Puttin' Perfume on a Pig...307 Tech?!

My heads are from 283 with no mounting bosses for external accessories. Are these powerpack heads??

 

Power pack heads


Mutt

 

THANKS MUTT!!!! Thats the ones on my engine.

 

CAM-TANKEROUS THINKING FOR THE 307...

Picking a cam for any performance engine can be one of the most important decisions you'll make regarding how well it performs and whether or not it does what you want it to do. Given the importance of that one vital component, I thought I'd reflect on the subject a bit here.

First off, you must set an honest performance goal for your motor, and choose parts that will work together well to acheive that goal. My target for this hypothetical build is to assemble a fully streetable 307 that can be driven daily by anyone, and I'd want it to make somwhere around 325-350 horsepower on pump gas. That's certainly not an unreasonable goal, and more power from a streetable engine of that displacement is certainly possible (who knows...I may well exceed my own expectations!), but I think it makes for a good starting point, and is something that can be done on a budget, yet still provide enough power to get a light car down the street or 1320 pretty quickly!

(Tuning and parts swapping later can lead to even more performance, but for openers, I think I've set an obtainable objective!)

Now, how are we gonna GET to that goal?

For starters, I knew that I'd wante a hydraulic flat tappet cam, and even though this motor is just odd enough to justify having a cam custom ground specifically for it, I wanted to limit the choices to cams available off-the-shelf to anyone. If nothing else, I think this approach reinforces the home-built, budget minded nature of the project, and it made shopping for a cam sort of enjoyable, too!

Next, I thought through the specifics of this project...the engine's displacement, it's bore/stroke ratio, valve size, the selected induction system, header and exhaust design, the RPM range and my power figure goals. Then, I factored in the variables that will affect this engine...the fact that I want it to be reliable and potent, yet civil and streetable at the same time. Keeping all of that in mind, I ran through what I've learned from past builds...

The first thing I've come to regard as a good rule of thumb, is that smaller displacement motors work best in real-world street applications if you limit the duration @ .050" valve lift to 224 degrees or less on the intake side. I know, lots of you may be running more than that in your street driven cars, but I've found that being a bit conservative in this area yields you a motor that will be equally as happy on a slow crawl through traffic as it will winding through the gears at the strip. (This is especially true if you plan to run a mild converter and moderate rear axle gearing as I do).

Next up, you need to consider valve sizes and exhaust system design. It's fairly well known that I'm a strong advocate of dual pattern camshafts for the majority of street driven vehicles, and I stand by that theory 90% of the time. The exceptions come when valve sizes are reduced, and a free flowing exhaust system is incorporated. Dual pattern grinds help to make more power by compensating for the disparity of valve sizes (intake being bigger) and the presence of back pressure in vehicles equipped with mufflers and full exhaust systems. They provide a little extra lift and duration to the exhaust valve to aid in cylinder scavaging so that there is more room in the cylinder for a fresh air/fuel charge after the intake valve takes over.

When running a smaller intake valve size, and/or when running open headers, the benefits of a dual pattern cam begin to diminish, and single pattern grinds become viable candidates once more.

Given that the 307 runs the small 1.72" intake valves, I made myself open to the inclusion of at least ONE single pattern grind in my list of possible choices. The engine will be equipped with headers, and the exhaust system will consist of a straight-through muffler attatched to each collector with a short length of pipe in between...pretty free-flowing!

So, with all of that in mind, I singled out the following cams as being contenders for this engine:

CROWER COMPU-PRO Level 3

Lift: .462" Intake, .470" Exhaust
Advertised Duration: 280 degrees intake, 286 degrees exhaust
Duration @ .050": 220 degrees intake, 226 degrees exhaust, 112 degree lobe center

CRANE POWERMAX # 113941

Lift: .454" Intake, .480" Exhaust
Advertised Duration: 272 degrees intake, 284 degrees exhaust
Duration @ .050": 216 degrees intake, 228 degrees exhaust, 112 degree lobe center

SSI # 10310 (from PAW)

Lift: .443" Intake, .465" Exhaust
Advertised Duration: 280 degrees intake, 290 degrees exhaust
Duration @.050": 214 degrees intake, 224 degrees exhaust, 112 degree lobe center

ISKY 270 MEGA-CAM

Lift: .465"
Advertised Duration: 270 degrees
Duration @ .050": 221 degrees

As you can see, all four cams have duration @ .050" specs of 224 degrees or less on the intake side as I specified earlier. Any one of them would surely work well in this project, and they should give you the power you want and also deliver the driveability you're after.

 

Fat Hack,

Your one of the most enjoyable authors to read on this board - I look forward to everyone of of your killer engine tech posts...

Danny

 

Interesting read.

20 sumptim' years ago I bought my 49 GMC p/u. The guy threw in a 307 and Saginaw 4 spd.

I was a kid with little money, so I rebuilt that engine, bought a Comp Cams 260 HE cam, a swapmeet Torker intake and Carter AFB, and later added headers and a 2-1/2" exhaust system.

I have run the snot out of that thing for the last 20+ years and it is still a good runner.

Carry on...

Neal

 

Hey Hack, Great idea. I've got the 307 out of my dad's 70 chevelle sitting in storage right now. I've often thought about the possibilities for it. I am looking forward to seeing how this turns out.

 

A clear example of what I posted earlier, it doesn't take a rocket scientist. I'm not deminishing your efforts , just pointing out the obvious.

Frank

 

Hack, this is an eye opener. Myself and other's bought the same 'myth' that these motor's where to be a boat anchor. Dog! Pile o' poop. "Finda tree-fit-ee", ect. No one around here ever took your approach. Motor? Why it's a SG (Super Greg) 283......make a cool logo on the air cleaner or even valve cover(s).

 

I look foward to learning more from this thread.Does anyone have the PN for the power pak heads?

 

hey, what about 305 heads?
i don't rmember PP heads being all THAT great to spend money on...

just throwing something out top think about.

 

Great article Hack! There is no reason for the 307 to be considered any more of a pile of poop that any other sbc. Just tell the ignorant bastard naysayers you have a stroker 283, and they'll oh and ah. I bet the old Duntov solid would be really sweet here to if you're a masochist like me and like adjusting things.

 

Has this thread died? Currious minds wan't to know.

 

I built a decent little 316 cube motor a while ago, its in another thread. I used a 283 block with a 327 crank, all small journal, with 307 pistons. Worked fine.

There are lots of 327 small jounal cranks around and lots of the later small jounal 283 blocks with the larger crankcase. Easy 307 with parts that people usually throw away.

 

I read and here people say small journal 327s are easy to find. Here in NC I can't find one at all.

 

I wish you would have posted this a week ago. Just last Sat. I bought a 350 block and crank to replace the 307 in my daughters 69 Camaro she has had since she was 16. She is 34 now with 3 kids but she hung on to that Camaro. We are planning on useing Vortec heads. How would they work on the 307 ?

 

The 4" bore 327 blocks seem to be scarce but there are lots of cranks around.

There also seems to be lots of 283s around.

 

I know this is an old thread, but I just picked up my 69 Chevelle with a 307. I have a 350 block (1 pc) and am debating whether or not to do a build with the 350 or just do some changes to the 307.

Any new info on the 307?

 

First off. Do an Intro... Like the rules say. PM fathack and save some bandwidth. Last time I talked to him , he has not found a good donor. I used alot of that info when I had my 307 in my plymouth. Good cheap, strong running motor.

 

Glad this thread got drug up, I have a 307 in my 69 C-20 "work truck" and based on always hearing bad things about 307s, I would have never thought to search for this.

Mine is getting pretty tired and I was just going to trash it and get a 350 but after reading this (well, part of it, I need to reread it a dozen times to take it all in) I think I will reconsider.

Cool post for "tech" week.

 

true, the 400 small block had what is called "siamezed" cylinders. i had a 400 in a chevelle, that was mildly built up. it was a stump puller, but not very high revving. i had a big 4 core radiator in the chevelle, and the 400 ran at 200 degrees constantly. never overheated, and never ran cooler than 200, no matter what the outside temp was. i built this motor myself, so i know that everything was ok with the motor, and the cooling system.
200 isn't all that hot (in my opinion) on a mild street engine.(especially a 400).

 

so...even tho this may be off the topic of the 307...what makes a 305 ?

 

The 64 cc Vortec heads work great on a 307. They really wake the 'lil bitch up with the proper cam.

 

Lets see, since I'm a FNG, here's my intro. Live in Florida. Retired military. Picking up my 69 Chevelle with a 307 and PG. I will PM him since he seems like a knowledgeable engine guy.

 

if you had pistons for a 3.905 bore, mine are from venolia ,you use a 6" h beam rod and a 383 stroker crankshaft you get 359 cubic inches
it takes a lot of grinding on the block , about the same as you would in making a 434 of of a 400block or 383 out of a 350 block

 

So what happened with the 307 in question?
A good friend of my Dad's had a 307 bored to 327 in the 70s ( here in Oz where SBCs are kinda rare )

All reports are that it used to run low 11s in a "street" car

 

my motor is a 70' 307 bored 30 over and stroked to 359 cid using the combination above

 

I'll take exception to this statement. The 68-73 307 used the '929' cam. The EXACT same cam used in low / medium hp 327 and 350 engines in the same era. No reason for a 307 to eat a cam quicker that a 350. Also, the "wimpy" cam will have a broader powerband in a 307 than a larger displacement 350. This was the cam used in the 300hp/350 and these were not "wimpy".

The real problem with the 307 was the low compression ratio, TINY 2GC carb, single 2" exhaust, and the fact that most were coupled to Powerglides in heavy cars with tall gears.

I agree 100% that this can be a great building block for a strong street engine.

 

307's? the last really good one i had really caused me grief and i don't mean how it ran because it ran strong. the motor in question when reading the stamped #'s in front said 71' nova and when you ran the cast #'s on the bellhousing flange it came back as 283! from what the engine builders the time(mid 80's) said that gm used left over blocks to produce 307's anyone else had this issue? this version is short one on this engine.

 

Here's another 307 thread... http://www.jalopyjournal.com/forum/showthread.php?t=204736

I was able to get a pair of the World Heads from a fellow HAMB'er for mine... someday when I get the car all put together and get it running I'll let you all know how it turned out as I plan to follow fairly close to what Fat Hack started but never finished in this thread.