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Here's my 307 story, When I built my beater 67 Camaro (go to Build Section and type in Low Buck in search for the story) . I got a running 307 with a parts car so I went with it to get the car running. Did a in frame rebuild (rings and bearings) then bolted on a set of Camel Hump heads (small valve) Summit stock 350 cam and lifters, Edelbrock Air Gap intake and Holley 600 (from my parts stash). The plan was to get it running then build a 350 but guess what ? The 307 is still in the car purrs like a kitty cat and I just can't bring myself to pull a perfectly running motor out . More then a few guys have said pull the 307 put it in my pick up drive around the corner and kick it off the back. But the numbers line up great (heads and gaskets) and give me a 9.1 motor with perfect quench numbers for a good pump gas motor.
I have 2 standard bore 350 blocks under my bench now but I can get in the "Beater" hit the key and she fires rite up and idles perfect (still has the points distributor) and drives nice on the freeway (2:73 gear) took it to the strip raced it (15.50 in the 1/4) and it doesn't leak a drop of oil or run hot, not a bad little motor.
 

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Here's my 307 story, When I built my beater 67 Camaro (go to Build Section and type in Low Buck in search for the story) . I got a running 307 with a parts car so I went with it to get the car running. Did a in frame rebuild (rings and bearings) then bolted on a set of Camel Hump heads (small valve) Summit stock 350 cam and lifters, Edelbrock Air Gap intake and Holley 600 (from my parts stash). The plan was to get it running then build a 350 but guess what ? The 307 is still in the car purrs like a kitty cat and I just can't bring myself to pull a perfectly running motor out . More then a few guys have said pull the 307 put it in my pick up drive around the corner and kick it off the back. But the numbers line up great (heads and gaskets) and give me a 9.1 motor with perfect quench numbers for a good pump gas motor.
I have 2 standard bore 350 blocks under my bench now but I can get in the "Beater" hit the key and she fires rite up and idles perfect (still has the points distributor) and drives nice on the freeway (2:73 gear) took it to the strip raced it (15.50 in the 1/4) and it doesn't leak a drop of oil or run hot, not a bad little motor.
Here's the link for the build My low buck 67 build...
 

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If you wanna run the 307, run it. But, you thought of maybe bolting those parts on a 350 later is probably not the best path to take. Yeah, they will bolt up and run but they are sub optimal for a 350. Small valves and 170cc intake runners are small for a 350. And those heads are a little on the pricey side for just a cruiser. $800 each, right? As far as putting your blood into it, you’ll bleed just fine swapping engines.

But do what you want. Its your car.
 

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Discussion Starter · #24 ·
Here's the link for the build My low buck 67 build...
Dude this is what I'm talking about right here. That's one of the best threads I've ever seen. You started with a bucket of rust and saved it from destruction by turning it into a car to be fucking proud of!

I'm more than willing to put in the work to treat my 307 to new heads/cam/timing/intake/exhaust. Because that's what's in it and that's what it was born with so it's only right. I just need a little guidance on matching cam/heads/etc and what people who know such things would recommend.

So... tell me more about the cam/heads you used... and basically everything else you did motor-wise! lol. But really if I can just get a baseline understanding of what cam works well with what heads on this motor then I can go from there.
 

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Discussion Starter · #25 ·
If you wanna run the 307, run it. But, you thought of maybe bolting those parts on a 350 later is probably not the best path to take. Yeah, they will bolt up and run but they are sub optimal for a 350. Small valves and 170cc intake runners are small for a 350. And those heads are a little on the pricey side for just a cruiser. $800 each, right? As far as putting your blood into it, you’ll bleed just fine swapping engines.
Yeah that makes sense, I see what you're saying. But I have a running 307 as it is and I want to see what she's got.

As far as bleeding, I did replace the transmission already. The original one lost 3rd gear and I happened to live next door to a guy who had a spare th350 so (a friend and) I pulled the old one out and stuck this replacement one in. That sucked. The original one's still on the floor in my garage and I'll get it rebuilt eventually.
 

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OP, you're clearly intent on sticking with the 307 so here's my general advice for building it:

Your first issue with the 307 is going to be compression ratio. If you're not bumping this up you'll end up with an engine that can't utilise the parts you throw at it properly. You'll want to aim for around 10-11:1 compression assuming you have good access to high octane pump fuel. In Australia we have 98 RON pump fuel at basically every pump which I believe is equivalent to the US 93 octane pump fuel. You'll need to run this. 11:1 sounds high to some people but the aluminium heads you'll need to run for decent power allow a higher compression than cast iron. 10.5:1 is a good goal to aim for and right in the middle of the preferred range. Aim for zero deck-height, potentially a domed piston, and pay particular attention to the cylinder head chamber volume as this all comprises your final compression ratio. Speaking of cylinder heads, this leads to the next point...

Your second biggest issue is going to be bore sizing restricting the heads you use, mainly for valve sizing problems. 2.02 inch intake valves will hit the bore so 1.94 inch intake valves will be your limit - you're inherently at a disadvantage from this as a result. Generally, look for a cylinder head with a 170cc intake port or less and a 1.94 intake valve. Edelbrock, Trickflow, and others, all have something in this range. Generally speaking again, you'll be looking at a camshaft around 215-225 on the intake duration and 220-230 on the exhaust duration for something mild and 225+ on the intake/230+ on the exhaust for something wild. This seems small by larger engine standards by don't forget this is a smaller engine where a camshaft 'acts' bigger. Call a reputable camshaft company and they can recommend you a grind after a discussion on the rest of your setup and what you're after performance/driveability wise. I strongly recommend spending the money on a hydraulic roller setup. You'll pay a little more but the performance from a modern grind and the peace of mind from a hydraulic roller is worth it. I also strongly recommend thinking of the short block, valvetrain and heads as a triangle. They all rely on being matched for each other to produce a good combination.

Once you've sorted out the long block, select a good quality dual-plane intake and carburettor suited to the combination you've gone for. To finish off: you'll need to consider potentially changing out the following parts to make this combination work as intended (and reliably!), some of which I note you already had in mind but others you might've missed:
  • Ignition - A HEI system of some kind most likely
  • Headers - 1 3/4" ideally
  • Cooling system - More HP = more heat. At the very least, you'll need to ensure your cooling system is in 100% working condition/radiator & engine coolant passages aren't gunked up etc. Don't be surprised, given your increase in horsepower and your intention to autocross, that you'll be replacing your radiator and upgrading to twin electric fans before long...
  • Fuel system - More HP = more fuel required. Pump/lines/fittings/etc. You don't want to starve your engine for fuel, particularly during spirited driving.
  • TH350 mods - Increase power handling capability/firm-up shifts/etc. Particularly for the fun factor and autocross intentions!
  • Converter - Match to engine combo. Don't forget the trans cooler!
  • Rear gears - No point having tall gears with an engine you've just modified to make power higher in the rpm range.
  • If you plan on getting traction during spirited driving - you can begin counting down the days until the demise of your 10-bolt diff... so factor this in too.

After all of this, you'll probably have a lot of engine parts that aren't good for something bigger like a 350 so keep that in mind too if you go down that path in the future.

Note: Everything I've said above is recommendations based on one cohesive package. I know you haven't mentioned any bottom end work but if you really want to throw money at your 307 and care about more than just peak HP/tq figures (driveability, reliability, solid performance for your usage, etc), this is what it'll take. Anything else is a large compromise that might end up disappointing and expensive.

Hope that gives you something to work with. My father used to tell me all the time: "Speed costs money – How fast do you want to go?". Having gone down this path multiple times - I can confirm this is very accurate... and he took great pride in ensuring I remembered each time :)
 

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Discussion Starter · #27 · (Edited)
OP, you're clearly intent on sticking with the 307 so here's my general advice for building it:
...
That was an excellent post. Thank you for providing specific advice, that's the kind of information that helps to guide me in the right direction.

I'm just a new guy trying to learn here so I'm as dumb and clueless as you all were when you started out. I've bought several books including Auto Math Handbook and some others to this end.

My history includes rebuilding motorcycles and doing only basic maintenance/repairs on my vehicles. But it's finally time to dig into the world of SBC's. I've been saving up for over a decade and I'm perfectly ok with putting my money into a 307 which I already have in my possession and which already runs well vs an imaginary 350 that I don't have in my possession.

This is a "run what you brung" situation.
 

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Personally if I was sticking iwth the 307, I would just add some compression and a 300 horse 350 intake and quadra jet. It's not going to be a hot rod, but it would spice it up a bit and still look very stock under the hood. Maybe a higher lift roller cam that doesn't have much overlap so it still idles silky smooth.
 

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That was an excellent post. Thank you for providing specific advice, that's the kind of information that helps to guide me in the right direction.

I'm just a new guy trying to learn here so I'm as dumb and clueless as you all were when you started out. I've bought several books including Auto Math Handbook and some others to this end.

My history includes rebuilding motorcycles and doing only basic maintenance/repairs on my vehicles. But it's finally time to dig into the world of SBC's. I've been saving up for over a decade and I'm perfectly ok with putting my money into a 307 which I already have in my possession and which already runs well vs an imaginary 350 that I don't have in my possession.

This is a "run what you brung" situation.
Most of the folks urging you to scrap the 307 block have "been there and done that." Power comes from displacement and good flowing heads. Sticking with the 307 block puts you in the hole on both counts right off the bat. You also have said that you don't care about originality, yet you're insisting on sticking with the 307, apparently only because you already have it.

Chevy 350 blocks, short blocks and engines can be purchased almost anywhere for, relatively speaking, pennies. You say you've saved for a decade to get to do this build. You've gotten the advice of lots of members here who have no dog in this fight other than trying to give you their best advice on how to spend your savings to get the most bang for your buck.

If you stick with the 307, I'd suggest two things: (1) do an internet search on something like "Chevy 307 builds" - you'll get a number of hits for magazine articles, forum posts, blog posts, etc. detailing various "high performance" builds if you want to spend a lot on this build; and (2) seriously consider sticking a well selected cam, carb and good used Vortec heads and intake on your 307 without doing anything else and see how you like it with minimal investment.

I'm a strong believer in "buy once, cry once." Most of us here believe that if you build the 307, you'll be crying.
 

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I went back and reread your post first and have a few questions. Are you driving the car now or is it sitting ? Does it run ? Do you have a budget for your build ?
307's came stock with bad parts, 2 bbl carb, stock smog heads (78cc) and soft camshafts. Guys have good points about if your spending money step up to a bigger engine (350 or 383). When I first got my 307 running it had a quadrajet carb on a cast iron intake a used set of camel hump heads (off a 327) small valve 1.94 intake. I put in a stock Summit 350 cam (stock lift) and lifters also a new timing gear and chain. Since that time I did a in frame rebuild, rings (dingleberry hone) and bearings and had a valve job done on the heads and a new converter (2200 stall) It does have cylinder taper but in my case it wasn't worth pulling the engine and boring it (I would go 350 or 327). So in your case do you wanna cruise it or go fast ($$). If I was in your shoes I would clean it up and drive it and enjoy it as someone above said speed cost money how fast do you wanna go ? ( I bracket raced a small bock Vega for years) But stock running Camaro's are getting thinner and thinner because everybody is tearing them apart then upgrading with modern driveline ($$) . Tell me about your Camaro.
 

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Discussion Starter · #31 ·
I went back and reread your post first and have a few questions. Are you driving the car now or is it sitting ? Does it run ? Do you have a budget for your build ?
Tell me about your Camaro.
I'm driving it and it runs well. It was actually my daily driver for a couple years. My budget is on the low end of a few grand, nothing crazy, but enough to get some good parts in her.

I want to continue driving it and take it to the autocross track to get a feel for how it handles bone stock, vs how it handles with upgrades in both drivetrain and suspension and make educated decisions going forward based on the effects of the changes. I have no illusions about going "fast" in a 307, but in reality most of you guys don't spend much time above 100mph in these cars anyway. I think people often get too hung up on the numbers/specifications the majority of the limits of which they will never approach. Autocross certainly doesn't reach those speeds. So a 307 is perfectly fine for my needs currently. Eventually sure I may grow out of it. But I'm not interested in growing out of it before I even get started. So all the posts about swapping it for something bigger are not useful to me at this stage. I will run what I brung, I'm not sitting here dreaming about a motor I don't have.
 

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Discussion Starter · #32 ·
You also have said that you don't care about originality, yet you're insisting on sticking with the 307, apparently only because you already have it.
I didn't say I don't care about originality, I questioned everyone telling me to junk the 307 and in the same breath telling me that having the original motor adds value, which I questioned because those two ideas seem to conflict. So which is it-how does an original "boat anchor" add value to the car (a car I never plan on selling)?

Chevy 350 blocks, short blocks and engines can be purchased almost anywhere for, relatively speaking, pennies.
Then I should be able to pick up a 350 pretty cheap when I'm done with the 307, no?

do an internet search on something like "Chevy 307 builds" - you'll get a number of hits for magazine articles, forum posts, blog posts, etc. detailing various "high performance" builds if you want to spend a lot on this build; and
That's ..what I did ..and that's why I came here because the best article I found on it seemed to have bad information so I came here to seek clarification to see if Motortrend was wrong or if I misunderstood something. And apparently Motortrend was wrong.

(2) seriously consider sticking a well selected cam, carb and good used Vortec heads and intake on your 307 without doing anything else and see how you like it with minimal investment.
Yes, that's the whole point! I'm trying to find suggestions/advice on selecting the cam/heads. That sort of automotive math is currently above my head. That's what I came here for.

I'm a strong believer in "buy once, cry once." Most of us here believe that if you build the 307, you'll be crying.
I understand why you all think that. But it's the motor I have. And it runs well. And plenty of blog posts and articles online say you can get surprisingly good results out of it, but most such articles fail to provide a convenient shopping list which a new guy like me needs in order to establish a baseline.

I'm not trying to argue with everyone about whether or not to replace the 307. I am NOT replacing the 307. I came here for advice on which heads/cam to use and whatever other nuggets of wisdom those in the know could share. So far I've gotten a couple helpful posts and a lot of wasted time bickering about how a 307 isn't enough motor for everyone else despite the fact that I think I've made it clear that I truly don't care what kind of motor everyone else likes. This is my car and she's got a perfectly good running 307. So that's what I'm driving.
 

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Build the 307, I have had 3 Chevies with that motor back in the day. I went 283,327, 3-307, then more and more. Oh and I Had a 302 and nobody suggested I change it .LOL, 50 years later I build bb and LS. Have fun.

Bruce
 

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Are you just looking at bolt-ons (heads, cam, intake) , or are you planning on rebuilding the engine?
 

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Build the 307, I have had 3 Chevies with that motor back in the day. I went 283,327, 3-307, then more and more. Oh and I Had a 302 and nobody suggested I change it .LOL, 50 years later I build bb and LS. Have fun.

Bruce
307 small bore tiny valves poor head. = poor performance
302, large bore, big valves good heads(for the day) = Good performance. That's why nobody suggested you change it. but you knew that :)

307 with a good head w/larger valve & more compression and appropriate cam should get the OP around okay. for now...


As far as the OP's autocross plan,
I'd want to try and get all the torque I could out of the little 307 if I was going to try Auto-x with it. Just run the fun class to try it out.
I run a manual and keep it in 2nd gear, I run 2000rpm all the way to the rev limiter @6500 on the track. normally peak around 60~65 mph.
and I'm the slower guy in CAM-T one of the very very last few that doesn't have an LS and 315 tires on the front, or $150k+ into my car.
I like to say, I'm the fastest slow guy. lol.
 

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If I was to build a 307 today I would go with this. Heads , since your looking at auto crossing the car big valve heads (2.02) are not going to benefit your use (or 307 block) with short throttle hits on the course (my neighbor does auto crossing) if it was me I like the Vortec heads at Summit ( NAL-12691728) two of those will be $1120.00 . I like them because they are bolt on ready to go, to find a set of used clean camel hump 64cc heads or later ones with accs. holes your looking at $300 to $400 bucks then take them for a valve job another $500 to $600 (if good and no cracks), so your only a few bucks away from a better set of heads. Plus side, you can use your old parts (head bolts, rocker arms and push rods ?, brackets) and they are peanut spark plug (5/8) heads and not the old (13/16) ones. With a FelPro .015 headgaskets that gives you a 9.07 compression and a .040 quench are nice pump gas numbers. Your old set up (Heads) gives you only a 7.77 compression (with rebuild kit head gasket .041) and a quench of 66 (I see pinging with that). I run headers and the Accel shorty plugs ($5 bucks each) are the only 13/16 plug that clear the headers where the smaller peanut plug mite give you more options. Down side, you have to run a different intake manifold and valve covers, go to Ebay and check out the prices on both not to bad. Carb , a old Holley 600 1850 would work great and you can buy them cheap and a gasket kit for it.
Camshaft, I wouldn't touch it because to change the cam you gotta pull the front timing cover, pull the blancer, loosen the oil pan bolts to pull the pan down a little get the cover off (you just broke a few seals) . If I went that far I would drop the pan check the bearings and since I'm there change the bearings upper and lower, rear main seal and oil pump (since I'm there) then back together with new gaskets. One thing leads to another so I would go with a top end job (heads, intake ,carb) but take a compression test first and see what you have. That's what I would do or save up and get this 350 / 355 CUBIC INCH SBC ENGINESUP TO 390 HPSTARTING AT $3,699.00 later Rich.
 

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You know the 307 is basically a stroked 283 whereas the 302 is a bored 283. I got beat up a little after asking questions about my 302 mainly because guys didn't get where I was going. My first motor was a 283 11:1 unknown cam and was very enjoyable, then a so so 327, a nice 350 until a pressed in wrist pin walked out into the cylinder wall. 302 is my favorite although is is a little beasty for the times.
Your limiting factor is going to be the heads, the small bore is not gong to allow the larger valves but for what you are doing probably not be a problem EXCEPT if you later decide to upsize to a 4" bore motor your bolt on parts for the small bore 307 will not be optimal and will ultimately be a drag. JMO
 
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