Small Block Pontiac 307

[68 Stang]

What do you guys know about 307 small blocks? I am wondering because I currently own one. I am only 14, so I am on a budget. I had a few performance questions such as can I stroke it into a high-revving 327 very easily? What camshaft would be best for my application giving it performance(but not that loping blurble). Which camshaft is best? What type of lifters, and what kind of ratio do I want on my rocker arms? Can I just hone the cylinders, or do I need to bore them? My setup so far performance wise is switching out the stock 2-barrel intake and carb to a 4 barrel intake and carb(but not a Q-jet).So, where do you guys suggest I should go from now?I haven't recieved the engine at my place just yet, but I do have the intake and carb. Thank you in advance for your help...

[Dan_in_WA]

First off, if it's a 307 is it a small-block Chevy? Chevy small blocks found their way into several other GM cars, various years and models. What year of car did it come out of? Which model?

It would be unwise to tell you how to build it up until it's known what car the engine will go into. Other things like the car's weight, final drive gear ratio, tire size, transmission type and number of gears, yada yada yada ad nauseam will determine this. And how you plan to drive it!

If it's the SBC, there's performance parts galore! If it's a BOP [Buick-Olds-Pontiac] engine, performance parts are a little harder to come by.

I notice the 'Stang in your sig area; have you been to www.fordsix.com lately?

Good luck and keep us posted.

[68 Stang]

I have fallen in love with '48 Ford Pickups, so that will be the car I am using it for, and the transmission, I would like to be a 700R4. Gear ratio is undecided, I can't decide how bad of gas mileage I want yet... I am thinking somewhere in the mid 3.'s, but definitely not 4:10's. The stang in the sig is my pop's, he started using this site as a restoration reference and now I am using it since we have finished. By they way, I don't know how to put a picture of it under my name, or in my sig, or in a post at all for that matter.*Any help would be appreciated* I am not sure exactly what the engine was, and I have no idea what it came out of. It was given to me, and the guy who gave it to me didn't know either. I looked up the numbers and they say it is a 1969 Pontiac 307. I don't know if the numbers would read as a Chevy or not, if it were. Well, theres the info, hope it gives you a little more to go off of.

[Dan_in_WA]

I'll do a little bit of research, as I'm curious.

Do you HAVE a '48 Ford pickup?!?!

Because if so, try checking out www.bobdrake.com for some real neat, high quality stuff. A few of the guys here at work are into old pre-war Fords, and like this place. A '48 isn't that much of a stretch, worth a look.

Do you have the engine yet?

I'm more gearhead than geek, and have no idea how to post a picture either. It's probably easy, but I haven't taken the time to learn.

Dan

[68 Stang]

No, I don't have the '48 Ford Pickup yet, my pop says I can't have one for a while, and to just concentrate on my studies. Which is hard to do when all I am thinking about is the truck and my engine. Luckily he did allow me to get the engine though, which isn't at my house at the moment, but should be by spring. I have an '85 chevy 305 in our garage right now, but when I get it back together, and ready to throw away( it is just being used as a learning tool, and is no good), I can then get the 307 ready.So, thats my plan. Show my dad that I can maintain straight A's while working on the engine, and then start asking about the truck.

[Dan_in_WA]

It seems this IS the small-block Chevy! I have one in my '70 Camaro.

The difference between the 307 and the 327 is the size of the bore: The 327 has a 4" dia. bore, and the 307 has a 3 7/8" dia. bore. You can't bore a 307 block to the 4" bore, there isn't enough wall thickness.

The 307 uses heads that have ports meant for economy, rather than performance. Heads are swappable, though.

Now for the good news: The crank and rods are the same as the later 327, and there isn't THAT much difference in bore size. But when it comes time to put insurance on this baby, there's a whole world of difference in what you pay for a 307 vs. 327!!

This is an EXCELLENT engine for you to start with - great for street use, parts easy to come by, and no 'high performance' stigma associated with it, at least in the eyes of the insurance companies. But it is still a powerful engine. More power than you or I will find a legal use for, that is for sure!

What you'll want to do is a high quality, more-or-less stock-type rebuild.
Smokey Yunick said it best: "I've looked at these trick of the week engines, and when you open them up, - the really important stuff - the ring seal, port prep and valve job were laughable".

So to Smokey, the "Really important stuff" is the ring seal, port prep and valve job. That's where to concentrate your time and effort!

Have you gone around Summit Racing and PAW sites? You can find parts there at reasonable prices for high quality stuff. If you're really set on spending money somewhere, consider the 'gapless' rings.

Is your Dad going to help you with this? Bet he will if you only ask. Lastly, consider fuel injection. You can get an FI set up off of a 305 for not a whole lot of money if you shop around. Better mileage, more power, and the GM ECM is programmable. Just check out http://moates.net

Type to you again soon!

[68 Stang]

Yea, about the FI. I found a fuel injection kit off of an '86 Iroc Camaro. It is on Ebay and is standing at $175. It has 3 days left, but no bids yet. The problem is, I don't have the money... See, I have a one-way bank account, the money goes in but parents don't allow it to come out. If I were to buy this TPI system, I would have to convinve my Dad to let me borrow the money, and slowly pay him back. I doubt it will work, but it is worth a shot!

[Dan_in_WA]

Definitely the way to go, if you can convince him!

You'll need the FI set-up for the engine, and the computer, all the sensors, and the wiring harness. $175 is a good deal if EVERYTHING is included. But if you've got to hunt up your own 'puter, don't get all the sensors, will still need the wiring harness, or whatever - take a pass on this one. Another, better deal is out there. There's literally millions of these things out there, and it will have to be tuned to your engine anyway so it doesn't matter, so much, what you start with.

Now's the time to go to the library and start reading. Just remember not to get sucked in by all the hype - you're building a street motor, not a NASCAR racing engine. Aluminum roller rockers are nice, but if you don't need 'em they won't give you any power.

At this point, figure a reasonable redline of 5500 or 6000 RPM for your engine. That's redline, not power band.

Here's a formula for you: Horsepower = Torque x RPM divided by 5252

It's easier to raise RPM than build torque to get the same HP, but it isn't nearly as much fun to drive. Please believe me, power coming off the line is a whole lot more important than being able to post a big number on a dyno. Coming away from the stoplight is where a street drag is won or lost, not that I recommend street racing!

Import guys really have to wind up their engines to make the HP that the advertisements state! Doesn't do anything good for wear and tear on the engine, or gas mileage. Friction rises dramatically with RPM.

More later,
Dan

[68 Stang]

http://cgi.ebay.com/ebaymotors/ws/eB...category=33553
That is the TPI for sale, but like you said, I got to wondering about the computer and harnes... Maybe it would be easier to get one from a junkyard, and pick the things that I know I need from the start. Hopefully it won't run too much.What is your recommendation on pistons? Stock, or aftermarket? What about the cam, have you had a good, or bad experience with any? Thank for your advice and help so far, looking forward to reading later posts!

[Dan_in_WA]

The surest way to get everything you need for an EFI swap is to get your hands on a whole donor car. Maybe a junkyard will cut you a deal, e.g. you buy 'the whole package', and just keep coming back for stuff as you need it.

The best bet, IMO, for pistons is to use stock-type, flat top cast replacement pistons. Especially for a street motor, these have some real advantages that most guys overlook because they're just not as glamorous as a forged piston. One advantage is cost. But the most important is they are stable, dimensionally.

Forged pistons grow more as they heat up, and need more clearance (.004 and up) between the piston and bore than a cast piston does. Cast pistons will last longer, and give better support (again, IMO) to the ALL IMPORTANT RING SEAL than the forged ones.

As far as cams go, stay conservative. Here's another "Secret" that 90% of all hot rodders simply ignore: Match the camshaft and the induction to the intended power band of the engine. Lots of guys take a stock engine, throw on big cam and induction, maybe even a set of headers, and the thing simply won't perform worth a bleep on the street. They forgot that the engine is still trying to breath through small ports in the cylinder heads and trying to exhale through the stock exhaust system!

What happens is they didn't match everything up as a whole package with everything working together. And it's a disappointment. An expensive disappointment!

Here's another great site to furthur your education: www.headersbyed.com and if you can spare the $22 get the Header InfoPak! This is money well spent. You are looking at a Tuned Port Injection set-up, which is the induction side. Well, the exhaust side needs to be 'tuned' just as the induction side does - and they need to be tuned for the same RPM power band. Look around that site, he explains it better than I can.

By now, you're no doubt on Information Overload. So I'll add one more thing.

Start saving your money for the absolute, very best, top notch multi-angle valve job that you can afford! The '3-angle' valve job was a big thing when I first got into this game. I've heard of four, and even FIVE angle jobs being done, but have never seen any. This is a topic for my next post, due to it's complexity.

So here's what's important in a nutshell: Basic stock-type rebuild, with whatever funds you can scrounge poured in where they'll do you the most good. Ring seal, valve job, (more later) and port prep (will touch on that in the future. Mainly match the intake ports together between the intake manifold and the heads.)
All the systems; induction, cam timing, valve size and valve job, and exhaust, must be built so they give best performance in the same RPM range.

PS Anyone else following this is free to jump in if you don't agree.

Dan

[Dan_in_WA]

Now for a few words about the cylinder heads that came with your 307.

I'm running the same heads on my Camaro engine; these aren't the very best head castings available, but if you already have them they're priced right!

These heads were meant more for economy than performance, but with a little work will run just as well as any high-dollar set of heads on the street today. (My )

To start with, the exhaust ports are very efficient on the small Chevy and need nothing (other than a top quality valve grind) in the way of special attention. The intake side is another matter!

The stock intake valve is 1.72" in diameter at the valve head. The intake port does not flow real well either, although for the RPM's your engine should be turning, port shape isn't a major issue. The smaller ports will build low-end and mid-range torque better than the larger ports of some of the 'performance' castings. This is EXACTLY what you want for the street! But there are some improvements that can be made.

You'll need to find a good local machine shop, and go talk to them. Let them look your heads over, and ask them about putting larger valves in the heads. I'd recommend 1.94" diameter valves for the intake. 2.02" valves are available, but I'd not run them in a street engine due to shrouding issues, and loss of Air/Fuel mixture velocity at lower RPM.

Valve 'shrouding' is where the edge of the combustion chamber gets too close to the valve head, and "squeezes" down the gap that air/fuel must pass through as it goes into the chamber.

To illustrate this, take your bare 305 block and put the heads on. Then flip the thing over, and look up the bottom of the bores at the valve heads. You're going to learn a lot! See how close the edge of the bore comes to the valve, when the valve is open? Air flows around the valve head in a cone shape. Anything that interferes with the 'cone' of moving air will MURDER the ability of the port and valve to pass air/fuel into the cylinder! Which means Less Power.

I'd follow the shop's recommendation as to valve size on the exhaust as well. 1.5" dia. and 1.6" dia. valves are both available, IIRC. The whole secret here is to find a good shop and listen to them. I'd imagine that they'd be willing to talk to you and help you out with this stuff if you're truly wanting to learn, because at 14 years old you represent a lot of future business for them if they treat you right!

Part of the valve grind job is paying attention to the valve guides. Once again, listen to the guy in the shop. No doubt the valve guides are worn, and will need to be serviced. You might even wind up buying new valves for this reason alone - the valve stems may be worn down.

Lastly, when buying parts, make absolutely sure that the seals are stamped "Made in USA", or Canada, or Mexico. Seals made in Taiwan or China use an inferior material that turns rock hard in about 20,000 miles, and will start leaking oil like a sieve! Been there, done that. Changing out seals with an engine in the car is NO FUN.

The cylinder heads are the most important place to spend your time and money. You can't skimp on ring seal either, but when it comes to making power, the quality of the head prep will make you, or break you.

More later,
Dan

[68 Stang]

The man that I got the engine from, said that the heads that he was giving me with the 307 just had a valve job. So should I still look into getting bigger valves, and another valve job, or should I leave it as it is? Also, I would REALLLLY like to have the EFI, but I just don't know if I will be able to afford it( I don't have a job since I am not 15 yet). Since I don't have the money now though, how would it do with a 2 barrell manifold and carb until I can get the cash? Would it still run pretty good, considering I take care of it and don't trash the engine? I love cars, so my money at the moment is washing+waxing cars. This is decent money if you can find someone to do it, but there doesn't seem to be anyone that wants to pay $40 for the job($40 is compared to $60 and $80 at auto body shops). So I am needing funds, but am trying to work with what I have, a little hardwork, and SOME money. Now seeing my state of being should I still go with the valves? Thank you very much for your help so far!


Grant

[Dan_in_WA]

At this point, you'll be fine with the valves the way they are. I might take things apart and inspect it, if you have the tools, but what you'll gain from a fresh valve job vs. new, bigger valves and such isn't enough to worry about right now.

I'd figured the engine would be in need of a valve job anyway, and that's the way I'd do it.

As far as a two-barrel carb, it certainly isn't going to hurt anything. At least you'll have an engine in running condition - you can build on it later, as you can afford to. Naturally, you'll see quite a horsepower increase when you swap to EFI, but until then, a running engine has a lot more power than one that doesn't!

What all do you know about the engine right now? It's had a valve job, has it ever been bored out during a rebuild? Has it ever been rebuilt?

Type to you later.
Dan

[68 Stang]

No, I don't think it has been bored, but yes, I think I am sure it has been rebuilt to some extent. Its state isn't so good, but not so bad either, the 305 is much worse than the 307 not that the 305's condition matters at all. The 307 at one time had a 350 cam, would that be a good modification to do again, or stay stock? I have heard that 305 cams wear down more than other engines and they lose a lot of power?
As I am only 14, I haven't had any prior experience with these parts, so I wouldn't know. The 307 has its lifters locked in position as of right now. Which obviously are junk, I pulled one(had to use vise grips!) and it had too much of a bowled shape to use from cam wear, so thats another part on my list! It has no oil pan, or valve covers but I am sure stock would work fine for the oil pan, and the covers dont really matter. Where should I go to for headers!? I don't want to use the manifolds, and can't use them anyway, becuase the heads were seperate from the engine, and had none on them. Your info has been great again! I look forward to your next post!

[Dan_in_WA]

If the heads are off the engine, could you look for the casting number on them? There should be a number cast into the metal on the combustion chamber side of the head, up around the intake ports. It will be a number like 186 or 362, or may even be a complete GM part number. Could you tell me what the number is? Thanks.

Also, on the ends of the heads there is a specific shape cast into the metal. (You may have heard of "double hump" or "camel hump" heads.) This is so the head casting can be identified without taking anything apart. All you need is a quick glance, and the book that tells you which different shapes are for what. My 307 heads have what looks like 3 boxes stacked one on top of another, big on bottom, medium in middle and small on top. What shape are yours?

As far as the block goes, the first thing is to tear it all apart and have it "hot tanked" at your local machine shop. All the steel parts should go down to the shop together, and you'll spend about $50 or so getting it done. If the deposits of crud and gunk are heavy, spend some time with a putty knife and a screwdriver and knock the worst of it away. The hot tank will clean away the rest. The hot tank is a big vat of super-strong detergent that will clean those parts up and have 'em looking like near new! But it will eat rubber and aluminum. While the block is there at the shop, they can 'mike' it with a micrometer and see if it needs to be bored out and new pistons installed. It most likely does. Go with the smallest overbore you can get away with! Keep those cylinder walls as thick as you can.

As far as camshafts go, any of the GM high performance grinds should be fine. Talk to the guy at the counter, one of the early Corvette 327 or 350 grinds will work great. Crane, Isky, Crower, Competition Cams and all the other aftermarket outlets make good stuff too. Expect to pay around $300 for a high quality cam and lifters; you will probably find better prices than this but that gives you an idea of what to expect.

Just remember to stay conservative! You're looking for an RV type cam that will give you great low end and midrange torque. Don't worry about the high end power - the heads won't flow it anyway. And the intake won't be happy trying to deliver it either.

As far as headers, you're looking for three general things. Most important is EQUAL LENGTH primary tubes! Those are the individual tubes that carry the exhaust away from the head ports. The longer, the better as well. I'd consider 30" or so the absolute minimum length that I'd want to use. The next thing is primary tube size. A LOT of guys will try to fill you with BS on this subject - but 1 5/8" or SMALLER for primary tube diameter! Bigger tubes only hurt flow velocity and radiate heat faster. No doubt you've noticed the 'heat wrap' available for tube headers - there are no 'tube coolers' available, either. That says something. Nobody in their right mind would put a Holley Dominator carb on their stock, inline six cylinder and expect to run it on the street. The exhaust is the same way. Too big is BAD. See www.headersbyed.com for details.

Years ago, I bought the re-ring kit for my 307 from Performance Automotive Warehouse. I'd check them out, they have good prices on good stuff. You can get a whole overhaul kit for a little less than what you'll pay at the local parts outlet, and their stuff is selected with performance in mind, too.