Thread: Budget 350 build questions

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Hey guys, I'm new to the forums. I haven't done any engine work before and i thought that a 350 would be a perfect platform to learn on. I just have a few questions to ask if you all don't mind: I want to put vortec heads on with a edelbrock performer intake as starters. Other stuff will fall into place as i do further research. I want to keep within a small budget but I want 350 HP+ I will be installing it into a chevy astro. Other than price, my main concern is gas mileage. I have a fullsize G20 van with a 350 in stock condition with a TBI getting 15 MPG and was wondering if id get better gas mileage with a carb and more horsepower. I have both 700r4 and TH350 trannies too. If there is any info you can give, I would definitely appreciate it. Thanks!

Joey

HI,
Vortec heads require an intake manifold that has a diffrent bolt hole pattern so check your Edelbrock first to make sure its going to bolt up. Next if you have FI already in place and its in working condition, I would stay with it. FI will get you better gas milage and should yeild a bit more power IMO.
Vortec heads do give a good bit of gain in hp but alot to do when changing over I would read up on em.
follow this link
http://chevyhiperformance.com/techar...148_0208_vort/
good luck,
LOST

I too have worried over mpg for a '29 roadster in the building stage with a 0.030" bored 350 with a Crane street cam, tube headers, Edelbrock Performer and 1.60 ratio rockers. After a lot of research I have settled on a 3.50 ratio rear and a beefed up 700R4 in the hope of getting 20+ mpg. Folks tell me that is iffy at best but yet Corvettes get about 26 mpg with a 700R4 and 2.90 ratio or thereabouts. As yet the car is not on the street so I do not know if I will get 20 mpg on the Interstate, but that overdrive gear should give good mileage at 65 mph and yet the low gear should give tire burning performance. Note that the 700R4 is said to require some beefing up for engines over 300 HP (???) so I bought an upgraded 700R4 from the "Eat My Shift" folks in Florida. You need to play around with some on-line gear ratio-rpm programs to figure out your rpm range and rear ratio. Take a look at this site:

http://home.tampabay.rr.com/1bking/c...calculator.htm

Don Shillady
Retired Scientist/teen rodder

a 350 is a great motor to learn on if you get a mild cam and a mild carb you sholud easily be able to reach ur horsepower goal as for heads i would stay with the stock ones and have them shaved by a machine shop you shouldnt have to have new heads to acheive your horsepower goals

Well, my block (casting number 3970010 350 4 bolt) came with 462624 heads which I have heard are Chevy's "lightweight" heads that are 6 pounds lighter and are said to be crack prone. I want to upgrade to Vortec heads because it isnt all that much money from GM Performance. I haven't gotten the intake yet, and I wanted to get a new one anyway.
I also hope the heads/intake give me better gas mileage than my current configuration too. If anyone cares to list the mileage they get with their configurations and vehicle, that would be awesome. I just want to get 15 or better city installed in the astro. Also, would a 650 cfm carb be what I need? or more/less?
I meant to say that I have a 350 i want to put in an astro, and the G20 is what I'm driving now. I was saying i get 15 with it currently and would like to get that or better on the astro project. Sorry about the confusion.
Thanks again!!

Yup!, You are still pushin a barn door against the wind. A 650 carb is all you will need. The Vortec heads are also liteweight castings. Prone to the same fate of all other GM castings. Plus the stupid, oddball intake bolt pattern that invites leaks and the manifold has no heat provision for a carb. Makes driving in other than sunny weather a pain.

Well I just saw that my heads were specifically prone to cracking.. so I think I will stay away from them. Also, does anyone know if a 383 will get much less gas mileage?

Hey dpf,
I'm just planning a project. I have a 1983 fullsize G20 with a stock 350 and a 700 Trans, roughly the same setup as you. I want to build an engine that gets me 18 mpg city and 20+ on the IS. At the moment I get 12. No joke. I've just installed a 600 cfm Edelbrock along with the performer intake and filter, new fuel filter and gave it good oil (10/40) (cost about 300 bucks all together used in mint condition, oil new :-)) now I get 15 mpg. you can get more by tuning your carb (rods and jets) and using headers and good flowing exhaust. That much I have learned so far. As for internals, I'm going to stick with a 350 (no stroker) and have it all machined and balanced for sure. Don't know about heads, cam and pistons yet... If you do any changes to your engine please keep me posted whether it's a good idea or not. Thanks,
Max