Tow/MPG Engine Build
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,743
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From: Stockton Ca
Tow/MPG Engine Build
Forum: It is said that TQ is what gets the car moving. After that, how much do we need? I understand more is better for many!
My question is: What kind of MPG would a towing TQ motor get?
I'm thinking of a 350/383 w/AFR 180 heads and a very short HR cam.
Might as well use some 1.6 RRs to get the most from the short cam.
Don't forget the AFR intake!
Any experience out there?
Your thoughts?
R
My question is: What kind of MPG would a towing TQ motor get?
I'm thinking of a 350/383 w/AFR 180 heads and a very short HR cam.
Might as well use some 1.6 RRs to get the most from the short cam.
Don't forget the AFR intake!
Any experience out there?
Your thoughts?
R
Pro
Joined: Feb 2012
Posts: 577
Likes: 6
For torque I would say a 400 would keep you balanced with economy. The 350 would have to work harder. The 383 is a great power maker but they like RPMs and those consume a lot of fuel. Big blocks generate gobs of power but use a lot of fuel too. The 400 is a torque making small block. Keeps weight down and keeps things manageable in fuel consumption. That being said, sometimes fuel consumption has more to do with how you drive.
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,743
Likes: 37
From: Stockton Ca
A 400 TQ Monster would get things moving off the line. After that the extra cubes will suck gas.
A 400 gets peak tq at 2500 I think?
A 425 tq @ 2500 and 425 hp @ 400 could pull a big OD at 2000.
Many forum members get close to 25mpg w/OD as is.
Anyone have some data from a tow engine?
R
A 400 gets peak tq at 2500 I think?
A 425 tq @ 2500 and 425 hp @ 400 could pull a big OD at 2000.
Many forum members get close to 25mpg w/OD as is.
Anyone have some data from a tow engine?
R
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,743
Likes: 37
From: Stockton Ca
Pull some tall gears OD w/low RPM.
That should pull hard off the line.
Good mpg on the Hwy.
I would like to see an all AFR engine on dyno.
Usually they are high rpm big HP builds.
A small head on a big engine might be interesting?
That should pull hard off the line.
Good mpg on the Hwy.
I would like to see an all AFR engine on dyno.
Usually they are high rpm big HP builds.
A small head on a big engine might be interesting?
Drifting
Joined: Jun 2012
Posts: 1,990
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From: Port St. Lucie Fl
27" tall stock size tires w700r4 and 355s is just over 2k at 70, if you want lower RPM your gonna have to use the stock 308 or 273(?) option. My car is alot of fun off the line and locking up OD will make the car gain 5mph easy with barely touching the gas and the 3k stall in it. If you decide on a big cube stroker motor for this build it to spin 6k you will have alot of fun with it.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
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Le Mans Master
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From: Hermosa
Torque is going to be a function of how much charge you can get into the cylinder for a given stroke/rod combo at a given displacement.
More displacement = more torque if all else remains the same.
Longer throw on the crank gives more displacement so more torque also.
Better rod to crank angularity gives more usable torque vs forcing the piston into the wall of the cylinder. So this means longer con rods.
A 383 with a 180 cc head might be more sensitive to throttle but I'm not sure it would develop more torque necessarily. It might sacrifice some top end power due to choke at a certain RPM and some mid range torque as well.
Lots of lift on the valves with a wide LSA and low overlap would probably develop better torque down low while sacrificing some top end power.
Good high compression makes the engine more efficient during the power stroke, so nothing less than 10.0 to 10.5 CR. Keeping DCR in mind as well.
Iron heads keep more heat in the combustion chamber, and heat is energy used to push the piston.
Straub recently posted up a link to a dyno that the guy had a nearly flat torque curve. That seems to be what you may be looking for.
More displacement = more torque if all else remains the same.
Longer throw on the crank gives more displacement so more torque also.
Better rod to crank angularity gives more usable torque vs forcing the piston into the wall of the cylinder. So this means longer con rods.
A 383 with a 180 cc head might be more sensitive to throttle but I'm not sure it would develop more torque necessarily. It might sacrifice some top end power due to choke at a certain RPM and some mid range torque as well.
Lots of lift on the valves with a wide LSA and low overlap would probably develop better torque down low while sacrificing some top end power.
Good high compression makes the engine more efficient during the power stroke, so nothing less than 10.0 to 10.5 CR. Keeping DCR in mind as well.
Iron heads keep more heat in the combustion chamber, and heat is energy used to push the piston.
Straub recently posted up a link to a dyno that the guy had a nearly flat torque curve. That seems to be what you may be looking for.
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
ANy engine can rpm dimensionally look at a 406 as a larger 383 thats all they can either be tow beasts or run upstairs pick your parts accordingly
the 383 for exwith the 180 head and a short cam would tow well....make more tq then the 195 although may lose 5hp way up top...on a tow motor no big deal.;dual plane best here
Build big as you can
or stick a 4" crank in your 350 so many ways to skin a cat
For towing Id want the biggest arm I could get in that block.
the 383 for exwith the 180 head and a short cam would tow well....make more tq then the 195 although may lose 5hp way up top...on a tow motor no big deal.;dual plane best here
Build big as you can
or stick a 4" crank in your 350 so many ways to skin a cat
For towing Id want the biggest arm I could get in that block.
Last edited by cv67; Dec 24, 2015 at 10:46 AM.
Thread Starter
Drifting
Joined: Apr 2002
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From: Stockton Ca
Years ago I had a 400 sb w/RV cam. It was very strong down low.
It actually got good mileage around town.
I am aware that big tq down low comes from displacement.
Then the big displacement sucks gas on the Hwy.
I think a strong 383 would work?
It actually got good mileage around town.
I am aware that big tq down low comes from displacement.
Then the big displacement sucks gas on the Hwy.
I think a strong 383 would work?
Team Owner
Joined: Oct 2004
Posts: 81,241
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From: altered state
St. Jude Donor '05
Sure it would if you were closer you could come drive mine...anything but atow motor but youd get the idea
What kind of truck? 12s is asking a lot. It would move though
Get a dual plane with NO notch cut out of it.
Had a buddie with a 70 longhorn 4x4....had a very basic cheapo 400 teeny cam and an old 144 B and M blower. It could smoke all 4 tires with his contruction equiptment in back. wasnt cool, was something you look at and give a
then start laughing. Been together for almost 20 yrs now
What kind of truck? 12s is asking a lot. It would move though
Get a dual plane with NO notch cut out of it.
Had a buddie with a 70 longhorn 4x4....had a very basic cheapo 400 teeny cam and an old 144 B and M blower. It could smoke all 4 tires with his contruction equiptment in back. wasnt cool, was something you look at and give a
then start laughing. Been together for almost 20 yrs now
Safety Car
Joined: Mar 2007
Posts: 3,652
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From: Bridgewater nj
Cubic inches + velocity + compression = torque . When I build my truck engines, I use the parts you outlined. 180 cfm heads, a tow cam and usually a smaller carb makes things snappy at the gas pedal. Obviously the more cubes the more flow needed. Lock up converters on an overdrive trans is ideal or a 5 speed stick.
The only other critical question is regular or premium gas. When I tow with a truck, I want regular. So 9-1/2 to 1 is max with cast iron heads. 10 with aluminum .
The only other critical question is regular or premium gas. When I tow with a truck, I want regular. So 9-1/2 to 1 is max with cast iron heads. 10 with aluminum .
Pro
Joined: Feb 2012
Posts: 577
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I once had an El Camino with a 400 and I managed to get great fuel economy out of it when I didn't drive like a loon. It had the grunt to get the car moving without a ton of revs and that's where the efficiency comes from. I think I could have gotten over 20mpg if I had it now and knew I could put in a transmission with more gears or an overdrive. A 200 or 700 would be good to replace the autos that came in our cars. The 200 has similar gearing to the TH350 but it has the extra gear and overdrive. They're hard to build as strong as the 700 but for gearing the 200 would help more with economy and you won't break a good 200 if you keep the revs and traction in check.
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,743
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From: Stockton Ca
I was interested if a tq monster motor could have some performance & MPG. My overall goal has been to have a 12 sec, 20 mpg w/4 speed. I think it can be done. Adding a 5 speed would make it too easy.
Drifting
Joined: Jun 2012
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From: Port St. Lucie Fl