roadnotca
3/4 ton status
Right on the money.
CK5
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- Thread starter 77crewcab
- Start date
So all that and 13mpg or so?
Doesn't seem worth it to me.
Diesel is within 50 cents of the average on 87 octane around here...would that 383 above be able to comfortably run on 87 octane?
A take out 6.5L will get in the upper teens bone stock and is rated stock for 190hp and something like 390ft/lbs, all nice and low in the rpm's. Some of those optimizers mentioned before can make a lot more power and still get good gas mileage.
Doesn't seem worth it to me.
Diesel is within 50 cents of the average on 87 octane around here...would that 383 above be able to comfortably run on 87 octane?
A take out 6.5L will get in the upper teens bone stock and is rated stock for 190hp and something like 390ft/lbs, all nice and low in the rpm's. Some of those optimizers mentioned before can make a lot more power and still get good gas mileage.
where we (77crewcab and i) live in texas, diesel is currently within 20-25 cents of unleaded. it seems most guys are getting around 18-20 mpg even in mildly built blazers with the 6.2.
2 that come to mind are colbystephens and tRustyK5; although rene is not getting that good, but is more built.
i am hoping to build my m1009 some to see what kind of mileage i can get.
Yeah, that tips it even further towards the diesel for me. Unless diesel was a good buck a gallon more I really can't see the economic disadvantage of the diesel. Torque, decent power, and good gas mileage...
Col_Sanders
3/4 ton status
I'm running a TBI 383. Compression is 8.5:1 so I can run on 87 octane, but I normally put in mid grade. With 3.42s and 35s I average 13mpg with a mix of city and hwy.
77crewcab
1/2 ton status
How is the TBI better than the TPI when talking about low to mid range. I have no need to top 5K rpm. The TPI is designed to provide torque at the low to mid range so I am not understanding how a TBI system would be better. I actually have the TBI heads that came off the block I am using as well as some 083 TPI heads that could be used. Vortec heads are supposed to be the best factory GM head ever before the LSx heads so how would using the TBI heads be better?
K5dreamer
1/2 ton status
havent read all the posts, but TPI is a far better low to mid rpm setup than TBI. TBI is better in the high rpm range. I always get my IROC joked for having the best truck engine GM produced up to that time.... the TPI 350. And yeah, the vortecs have the LT1 (not to be confused with LT-1) style intake ports and combustion chambers. which are far more efficient, but require a few special mods to be emissions legal. which kind of detracts from their appeal, unless your car isnt emissions controlled.
77crewcab
1/2 ton status
Emissions is of no concern. Yeah, I don't really get how the TBI is better than TPI like the previous poster said. And certainly not how TBI heads are better than Vortecs. Like I said before I realize diesel would be the best and I may in the future still do a diesel swap. But for the mean time, I have a lot already into the 383 TPI and am really close to having it done at least with the engine build. So I might as well go ahead and give it a try and I think I should be able to get at least 15mpg average which would be good with me. If I am not happy with it in the K5 then I will just put the 383 TPI in my 60 short wide and start looking for a diesel to put in.
Just wondering but has ANYONE ever gotten more than 13mpg in one of these trucks? Maybe in a 2wd but a V8 powered 4x4? Not buying it.
I used to get 17mpg average on the highway in my K5 with the worn out 305 and 3:08 gears...31" tires.
K5dreamer
1/2 ton status
say hello to my friend diesel
with manual locking front hubs. 1986 M1009 Military Blazer. 6.2L diesel/TH400/NP208/10 bolt setup with 3.08 gears front and rear, riding on 33x12.5 Goodyear MTR's.
cruising at 55-60mph i get at least 20 mpg.... i dont even have overdrive, i cant wait for the 4L80E swap and 35's
cheyennek20
1/2 ton status
I know most probably won't agree but a 383 is probably the best balance. You have small block reliability, stroker kits have come down in price and just about everyone makes them. You can also get gobs of power out of it!!
77crewcab
1/2 ton status
Thats what I was thinking when I started building the 383, and also that the extra torque down low would help a lot with a mileage increase over my tired 350.
Col_Sanders
3/4 ton status
I seem to remember getting ~16 hwy or so back with the stock 350, 3.42s and 31s. Its been a while though. I think the power difference is worth the 3mpg I lost.
I meant city with a gas engine.
Most people only see city mpg and that's generally the mpg most people go by not to mention I'm arguing for a diesel so I'm well aware of the fact that you can get 20mpg out of a K5 with the 6.2L.
My '92 K1500 Blazer got 14mpg for a while around town. 350 TBI, TH700R4, 3.73's, and 32" AT tires with less than 100k and well cared for. That was with a more aerodynamic body than a K5 and numerous other improvements. As soon as I put 33" tires on it and lifted it the mileage went south quick.
Most people only see city mpg and that's generally the mpg most people go by not to mention I'm arguing for a diesel so I'm well aware of the fact that you can get 20mpg out of a K5 with the 6.2L.
My '92 K1500 Blazer got 14mpg for a while around town. 350 TBI, TH700R4, 3.73's, and 32" AT tires with less than 100k and well cared for. That was with a more aerodynamic body than a K5 and numerous other improvements. As soon as I put 33" tires on it and lifted it the mileage went south quick.
guz71
1/2 ton status
13mpg in the city out of one on 33's would be damn impressive to me, I think with 33's and building that motor like that you will be doing good to get 11-12 out of it. Yeah the 383 is going to have better low end grunt but you are going to use it. I have crate tbi 350 in mine it needs some more umph. 38's are not helping me out but I dont romp on mine and I am hard pressed to get 9 mpg out of it in town. I know its mathematically proveable to get 15 out of one at a sea level, but in the real world (I also am in lubbock) I just dont think its going to happen. Weight, aerodynamics of a brick, old technology, and drag are working against you pretty hard.
that said, I would probably just build the 383 too, especially if you have the parts laying around. Its going to feel a lot quicker and have more grunt. Unless you drive a ton of miles in it every year I think it would take forever for the diesel to pay for itself. The diesel is a drop in ordeal but there are a lot of other things that go along with that swap.
that said, I would probably just build the 383 too, especially if you have the parts laying around. Its going to feel a lot quicker and have more grunt. Unless you drive a ton of miles in it every year I think it would take forever for the diesel to pay for itself. The diesel is a drop in ordeal but there are a lot of other things that go along with that swap.
x2. I got the exact same mileage with the same combo. Flat ground, 55MPH, cool night, unloaded. 500 miles on one tank and it wasn't empty. Yes, the speedometer was dead on, it was stock, and I timed/checked it through the speedometer check signs just to be sure.
Loaded up with junk (1000lbs extra I suppose) as I moved across country, the same truck averaged 13MPG every tank.
I got 18MPG the last trip in my truck, but that was about 50% downhill and 50% flat.
TPI "sucks" because it doesn't flow well. Period. It was designed around a 305, and anything larger needs more air to work well. If the heads flow better, it doesn't matter, because the restriction is all before that point. The long tube runners and throttle body are restrictive. It makes good low end torque (not awesome, because the LS motors make awesome power) but at the sacrifice of upper end. I guess some people can handle running out of steam around 3500RPM, but I'm not going to lie, I don't like it, and I have 3.42's and 33" tires.
Just look at anyone making power with 383's...their either carbed, TBI, or injected, but not TPI, and certainly not TPI without serious, costly mods.
CUCV2
5/4 ton fun
Here's a solution to help with mileage. Put on 33x10.5s with no lift. A 4" lift seems way to high for 33s anyways. If you still want to lift it, you could consider a smaller lift or maybe even a 1" body lift.
In the engine dept., my .02 cents is to use what you've got. The money you save by that will offset any mileage difference for a while.
77crewcab
1/2 ton status
I think that might be exactly what I do. Wait on the lift and either stay with the 31x10.50 or go up to 33X10.50. I think I will also stay with the 700R4 I have instead of swapping to a NV4500. I would have the 700 rebuilt by a local shop that I know does good work.
As to the TPI on the 383, yes there are modifications needed to the TPI intake system. Things like boring out the plenum, runners, base manifold. Then there is always the aftermarket replacement parts, or something like the FIRST intake. But as stated there are also modifications needed to run the TBI well, so I call it a draw. The TPI will provide better low to mid range torque, more precise metering of fuel, and there is the opportunity to upgrade to the OBDII computer which allows for sequential injection as well as many other benefits. You just have to check out thirdgen to see that there are many people with very good results from the 383TPI setup. I have decided that 15mpg avg. is my goal, and I can live with that number. I think that with proper tuning that it is entirely possible.
As to the TPI on the 383, yes there are modifications needed to the TPI intake system. Things like boring out the plenum, runners, base manifold. Then there is always the aftermarket replacement parts, or something like the FIRST intake. But as stated there are also modifications needed to run the TBI well, so I call it a draw. The TPI will provide better low to mid range torque, more precise metering of fuel, and there is the opportunity to upgrade to the OBDII computer which allows for sequential injection as well as many other benefits. You just have to check out thirdgen to see that there are many people with very good results from the 383TPI setup. I have decided that 15mpg avg. is my goal, and I can live with that number. I think that with proper tuning that it is entirely possible.
Thunder
3/4 ton status
The reason I suggested building a TBI 383 is. It is the cheapest and easist way to get to your goals of 15+ MPG and have the power of a BBC. The stock TB with an AFPR will support 280 HP. If you use TBI heads it will require no mods except cam and chip. Unless you want to make over 300 HP. then you will need a bigger TB and 68 lb injectors and a chip. Still far cheaper than modding a TPI for a 383.
It is a total myth that TBI does not make lowend torque. Why do you think GM used TBI on trucks for all those years? Why didn't they use TPI if it was better at at making low end torque in a truck? The TPI system was there for the using. GM only used TPI on its lightest smallest V8 cars. Hmm..... kinda makes you wonder.........??????
Stock truck TBI makes all its torque by 2800 RPM.
Stock TPI makes its torque higher up. The dyno charts I have seen for stock TPI put its torque peak at 3200
Modding a TPI for a vortec head HT383 will get expensive.
Besides the manifold/runners. You will also need at least 28 lb injectors and bigger fuel rails. Basicly you are building a complete new fuel system.
Those are some of the reasons I favor TBI over TPI In a Truck. If I was building an engine for a car I would prolly go TPI.
It is a total myth that TBI does not make lowend torque. Why do you think GM used TBI on trucks for all those years? Why didn't they use TPI if it was better at at making low end torque in a truck? The TPI system was there for the using. GM only used TPI on its lightest smallest V8 cars. Hmm..... kinda makes you wonder.........??????
Stock truck TBI makes all its torque by 2800 RPM.
Stock TPI makes its torque higher up. The dyno charts I have seen for stock TPI put its torque peak at 3200
Modding a TPI for a vortec head HT383 will get expensive.
Besides the manifold/runners. You will also need at least 28 lb injectors and bigger fuel rails. Basicly you are building a complete new fuel system.
Those are some of the reasons I favor TBI over TPI In a Truck. If I was building an engine for a car I would prolly go TPI.
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