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#1 |
Registered User
Join Date: Oct 2000
Location: From Chicago, Live in Phoenix, AZ
Posts: 6,802
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Should I, or Shouldn't I?
Right now I have a stock 1976 L-48 engine. With tweeking and such, I have gotten it in the 19-20 mpg range on 87 octane.
I have a Mild RV cam and some Vortec heads that I have been wanting to put on the engine. Im worried I am going to ruin my gas mileage. Some say that it will help the mileage. Any comments? Im also going to be installing the underdrive unit I have.
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Just sitting here contemplating contemplation. Last edited by 68 Suburban; 03-12-2004 at 04:30 PM. |
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#2 |
Registered User
Join Date: Mar 2003
Location: Northern Illinois
Posts: 2,181
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68,
Those Vortec heads are pretty effecient little buggers. They may help your fuel economy. The RV cam I'm not so sure about. On the other hand, 20 mpg in a 350 almost smacks of alien intervention. I'd be tempted to leave it alone. Brian |
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#3 |
Registered User
Join Date: Oct 2000
Location: From Chicago, Live in Phoenix, AZ
Posts: 6,802
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I am just looking for a little more umfff. Maybe the heads, but not the cam?
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Just sitting here contemplating contemplation. |
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#4 |
Registered User
Join Date: Nov 2001
Location: Springfield, MO
Posts: 2,932
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Chris I bet with that underdrive you will get that umff you are looking for. Will the vortec heads increase your compression? I wonder what that will do. They are a smaller chamber I bet.
with the changes you will certainly get the hp but that "alien intervention" lol of a fuel mileage may go away. Heck try it, you can always go back ![]()
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Dave 1968 Custom Chevy with turbo charged 5.3 gen III 4l80e swap 1967-71 GMC 3/4 ton long step 4x4 (not sure what year exactly?) "A good friend will bail you out of jail...but a true friend will be sitting next to you saying "that was frekin awesome". "If it doesn't fit force it...If it breaks then it needed to be replaced anyway!" |
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#5 |
Registered User
Join Date: Dec 2002
Location: Canada
Posts: 695
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RV cams are supposed to enhance torque and mileage. It should be alright. Not so sure about the heads. You might want to do some more research on that issue and the combination of the two items. Have a look at this http://purplesagetradingpost.com/sum...fo/heads1.html
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1968 Chevy - 292 with a powerglide Last edited by oldsub86; 03-12-2004 at 07:52 PM. |
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#6 |
Registered User
Join Date: Jan 2004
Location: NH
Posts: 2,266
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Efficiency is where it is at, the vortecs are very efficient heads, the L48 heads had 76cc chmbers the vortecs are 64cc, also vortecs came in a few flavors of valve sizes. your stock heads are probally 172/150 valves, if the vortec heads are 194/150 these would be a nice economy head but if you have 202/160 fuel milage will drop. Because of the Chamber of the heads you will be going from 8.5 to 9.7CR and may have to run a higher octane fuel. Raising the Compression and the stock cam may cause some other issues here as well. The stock cams are what they are STOCK and was nevery intended for high compression depending on which RV cam you have will help the overall difference.. Also note that depending how much milage is on your motor could also play a factor of a suddenl CR boost and cause the lower end to go. If your getting good gas milage and things run well. "Don't fix it unless it's broke." If the motor has seen some milage to it and its getting tired, think about a nother block and take you time and put a new motor together and when your done drop it in. JMO
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#7 |
Registered User
Join Date: Oct 2000
Location: From Chicago, Live in Phoenix, AZ
Posts: 6,802
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The motor only has about 40k on it. The blue smoke at start up is pissing me off.....lol
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Just sitting here contemplating contemplation. |
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#8 |
huh ???
Join Date: Nov 2002
Location: Fredericksburg,Va.
Posts: 3,369
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The blue smoke at start up is usually you valve seals going bad. My Toyota has been doing it for years now...
Chuck
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90 Blazer Silverado 350w/ 700R4 and 32" Kelly's "I am a bomb technician. If you see me running try to keep up!" |
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#9 |
Designated A-hole!
Join Date: Mar 2003
Location: South Mississippi
Posts: 36,450
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Sounds like valve seals to me.
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"If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. ![]() We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck" |
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#10 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Higher compression can mean higher MPG too though.
In the 70's, one of the hi performance mags took a 67 camarow, and made it a MPG king. High compression 350 that got OVER 20 MPG. I wish I could remember who and what the combo was, but it was pretty cool. I'd say slap the heads on, dip the cam in it's dippin sauce and stab that sucker. |
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