ive done searchs on this topic but i cant seem to pick the best power upgrades so what are the BEST bolt on upgrades that you've noticed an increase of power on, or what combinations are you running. the more results the better :D

thanks

Not my own, but a 70 Malibu I've helped work on since my friend had it.

First modification we did to it was to put flowmasters on and ditch the tailpipes. He bought the car with a 2inch dual exhuast system and the tailpipes had some horrible crimping, very restrictive over the axle. Throttle response was much better, but it was a bit too loud for my taste.

A Qjet carb on top of a Performer RPM was all it ever needed. The original cam couldn't keep up with the gearing though. He's got 3.xx gears and it didn't take too long to over-rev the engine.

That's all we really did to it though, it never got headers or much else. It already had an HEI before he got it too.

It would out run my old roller-cammed 305 all the time as long as he got traction on his skinny tires.

Given the bore size, you're limited on the valve size (no 2.02" intake valves allowed). I've heard that heads from a 305 H.O. work nicely on an old 307.

The 307 in the '71 I sold (see link) had an edelbrock performer intake with a Q-jet, 1-5/8" headers and a small cam, I'm not sure of the specs as it was in the car when I bought it, but it did have a slight rumpity rump to it, and it was running 2-1/4" dual with cheap summit turbo mufflers.

It was very responsive and a lot of fun, but the absolutly best upgrade was adding a Transgo shift improving kit to the th350 tranny. That made it feel like a totally different car!

I see this over 'n' over, so I'm gonna ask:

Why can't you use 2.02 valves in a 307?

Originally posted by Schurkey:
Why can't you use 2.02 valves in a 307? The cylinder bore is too small to clear that size valve. With decent valve lift, the intake valve will hit the top edge of the cylinder.

I was running a comp high energy 260 w/ 305 heads and a performer manifold and 600 carb. Can't say which was the best bang for the buck because I did it all during a rebuild ( probably the four barrel though), but with the stock 2.73 geared one legger it would light that tire up at will :D

You can run big valve heads on a 307 but you have to limit the valve lift to about .440"/.450"s b/c you can hit the cylinder walls like mentioned.

My nephew's 283 motor had a good set of big valve -291's on it and the cam was only about .433"s or so in lift..

Like already said, a good set of 305HO, -601 heads with 58 cc chambers, 1.84"/1.50" valves and hardened seats along with .020" steel shim headgaskets will do wonders for the little motor!!

Should put you up right close to 9.88 to 1 CR., so you can still run good pump gas!!

A 600 cfm, 1850 Holley 4-barrel on a 300-36 high-rise Holley intake, NO bigger then a CC 268HE cam and probably better, a Crane 266/266 Energizer cam or CC 260HE cam and add a cheap set of 1.625", four tube long headers and go play!!!!!

Sucker should run VERY WELL, imho!!! For a little motor that nobody seems ta want nowadays...

pdq67

ok so when searching for 305 heads what should i look for? and what years of engines casting numbers etc. to get the proper heads for my car?

also if it makes a difference its a gota 2 speed powerglide.

thank you to all who repllied

Try Mortec's site for years and head casting numbers.

Here's a link.

http://www.mortec.com

pdq67

Build a 350, you'll be much happier graemlins/thumbsup.gif

And put the Powerglide in storage. Almost any other 3 or 4 speed automatic that GM made since '65 would be a GIGANTIC improvement.

My 68 with a otherwise stock 307, I added a performer intake, 1-1/2 inch headers and vacumn 750 and it ran 15.7s with a glide and 14.9s with a turbo 350 and a 11 inch converter. I figure it was putting out about 250hp. There is no reason a 307 can't make 350-400+hp. The problem with the 307 is that most aftermarket parts are designed to work on larger (350+) motors. The biggest problem is finding a "good" head with a small enough chamber and runner to match the 307 displacement. IMO heads are the corner stone to making an engine work. The summit catalog has just added a trickflow head that has a 1.94 inch intake valve, 58cc chamber and a 175cc intake runner designed to work on smaller displacement engines. Don't know anything more about them, but they would seem to be worth a look. My thought is those heads a agressive cam and then match, intake, carb, headers gear etc and you are looking a 350-400hp and hopefully a 12 second time slip. Of course if you do all this, realize you could have built a 350 or bigger motor for about the same price, and it would probably have run better.

I've got a 307 in my 77 2WD Jimmy bored it 60 over stock replacement pistons, performer intake performer cam ( free from friend) had 1.94 valves installed during the valve job 1.5 headers 500 cfm carter afb runs great plenty of power for a daily driver havent checked the milage, kind afraid to, I think I'm running 3.73s Jim

the only head that matches with your descriptions are :

10088113...88-up...350..........Aluminum, 58cc, angle plug, raised "D" port exhaust, 1.94"/1.5" valves
you guys are saying a 305 heads whats the diffenence? will it still work? also what does a angled plug, raised d port mean?

thank you to all who responded graemlins/thumbsup.gif

I think I've killed my 307. I have a Qjet on it, and it has an old 'blue racer' cam in it, but otherwise it's basically stock. Ran a 16.2 at the track :( . Anyway, I put a built TH350 in the car a while back, and 3.42 gears. I'm pretty sure I've over-revved the little motor too many times now and I have what sounds like a rod knocking.

No problem, the 357 is on the way smile.gif

I don't know much about them but the mid 80's 305 truck head had a 1.85 or so intake valve. This head might be worth checking into.

Originally posted by 70chevellemalibu:
also what does a angled plug, raised d port mean?Angled plugs are exactly that. Instead of the spark plug sticking straight out and "pointing" towards your A arms, they are either "pointing" towards the front or the back of the engine bay. Spark plug #'s 1, 5, 2, & 6 will be "pointing", at an angle, towards the rear, (or header primaries/exhaust manifold) while spark plug numbers 3, 7, 4, & 8 will be "pointing" towards the front of the engine bay. Sorry if it sounds confusing, but you'll know it when you see it ;)

As for "raised D ports", I believe that refers to the exhaust ports. They are slightly higher then the stock location, hence the "raised" part. And the "D ports" are their shape. Some exhaust ports are round/oval while others slightly more "squareish" or shaped like the letter "D". Hope that helps. smile.gif


Edit: Think of the letter "D" lying on it's back, with the "hump/belly" up in the air, (yeah I know it sounds stupid tongue.gif ). Well, that's how the port looks. Just thought I'd try to clearify what it looks like, in case you start shopping for heads at the swap meets or something.

thanks LXS, so what do you think about that head? from the 350 is it worth alook? will it give me what i want? or is it the wrong head b/c everyone is saying a 305 head is the way to go?

I would like to see someone try a vortec head on a 307. IMO it would work well, it has a 1.94 intake, a smaller 170cc volume runner, and you should be able to cut enough off the head to get its chamber small enough to keep the compression reasonable. What do you guys think?

Originally posted by 68chevelle533:
I would like to see someone try a vortec head on a 307. IMO it would work well, it has a 1.94 intake, a smaller 170cc volume runner, and you should be able to cut enough off the head to get its chamber small enough to keep the compression reasonable. What do you guys think? If someone out there has a pair of vortecs, I've got a 307 we might be able to borrow to try this, lol.

Actually, we'd need to rebuild the 307 to make it fair, the shortblock hasn't been taken apart since GM put it together!

From what I have read the vortecs are a mucher better head than the stock 307 head and probably better than the 305 heads too. Enrique if end up with a set on your 307, I would love to know how they run.

what year chevys had vortec heads? 96+

I'm still running the original 307. I have added and edelbrock performer eps and edelbrock 600 cfm manual choke carb. It also has a crane energizer cam 274h (.450 lift / 218@.050) and 1.5 roller rockers on the stock heads. I also added a set of dynomax headers and a 2 1/4" exhaust system. The transmission is a powerglide with a fairbanks shift kit and a tci breakaway 11" converter along with a 3.36 geared open rear end. It sounds pretty nice and has runs pretty well. I have never ran it at the track but it has enough power to keep me from getting run over now. It is starting to smoke pretty bad whenever it gets to about 4k. Probably to many runs to 6k. I will soon hopefully replace it with a 350 and a turbo 350 trans.

Actually, I don't have my original 307 anymore. But my neighbor/buddy/racing partner let my brother borrow his 307 so we could mock-up the small block swap in my brother's Nova. Funny though, soon we'll be doing a BBC, LOL.

If I ever get my hands on a decent 307/200hp (stock) and I have something to put it into, I'll surely try out the Vortec swap.

70ChevelleMalibu- The Vortec came on 96+ Trucks (maybe vans too?) with 5.7L (350ci) V8's. NOT the 5.3L V8 though, those are LS1-style engines. (Gen iii).

Alright, a post about 307's!! :D. My 69 has the original 307 in it. I rebuilt it when I restored the car. It is built to original specs as well. I must say, and some don't believe me when I say this, that little turd of an engine will burn the one tire right off the rim witht he 2.73 gears in it. The throttle response is right there and it never bogs or hesitates. I did want to throw a Q-jet on there and an HEI, but I decided to leave it original restored for now. I do plan on taking it to the track to see what it will do. See link below for the burnout video of the 307....
http://www.chevelles.com/cgi-bin/video/dirwrap.cgi?rt=count&path=video//69Burnout1.wmv

thanks LXS, so what do you think about that head? from the 350 is it worth alook? will it give me what i want? or is it the wrong head b/c everyone is saying a 305 head is the way to go?

Honestly, for a 307, I have no idea which head is better. From the posts I've read so far, I think that a pair of Vortechs would work pretty good, but thats if everything bolts up. If your comparing angle plugs to straight plugs, the decision is up to you, just know that for whichever head you choose, you have to buy a specific type header design, i.e. angle plug heads need headers designed for angled plugs, they will not work with straight plugs. Looking at the "raised D port", I don't think there's much, if any, difference in performance. But, like I mentioned a little while ago, I think Vortechs sound like a really good idea! :thumbsup:

What are the stock valve sizes and combustion chamber sizes on a 307?

I believe it's a 70 cc chamber. Not sure about the valve sizes.

1.72/1.5

Fwiw, the 305HO, -601 head's chambers are shaped almost like mini double-hump head chambers!

They are "kidney-bean" shaped like the old double-humpers!!

To me, a good design just like the old double-humpers!!

My set cc'ed at 55 cc's! And have 160 cc intake ports to boot!!

Just bringing this up again..

AND I figure that the 50 cc heads that Powerhouse is advertising would be great on the smaller motors with true flat-top pistons in them like we are talking about.. 265/274, 283/292, 302/306, 305 and 307 motors????????

pdq67

I have a 307 with an old E-brock manifold,I think it says 'streetmaster' on it,with a 4 bbl holley attached to a glide sitting in the garage,it runs like a top,no balls or anything but it runs perfect.I can't see chucking it since it's complete and runs so well and I don't think anyone would be interested in buying it so I'm hoping to come across something to put it in,I'd like to find an early 70's pick up.

I am currently installing a 307 in a mid 80's camaro to have a little fun with. The motor is stock except for a streetmaster intake and Holley carb The car has a 5500 stall converter and a 4.10 gear. We are interested in what the car is going to do, we plan on spraying the heck out of it till something lets go. Should be a blast.

I know a local guy with a Nova that runs high 10's, low 11's with a 307. Yep, I was surprised myself. It's nothing exotic though. Basically he put some forged internals in it and sprays the bejeezus out of it, and the motor just won't die :). I'm talkin like a 250 shot. The car is also completely stripped down w/ some fiberglass body parts, and he has it hooking very well, that helps.

the only head that matches with your descriptions are :

10088113...88-up...350..........Aluminum, 58cc, angle plug, raised "D" port exhaust, 1.94"/1.5" valves
you guys are saying a 305 heads whats the diffenence? will it still work? also what does a angled plug, raised d port mean?

thank you to all who responded graemlins/thumbsup.gif

from 84 up the 305 came in two flavors in performance cars<sic>
the standard 305 and the "h o" the h o heads are the ones you want on a carbed car 84-89 your looking for a "g" in the eighth digit in the vin... an "h" is a standard 305 the G is the h o.. or go vortecs and notch the cyl. wall for clearance..........the vortecs will out flow the 307 no matter what you do.... any good machine shop can notch the walls..

A 283/307, 3.875" bore motor CAN run 1.94"/1.50" valves FINE!!

B/c stock, 315hp/283 FI motors had them from the factory.

pdq67