Hey all,
I picked up a rare 1968 350 sbc with a good pair of stock casting 414 heads. I am planning on swaping my 305 tbi in my 1991 formula to this 350 motor with carb. I want atleast 350hp. How should I build this thing???? I dropped off the block and heads to the machine shop today, and am relying on my machinist to plan this build for me. He suggested I start by finding out the weight of my car and the gear ratio (number of revolutions in one spin of back tire). Any suggestions??? My price range is a little over a grand and I want a street/race performance motor. thanks.

 

Some things to consider:

1) I'm assuming the heads to be the 3973414 castings - they are listed as 1970 LT1 350 370hp camel hump heads - these heads will NOT have accessory bolt holes, so you'll have to swap out your stock serpentine belt system for older pulley system type brackets that connect to block, intake, and waterpump - or have the machine shop drill and tap the accessory bolt holes in them if possible.

2) This will not be a legal swap - some states/counties don't check that well, but you should be aware of your particular location if this is to be a licensed street driven inspected vehicle.

3) Assuming your car is stock with automatic, your rear gears will be 2.73 and NOT positraction - great for mileage, sucks for performance - but this can be changed later when more funds are available for $200 - $3000 depending on what you want.

4) Your vehicle weight will be listed on the sticker on the driver door. Not sure what weight has to do with anything, but whatever - stock it's about 3700 pounds (the doors alone weigh 3000 pounds it seems lol).

5) Exhaust - your TBI exhaust manifolds will NOT bolt up to those heads, you'll need exhaust manifolds from a carbed car from JY or headers & Y-pipe.

With your budget, you'll be lucky to get this done and installed at all - $1000 doesn't go anywhere when you are dropping $250 here and $100 there - really need more like $3000 just to pull it off. So concentrate your efforts in the block for now - heads, cams, intakes, exhaust, carbs can all be swapped out later when more funds are available.

6) Keep these expenses in mind:
carb $250 - $400+
intake $200 if needed
throttle bracket $40
TV corrector for carb $25
Return-style fuel pump regulator to use with the intank fuel pump you have $90, or $50 for the carb pickup and mechanical fuel pump to use on the block
gaskets $100
head bolts $40 (can't reuse head bolts)
exhaust - manifolds from non TBI car $40 at JY? or Headers and Y-pipe $250
$100 in gas for 28 misc trips back and forth to the local auto parts store - I'm being realistic here!
$200 at least for everything that I'm forgetting, and every little thing needed to complete the job (those 28 trips to the autoparts store)

If you need for the heads:
Rocker arms $100
Pushrods $50
Lifters $50
Valve seals $40
Springs ?
Valves ? (nice ones are going to be $200 minimum)
That's $300 minimum in heads BEFORE machine work!

The machine shop is going to get at least $500 out of you right off the bat - it's $300 minimum just for head machining and valve job - I have no idea what block work/checking costs. So you better reconsider your budget and such - if you aren't in a hurry, and can get the machine work done and the major things taken care of for the $1000, and can wait for more savings to accrue to finish the job at a later date, great. But I did my swap all myself with no machine work and I spent at least $1000 on top of the cost of my motor, and it was complete carb to pan motor purchase.

One last thing - typically, the 305 motor will run fine with the 700R4 automatic tranny for years, but when the extra power/torque of the 350 is attached, alot of folks find out quick that their 700R4 needs rebuilt - this can be $600 - $1500 or more for a tranny rebuild.

And all though this, I'm assuming you have the 700R4 auto transmission - if you have the T5 manual, it won't last long behind any 350, and you'll need a T-56 6speed from a 4th gen car to swap in (as the cheapest manual swap).

I'm sorry - really don't want to be a wet blanket here and rain on your parade - just want you to know up front what your getting into BEFORE you commit. $1000 is really not enough to pull it off. I started my project 5 years ago, I'm into her for well over $15k, and I've done EVERYTHING myself except tranny rebuild and paint. And today, I spent another $40 just on radiator hose and valve cover gaskets. And I'm no where near 300hp - that will require another 2 years of saving for me!

The ONLY thing that will take your money faster than a car is a woman!

 

Thanks for giving it to me straight man. I am willing to increase the budget a few hundred. I just wanted to give the machinist a range to make available my options for a performance motor with the lowest cost. I agree starting with the block and heads is pratical. I actually have a decent intake and carb but the machinist said the carb was too small for what i wanted and the intake would give out too little rpm, so i don't know. Thanks though.

 

Before spending dollar one, get the machine shop to estimate the cost of hardened exhaust seats. You hafta have them, and '68 heads don't. At that point, you may find it cheaper to just get some good used late heads.
You probably need the block bored and honed, which means new pistons and rings.
Start checking your local salvage yards for an '87-up truck 350. These usually run 150,000 miles without any real bore wear, and the cross hatch from the original honing is usually still easily visible.
You should be able to sell the '68 engine to someone doing a restoration, and make enough off that to cover the late 350.
If you do find a late 350 as I described, you can do a re-ring on that and be about $500 ahead of where you are now. That $500 will let you do used Vortec heads, or at least 081 heads.