Motor Options (Need Opinions)

[BHRS]

I drove a '70 1/2 Ton LWB 307/2bbl stock 4-speed for 100K+miles in high school, army, and college. The truck was 100% stock and had plenty of power and got 19+ mpg. The 307 is a good motor, but don't expect a lot of power like a 350 has. I'd install a Edelbrock Performer intake with the matching cam kit and a 500 cfm carb. The 600 will be too much for the motor. The 500 cfm carb will help with bottom end and mileage.

I agree with others on swapping out the 400 turbo with the 350 turbo, but if the truck is stock with the 400 turbo keep it. It is bullet proof and everything is setup for it mounting it.

Sometimes different is good.

[pat123]

I could do alot of things depending on how muck i want to spend. I want to have the power but keep the best fuel econmoy that i can. I dont think its a waist of money spending it on a 307 but everyone has their own opinion. I was also wondering if anyone had these specs for my 307 heads ?
Chamber Size, Intake Port Size, Valve Sizes (in/ex)

Pat

Sorry for the delay, its been busy around here with Christmas.
Are the ID numbers for the head under the valve cover? Or is it possble to ID them th the block number?

[kcjones]

Yes, you'll need to remove the valve cover to see the head casting number. Chances are the heads are the factory installed on that block, so you can make some assumptions based on that. Mortec.com is a great source for casting number information.

I'd bet 76cc chambers, 1.94/1.50 valves, very small intake runners (although not sure how small). That 307 could make some nice power, but if you want anything more than about 275HP, I'd look into vortec heads...

[pat123]

I could do alot of things depending on how muck i want to spend. I want to have the power but keep the best fuel econmoy that i can. I dont think its a waist of money spending it on a 307 but everyone has their own opinion. I was also wondering if anyone had these specs for my 307 heads ?
Chamber Size, Intake Port Size, Valve Sizes (in/ex)

Pat

Well i finally got the number. I looked on Mortec but couldnt find it.
Heres the number under teh valve cover

8927185
Not really sure if this makes a difference but they were made in Canada.

Thanks Pat

[kcjones]

Here's what you have:

3927185....69-76...307/327/350..70cc chambers.

Valves almost assuredly 1.94/1.50, runner volume...I dunno, need some help!

[pat123]

Did you have to convert the number i gave??
Ill try and do some more research on the runners
Thanks Pat

[pat123]

Also would 202 valved head fit a 283 bore??

[68Stepbed]

The later 283 and 307 blocks could be safely bored out .125 over, which would give you 327ci. I don't think I would max out the bore for the first rebuild though.

The thing to pay attention to the most is your compression ratio with the heads you choose. You need smaller cc heads with the smaller engines. IIRC 307's came from the factory with flat top pistons to raise compression with the 70cc heads and they still only squeezed about 8.0:1 CR. Rebuilding with flat tops wont gain you much unless you change to a smaller cc head.

The vortec heads have 64cc chambers, so they will help some and they flow VERY well. they will outflow your stock heads even if they were ported. You could go with aluminum heads, but for the daily driver aspect your going with, it's not necessary. Dart makes 58cc heads which would be great if you make sure you have proper valve clearance. When you order your pistons, see if you can get a chart telling you the CR with different sized head cc's. Pricewise, the Vortecs are a sure thing. Scoggin Dickey and Pace performance both have Vortec conversion kits which take the guess work out of ordering all the seperate parts needed. They come with the heads, intake, rockers, pushrods, gaskets and all the hardware needed.

No matter which heads you get, call some GM dealers and let them know your building a 307. GM makes a set of head gaskets specifically for the smaller bore 283 and 307 engines.

Also, be vary careful choosing the right carb for this engine. 600 will be way too much for an engine this small. I would recommend no bigger than 500 cfm. My recommendation would be a 500 Holley 2bbl. If you don't like Holleys, you could get a 500 Edelbrock.

I would love to build a 307, just to prove you don't have to have 43 more cubes to make decent power.
Here's how I would build it:

-.060 overbore with flat top pistons
-Vortec cylinder heads
-CompCams XE258 or XE262 cam
-dual plane aluminum intake (with Vortec pattern of course)
-500cfm Holley 2bbl carb
-MSD StreetFire HEI ignition
-headers(1 5/8" primary tubes) and 2 1/2" exhaust
-TH350 with 3.42 gears or 700R4 or 2004R trans. with 3.73 gears.

[Old Yeller 1970]

Originally Posted by 68Stepbed

-.060 overbore with flat top pistons
-Vortec cylinder heads
-CompCams XE258 or XE262 cam
-dual plane aluminum intake (with Vortec pattern of course)
-500cfm Holley 2bbl carb
-MSD StreetFire HEI ignition
-headers(1 5/8" primary tubes) and 2 1/2" exhaust
-TH350 with 3.42 gears or 700R4 or 2004R trans. with 3.73 gears.

Particularly with the Vortec heads. They'll make a 307 run as good as or better (with the other performance mods) than a stock 350 without Vortec heads.

[kcjones]

Originally Posted by Old Yeller 1970

Particularly with the Vortec heads. They'll make a 307 run as good as or better (with the other performance mods) than a stock 350 without Vortec heads.

I think you can mod vortec heads for bigger valves, but you wouldn't need to...they flow fine at mid-range lift, as good as most stock big-valved (2.02intake) at mid-range. At full lift, in the higher rpms, you may want bigger valves & intake runners, but with a truck and 3.07-3.73 gears, you probably won't spend much time in the 4000+ rpm range. Daily street use usually has you idle-4500 at most, and with a 307 with an auto in a truck, I'd target torque almost exclusively. Vortec heads are absolutely perfect for that purpose, as they're designed to flow higher cfm at lower speeds/valve lift. The next question becomes - machine the heads for higher cam lift (.490+) so you can use them on higher hp engine later, or leave them stock and enjoy for cheap....

[Slik69]

Good post and something I in the middle of debating myself. I have come to the conclusion to just rebuild a nice stock 350 with flatops and am thinking about using the vortec head. I will get everything balanced and should have a good powerful motor for a long time. I asm pretty much after the same goal. Power/economy.

I also debated on going 700/200R, but after speakign with some folks, they advised me to leave the turbo350 in it for a lot of reasons. One because it's a good tranny and 2, I was told you really don't save that much mpg wise going overdrive, and last, I was told it's better for towing should I decide to hook her up to something. I will be leaving my th350 in place.

I also thought about going roller (retro kit) with this build. Should be nice.

[5150.4.67]

We should start a "Best bang for the buck, small bore edition" thread for small bore motors. I'm sure we could give folks some good info.

[67_C-30]

Originally Posted by kcjones

Here's what you have:

3927185....69-76...307/327/350..70cc chambers.

Valves almost assuredly 1.94/1.50, runner volume...I dunno, need some help!

The 3927185 307 heads have 148cc intake runners are have 1.72/1.50 valves.

58cc 305 H.O. heads (14014416 casting #) with 1.84/1.50 valves really wake up a 307 with cam and intake. They came on 4bbl 305's and 85-86 TPI 305's Camaros/Birds. They are very underrated head and can be had cheap. They will boost the CR to around 9.6 :1 and the smaller valve 1.84" works great on with the 3.875" bore of 307.

[pat123]

Also would 202 valved head fit a 283 bore??

Anyone know?

[corn]

That would be a waste of money to go from 1.94 to 2.02 valves on a small street engine. There would be no flow difference until at least around 7000 rpm. Aluminum heads & forged pistons are a waste as well. Not knocking a 307 engine, Ive seen some run like a scalded cat...

[pat123]

Sounds like like 50% of people like the 307 and the other dont. I guess their just not as common as a 327 or a 350. I think its worth the money to "pep" mine up. Im no dissing anyones opinion, i like reading your comments. keep them coming.

Pat

[67_C-30]

Just adding to my post above, we built a 307 with the 305 H.O. heads I mentioned above with a Comp 268 hyd. cam, an old Holley Contender dual plane intake with a 600 Carter carb for a '70 Nova and it ran very good. The car had a TH3500 with a little 1800-2000 converter and 3.73 gears and it ran 13.90's - 14.00's all day in quarter and was decent on fuel for the gearing. I built it for a buddy years ago when we were in college on a shoestring budget. It was built mainly of leftover parts he and I had accumulated. It was the original 307 in Nova and was fairly low mileage car. We took it to track bone and it pulled 16.60's stock. We added the 4 bbl and intake and headers and a little tuning and got it shaved down to high 15's. The heads, cam, converter and gears knocked off almost 2 seconds, so I know from experience that this combination of parts works well on a 307. We spanked many an IROC and 5.0L Mustangs on the street with that little pea green 307Nova back in the early 90's!

[Slik69]

Originally Posted by corn

That would be a waste of money to go from 1.94 to 2.02 valves on a small street engine. There would be no flow difference until at least around 7000 rpm. Aluminum heads & forged pistons are a waste as well. Not knocking a 307 engine, Ive seen some run like a scalded cat...

My man.. you have helped me believe it or not.. I had an intention to do just that, but it seems like you think this (forged, alum, 2.02's) are a waste or overkill for a street driven vehicle.

[5150.4.67]

IMHO, Aluminum heads allow for greater compression ratio (dynamic is best figure) and therefore greater effiency and power without detonation. I do agree 2.02 heads are a waist though, as are forged pistons. That being said, there is nothing wrong with iron heads as they are more affordable. The 305 h.o. heads work well also, as was mentioned previously. And that's my 2 cents.
Check out this thread:http://www.jalopyjournal.com/forum/s...ad.php?t=45615

[pat123]

Will my 307 be a 4 bolt main or 2?

[pat123]

The 3927185 307 heads have 148cc intake runners are have 1.72/1.50 valves.

58cc 305 H.O. heads (14014416 casting #) with 1.84/1.50 valves really wake up a 307 with cam and intake. They came on 4bbl 305's and 85-86 TPI 305's Camaros/Birds. They are very underrated head and can be had cheap. They will boost the CR to around 9.6 :1 and the smaller valve 1.84" works great on with the 3.875" bore of 307.

Im guessing their cast. Are they hard to find or expensive? Alos if their cast will their be a problem with detonation? THanks again 67 C-30

Pat

[longhorn_SD69]

i dont know what your plans particularly are for horsepower but there's a company out there cal Aries that make hemi heads for chevy's that come with custom rolloers and lifters aswell as valves, i've seen them on a 454 and 572... very very impressive it would deffinitely and some scoot to your 307

[Green Machine]

I have a rebuild 307 and like it, well because the heads and block are original to the truck. Spent some $$$ adding hard seats, guides and valve job to those stock small valve heads. Comp 256 cam and 4bbl and it runs pretty hard. But heads are the limiting factor.

Be aware that 307's all had flat top pistons IIRC. More important is that you will most likely have very limited piston selection. Mine had to go .60 over because of wear. Any pistons I have found for this engine are flat tops, but are "destroked" .020. The pistons are .020 shorter than stock.

These engines came with a .018-.020 steel shim head gasket, so if you use pistons that are .020 shorter and a typical gasket that is .040, you end up with a huge .085 piston to head clearance, instead of the stock .045. Makes it ping easier and you lose a bunch of compression. Just something to think about.

Perhaps the best thing would be to find a 350 block, and use your 307 crank to build a 327, the crank is the most valuable part in a 307 IMHO. My son has a mild 305 in his 1970 truck and he kicks my butt in the 1968 with the 307, 305 is the way to go if you want small cubes, again IMHO.

[pat123]

I had to rebiuld the top half of it this summer becuase i had the old rad in it and over heated it. So i took the intake and heads off and found that it had harden seats. I replaced the stock steel gaskets and put felpro in it. If my heads have harden seats do you guys think i should just leave it alone? Or possible look for some 202 heads, 305 H.O. heads, or get some new aluminum heads?

[bhoeger70]

I wouldnt put 202 heads on a 283 or 307 because the intake valve is shrouded by the cylinder wall and will flow less than the 172 valves. The best bang for the buck would be a set of 416 casting 305 ho heads, they will flow well enough for a small motor just match everything else to the heads and what you what to do with the truck and it will run great and have plenty of power.