looking for input on this build

[werewolfx13]

I've got a 350 out of a '73 truck, I'm 95% sure its a 4 bolt main, I haven't pulled the pan off to find out yet. It was running when my uncle pulled it 15 years ago, but used a little oil. Its currently locked up, but shouldn't be too bad to un-stick. I'm also going to track down a 700r4 or 4l60 to rebuild to mate to the new motor.

The truck its going into is an '83 shortbed 2wd, currently running a good 305, or a 350 out of a car, with a non lockup 350 trans. Both the motor and trans are swaps from somthing else. I already have dual 2.25" exhaust. The gears are unknown, somone changed the diff cover for a chrome one, and may have swapped the gears out. It did come with 2.73 gears from the factory..if its still stock, I'm keeping em, but if its somthing else, they're going back to 2.xx gears. The truck is going to be a daily driver, spending a great deal of time at freeway speeds and thus needs to get 17+ mpg on the highway. Right now, it gets about 6-10 mpg in town, 10-12 at 75 mph, 14-15 at 60 mph, the overdrive should help the highway mileage a LOT. The bad city mileage is due to two things: a lead foot, and a bad modulator valve or a leak in the hose to the modulator valve. The motor needs to make some sexy torque from off idle-2500 rpm for towing. I tow 8,000-12,000 lbs with it as it is without a LOT of trouble getting up to speed and it holds speed easily even on hills, but takeoffs on a hill are not fun.

I plan to build the new motor in my spare time and as I get extra money. Eventually, it will get a holley commander 950 injection system, but that will be the last thing to go on the motor..it may even be run for awhile with a carb. Compression needs to stay low enough to run on 87 or MAYBE 89 octane fuel without a problem. I'll have the heads worked on a bit, but need some idea on specifics for what to have done to em. I'm going to spring for roller tip rockers, and I'd like to go as agressive as possible with the cam, while still allowing the holley FI kit to work well, and with luck, see 20+ mpg on the highway with no load.

Block work: I'm leaning toward a simple .030, 355 build..I'm not really comfortable with the idea of building a 383 myself.

I need some input on a good intake that will work really well with the commander 950 kit, and be acceptable for carb use as well, whether or not I should go with headers, and what headers to go with, cam specs, specs for head work (i'll see if I can find my sheet that has the casting numbers for the heads, I pulled the valve covers and wrote em down.) What CFM  I should be looking at for the injection kit (400, 670, 700, 900).
Any other relevent comments are welcomed as well. 

[eventhorizon66]

I'm sure someone will chime in to disagree with me, but I think 2.73s behind a 700R4 would be to high, especially if you tow.  I would shoot lower for about 3.42s or 3.73s (my truck's getting 3.73s soon).  You lose performance and MPG by bogging the motor down too much and if you head up the slightest hill it will just drop into 3rd (making OD ineffective for hilly areas).  The biggest gain you can make in MPG is the driver mod where you cruise at 65 instead of 75, as the aerodynamics of the truck have more to do with mileage than a few hundred rpm at cruise.  Also if you accelerate moderately lower gears will undoubtedly improve city mileage.  That's just my two cents about your gearing.

Also if you want "sexy" torque from idle to 2500 rpm, you don't want an aggresive cam.  Look more towards a cam with 0.05" duration around 200 - 212.  Example: Comp Cams XE250H (206/212  .432"/.444"  110* LS).  Such a cam will run out of breath before 5000 like a stocker but idle smoothly and make nice low-end.

[werewolfx13]

I usually tow heavy loads in town, nothing over 30 mph since one of the big trailers I pull has no brakes. Highway towing is fairly uncommon for me, and usually fairly light, 2000-4000 lbs.

A very large part of my mileage issues can and do stem from driving style. In town, I accelerate fairly hard, and probably wont change much. On the highway, I drive with a really heavy lead foot if I don't have functional cruise control...

That reminds me of somthing else I wanted to do..My truck had cruise control, the stalk is intact, and theres a vacuum line and electrical connection that I know to be for the CC thats been re-routed to the charcoal canister..anyone know of an aftermarket CC that can interface with the stock CC stalk, or one that actually replaces the stalk to look factory, and will work with the previously mentioned injection system? I know thats asking a lot, but I just remembered it and haven't looked into it myself yet.

Thanks for the advice on the cam, aggressive wasn't the right term really, I was thinking of somthing along the lines of an RV cam, which I've heard has been problematic for some injected vehicles, though the holley system claims to be able to handle performance cams without a problem.

I'll reconsider some gear options, but I still want to stick with a fairly high final drive ratio..higher than what it is now for sure.

[Captkaos]

With overdrive you will still have an effective high final drive and it is .70:1  Going to a higher numerical gearing like around 3.42/3.73 with the 700R4 will probably pickup up mileage on the highway.  It will be like the current setup in overdrive at about 2.60:1 effective ratio with 3.73's

RV cams should be fine with EFI.  It is cams for example with a lot of lobe sepeation that will cause problems.  Why not go with factory TBI, it is inexpensive and very common to find setups in the salvage yard.

[werewolfx13]

The two local salvage yards have been pretty much picked clean, they have hundreds of vortecs, quite a few carbed trucks, and a bunch of TBI 4.3s, but the 87-92 305/350 trucks have been pretty much stripped..The holley systems I've been looking at are priced between $1200-1600, and are designed for use on a carb intake w/o EGR. They include all the sensors and the fuel pump, so it seems to be a really straightforward install, without having to fight with removing all the stuff from another truck. I'm not completely ruling out factory TBI, it just seems to be a LOT of extra work.

Here is the holley system I was looking at:

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY%2D950%2D21S&N=700+4294925239+4294839074+4294853151+400178+4294908216+4294871516+4294840140+115&autoview=sku

[werewolfx13]

I tracked down the sheet I wrote the casting numbers on. The casting number on the heads was 3998993. From what I could find, the heads have 1.72 intake/1.5 exhaust valves, but I couldn't find out what size the combustion chambers were. The C/R was supposedly 8.5:1, which is about where I'd like to keep it..I want to be absolutely sure I can run it on 87 octane gas safely. I'd like to know what to have done to the heads to optimize power and economy. I'm planning on all new valves, springs, etc. I'm also going to try to budget for a set of tri-y headers and roller tip rockers.

[Captkaos]

Chamber size on the 993 heads are 75cc.

Have a look at this TBI setup:  http://www.customefis.com/tbidiy.html
It is $895 an included what is listed on the page, you just need to source a few parts.

Here is a Holley kit that is brand new with everything. 670cfm (same as stock TBI)
http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY%2D502%2D20S&N=700+400178+4294853151+115&autoview=sku

[werewolfx13]

Thanks, I was toying with getting dished pistons to be sure my C/R was low enough, but glad I hadn't ordered anything yet..75cc chambers with dish pistons would be way too low.

I noticed the 670 holley kit and was pondering whether or not that was sufficient..the old guy at the salvage yard I go to most often said he thought EFI was usually higher CFM than a carb on the same engine, but wasn't sure.

[Captkaos]

Factory carbs for these were Vacuum rated.  It only pulled the amount the truck needed.  350's only need 600cfm unless you are spinning it over the normal 5500rpm.

Factory TBI can handle 300hp.

[mike357]

i have an '80 model that has 3.08 gears in it and a RV cam. when i had an edelbrock 650 carb and a 350 tranny it got 12 mpg @90 mph over a 6 hour trip. i've since went to a 700r4 and a TPI setup from customefis.com. the best i've got out of it now was 14.5 in the city. i was hoping for 17-18 when i started the changeover. i think your 2.73 will kill any type of mileage. i agree with everyone else and suggest at least 3.42's or 3.73's. i'm going to swap over to 3.73's when i get the chance.

[werewolfx13]

I'll see how it does with whats in it now, assuming the diff doesn't give out between now and then..it'll probably be close to a year before I have anything ready to install. If the mileage works out to be too poor in town, as in as bad as it is now, I'll definitely try a higher numerical gear, especially since I've been considering an air or electric locker.

This past weekend, I took it on a 130 mile (each way) trip and it averaged about 14 mpg at 55-65 mph.