You Can't get to 350, From 307........ You Don't have enough to bore that big........

The Reason it has timing Gears, Instead of a Chain is,
It's a Reverse Rotation engine......... Clock-wize.........

It Might be a Great Core,..... But Not for what You Want...............

 

Thanks Bondo,

Can I change the rotation by using timing chain and aftermarket camshaft?

What other things are different in reverse rotating engines?

By the way, is the cylinder wall thickness in a 307 different then a 350 block? How much bigger could I go with this engine?

Thanks,
Houman

 

It's the Crank that turns Backwards,..... Not the Cam......

The Cam would be a Marine cut,.. Standard Rotation..... Same with the Dist......

Crank,.. Pistons,+ Possibly the Rods are Reverse.......

Over bores would be .030,.. .060..... Same as usual.....

The 307 block is closer to the 283, than the 327..........

 

A 307 has a bore diameter of 3.875
A 350 has a bore diameter of 4.000

The 307 block cannot be safely bored .125 ( or a 1/8 of a inch :nono: )

You could put a 350 crank in the 307 block ....and be at 320 + inches
You could put a 400 crank in the 307 block for....352 inches.

JUST find another block.......cheaper in the long run...

.

 

Bondo,

How can I make sure that these are definitely reverse rotating engines? Is there a way to make sure?

The casting no.'s are same as crank castings on a car engine. How could that be? Just want to make sure first.

Thanks,
Houman SS '70

 

i have the chevrolet by the numbers book and it says nothing about reverse rotation,you had to have an LT1 for that.the book does say it was designed as a lo po motor from the get go.if you bore it out .060's you still won't have a 350.take the loss or resell it and get a 350.

 

keep the 307, keep boring her out tho, eventually she will reach 327 cubes.

 

Rocknrodder nz,

Can 305 pistons be used in this block? Just want to know, because 307 pistons are not available here, only 305 and 350.

Thanks for your assistance.

Houman

 

i have the chevrolet by the numbers book and it says nothing about reverse rotation,you had to have an LT1 for that.the book does say it was designed as a lo po motor from the get go.if you bore it out .060's you still won't have a 350.take the loss or resell it and get a 350.

Reverse rotation is very common in marine engines. Mercruiser which assembles all of GMPP engines makes a number of reverse rotation Chevy marine engines.

Also the 307 is not the dog everyone thinks it is, they can be made to talk.

Vince

 

keep the 307, keep boring her out tho, eventually she will reach 327 cubes.

no, dude, we just talked about that. 327 has a 3.25 and a 4.0 inch bore. 307 has the 3.25 crank, too, and just a 3.875 inch bore. You'd still have to bore it to 4 inches to make a 327, and like we just got done saying, you can't do that. I suppose you could stroke the 307, or something, but the small bore makes it pretty worthless in that respect, too (although considerably better than these WORTHLESS 305 stroker motors everybody and their brother seems to be on about lately).

K

 

O.K. but can anyone tell me how I can distinquish a revers rotation engine from the other?

Can it be changed by changin the firing order and the timing chain? Because the crankshaft is just the same a 327 with the same casting no. how could it be a reverse rotation?

Thanks for replies.

Houman

 

no im pretty sure 305 pistons have a different compresion height. Ill have a flick through the hot to hotrod small block chev book when im back at work becuase it includes all the details.

Killerformula: early 283s can be bored safely to 4' bore

 

Have the block sonic checked. You may be very surprised.

Lots of fun things are being done with 307 and 305 blocks cause nobody thinks they want them.

 

Have the block sonic checked. You may be very surprised.

Lots of fun things are being done with 307 and 305 blocks cause nobody thinks they want them.

What is that Rick WI? What do you think I can do with it?
My problem is that I'm looking for a 350 SBC and I can't find it here.

What could be done with this 307?

Thanks,
Houman

 

It seems that a few people have stroked the 307. Way back when I looked into doing this. I ended up not because the cost per. benifit of a 350 out weighed the 307. In your case it may be a much more reasonable option.

The 307 bore of 3.875 does hurt the stroker idea slightly but cube in an engine do help. The stroker idea is (this is with a 30 bore *3.905*) and a 350's crank (3.48) to make a 333 stroker. If you search this site you should find more info on it.

Ohio-Dan emailed me this a long time ago
1/2 the stroke + rod length + pin height = deck height

The factory spec on deck height is 9.025".

Chevy used 3 length rods. 5.7" being the most common. The 400 used a 5.565", and the Gen II L99 used a 5.94"

3.48 / 2 = 1.74"

1.74" + 5.565" + 1.675(Stock pin height on a 307) = 8.98"

That is .020" shorter than the factory spec of 9.00"(The factory specs the piston at .025" in the hole). A .020" cut off the deck should put you back to .025" in the hole and ensure a flat surface for head gasket sealing. The 1094 Fel-Pro is .015" thick rubber coated steel shim type gasket that needs a good true surface to seal. Combined with the .025", it would give you a .040" piston to head clearance that is considered ideal by most.

*thanks dan*


Some people I guess where good enough to sneak in a 400's (3.75) crank though I think this would be extrmemly hard with the rather tight sapce a 307 gives. This does however give you a 354

Chris

 

What could be done with this 307?

Thanks,
Houman

I had a 70 Nova with a box stock 307 2 bbl, 3 speed floor shift when I bought it with 17,000 miles on it. I never took the heads off and here is what I did to it.

Crower 280 hydraulic cam
Crower springs, and aluminum retainers
Edelbrock Trantula intake
Holley 600cfm #3310
Cyclone headers with turbo mufflers
Mallory dual point dist.
Muncie 4 speed M21
Bolt on traction bars

The Nova was a very solid 13.5 second quarter mile car. It had outstanding throttle response and I was constantly trying to convince people it was not a 350.

Vince

 

I had a 70 Nova with a box stock 307 2 bbl, 3 speed floor shift when I bought it with 17,000 miles on it. I never took the heads off and here is what I did to it.

Crower 280 hydraulic cam
Crower springs, and aluminum retainers
Edelbrock Trantula intake
Holley 600cfm #3310
Cyclone headers with turbo mufflers
Mallory dual point dist.
Muncie 4 speed M21
Bolt on traction bars

The Nova was a very solid 13.5 second quarter mile car. It had outstanding throttle response and I was constantly trying to convince people it was not a 350.

Vince

Yes, listen to this guy. 307 is a great smaller cube performance mill, second only in its size class to the 302. It can be made to run hard.

K

 

What could be done with this 307?

Thanks,
Houman

Just take it to a high performance machine shop and have them sonic test the cylinder walls. That will tell you how much you can overbore the block.

 

I have bored these blocks .125 thou. to a 4" standard with no problems. But unless you can bore it yourself you will probably find its cheaper to get a 350 block.

 

25 years ago it was fairly common to see 307 blocks bored to 4.00". Every now and then, one wouldn't make it because of porosity or core shift. To be sure on the amount of overbore your block can take, it will require a sonic check. 30+ years of water jacket corrosion may have the cylinder walls thinner than you think.

Try and find the article on Beck Racings 307 base entry in the Engine Masters Challenge. I believe they placed 3rd, 2 or 3 years ago. Sherman placed 1st that year. The motor used stock GM Fast Burn heads, and a 400 crank.


If the gear drive on your motor uses two gears( one on the crank, and one on the cam), the cam, oil pump, and distributor are all standard rotation pieces. The crank would be the only piece turning backward..... Before you run the crank in a standard rotation application, I would at least have it polished. The direction the crank is chucked during the polishing process will have an effect on bearing life. Dan

 

Dear Dan,

I want to thank you for the professional advises and suggestion you gave me. I'm still looking around for a 350 block, the 307 would be my last choice, because here we don't even have the pistons available?! And that's a problem.

Thanks a lot.
Houman

 

For getting performance I thought the 307 was better than the 305. I think the 305 has internal compromises so it could be a 70s economy motor. Everytime anyone talks about building up a 305 they are told to swap in a 350.