307 questions - Chevelle Tech
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post #1 of 24 (permalink) Old Aug 16th, 19, 1:47 AM Thread Starter
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307 questions

In the winter i'm going to take the engine out of my 70 chevelle and do some work on it. Being on a limited budget and still in highschool i'm just going to leave the 307 in it. Does anybody know what the redline is or what you should at least shift at? I am going to try to do a manual swap in it. I'm also going to try and increase the engine's ability to rev higher and to achieve this I would need bigger cam, stronger pushrods, springs, rocker arms and maybe some bearings? Any tips or information would be helpful, thanks!
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post #2 of 24 (permalink) Old Aug 16th, 19, 1:51 AM
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Re: 307 questions

Your 307 is limited by the bottom end and will not support major upgrades. All the parts need to work together. Max rpm stock would be around 5K.

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post #3 of 24 (permalink) Old Aug 16th, 19, 2:02 AM
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Re: 307 questions

You can find 1970ís and early-80ís long block 350 cores for $100-200. Iíd get one of them and build it. Even an 86 and newer 350 block that had provisions for an OE roller cam wouldnít be a bad idea. You can save in the back end by scouring swapmeet, Facebook marketplace and Craigslist for used parts. Try not to lock yourself in until you have explored all of your options.

Good luck.

You may also want to update your profile to include where you live. There may be someone one this site located near you that knows of some good inexpensive parts.

Steve R
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Last edited by Steve R; Aug 16th, 19 at 2:03 AM. Reason: Z
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post #4 of 24 (permalink) Old Aug 16th, 19, 3:32 AM
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307 questions

I agree; state your location! Who knows, someone may have something 10 miles away you need.
That PSA said; you arenít saving money by hot rodding your 307. This is coming from someone who put in a cam and swapped intake/carbs on a 307; but I knew a big block was coming so I was prolonging the 307ís life.
My guess is you have 3.08 ish gears, since the 307 was a low power/economy engine, so whatever you do to it is going to be hurt by that. Add a manual swap, and youíre going to kill clutches really fast because the rear gears and no torque to move the car.
So, ya, terrible right?! Not really. I put an edelbrock performer manifold with a quadrajet on mine. Also added flowmasters and dual exhaust and it really changed the performance of that 307! And I got it for $20 intake, $10 carb (plus $35 rebuild kit), $30 take off Exhaust all of Craigslist / offerup. Fun can be had inexpensive and if you upgrade to a 350 later, it all swaps over.
That said, the 307 cam is notorious for going flat. Happened on mine, thatís why I did a summit grind swap.

But to answer your original question about rpmís, you arenít limited by valve springs, rockers or even cam. Itís low compression heads and a design that isnít meant for high revs. Iíd manually shift mine with the powerglide with all that done to it when it was screaming and I bet I never broke 5000.

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post #5 of 24 (permalink) Old Aug 16th, 19, 9:24 AM
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Re: 307 questions

Yeah, it was a 600 Holley on a junkyard intake with Cragar Hot Pipe headers for my 307 back in the day. This sort of woke things up but it all wasn't working miracles.

It's a smog motor with low compression.


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post #6 of 24 (permalink) Old Aug 16th, 19, 11:46 AM Thread Starter
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I'm not trying to get max performance out of this engine, I know it wasn't made for performance i'm just trying to give it a little bit more balls
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post #7 of 24 (permalink) Old Aug 16th, 19, 1:26 PM
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Re: 307 questions

People act like the 307 is some object from a foreign galaxy. Its a 283 block with a large journal 327 cast crank. If you put a decent set of heads on them, they respond just about like any 283 or 327 would. Other than the obvious of giving up some cubes to a 350, there really is no reason not to run one if you have it. The stock parts, other than the valve size aren't any worse than what 90% of the 350 cores most people start off with anyway, and most of those parts get replaced anyway. All things being equal, a 350 makes more economic sense, but it's not because of any inherent deficiency in the 307. I'd rather have ONE 307 than fifty 305's.
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post #8 of 24 (permalink) Old Aug 16th, 19, 1:42 PM
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Re: 307 questions

thatonedrifter I like the fact that you are going to run what you have.
That is the way i started out and i do not regret it. I had a buddy with a 305'' that was my first sbc to work on.
I was running Oldsmobiles and anything but Chevy back then.

First up was dual exhaust and some straight through mufflers.
Huge gains over the puny single.

later I stuck a recurve kit in the distributor but found the stock weights and center with the curve kit light springs was best.

many years later i got the old 78 Nova for myself. engine we stuck in a buddies truck.

Stock pushrods are fine as are stock rockers and studs if you do not go wild on the camshaft.
A little 268H is a good cam or since yours is low compression the 268 on a 108 works well.

You can get by with the comp high energy 268 with stock springs and stock everything and it will rev to 5500rpm.

For more RPM and power you can bowl port the heads (actually not hard) and add some slightly stiffer valve springs.
80 psi seat pressure is plenty for that cam and will allow it to rev to 7000 rpm without issues.
I ran 1.84-1.50 valves with 80 psi seat and ported 305 heads 7200 rpm before valve float in a 350"

I tested the 268H in a 350 with stock 487X heads that had 1.94-1.50 valves but not ported vs ported small valve 305 and the 487 gave up at 5500 and the small valve went 6500 rpm.

Do not get caught up in valve size at this point.
I have went 12.51 at 111 with 1978 nova 1.72-1.50 valved heads and the 280H cam.

I would small cam it and recurve the distributor and if you have a 4 barrel iron intake already run it.
I ported my exhaust manifolds and my iron intake years ago and gained a lot and done it for less than a #1 meal at McDonalds. Minus gaskets of course.. that is another meal.

There are great books out there and acquiring tools for the job will be money well spent and you will use them 30 more years or more.
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post #9 of 24 (permalink) Old Aug 16th, 19, 1:53 PM
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Re: 307 questions

As a fellow 307 owner I think it's my duty to say just don't. Save your money for a better engine. There is nothing inherently wrong with the 307 but since it's 50 years old it probably needs bearings and rings and everything else. Sure you could throw a four barrel and headers and gain some power but the added stress is likely to not be kind to the bottom end. This engine may chug along happily in stock form for years to come but once you upset the balance and damage the fragile ecosystem it was established you'll find that you're throwing good money after bad. I've been down this road and wished I had done what I suggest to you after wasting so much time and effort. But- your money, your car. It's a very slippery slope with a 50 year old engine.
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70 Camino...Roller

69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #10 of 24 (permalink) Old Aug 16th, 19, 3:33 PM
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Re: 307 questions

Ok, here's my 307 story:
1978 on my 16th birthday I got a 71 Malibu with a 307 2-barrel. Really clean car, no options.

I found a stock 4-barrel cast iron intake and quadrajet carb (off a Nova) at the local wrecking yard for $25. Had a local mechanic re-build the carb, and we installed the set-up in my high school auto shop class. My teacher allowed this because we were using factory parts - header installation was not allowed.
Anyway, we knew nothing about re-curving a distributor, just timed it at idle. It ran great and really came alive.
Later on I scored some used Blackjack headers for free, installed them and drove it to the muffler shop un-corked. A 2 1/4" dual exhaust on turbo mufflers, and I could lay a 1-legged burnout for a whole city block. Flipped the air cleaner lid upside-down, I thought I was Daddy Don himself.

So here's my 2 cents: Playing around with your 307 is awesome as long as they are basic, inexpensive mods.
But, as others have stated, if you are going to start changing things like heads and/or cam, you should consider a used 350 locally and modify that according to your budget. You'll get more bang-for the-buck.

Good luck and have fun with it.

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post #11 of 24 (permalink) Old Aug 16th, 19, 5:36 PM
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Re: 307 questions

I too had a 307. Proud to say was my first engine rebuild. Well, re-ring anyway. Had it cooked out. One piston had a cracked skirt, I prolly cracked it myself when I was taking it apart. So I bought one stock replacement piston. I did some grinding on the heads and intake. Not knowing anything, I was 15, I just did what I thought was a good amount of grinding. Then did a gasket match for heads to intake. Dad worked at a diesel shop with a valve grind machine, so on a Sunday, we went in and did a valve job on it. I had a pretty good quardajet off a circle track car, so it went on the cast iron intake manifold. I put a comp, I think 260 something cam in it, with new z28 valve springs. New rings and bearings of course, and away we went. Was a fun runner. I ran the hell outta that engine. Went into a 68 Chevelle I had. Would hang right with a couple stockish 5.0 mustangs around town. Revved the hell outta it cuz I didn't care if it popped..
Ended up in a buddys circle track car for a night, he was out of motors, was the final night. So in it went. I told him, put it on the rim around the track and keep er wound up best you can, cuz I'm sure it won't pull off the bottom like a 383 will. He did, make the A Main, think top 15 from it.

It was fun cuz I didn't know much, and was having a hell of a good time learning by doing. Knowing what I know now, I'd build something and overspend and take away any fun that could be had by being over critical in every aspect of the build.

Anyway. Build it. Sometimes we just need to build what we have to learn, have fun, save some dimes, and not get bent if it breaks. Good luck to you.
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post #12 of 24 (permalink) Old Aug 16th, 19, 11:45 PM
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Re: 307 questions

Build it and learn from the build. Use those lessons when you go for a bigger engine. Have fun with the car. I wish Iíd have had a Chevelle when I was in school. I had to wait until this past June to finally get mine.

My father tells me I was born 30 years too late.
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post #13 of 24 (permalink) Old Aug 16th, 19, 11:56 PM
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I’d say drive it and enjoy it. Find a block locally get it machined and slowly build it up then swap it out in a weekend. This is exactly what I did my senior year of high school a few years ago.

1974 chevelle with 73 laguna nose sbc 357 Brodix IK180 heads Comp Cams XE274H Edelbrock RPM airgap 650 AED double pumper, M20 muncie, Truetrac with 3.73s
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post #14 of 24 (permalink) Old Aug 17th, 19, 1:32 AM
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Re: 307 questions

Originally Posted by thatonedrifter View Post
In the winter i'm going to take the engine out of my 70 chevelle and do some work on it. Being on a limited budget and still in highschool i'm just going to leave the 307 in it. Does anybody know what the redline is or what you should at least shift at? I am going to try to do a manual swap in it. I'm also going to try and increase the engine's ability to rev higher and to achieve this I would need bigger cam, stronger pushrods, springs, rocker arms and maybe some bearings? Any tips or information would be helpful, thanks!
I had a 307 back in the mid-80's that I got to fly. After I ran the RPM's so high on it I floated the valves and ruined them I was ready to do some work on it. I switched to a redone set of 441's and the car was a dog, found out it had super low compression so those came off. What I switched to was a pair of 283 520 castings with the small valves and the car flew after that. I never even did a valve job, the Nova still had the stock cam with the old performer and a 600 Holley VS. Took it to the track and she ran 13.90's to 14.20 all day until I popped the 4 speed but that little 307 was a blast to drive. I bet if I would have tossed in a 268H cam it would have went even better. Even though those old 283 heads are not worth much I would put them on a 307 any day of the week.
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post #15 of 24 (permalink) Old Aug 22nd, 19, 1:13 AM
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your stock 307 has the same cam as a stock 350. The 929 cam at 194/202 deg at .050”. Neither will rpm very high with that cam but investing in a cam won’t help because the heads exhaust and 2 bbl carb are also holding back your 307. A cam swap will get you nowhere if you don’t upgrade those components as well. In your situation I would add a set of basic headers and dual exhaust, as well as a 4 bbl carb and manifold before you do anything else to your 307. Those factory cast iron manifolds are a major hp killer. Even with dual exhaust. Also you will have a good foundation if you decide to add a 350 later on. Those cast iron manifolds will only be a bigger restriction with more cubic inches.
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