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 Post subject: Re: Engine rebuild
PostPosted: Tue Jun 21, 2022 3:20 pm 
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TBI Slant 6
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Joined: Mon Aug 03, 2015 2:39 pm
Posts: 221
Location: Dallas Texas
Car Model:
volaredon wrote:
Huh. When I had my 81 w150 with it's 318 it surprised me in mileage. Factory thermoquad (I love those carbs on a v8) 3.21 gears, manual lockouts up front 32" tires (32x11.50-15) 727, long bed, that thing got 20 on the highway and not much under 16 in combo driving. I always thought that truck was somehow a fluke but in a good way. One that I miss.
Also had an 83 D250 with another 318/727 that I put a stock 360 cam into, EQ heads, performer intake and carb, and that really woke that engine up and mileage was better than originally. Not quite as good on the highway mpg as the w150 was, but still better than yours gets. Still around 16 in mixed driving. And better than yours gets, even with a loaded car trailer on the ball. There are times that the smaller engine doesn't win the economy race.
I've had what now, 6 Dakota's? Maybe 7. 3.9s and 318s. No 318 was worse on mileage than any of the (magnum) 3.9s
Except for my my 1st 3.9. that one wasn't a magnum, and got me 20. Best of the 3.9s I had. Other 2, 3.9s, (both magnums) struggled with 17 mpg on a good day.
My 93 club cab which was a 318 and came to me with a bad trans, I converted to a 5 speed stick. That truck was good for a consistent 20 without even trying.


Maybe I should consider building a better 318. I have an '89 roller block with "302" heads to work with. I also have a small port Offy dual port intake that I've been saving for something. Roller 318, dual port and an A500?

Current 318 has plenty of power, just poor economy.

_________________
1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH


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 Post subject: Re: Engine rebuild
PostPosted: Tue Jun 21, 2022 6:04 pm 
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Supercharged
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Joined: Wed Oct 12, 2005 9:00 pm
Posts: 2798
Location: kankakee IL
Car Model: 80 volare, 78 fury 2 dr, 85 D150
I hope I didn't open a can of worms here by talking other engines than the/6.
Depending on "how" tired that 318 is, and how "fresh" the /6 is, the /6 may well do a better job moving that truck along.
I like the '302 heads myself.
But with either engine, in equal states of health, alot of getting peak power and efficiency out of either, is in the tune. Jetting, ignition advance, both initial settings and vacuum/mechanical play a bigger part in how one runs vs another "just like it". Most people take what they get and "live with it" but the carb setup, ignition setup, cam choice and more need to be tailored to your needs and your vehicle.
The same settings as would be ideal for grandma in her 5th avenue won't give the best results in your truck.
It takes lots of asking questions/what's worked in what chassis for who (and what hasn't) in helping pick the best parts for what you want. I have taken to making the engine and chassis I have the best it can be "for what it is".
That said, there's TONS of posts here to help you, but you gotta weed thru the ones that don't pertain. The guy with the 66 barracuda that races on the 1/4 mile track and wants every last hundredth of a second won't have the right build for your application. And even Uncle Tony, as much as people like to pick on him does have some useful information that can help.
The biggest thing is not to believe your stock engine ever was as advertised... You have to measure EVERYTHING.
Just the fact that most assembly line run of the mill /6s don't come close, as built from the factory, to the rated 8.4:1 compression ratio claimed in every service manual printed in the 70s and 80s claimed they had, means they are down on power from where they could be.
And many aftermarket pistons are actually "shorter" than the OEM ones were reduces it even more. So it has to be moc up assembled, measured, and then the block and head need to be milled accordingly to correct that. Sloppy head castings and manifold ports need an appointment with a die grinder. And a little common sense as to where to use it. And the more of this that you can do helps keep the machine shop tab more manageable.


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 Post subject: Re: Engine rebuild
PostPosted: Tue Jun 21, 2022 7:57 pm 
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TBI Slant 6
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Joined: Mon Aug 03, 2015 2:39 pm
Posts: 221
Location: Dallas Texas
Car Model:
volaredon wrote:
I hope I didn't open a can of worms here by talking other engines than the/6.
Depending on "how" tired that 318 is, and how "fresh" the /6 is, the /6 may well do a better job moving that truck along.
I like the '302 heads myself.
But with either engine, in equal states of health, alot of getting peak power and efficiency out of either, is in the tune. Jetting, ignition advance, both initial settings and vacuum/mechanical play a bigger part in how one runs vs another "just like it". Most people take what they get and "live with it" but the carb setup, ignition setup, cam choice and more need to be tailored to your needs and your vehicle.
The same settings as would be ideal for grandma in her 5th avenue won't give the best results in your truck.
It takes lots of asking questions/what's worked in what chassis for who (and what hasn't) in helping pick the best parts for what you want. I have taken to making the engine and chassis I have the best it can be "for what it is".
That said, there's TONS of posts here to help you, but you gotta weed thru the ones that don't pertain. The guy with the 66 barracuda that races on the 1/4 mile track and wants every last hundredth of a second won't have the right build for your application. And even Uncle Tony, as much as people like to pick on him does have some useful information that can help.
The biggest thing is not to believe your stock engine ever was as advertised... You have to measure EVERYTHING.
Just the fact that most assembly line run of the mill /6s don't come close, as built from the factory, to the rated 8.4:1 compression ratio claimed in every service manual printed in the 70s and 80s claimed they had, means they are down on power from where they could be.
And many aftermarket pistons are actually "shorter" than the OEM ones were reduces it even more. So it has to be moc up assembled, measured, and then the block and head need to be milled accordingly to correct that. Sloppy head castings and manifold ports need an appointment with a die grinder. And a little common sense as to where to use it. And the more of this that you can do helps keep the machine shop tab more manageable.



I agree with all of this. I'm not a first time engine builder but a first time slant builder. I'm no expert but have done lots of research. I'm looking for advice specific to the slant from anyone with experience. I can apply that knowlege to my application. Ideas are always helpful because no one thinks of every possibility.

I will build the slant because I think it will do what I need. If it doesn't, I have an '85 D250 or a '76 Feather Duster that I can put the slant in. I can always build a 318, 360 mag or even a 440 if need be. All my projects need fresh engines so nothing will be a waste. I believe I can get adequate power and economy without going overboard.

Basic modern building techniques should be the secret here. I'll get it apart and measure the piston hieght and cc the chambers to see where I'm at. Then I might need help with a cam choice. I think the rest is cake.

I remember doing some curve work on the dizzy at D.I.'s adive back when I did the hei conversion. That really helped. The one barrel carb was probably the biggest restriction. It used a lot of oil is why I pulled it. I was planning to rebuild it and put it back in but I've had life problems. Now I'm good to go.

_________________
1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH


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