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-   -   350 vs 400 (http://www.hotrodders.com/forum/350-vs-400-a-33562.html)

slu 02-05-2004 03:37 PM

350 vs 400
 
I have looked but haven't found a direct answer to this question and I hope I am not cluttering the board with something that has been discussed over and over.

I have an F1 running a 350 4-bolt with 881 heads w/ roller tip lifters and a "268" Comp Cam, 650 Holley Carb and behind it is a 350 Turbo trans and a 12 bolt GM rear end with the biggest (tallest) radials I could find. Sorry I don't have the rear end ratio or exact tire size.

I am currently going through the truck from the frame up. It will be a "daily driver" 10 miles round trip in town, 5 days a week. Weekend trips on the interstate. I am not interested in performance other than I want to be able to get on the interstate w/o getting run over and then cruise at 75-80 all day. MPG is of interest but being a realist, I know it's like wanting your cake and eat it too. The motor wasn't much on the low end, but I could cruise all day w/o a strain.

The motor is going to have to be rebuilt. Would I be better off with the CI's of a 400 set up the same way or would there not be that much difference? Someone has told me that I might get better performance and gas mileage by going with the torqueier 400.

Thanks

lluciano77 02-06-2004 12:19 AM

I think a 350 has the best gas mileage potential. For some reason 350 is a magic number. It is a good compromise between power and mileage. The 400 will get you more torque, but at some expense.

slu 02-06-2004 11:24 AM

Quote:

Originally posted by lluciano77
I think a 350 has the best gas mileage potential. For some reason 350 is a magic number. It is a good compromise between power and mileage. The 400 will get you more torque, but at some expense.
Thanks, lluciano77, I appreciate your response. If I don't go with a rebuilt 400, I'll go with a crate 350. Around here it's cheaper to go with a crate than with a re-build on the 350.

bullheimer 02-06-2004 12:24 PM

more cubic inches means worse milage. how in the world could a crate engine be less than a rebuild? at least you get a new crank, rods pistons etc. not like a crate is a bad idea tho.

slu 02-06-2004 04:06 PM

Quote:

Originally posted by bullheimer
more cubic inches means worse milage. how in the world could a crate engine be less than a rebuild? at least you get a new crank, rods pistons etc. not like a crate is a bad idea tho.
I'm not exactly comparing apples to apples. Out of Nashville, I can get a new, not rebuilt 350, long block for about $1500. The machine shop that most swear by around here has quoted me a price of $2500 for rebuilding my 350. That price includes balancing and any work necessary such as head work, line boring, etc. That is just plain machine shop work, stock rebuild, no performance parts or blue-printing. 30 day warranty.

Most likely, the motor could get by with just a boring and new pistons, rods, but you know how that goes. When I bought it, the guy had had a crank kit put in and head work done . The motor should have been bored when he put in the kit, but hadn't. It ran good, didn't use excessive oil, but would develop a slight miss and foul a plug after a couple days of running. The motor probably has 10,000 miles on it.

In a discussion, a fellow told me with the 400, even with more CI, the added torque could keep the foot out of the carb increasing mpg and that was the only reason I considered it.

astroracer 02-08-2004 03:47 PM

I would go through the 350. If you aren't looking strictly for performance it is more cost effective. You can do a good rebuild with a kit from Nortern Auto Parts... http://www.northernautoparts.com/Pro...uctModelId=380
I doubt you would have to replace the rods so this kit will work for you. They have other more expensive kits so look around on their site.
What I would replace is the TH350 trans. Lose it. Put in a 700R4 rebuilt to Corvette specs and will you see a major increase in mileage, more response off the line and less engine wear at highway speeds. Look here... http://www.smokemup.com/tech/700r4.php
Lots of good info. Run through the RPM calculaters to see the benefits of the O.D. swap... Best thing you can do.
Mark

Ghetto Jet 02-08-2004 09:06 PM

Here's a brand new 350 with 4 bolt mains $1200.00 made by GM, has a 3 year 50,000 mile warranty and makes 260 horses with a extremely tame cam, 8.5:1 compression, will give you great gas mileage. Great motor, I bought one. Heres the link, I only paid about $100 for shipping. http://www.paceparts.com/product.asp?0=0&1=0&3=3169

slu 02-09-2004 07:58 AM

Many Thanks
 
Thanks for the comments and suggestions. Another machine shop, recommended to me, quoted $2500 for a rebuilt 400, 4-bolt.

I don't think, that with what I'm looking for in a motor, I'm going to go wrong with the 350 crate. Thanks, Ghetto Jet, for the link.

Astroracer, thanks for the link, too. I have thought about this off and on and now would be the time. This probably is the best answer to the mpg. issue.


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