performance of a 307 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1971chevrolet · 06-23-2002, 02:30 PM

i'm getting a '69 lwb with a 307 in it. it has headers and a edelbrock carb. what all can i do to it to get more power out of it? have any of you'll ever bored out a 307 to a 320 or anything like that? can you put a 327 crank in it? any help would be appreciated. Thanks alot

hanssolo · 06-23-2002, 02:47 PM

For that hassle & money, get a 350. A 327 crank does'nt have the stroke to put out torque till higher revs. But a 307 is good for fuel economy. I know! Put a 144 blower on it! Superchargers produce mondo torque.

Super Chevy · 06-23-2002, 05:43 PM

actually, a 307 is a 283 with a 327 crank allready,so putting in a 327 crank ,you will still have a 307 ,if i were you ,mabe just get a bigger motor or a nice cam and heads for this one,but the 307 is no powerhouse by far.....

SC

Longhorn Man · 06-23-2002, 05:45 PM

305 heads are a good set for this mini-mouse. It is an ok moter, but no power house.
very durable though.

*Fast68Chevy* · 06-23-2002, 06:45 PM

yeah the 305 heads would jump your compression up up and away, i have a set of clean good running '82 305 heads i could sell for cheap but have the 7 bolt camaro firebird exh manifold pattern.. so.,...

i know ppl bore out the 283 blocks to .080, cant see why not a 307 either.. i dunno what size engine that would be then after that,. would unshroud the valves though and breathe better

Longhorn Man · 06-23-2002, 08:43 PM

The 7 bolt exhaust is no problem, you just ignore the 7th hole.
Another advantage to the 305 heads is the hardened exhaust valve seals...unleaded friendly.

*Fast68Chevy* · 06-23-2002, 11:48 PM

the rear two 6 bolt manifolds bolts wont bolt on 7 bolt heads, ive done been through this three times at least, in fact just friday we ran into this problem again on a firebird engine we put in a 79 shortbed, the truck manifolds wont bolt on in the rear, and also i have same heads on the engine in the 71 so i cannot use ram horns either, the pattern is wider just enough that you cant get the rear two in, im talking bout the 5th and 6th holes, not the 7th one, the 80's firebird,camaro, LG4 and L69 caprice heads with the two stud exh flanges

Longhorn Man · 06-23-2002, 11:58 PM

Hmmmm, the old Longhorn had later model heads and hod the ram horn manifolds on it....
I can't remember the details on that though...been over 2 years ago.

mikep · 06-24-2002, 12:45 AM

307's wont bore to .080" reliably like 283's could sometimes. Thinner walled castings came on the 3 7/8" blocks after 68. .060" is pushing it with those. You could always just pick up a 4 inch bore 2 bolt block for $50 or less and build yourself a 327 since your'e going to be needing new pistons and a bore job anyway.

chaptr2 · 06-24-2002, 11:33 AM

IMO I would do some cheap upgrades to it. It won't be a powerhouse, but still would be fun to drive. If it is like my old 307 then it would turn 6000 rpms, just because it was loose and I didn't' care.

I would look into a mild cam, you could even go with a wild solid lifter cam. Take a look at the ignition, maybe upgrade that to HEI or a pertronixs kit. If it has headers on it, then you can make your own duel exhaust for it. Maybe get some flowmasters or cherry bombs a welder or just clamp together exhaust. If you use 15 to 20 inches of 2 1/2in exhaust pipe, some flowmaster or cherry bombs and some turn down, you have a good sounding truck. If it has an Edelbrock carb, most likely it has a 4bbl intake on it. If it is the cast iron one, then upgrade to an aluminum intake (easily bought for cheap used).

Does anyone remember what it is supposed to be like hot rodding? Trying to do things on a budget. IF that 307 is still in good shape I would upgrade a few things on it before I would go get a 350.

A friends dad put together (what he called the dumb $hit 305). He put a aluminum intake with a large holley carb (not sure what size), a solid lifter cam, duel 3 in exhaust with turminator mufflers, 456 posi, a vega torque converter, and a nice th350 tranny. Now this was all in a 68 or so Chevelle wagon. It would turn 7000 rpms and pull low 13, high 12 second quarter miles (if I remember right). The engine would only turn 7000 rpms because he still had points in it.

I say go for it!!

Longhorn Man · 06-24-2002, 05:17 PM

I'll agree with external bolt ons...they will all swap onto a 350 or 400. But I would not dig into it, not if I was looking for power.
Learn on the little engine, then have fun with the bigger one some time down the road.

**MikeB** · 06-24-2002, 06:38 PM

If the ignition is stock, add an MSD 6A or Blaster ignition system and Blaster coil to the points distributor. Also, make sure your advance is working properly and replace the plug wires with some spiral wound wires from MSD or Taylor. Don't forget to gap your plugs at .050" because the hotter spark can now jump a bigger gap. The 6A will work with an HEI distributor, if you ever want to add one. The Blaster ignition will not. Don't waste your money on "high voltage" coils. High current is key, not high voltage!

06-23-2002, 02:30 PM	#1
1971chevrolet Registered User Join Date: Apr 2002 Location: Texas Posts: 12	performance of a 307 i'm getting a '69 lwb with a 307 in it. it has headers and a edelbrock carb. what all can i do to it to get more power out of it? have any of you'll ever bored out a 307 to a 320 or anything like that? can you put a 327 crank in it? any help would be appreciated. Thanks alot

06-23-2002, 02:47 PM	#2
hanssolo Registered User Join Date: Sep 2001 Location: central Ill. USA Posts: 447	For that hassle & money, get a 350. A 327 crank does'nt have the stroke to put out torque till higher revs. But a 307 is good for fuel economy. I know! Put a 144 blower on it! Superchargers produce mondo torque. __________________ 69 C10 longbed: 357c.i. /TH400/3.73s/AC/ beige primer/saving $ for paint ______________________________

06-23-2002, 11:48 PM	#7
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	the rear two 6 bolt manifolds bolts wont bolt on 7 bolt heads, ive done been through this three times at least, in fact just friday we ran into this problem again on a firebird engine we put in a 79 shortbed, the truck manifolds wont bolt on in the rear, and also i have same heads on the engine in the 71 so i cannot use ram horns either, the pattern is wider just enough that you cant get the rear two in, im talking bout the 5th and 6th holes, not the 7th one, the 80's firebird,camaro, LG4 and L69 caprice heads with the two stud exh flanges Last edited by Fast68Chevy; 06-23-2002 at 11:50 PM.

06-24-2002, 12:45 AM	#9
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	307's wont bore to .080" reliably like 283's could sometimes. Thinner walled castings came on the 3 7/8" blocks after 68. .060" is pushing it with those. You could always just pick up a 4 inch bore 2 bolt block for $50 or less and build yourself a 327 since your'e going to be needing new pistons and a bore job anyway. __________________ No truck :-(

06-24-2002, 11:33 AM	#10
chaptr2 Registered User Join Date: Mar 2000 Location: Olalla, WA Posts: 705	IMO I would do some cheap upgrades to it. It won't be a powerhouse, but still would be fun to drive. If it is like my old 307 then it would turn 6000 rpms, just because it was loose and I didn't' care. I would look into a mild cam, you could even go with a wild solid lifter cam. Take a look at the ignition, maybe upgrade that to HEI or a pertronixs kit. If it has headers on it, then you can make your own duel exhaust for it. Maybe get some flowmasters or cherry bombs a welder or just clamp together exhaust. If you use 15 to 20 inches of 2 1/2in exhaust pipe, some flowmaster or cherry bombs and some turn down, you have a good sounding truck. If it has an Edelbrock carb, most likely it has a 4bbl intake on it. If it is the cast iron one, then upgrade to an aluminum intake (easily bought for cheap used). Does anyone remember what it is supposed to be like hot rodding? Trying to do things on a budget. IF that 307 is still in good shape I would upgrade a few things on it before I would go get a 350. A friends dad put together (what he called the dumb $hit 305). He put a aluminum intake with a large holley carb (not sure what size), a solid lifter cam, duel 3 in exhaust with turminator mufflers, 456 posi, a vega torque converter, and a nice th350 tranny. Now this was all in a 68 or so Chevelle wagon. It would turn 7000 rpms and pull low 13, high 12 second quarter miles (if I remember right). The engine would only turn 7000 rpms because he still had points in it. I say go for it!! __________________ This is only my opinion and it is subject to change. 70 GMC Short box stepside Blown 388 Stroker 72 K/5 Blazer 350/SM465/205

06-23-2002, 05:43 PM	#3
Super Chevy Registered User Join Date: Feb 2001 Location: Ohio Posts: 1,025	actually, a 307 is a 283 with a 327 crank allready,so putting in a 327 crank ,you will still have a 307 ,if i were you ,mabe just get a bigger motor or a nice cam and heads for this one,but the 307 is no powerhouse by far..... SC

06-23-2002, 05:45 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	305 heads are a good set for this mini-mouse. It is an ok moter, but no power house. very durable though.

06-23-2002, 06:45 PM	#5
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	yeah the 305 heads would jump your compression up up and away, i have a set of clean good running '82 305 heads i could sell for cheap but have the 7 bolt camaro firebird exh manifold pattern.. so.,... i know ppl bore out the 283 blocks to .080, cant see why not a 307 either.. i dunno what size engine that would be then after that,. would unshroud the valves though and breathe better

06-23-2002, 08:43 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	The 7 bolt exhaust is no problem, you just ignore the 7th hole. Another advantage to the 305 heads is the hardened exhaust valve seals...unleaded friendly.

06-23-2002, 11:58 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Hmmmm, the old Longhorn had later model heads and hod the ram horn manifolds on it.... I can't remember the details on that though...been over 2 years ago.

06-24-2002, 05:17 PM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I'll agree with external bolt ons...they will all swap onto a 350 or 400. But I would not dig into it, not if I was looking for power. Learn on the little engine, then have fun with the bigger one some time down the road.

06-24-2002, 06:38 PM	#12
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,435	If the ignition is stock, add an MSD 6A or Blaster ignition system and Blaster coil to the points distributor. Also, make sure your advance is working properly and replace the plug wires with some spiral wound wires from MSD or Taylor. Don't forget to gap your plugs at .050" because the hotter spark can now jump a bigger gap. The 6A will work with an HEI distributor, if you ever want to add one. The Blaster ignition will not. Don't waste your money on "high voltage" coils. High current is key, not high voltage! __________________ Mike 1969 C10 LWB -- owned for 34 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 23 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!



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