounts. One of them is not attached to the Lower Cross Member. I'm certainly not going to do much Hotdogging like that. Since the other one is welded on top and bottom, i'm thinking of welding the other. This Truck was a Mess when i bought it. Still Ironing out all the Rig Jobs that were done. I'm really glad that i am a Member of this forum. Perhaps one day i'll be able to give good advice on Engine Performance.
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it's a really good intake,makes great torque down low and still flows well to 6500 rpm,way better than a single plane on the street.. I've got a performer RPM on the 355 in my 81 SWB and I run the Airgap version on the 468 in my 82
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^ Sweet. Does anybody know about the Dart II Sportsman intake? I have one on my truck and can't really find any information about it. I was given a regular Performer intake as a gift though and am wondering if it's worth the swap. I have a 60 over 350 with I believe to be stock heads, roller rockers of unknown ratio, either a stock or a 268 cam, a stock TH350 with a shift kit, Edelbrock 650 carb, full length headers, and I believe a 3.08 rear in my 81 GMC, morphed into an 85 Chevy C10 SWB. I'd estimate power in the 200 HP range.
Power is okay but nothing to write home about. My wifes 05 Magnum R/T will totally embarass my truck. It won't light up the 295/50-15 tires on launch and runs out of power at 4500 rpm.
Oh yeah, a great way to have power AND mileage is with an overdrive tranny or a Gear Vendors overdrive add-on unit. Then you can run a short rear gear and have decent highway cruising RPM.
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Well, 4500 RPM is nothing to sneeze at if it's a Stock or Nearly stock engine. Remember that Redline is gonna be 5500 RPM. I did a Quick look and it looks like all the Dart Intakes are Single Plane. I'm sure that you've read the other posts and have learned the same thing that i have learned about Single Plane Intakes. It would seem that the Performer will give you your Low End that you want. What the @#%$, take the Carb off and find out if it's Single Or Dual. That's what i would do based on what i've learned from this Thread alone.
BTW, Gear Vendors Tailshafts are $2500.
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Thanks for the reply. I'm familiar with the differences between single and dual plane though. I haven't actually had my carb off to take a look. I should one of these days, but then I might as well change the intake too lol I got a feeling it's suited for a higher RPM range than my motor, like a Performer RPM intake (1500-6500) whereas the Performer is for idle-5500 which is perfect for me.