SBC 307 build. amother one? - maybe

I think I agree on this one.
When you look at SBC s the 3" stroke motors have a higher rod ratio than the 3.25 stroke motors and then again the 3.5 stroke engines. They all have a different personality, how much of that is rod length to stroke is probably not much. Longevity might be a big factor because some of them seem to run forever and others not.

The 307 build Im contemplating here couldn't be considered average. I still haven't found a build designed specifically to take advantage of the alcohol/ water injection.

 

Something with too much cylinder pressure from either from compression ratio or supercharger.

 

One thing people overlook is piston speed. Short rods and Longer strokes increase piston speed at tdc. The higher piston speed makes cams come in at a lower rpm and makes for a brooder torque curve.

 

Yep, high compression . Hopefully imperial kustoms finds out some more about those pistons.

 

How much compression can you get before the dome screws up combustion? 11.5 with a 60 cc chamber?

 

Well I'm not sure exactly, the water alcohol injection might change the way it reacts. Could be one way or the other or not at all.

 

The first engine I ever built was a 283. I picked up the parts from the machinist and put the shortblock together. At top dead center the pistons didn't come all the way to the top. What the heck? The machinist gave me 307 pistons.

 

Friday night bench racing

 

TRW made a forged 307 piston in std, .030 and .060 over and they can still be found. The P/N was L2272F and was listed for two applications, stock stroke with a 5.7 rod and 3 9/16's crank and 400(5.565) rods. Depending on the combination, deck clearence, head gasket, etc they will yield 12.5-13.5:1 with a 64cc head.

http://dragtimes.com/parts/307-CHEVY-DOME-FORGED-PISTONS-L2272F-030-OVER_310371114630.html

 

Suggest, if you have time, listening to the following podcast:

http://www.adamcarolla.com/CarCastBlog/

The episode you want is the most recent one with G.Banks where they talk specifically about methanol/water injection among other things.

All episodes are pretty good because they really get into technical detail---no other podcast or program video, audio or otherwise i know of does this. And this is why i have to toot Adam Carolla's programs.

2) Suggest maybe calling Banks, they may be able/willing to help you with the water injection thing.

http://www.bankspower.com/

 

Well, I think the problem w/ water injection is it takes up volume in the combustion chamber that could be used up with air/fuel mix...natural aspiration I think gets up to 80% volumetric efficiency inside a cylinder, while a blower or turbo can surpass 100% b/c air and fuel droplets can be compressed into a denser form while the volume of the cylinder remains the same (at every millimeter of piston travel, natch. the volume changes as the piston goes up and down, you know what I mean).

so, an aluminum head and piston top coatings may be more germaine to a high compression naturally aspirated engine. I do remember Popular Hot rodding having a two-magazine article on getting 12:1 to last in a 454 cid engine. they used dimples like on a golf ball (which helps the golf ball fly straighter, supposedly the vinyl tops on plymouth superbirds beats the flat roofed dodge daytonas for the same reason, breaking up that surface boundary airflow) around where the valves were shrouded, swirl polishing of the chambers, etc.
dave vizard also worked with shaping the valve guide bosses to direct air like a fin towards the center of the chamber when it came out of the bowl.

 

I saw the combustion chambers dimpled on a Pontiac engine ( I believe it was nunzio's article) in a vortex pattern. Pretty interesting from what I remember. Thanks for the memory jog !!!

There's probably more than a few better ways and probably one or two perfect ways.
I'm not a cheapskate by any stretch, but I want to be on this one. Sort of another pet project like the first 307. The 307's have such a negative stigma attached to them ( rightfully so in bone stock GM issue) and thatts why I want to use it. Never mind there's a perfectly good one hiding in the corner here.

Here's a little funny story - my buddy comes over and wants me to figure out what's wrong with his Yvette. Brand new 383 5 grand engine and he doesn't like it at all. The Sound, drivability, low end performance, its just not a fun car "for him" to drive. Its built for 3k rpm &up. So I fired up the 307 for him and he starts salivating like Pavlov's puppy. Wing the throttle a couple times and he says "YEA ! That's what my vette should sound like." I asked if he wanted to trade engines. LOL. Even up and I'll install it too.

He asked how much HP- I said this 307 about 330 ish.
He says my 383 has 380 -400 ish though.
I said OK what did you pay for it, 5 gs right ?
Yea I just told you that.
I said well there's way less than 1000 in the whole engine you are looking at and your 383 was a long block.

So I tell him to figure out the money to HP ratio. (He's a math wizard) and you could see the color draining from his face. I told him remember I'll swap it for you too you won't even get dirty.

 

I agree with what you're saying...anyone from auto shop class can get an Impala 350, bolt on some heads, and declare it a hot rod engine. I'd rather throw some cheap/free tech on it, and be amazed at what I get as a result...or learn to never repeat

There's a time to buy peace of mind, and there's a time to not gold plate things. I'm dying to get my hands on an Olds 403 b/c someone once mentioned a 425 crank could get it out to 480cid due to its big bore. The main webs are not solid on those engines, but still, a small block that displacement in a Monza with IMSA fenders...wow. Or boring and stroking a Pontiac 350 out to 438cid. why? well, why not? the P350 has a bore and stroke similar to an LS1, and no one cried about their small bores. Or fooling around w/ Poly engines and MP's 4 inch crankshaft.

If your buddy's Vette came from the TPI era, I could see why his 383 left him a little short..those runners ran out of breath at 4k unless he had the Arizona Speed and Marine siasmesed runners. but, to get back to the point, you're right, build it for the RPM you will run it in, and it'll seem stronger than a dyno queen engine.

its not so much showing off the money you spent, its showing off what you pulled off with the restrictions you had. I'd love to see how the 307 comes out, I'd be trying it if I wasn't so tied up right now w/ probate baloney. but someday i'll get to try it...by that time, someone'll have a nice recipe for me to begin with lol

 

And all I thought 307's were good for is to bore the H blocks to 4 inch and use used L82 forged pistons. My test group was my 16 year old son and all of his buddies.
Tested and Teenager approved!

 

Oh, and another tidbit I always forget to add when I log in:

when you increase the stroke, you increase the amount the piston pokes its bottom out the end of the cylinder. It may contact with the counterweight or it may rock at the bottom of the cylinder and get scraped/scarred by a sharp edge of the bottom of the cylinder wall.

I like the idea of the 4" 307 block, you can offset grind that crank to the pre-'68 rods, and get I think 337cid (too lazy to grab the calculator and do the math).

 

Or just use a 350 and say it's a 307 Why dick around with fancy machine work when in the long run a 350 will make more HP and torque per dollar.

 

Now that would be cheating but if a few 350s get spanked by a 307 it won't be long before they start accusing you of cheating any way.

Doing fancy and exotic machine work takes everything fun out of this build and I mean everything.

307 = junk
283 HC pistons = junk
400 rods = junk
305 stuff = junk
Junk = cheap or free

The key must have item is that the above junk needs to be relieved of service because their only flaw is they arent a 350 & someone wanted a "THEE Treefiddy in it" instead of their/this/that junk.

It really would be completely senseless to spend big & long money on a 307. Its just dumb. But a little bit of money, some time, and some head scratching to figure out how to get that pile of Chevy cast off scrap to haul ass it just got fun.

 

Free is good..and I have been given good rebuildable 350's for free.In fact I had a standard bore and crank complete 307 for sale locally and here for months and finally scrapped them..Had a standard bore #010 complete 350 for sale here and locally,100 bucks,no takers.....
A few years ago I was doing electrical work for the local machine shop.He had a roller cam block 305 with HO pistons , mild Comp roller cam and heads all the new parts a customer never picked up.I got it for short money,assembled it,added an intake and Rams Horn manifolds.Dropped it in a 4 speed sorry ass G body car and it ran quite well.Well enough that some said it was a 350.
But like you say,not something to spend big bucks on.And the availability of good 500 buck 5.3 LS cores locally is making the SBC obsolete.

 

I always had heard (it's probably urban legend and therefore I'm wrong) that the vinyl tops were to hide how chewed up the cars were from acid dipping them to thin out the metal for weight reduction.

It's true that breaking up surface tension (the dimples) can/does lead to benefits, however, it can also lead to poor flow if not done in a correct (deliberately engineered) manner.

 

Hey 31, how bout a video of the first 307 you built running? Inquiring minds would like to hear it!!