8 MPG?

[Paladin]

You don't drive these squares for gas mileage

Exactly! The nickname we fondly refer to our trucks by says it all, "SQUAREbody!

 

[dvdswan]

Haha...
So then you don't know what I'm talking about?
It's the most overlooked aspect of engine building. You will never make any power or fuel economy without compression and a tight squish zone... like
.035. If the squish zone is as wide as say, a grape, you will get horrible fuel economy and be gutless at the same time.

LOL, I do. Long story behind how. Its used a lot more in 2 strokes because its "easier" to achieve. Most engine shops overlook it because of the time factor to achieve it properly. I was lucky enough that when I was a kid and built the engine for the K5, the machine shop had an "old racing dude" and taught me all about it because I was willing to learn. I learned a butt ton on info from him and sadly when you don't regularly use the info you lose it. Then you hear a word and "boom" "I know that term". LOL

 

[roundhouse]

My 91 3/4 ton 4wd 350 suburban was totally stock and never got more than 9.5

My 06 expedition gets 11.5 in town and 15 highway

A full size V8 powered truck isn’t going to get much better than that unless you spend $65k for a new Silverado with the V-8-6-4 and zillion speed automatic transmission
which I guarantee will be back in the shop for expensive repairs of the engine and the transmission

My brother has a 1/2 ton 4wd 2016 Silverado and gets 20 or more on the highway
But all the money you save on gas will go to repairs because they are so complicated

Plus you could buy a modest house in most of the US for $65k

 

[idahovette]

In our neck of the woods it's gonna be a damn modest house! Prices on real estate and homes around here are crazy ,along with new car prices!!!

 

[Vbb199]

My 91 3/4 ton 4wd 350 suburban was totally stock and never got more than 9.5

My 06 expedition gets 11.5 in town and 15 highway

A full size V8 powered truck isn’t going to get much better than that unless you spend $65k for a new Silverado with the V-8-6-4 and zillion speed automatic transmission
which I guarantee will be back in the shop for expensive repairs of the engine and the transmission

My brother has a 1/2 ton 4wd 2016 Silverado and gets 20 or more on the highway
But all the money you save on gas will go to repairs because they are so complicated

Plus you could buy a modest house in most of the US for $65k

You'd **** if you knew what my dad's 07 dirtymax was getting with 850 ft ibs of torque...

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[73c20jim]

From what I’ve seen, 3/4 ton trucks don’t come with full floats, but rather a sf.

My 3/4 has FF. Lucky I guess.

 

[73c20jim]

I was told by a friend of mine who used to be a mechanic in a Buick dealership back in the 60's, that when a customer complained about poor gas mileage, they would change the speedometer gear to make it look like better mileage.

Works for me.

 

[MikeB]

Pretty close, I was talking more like these...

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While driving keeping it close to 20 in. Hg. will help. Basically you're driving like a grandma.

My K5 I had a built 350 (10:1, mild cam, 2.02 corvette heads, performer intake with 750 Holley DP re-jetted), 4sp, 4.11 gears, 205, and 35s. No emissions bs either. If I wasn't playing I would get 16-18 mpg depending on city/hwy. If I was playing you would see the fuel gauge drop (40 gal. tank). Probably 4-6 mpg. Estimated about 300 HP.

A vacuum gauge is a good idea. I've had a couple newer cars over the years with an "ECO" lamp on the instrument cluster that would turn on at high vacuum. Either that or some combination of vacuum and throttle position.

As for your horsepower estimate, I have to say it's one of the few honest estimates for a "built" 350 that I've see on web forums. However, I have to ask how you manage that 750 DP! You must have a feather foot to get anything more than 8-10 mpg.

 

[MikeB]

Haha...
So then you don't know what I'm talking about?
It's the most overlooked aspect of engine building. You will never make any power or fuel economy without compression and a tight squish zone... like
.035. If the squish zone is as wide as say, a grape, you will get horrible fuel economy and be gutless at the same time.

It's more commonly known as "quench height". I always shoot for .040"-.045". Lingenfelter said .050" should be the max, and that .035" is getting close to the safe limit. Stock from the factory on a 60s-90s 350 could have been as high as .070" or more , depending on actual deck height and gasket thickness. Several years ago, I tore down a unmolested 1985 350 that had either a .038" or .041" gasket ( I forget which) with the pistons "down the hole" .030", for a quench of approx .070". Those GM engineers weren't dummies, so I have no idea why engines were built that way.

 

[shiftpro]

It's more commonly known as "quench height". I always shoot for .040"-.045". Lingenfelter said .050" should be the max, and that .035" is getting close to the safe limit. Stock from the factory on a 60s-90s 350 could have been as high as .070" or more , depending on actual deck height and gasket thickness. Several years ago, I tore down a unmolested 1985 350 that had either a .038" or .041" gasket ( I forget which) with the pistons "down the hole" .030", for a quench of approx .070". Those GM engineers weren't dummies, so I have no idea why engines were built that way.

Quench height... thank you! I couldn't remember the proper name. Squish zone... oh my Gawd pass the bong.
It is strange this gets looked over at the factory. Factory rebuilt engines are no better and that's twice the sin as it did had two chances to get done correctly.
IMO without a nice tight squished quench zone height (I just had too!) you have NOTHING and all the parts and cam you throw at will only gain a fraction of what's really available.
You want 20 mpg out of a 350...? Start here.

 

[dvdswan]

A vacuum gauge is a good idea. I've had a couple newer cars over the years with an "ECO" lamp on the instrument cluster that would turn on at high vacuum. Either that or some combination of vacuum and throttle position.

As for your horsepower estimate, I have to say it's one of the few honest estimates for a "built" 350 that I've see on web forums. However, I have to ask how you manage that 750 DP! You must have a feather foot to get anything more than 8-10 mpg.

Yeah, I didn't feather foot very much unless I was trying to limp to the next payday. Albeit gas was $.50 a gallon. I went through changing jets probably eight or so times. I was pretty handy changing jets and power valves by the end of it. Oh and a lot of u-joints until I swapped to a 14 bolt. It may have been a vacuum secondary now that I think about it as the jets were 2 different sizes for the primaries and secondaries. It probably would have done better with a 650 but jets were cheaper than a new carb.

Best part was seeing the look on some rich punk daddy-bought-me-my-car face as a lifted truck smoked them in the 1/4. 13.2 to 13.3 on average. I grinned a lot

I guess that's why I had to feather foot a lot to payday. lol

 

[Raybo135]

A warmed up 350 with 4 barrel in a 2wd can get 20 mpg... I've done it.

But that's Canadian, right? So down in the US is only 14!

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[shiftpro]

But that's Canadian, right? So down in the US is only 14!

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Oh I'm busted...

 

[shiftpro]

But that's Canadian, right? So down in the US is only 14!

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You do know it's actually the other way...? Imperial gallons, like Canadian average dick size, is larger than American..

 

[idahovette]

You do know it's actually the other way...? Imperial gallons, like Canadian average dick size, is larger than American..

PICS!!!!!