307 torque build

[Coalkracker]

So spring is right around the corner and once it starts warming up i will be replacing my valve seals in the heads of my 70 c10. I bought this truck to work and thats exactly what it will get used for. I will be hauling coal with it a few times a year along with other things such as pulling a stump or two and other general work here and there. My truck came with a 307 and i plan on keeping it, it has really amazed me how it has lasted through the years and is still going without any work done to it. Once i remove the heads from the block i figure it would be a good time to possibly upgrade the cam and maybe a few other things. Im not looking to dump a ton of money into it but to add a few upgrades that will give me more torque at the very bottom end. From idle up to 2000-2500 rpm is what im looking for. Im not looking to put a set of high flow heads or a giant carb on my engine that will give me a ton of flow at high rpm. I want a low rpm high torque work engine. Can anybody throw some suggestions my way?

[WorkinLonghorn]

If it was me, being cheap to the bone, I would replace the seals with the heads in place like I've done before with the rope into the spark hole trick. Actually I think I did it once without the rope. That is assuming your compression checks out OK.
Then I would get a serious RV cam and lifters and try a set of jets one size larger.
Check the compression first, engine warm, throttle open, all plugs removed, good battery.

[Coalkracker]

Great info thanks! How big can i go with the cam without changing it to a 4bbl?

[WorkinLonghorn]

I was thinking you had a 4 barrel carb. I never had a 307 but i see they came with the 2 bbl. I wonder how much grunt you would gain by hitting the pick your part and upgrading to a 4bbl manifold and a Q-jet. Maybe someone who has done this can add some info.
I do know that the '69 350 gained 20 gross ft/lbs with the switch to 4bbl and that also included higher compression pistons. So maybe not too much.

Stock torque rating for your motor was 260 ft/lbs (net) @ 2200 RPM when new. That's pretty low (RPMs) already. (figures are for 1969)

I'm not an expert on cams but my last '69 had a full RV cam (I was told) and that thing was amazing, up to about 4000 RPM, then it was done.
I would check with the cam companies and see what will work best. Comp Cams used to have a calculator that you added your info into and it spit out the best cams. Don't know if that still exists.

[Coalkracker]

Changing it to a 4bbl isnt a problem i have 2 of them and also 2 intakes laying around. I have a double pumper and a truck avenger. And intakes i have an edelbrock performer and a cast iron one from a 76 vette. Maybe calling a cam company would be helpful since they know what works with their specific products.

[Coalkracker]

Im not trying to do the "usual" modifications. Just trying to get some nice working power off idle. No need to rev it out or go fast.

[trac209]

Originally Posted by Coalkracker

Im not trying to do the "usual" modifications. Just trying to get some nice working power off idle. No need to rev it out or go fast.

If this is your goal then maybe look into a set of swirl port heads. They are dirt cheap and will have very good Throttle response and would work good with a stock cam or an torque cam in the 390-420 lift range. I had a set on a 350 with 8-1 compression and a very mild cam. I used the heads as I got them cheap and they were like new so I thought why not. Was very surprised how the engine ran,but you need a specific intake as the middle bolts are different not unlike a Vortec manifold but different yet. Summit uses these heads on their reman truck engines. They don’t like tons of timing though.

[weq92f]

.
The Comp Cams software is CamQuest. I've got it and tried to estimate your setup quickly found that I'd have to guess too many things...

Would need your head casting number ( or if you know: Int and Ext valve sizes, size of combustion chamber ), the stroke of your engine ( two listed: 3.25, 3.385 ), type of intake, type of exhaust manifolds and the CFM of your intended carb.

Also need to approximate the compression ratio... can do this online with the above data. If you'll oblige the above missing data, I'll see what it spits out for your low RPM torque use scenario.

The software is free to download if you'd rather run it yourself. It is an interesting thing to see the HP/TQ estimates for different cam grinds and how it moves them around in the RPM band.


-klb

[6T7 C10]

I would stick to a two barrel carb, stock intake manifold, and something similar to a Summit 1101 cam. Definitely a HEI if it does not already have it. I would up the compression ratio using a .015 shim head head gasket if the block and heads are smooth, or the thinnest mls gasket otherwise, as it will help the power in all rpm ranges. Keeping the rear tire height stock will help get off the line in a working situation. Yep nothing fancy but for off idle use the factory was not too far off for its intended usage.

[Coalkracker]

Thank you for all the help so far. I have the requested info. Head #3932441, valve size 1.94 and 1.5, stroke 3.25", intake stock cast, carb rochester 352 cfm, exhaust manifold ram horns, compression ratio 9:1, points ignition.

[Coalkracker]

Specs for the stock cam are 194/204 .390/.410 @.050

[68Gold/white]

Hmmm, the 441 heads are for 350 and 400 engines, and have 76 cc chambers. That would make comp ratio a little over 7.5:1, not enough compression!!! Sounds like those heads have been changed...???

Along with that fact that no 307's ever had 4 bbl carbs, none also had the bigger valves, such as the 1.94's Not trying to sound like a Beavis, just helpful... 307's don't need big valves to breathe.

THe stock cam is what I'd put back in it. THose specs are exactly the same as the Sealed Power replacement cam CS274. The stock cam is made for best over all drive-ability and MPG. I would stick with it. it's easy to over cam any engine, and small engines like a 307 or 283 are worse... If you don't want to use the Sealed Power cam, the Comp Hi Energy 252 would work, but NOT the XE version...

[Coalkracker]

I correct myself the heads are 1.72 and 1.5, i was going through old pics on my phone and the ones i listed may be a set that i sold. The stock cam is still in it. The engine has never been touched.

[kwmech]

Freshen it up and keep it as stock as possible. What transmission do you have

[Coalkracker]

3 speed on the column...saginaw i believe.

[weq92f]

.
With the info given, asking CamQuest for mild performance gain +torque and then taking the recommend list of candidate catalog grinds sorted by RPM range from lowest to highest...

Cam::RPM range::duration@50-Int/Ex::lift-Int/Ex::LCA::notes
-----------------------------------------------------------------------------------
XE250H::600-4600::206/212::.432/.444::110::Very strong torque,smooth idle
X4250H::600-4600::206/214::.432/.453::111::Very strong torque,smooth idle
252H::800-4800::206/206::.425/.425::110::Strong torque,smooth idle, likes high axle ratios
246PE::1200-5200::203/212::.429/.438::110::none
255DEH::1200-5500::203/212::.421/.451::110::Good torque, good RV&towing cam smooth idle

All of these are predicted to bring about 280-290 peak TQ at 3000 RPM and between 190 and 202 HP at 4000. The torque shows to be pretty high off idle on all these cams too, but the graphs are a bit vague and of course, they're all just predictions.

Stepping up the CamQuest request to the next level of performance the software spits out these cams but I believe this is overkill for the 307 with your specifications:

X4254H
265DEH
260H


Hth,

-klb

[Coalkracker]

Great thanks for the info!

[geezer#99]

Originally Posted by kwmech

Freshen it up and keep it as stock as possible.

Best advice there.
Nothing to be gained with a cam swap.
Your stock cam works about right with your compression ratio.
See this chart.
https://www.crankshaftcoalition.com/..._compatibility
Your compression ratio might be advertised as 9.00 to 1. Likely it’s less.

Any cam change moves the power and torque up the rpm scale. Not what you need.

[toolboxchev]

Why not a set of rebuilt Vortec Heads with Viton Seals? That would boost things up quit a bit yet not build a screamer.

They will add low end torque, cost effectively.

[AussieinNC]

Installing Vortec heads would require a different manifold...adding to the cost layer, with little end benefit...IMO....

If it were mine...pull the heads and install replacement guides, valves, springs and retainers....mill the guide top and install positive stem seals..mill then to make them flat and leave them alone...

2BBl carb is fine...make sure its clean....make sure intake manifold is not cracked...

Cam...keep it stock spec but replace it, use new lifters and tons of install lube...new chain and gear set...

Ignition....swap in a HEI unit and upgrade the Ign feed wire to remove resistance wire in stock truck Ign wiring

Clean out / replace radiator...new water pump...check heater core for leakage...

Make sure you use a High Zinc oil in these flat follower engines...

Drive and enjoy...

[garyd1961]

The 307 was a good motor. I thought the one in my truck was going to last forever but once they are worn out they aren't worth fooling with. A 350 with a set of vortec heads and a mild cam will give you more low end torque than you will ever squeeze out of that old 307.
I would run the 307 until it wouldn't go anymore and then buy a 350, no need to waste money on a 307.

[68Gold/white]

I agree that the 307 is nothing to write home about, but can get the job done.

I built a 283 in 1980-81. Spent money on it, in all areas did not scrimp anything, still did not spend a lot... I had engine bored and hones with torque plate, used forged pistons, had new guides installed (stock 552 heads), good valves. Crank train was properly balanced, stock rods resized. (Don't laugh too hard, here), I had it dyno'd. Cam was essentially the Sealed Power CS274. Engine builder was stern about not using a cam with too much duration, he was/is the expert!!! Engine made 295 HP. Sounds lame but numbers were NET HP numbers, nothing added, unlike magazine builds you read about...We experimented with headers, stock ex manifolds, timing, etc. headers only made like 4 HP than the stock rams horn manifolds. You can bet I used the stock manifolds. I was aiming for 25 MPG, with a 2.73 gear, and a TH350 (with lock up converter....Only got to 20 MPG, but a lot more power..

I was helping a good friend build an engine for his 66 C-10 LWB pickup. I found a small block 400 for him, he had it built around the same time as my 283, by same builder...I have taken a vow to never build an engine smaller than a 350, ever again!!!! THat 400 in his pickup ran incredible. My engine builders son built a 307 for his wifes 81 Z28 at the same time, that thing made like 250 HP, we were all surprised it performed so well!!!

There's a bunch of great suggestions concerning your 307. A stock rebuild or partial rebuild would be my best thought. You will need to have the pan off to check the condition of the cam. If one or more cam lobes are shiney all the way acroos the width of the lobe, the cam/lifters needs to go in the trash. If you remove the number 1 (front) rod cap, that sometimes tells the state of the rest of the bearings, because the front rod is the farthest from the oil pump.

Yes cam lube is needed on a new cam. I hear a lot of chatter from folks about using too much...I don't know what to think, except it needs to be moly paste and not something that will run off the lobe in an hour...If the lower end of the dist is NOT loose in the housing, I would re-use it...just my opinion...keeping cost down...

[54blackhornet]

This 71 C20 was ordered to work for Burlington Northern Railroad. 307 4spd 4.56 No Spin. The original engine is still present and only has 56K on the clock. It smokes a bit at startup but otherwise runs excellent, it will pull a building down if you ask it to. I feel bad about how I use it, it sits around all winter unused until fine wood gathering time, then it earns it’s keep...

[68Gold/white]

54,
I've read here about your 71, I like it!!!

[54blackhornet]

Thanks gold/white ! Lots of negative comments about 307’s but I think they have a place in our trucks history. My only complaint is the lack of power steering in truck. I don’t let anyone drive it because if you’re not careful the wheel can spin around and catch a finger or worse your wrist.