Questions about 307 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

zyggy72 · 02-09-2004, 01:26 PM

The 71 chevy 1/2-ton truck I brought home this past weekend has a 307 in it that runs good and doesn't smoke or anything. I don't plan on building the motor but I want to know if the 307 is good for an everyday driver/work truck. Were there any problems with them? What were the hp & torque ratings on the motor? Any other information about those motors would help. Any one with past experiences with them?

**CPNE** · 02-09-2004, 01:44 PM

For what you describe the 307 is an adequate engine. It's not the first choice for a small block build up though. It's got a 2bbl carb which I've always thought used more gas than the same engine with a 4bbl with small primaries (until you put your foot into it).

The good news is that all accessory brackets, intake and exhaust manifolds are the same as the 350, so these parts are easy to come by and cheap. So you can add a 4bbl and headers if you wish.

I don't have the factory specs on this for you.

JimKshortstep4x4 · 02-09-2004, 01:47 PM

We run a 307 in two of our daily drivers and the 307's are a very good serviceable engine. Gas mileage is good, power is OK but not like a 350. If you need to tow, it would be better to have a 350. They last a long time. I don't believe that I would ever rebuild one as they are more costly to build than a 350.

Overall, I think they work real well in these trucks, especially if you are doing long trips.

Jim

*1972C10* · 02-09-2004, 02:12 PM

283 bore with a 327 stroke.. Only good thing about them is that they use a large journal 3.25 stroke crank so you can build up a 350 block with 327 pistons good large journal rods and that 307 crank.

zyggy72 · 02-09-2004, 02:32 PM

Wow! This is a big help so far. Thank you for the information that you've given.

Zumo · 02-09-2004, 02:40 PM

Not a good motor to tow or haul heavy loads. I pushed my 307 to the limit and broke a rod. I am in the process of installing a rebuilt 350 now.

zyggy72 · 02-09-2004, 02:55 PM

I don't plan on doing any towing with this truck and it will only see an occasional heavy load besides the tool box I will have in it. The truck is only a 1/2-ton swb fleetside, just a light duty work truck/daily driver.

JimKshortstep4x4 · 02-09-2004, 03:04 PM

We run q-jets on both of the 307's. The mileage went up some with the q-jet under normal driving conditions.

Jim

zyggy72 · 02-09-2004, 03:12 PM

From the sounds of it, I'll change the intake to a 4-barrel intake and put the q-jet that I have on top of it. I also have a set of headers and a custom dual exhaust system that I will install too.
Come to think of it, I will clean one of the hei units that I have and add that to the 307 also. Anyhing else?

Z28Owner · 02-09-2004, 06:01 PM

I got a 307 I drive everyday. I have installed a HEI, 600cfm carb and performer intake, clutch fan. Gonna get the headers on there in a few weeks. I got a th350 with 4:11 gears, get anywhere from 12-15 mpg longs as I keep it aroun 50-55 and dont open the four barrell. It has no problem pulling itself around, can keep up with traffic easily, but put any weight in it and it is very noticable. All in all a good driver engine.

MrGoodpliers · 02-09-2004, 06:09 PM

I have thought about upgrading my 307 to a 350 using a different block and heads. Mine is a '69, do you think it has a cast or forged crank?

FirstGen · 02-09-2004, 09:31 PM

How do you tell if it is a 307 or 350 besides running the numbers? What is a good website to run the numbers on?

FirstGen · 02-09-2004, 09:32 PM

Don't think they used forged cranks on really any factory motors back then except for some of the rare HO motors? I'd put money on it that's its a cast crank...

Z28Owner · 02-10-2004, 12:11 AM

Quote:

Originally posted by FirstGen
How do you tell if it is a 307 or 350 besides running the numbers? What is a good website to run the numbers on?

http://www.mortec.com/castnum.htm

Hooter · 02-10-2004, 02:35 AM

I had a 307 in my 69, had a steel crank and a 4 barrel, the motor was a dog, it got the same mpg as my 454 does now, but was not even nearly as fast, in fact it was slow, but that was just my experience

FirstGen · 02-10-2004, 02:48 AM

Quote:

I had a 307 in my 69, had a steel crank...

I hope it had a steel crank

All cranks are steel. Most factory cranks are cast though(cheaper). Any steel crank could be cast, 4340 steel (forged), 5130 steel, etc.

MrGoodpliers · 02-10-2004, 10:12 AM

I had a '72 truck 4 bolt 350-- forged crank, and a no frills '67 327--forged crank. I figure chances are that it is a forged crank in my 2bbl 307. If someone knows for sure, Zyggy and I would like to know... (right, zyggy? hope I'm not stealing your thread)

zyggy72 · 02-10-2004, 10:27 AM

Thats OK, I would like to know also.

FirstGen · 02-10-2004, 12:13 PM

Quote:

'72 truck 4 bolt 350-- forged crank, and a no frills '67 327--forged crank

Nice! I'm surprized. Just courious, how did you know it was forged? I've got a 327 with a thrown rod, maybe it has a forged crank too?

70ChevyLongbed · 02-10-2004, 12:15 PM

I have a 307 and have some additional info from some past threads.

blazomatic posted:
"I have a 307 in my 71 K5. I also have the series 10 truck owners manual for 71. In it they rate the 307 with: 135 net hp @ 4,000 and 235 net tq @ 2,400."

In December I just finished making the following mods to mine:

Edelbrock Performer Carb 500cfm (#1404, manual choke), Edelbrock Performer intake manifold (#2101), Engine Works Cam (#135280H) with 214/214 @ .050 duration and .443/.443 lift, new lifters, HEI Distributor (new, for stock 1975 350) new plug wires, R46SZ plugs gapped at .045, short water pump, new fan clutch to fit the new water pump, new water pump pulley (two groove), Alan Grove Alternator bracket (#213L - ALT.), new crank pulleys (three groove – and special spacers for the press-on balancer), new detent cable, new Edelbrock Elite "Signature" air cleaner and some chrome stuff.

stepside454 posted:
"I punched your info into my desktop dyno 2000 .I assumed a 112 LSA on the cam & came up with: 213HP @ 4500 RPMs 277 ft. lbs. @ 3500 RPMS Than I added small tube headers: 226 HP @ 5000 RPMs 297 ft. lbs @ 3500 rpms for a low compression 307 with small valve heads, not to bad, good heads like Vortecs would be a huge gain"

I am very happy with the increased power and throttle response, but I'm not going to smoke my tires anytime soon. I started out wanting reliability for my daily driver, and ended up going a little overboard in a few places. It was a good experience.

Jason

MrGoodpliers · 02-10-2004, 01:11 PM

The parting lines on a forged crank are wide and flat, while on a cast crank they will be thin and raised slightly. Also, if the crank is out of the block, if you tap a forged crank with a hammer it will ring like a bell-- cast crank, a dull thud.

zyggy72 · 02-10-2004, 01:28 PM

Cool! That is good to know.

FirstGen · 02-10-2004, 03:25 PM

yeah I knew that about the casting lines, don't think I will be trying the hammer trick though

02-09-2004, 02:40 PM	#6
Zumo Hot Rods For Life Join Date: Sep 2001 Location: Waxahachie, TX Posts: 3,305	Not a good motor to tow or haul heavy loads. I pushed my 307 to the limit and broke a rod. I am in the process of installing a rebuilt 350 now. __________________ 1968 C10 LWB **SOLD* Andy Viva Los Bicicletas! Los Muertos Custom Bicycles

02-09-2004, 06:01 PM	#10
Z28Owner ......................... Join Date: Nov 2001 Location: benton, ky Posts: 285	I got a 307 I drive everyday. I have installed a HEI, 600cfm carb and performer intake, clutch fan. Gonna get the headers on there in a few weeks. I got a th350 with 4:11 gears, get anywhere from 12-15 mpg longs as I keep it aroun 50-55 and dont open the four barrell. It has no problem pulling itself around, can keep up with traffic easily, but put any weight in it and it is very noticable. All in all a good driver engine. __________________ 1971 LWB Chevy C-10 350/350 3:42 eaton

02-09-2004, 06:09 PM	#11
MrGoodpliers Registered User Join Date: May 2002 Location: Gainesville, Georgia Posts: 704	Hey 1972C10... I have thought about upgrading my 307 to a 350 using a different block and heads. Mine is a '69, do you think it has a cast or forged crank? __________________ We made Oklahoma a little after 3, Randy & his brother Bob & my old GMC...

02-09-2004, 09:31 PM	#12
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	How do you tell if it is a 307 or 350 besides running the numbers? What is a good website to run the numbers on? __________________ 1968 C10 build in process TT LSA/6L90e/9"

02-10-2004, 02:35 AM	#15
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,085	I had a 307 in my 69, had a steel crank and a 4 barrel, the motor was a dog, it got the same mpg as my 454 does now, but was not even nearly as fast, in fact it was slow, but that was just my experience __________________ Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life

02-09-2004, 01:26 PM	#1
zyggy72 Can't kick the addiction! Join Date: Jan 2002 Location: Riverton, CT 06065 Posts: 402	Questions about 307 The 71 chevy 1/2-ton truck I brought home this past weekend has a 307 in it that runs good and doesn't smoke or anything. I don't plan on building the motor but I want to know if the 307 is good for an everyday driver/work truck. Were there any problems with them? What were the hp & torque ratings on the motor? Any other information about those motors would help. Any one with past experiences with them?

02-09-2004, 01:44 PM	#2
CPNE Resident Curmudgeon Join Date: Dec 1999 Location: NH Posts: 6,662	For what you describe the 307 is an adequate engine. It's not the first choice for a small block build up though. It's got a 2bbl carb which I've always thought used more gas than the same engine with a 4bbl with small primaries (until you put your foot into it). The good news is that all accessory brackets, intake and exhaust manifolds are the same as the 350, so these parts are easy to come by and cheap. So you can add a 4bbl and headers if you wish. I don't have the factory specs on this for you. __________________ Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter Maybe I need to sell some of this crap Yet another Bozo with a sawz-all

02-09-2004, 01:47 PM	#3
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	We run a 307 in two of our daily drivers and the 307's are a very good serviceable engine. Gas mileage is good, power is OK but not like a 350. If you need to tow, it would be better to have a 350. They last a long time. I don't believe that I would ever rebuild one as they are more costly to build than a 350. Overall, I think they work real well in these trucks, especially if you are doing long trips. Jim

02-09-2004, 02:12 PM	#4
1972C10 Account Suspended Join Date: Dec 2003 Location: Texas Posts: 2,686	283 bore with a 327 stroke.. Only good thing about them is that they use a large journal 3.25 stroke crank so you can build up a 350 block with 327 pistons good large journal rods and that 307 crank.

02-09-2004, 02:32 PM	#5
zyggy72 Can't kick the addiction! Join Date: Jan 2002 Location: Riverton, CT 06065 Posts: 402	Wow! This is a big help so far. Thank you for the information that you've given.

02-09-2004, 02:55 PM	#7
zyggy72 Can't kick the addiction! Join Date: Jan 2002 Location: Riverton, CT 06065 Posts: 402	I don't plan on doing any towing with this truck and it will only see an occasional heavy load besides the tool box I will have in it. The truck is only a 1/2-ton swb fleetside, just a light duty work truck/daily driver.

02-09-2004, 03:04 PM	#8
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	We run q-jets on both of the 307's. The mileage went up some with the q-jet under normal driving conditions. Jim

02-09-2004, 03:12 PM	#9
zyggy72 Can't kick the addiction! Join Date: Jan 2002 Location: Riverton, CT 06065 Posts: 402	From the sounds of it, I'll change the intake to a 4-barrel intake and put the q-jet that I have on top of it. I also have a set of headers and a custom dual exhaust system that I will install too. Come to think of it, I will clean one of the hei units that I have and add that to the 307 also. Anyhing else?

02-09-2004, 09:32 PM	#13
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	Don't think they used forged cranks on really any factory motors back then except for some of the rare HO motors? I'd put money on it that's its a cast crank... __________________ 1968 C10 build in process TT LSA/6L90e/9"

02-10-2004, 10:12 AM	#17
MrGoodpliers Registered User Join Date: May 2002 Location: Gainesville, Georgia Posts: 704	I had a '72 truck 4 bolt 350-- forged crank, and a no frills '67 327--forged crank. I figure chances are that it is a forged crank in my 2bbl 307. If someone knows for sure, Zyggy and I would like to know... (right, zyggy? hope I'm not stealing your thread) __________________ We made Oklahoma a little after 3, Randy & his brother Bob & my old GMC...



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02-10-2004, 10:27 AM	#18
zyggy72 Can't kick the addiction! Join Date: Jan 2002 Location: Riverton, CT 06065 Posts: 402	Thats OK, I would like to know also.

02-10-2004, 12:15 PM	#20
70ChevyLongbed Howzit?!? Join Date: Jan 2003 Location: Maryville, TN Posts: 1,265	I have a 307 and have some additional info from some past threads. blazomatic posted: "I have a 307 in my 71 K5. I also have the series 10 truck owners manual for 71. In it they rate the 307 with: 135 net hp @ 4,000 and 235 net tq @ 2,400." In December I just finished making the following mods to mine: Edelbrock Performer Carb 500cfm (#1404, manual choke), Edelbrock Performer intake manifold (#2101), Engine Works Cam (#135280H) with 214/214 @ .050 duration and .443/.443 lift, new lifters, HEI Distributor (new, for stock 1975 350) new plug wires, R46SZ plugs gapped at .045, short water pump, new fan clutch to fit the new water pump, new water pump pulley (two groove), Alan Grove Alternator bracket (#213L - ALT.), new crank pulleys (three groove – and special spacers for the press-on balancer), new detent cable, new Edelbrock Elite "Signature" air cleaner and some chrome stuff. stepside454 posted: "I punched your info into my desktop dyno 2000 .I assumed a 112 LSA on the cam & came up with: 213HP @ 4500 RPMs 277 ft. lbs. @ 3500 RPMS Than I added small tube headers: 226 HP @ 5000 RPMs 297 ft. lbs @ 3500 rpms for a low compression 307 with small valve heads, not to bad, good heads like Vortecs would be a huge gain" I am very happy with the increased power and throttle response, but I'm not going to smoke my tires anytime soon. I started out wanting reliability for my daily driver, and ended up going a little overboard in a few places. It was a good experience. Jason __________________ Jason Hawaiian-J 70 Longbed, 307, Edelbrock Carb 1404, Edelbrock Intake 2101, Dual Roller Timing chain and gears, 214/214 cam, Comp Roller Rockers, dual Flowmasters. 1999 Chevy Tahoe 2004 Mini Cooper S 71 BMW 2002 - Sold

02-10-2004, 01:11 PM	#21
MrGoodpliers Registered User Join Date: May 2002 Location: Gainesville, Georgia Posts: 704	Answer for Firstgen The parting lines on a forged crank are wide and flat, while on a cast crank they will be thin and raised slightly. Also, if the crank is out of the block, if you tap a forged crank with a hammer it will ring like a bell-- cast crank, a dull thud. __________________ We made Oklahoma a little after 3, Randy & his brother Bob & my old GMC...

02-10-2004, 01:28 PM	#22
zyggy72 Can't kick the addiction! Join Date: Jan 2002 Location: Riverton, CT 06065 Posts: 402	Cool! That is good to know.

02-10-2004, 03:25 PM	#23
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	yeah I knew that about the casting lines, don't think I will be trying the hammer trick though __________________ 1968 C10 build in process TT LSA/6L90e/9"

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