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Need some 307 advice

8K views 45 replies 14 participants last post by  Bryan59EC 
#1 ·
Hey everyone, first time poster. I just came back from my overseas tour and thought it would be nice to get a project truck. Picked up a '68 chevy C20, hoping it had the 327, i got stuck with the old 307. Im looking for suggestions to get some horsepower out of this thing. I read that a lot of people said to trash it, but i want to see what shes got.
 
#2 ·
Welcome, how far did you want to go on the horsepower. The 307 was never a popular motor to build for performance. I don't believe they ever made a 307 with heads that didn't suffer from asthma. Again depending on what you want, a different set of heads would be a place to start...then there's the intake, if I'm right they where all 2 barrels. If you wanted to I'm sure you could make it go fast if you threw a bunch of parts and money at it.
 
#3 ·
Well seeing as how the only way i could determine which i had between the 327, and 307 was to pull a head and measure a cylinder, i might as well get some new heads. I already picked up a edelbrock high rise intake and 600cfm carb. I have some headers for it and an msd streetfire distributer. I would like to know where to go as far as heads, should i upgrade my cam, lifters, rocker arms, things of that nature.
 
#4 ·
think of your 307 as a stroker 283. 275 to 325 horse power would be as far as I would go. very simple build.Any decent small chamber heads, camel bump 194s or 202s, that 600 carb you bought,small dual plane z-28 clone manifold,9.5:1 CR , small solid flat tappet cam,(hydraulic if you must) small tube headers, good to go, balance the crank/rods/pistons. If you find other cheap heads,as long as they flow 200 cfm on the intake side and the exhaust side is cleaned up. Tune the engine for your cars application.
 
#5 ·
Again, how fast do you want to go, or how much power do you want to make. If your going to a head that's going to increase compression and by how much, then will the bottom end hold up. If you are getting new heads a more aggressive cam would help it breathe.

Many aftermarket heads out there, or even factory 194 or 202 heads, but remember all your parts need to work in conjunction with each other. Just because somebody puts a cylinder head on their engine with big valves doesn't mean the engine will make a bunch more power.

If you where to lay out a budget of how much you want to spend and let the Guru's here know how much power you want to make I'm sure you will have an engine you are happy with...You need a budget and plan first.

Ray
 
#10 ·
not likely you can bore it to 327.first decide what you want. 307s mostly have cast cranks. keep power levels low. If you want power do what ap said,go 350. if you want a fun 307,build it mostly stock like what I first posted. camel bump heads are era correct but not 307 correct. they are cheap.
 
#12 ·
I would suggest rebuilding the engine with all orginal parts. Freshing up heads etc. Then bolt on all the things you mentioned you had( headers etc). Then id swap out rear gears. if its an automatic id opt for a 700r4 with 373 gears. If manual it should alreafy have steep gears. Point being, my first performance purchase would be a new set of gears. Just my two cent
 
#15 ·
For a $1200 budget you can't go wrong with a junkyard 350.

If you plan on building up the 307, it's a lot like building up the 305 except it has a slightly better bore and a much worse reputation. As said before it shares it's bore with the 283 and it's stroke with the 327. Thanks to quality control issues these engines get avoided like the plague. There's a couple 3rd gen f-body guys on here that know the 305 well and have probably given great advice a million times on how to make power with them. Search the user "F-BIRD'88" on here and I'm sure you'll get a wealth of information on how to make great power with small cubes.
 
#16 ·
If you want a 327 you have part of what you need to build one.
A 307 has the bore of the 283 at 3.875 inches and the stroke of the 327 at 3.250 inches. Get a 350 block, get 327 pistons pressed on your rods. Throw the crank in the 350 block and you have a 327.
However, I like 307's. And they can make good power as well as good fuel economy if done right. You have $1200 to play with, providing the engine doesn't need a complete rebuild and your looking to step up the pep of the little mouse and not making it into a fire breather then it's easy.
First off, get a set of heads off a 305, the 416 casting.
These heads have 1.84 intake and 1.50 exhaust valves and a small 58cc chamber. This will give you right at a 9.5:1 compression ratio which is ideal for pump gas. Next install a summit racing cam part number SUM-1065.
This cam has duration @.050 .216 intake and exhaust and .454 lift.
Get a set of valve springs to match the cam.
Add a double roller timing chain. A set of small tube 1.5 inch primary headers. Dual exhaust with H pipe into mufflers of your choice.
Retain the intake, carb and ignition system you have.
This combo will not only give it excellant low end torque but it'll also improve the fuel economy. The cam has a slight lopey idle so it'll sound good.
If you find a set of 416 heads that don't need alot of work, then you'll have a good bit of your cash left over. If the heads need guides then it'll get a little more expensive. Either way, you'll still come out to the good money wise.
The 307 got a bad rap for 2 reasons. Number 1 is chevy never made a performance version of it. It was strictly a economy engine. number 2 is because chevy had a bad run of cams during a model year so the cam would go flat and usually take out the rest of the engine with it. However, it's still a small block chevy, given the right parts it'll come alive and run very nicely.
 
#17 ·
In the late 70's and early 80's dirt track super modified racers in Tx and Ok were forced by class rules to run 311's (.030 over 307). Reher and Morrison paid their rent grinding heads for them. There's still people in that part of the country that know how to make a 307 go like stink. On the other hand a 350 wouldn't hurt your value one bit.
 
#18 ·
If you're planning on reselling said truck, pull the 307 and dunk in a 350, your resale will go up. Most buyers will try to talk you down due to the supposed bad 307 (which since you would be changing the cam and timing set, would be perfectly fine. If you DO opt for the 350, keep the 307 for another hot rod project and tell everyone its a 283, which all the retro guys love.

If you build the 307, DV's advice is spot on. Realistically you could put 3.73s in the back of your truck, and a 700r4 or 200-4r overdrive automatic (or a T5 or 833-OD stickshift) and have an absolute riot for a street truck
 
#22 ·
to the majority of normal folks; if you put a factory aircleaner on there with "283" on it and some corvette finned aluminum valvecovers, they'd accept it.

I for one don't spend my time at carshows looking at casting numbers and other specifics. A smallblock is a smallblock to most people.

A purist numbers matching guy would know, or an engine builder, but if you're building a 60s era t bucket, does the displacement matter?

To the OP: you have several directions to go, just take stock in your abilities and evaluate the parts you have on hand carefully. You'll have a nice (307, 327 or 350 powered) truck you can be proud of.

There was a guy around here (HR.com) that had a 65 nova with glass fenders, hood & bumpers; little 14" cragars, M20 and a 307-based 310 out of a roundy round car. It has something like a 262H cam in it, manual brakes, manual steering and it was a HOOT to drive.
 
#23 ·
All the info I get says the 416 is 58cc and that's what I've been going by for the past 20 years. If they were 64cc then the compression ratio on a 305 that these heads came on would be dirt low.
Going with a set of camel humps isn't a bad idea, but you have to realize, if you find a set that has to be rebuilt you'll be sinking $600 in them just to bring them to spec. If they need rebuilt they'll need to be magnafluxed to check for cracks, milled to flatten the decks. Also will need valve guides, possibly new valves, hardened exhaust seats and of course the basic valve job. Vortecs aren't a bad idea either by no means. You can usually get a set for around $600 ready to bolt on. However you'll need center bolt valve covers, You will need a Vortec intake, you won't be able to use the intake you have, and you'll need a set of self guiding rocker arms. By the time you add that up, plus the price of the cam and timing set all $1200 will be gone and you won't even have a set of headers for it yet. I suggested the combo I did because it's cost effective to the parts you have and it will help performance. No it won't be a fire breather, but it will have great low end torque which is just what a street truck that isn't going to see any track time needs.
 
#24 ·
if you don't want to swap in a junkyard engine.. and rather build off what you have for now.. and build what you want for it later..
here is what I'd do...
find a 305HO in a monty SS or t/a,firebird,camaro..
in the SS the eighth vin # will be a letter "G" .. the foby it might be an "H" have to check on that..
grab the heads and if you want to run a q jet carb the intake.. if you'd rather a holley/etc get a edle intake used..
the 305"g" engine heads are the best flowing 305 heads.. and the chamber side is tiny iirc 55 cc.. that 'll get the compression up to about 8.9/9.1
in that 307.. add in a smallish cam (think 305 truck towing cam)
and it'll wake that 307 up..
best part .the parts are dirt cheap..
you can get 300hp out of this set up...

good luck... the swaping in a junkyard 350 isn't a bad one.. but food for thought..
g.m. sells the 96-02 truck vorect 350 all new.. for 1999.oo and with 1200.oo budget,, save a little more and you are there..
depending on where your at.. pace.com or s.d will have the new engine on the cheap
add intake and carb and headers and you have a stroung new 325-350hp 350 small block thats all new parts... with a roller cam...
if I keep a small block in my truck (71 c-10) this is the engine I'll install.. you can't build one for what g.m. sells it for..
I have a 496(489) in basement that I'm fighting with do I, or don't I..
good luck.. with whatever you choose..

oh and welcome :welcome:
 
#26 ·
most parts stores are capable of supplying parts. We have Lordco/TnT/mopac and many more. If you know what you are buying then put one company against the other and get a deal.Any local engine builder might fix you up with jobber parts. or buy quality parts example trw/speed pro pistons etc.
 
#27 ·
ALCON- found this article very interesting. Super chevy took a 1968 307 (exactly what i have) and did a nice makeover on it. Problem im having is when i do any investigating on the heads they used, every source is telling me it wont work on my motor. Any ideas? Plus the info i am gathering on the cam says its a 4X4 part. Summit says its either for off roading or towing?????
 
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