307 chevy

X2 on what double vision said

the 268 cam would be great with the smaller displacement, remember that the smaller the displacement, the more a cam will affect it, more cubes tend to eat up more cam, the 270 would still be nice but i wouldn't want to run a 280 in a 307, that's like running a 302 duration in a 350, it works but its a little high for the everyday cruiser

about the 4.56 rears, what size tires are you going to run, as this is very high on the street with a 3spd here are some RPM caculations @60mph

29" tire with 4.56=3170rpm @ 60 mph

29" tire with 4.10=2850rpm @ 60 mph

29" tire with 3.73=2593rpm @ 60 mph

i wouldn't want to run anything above 26-2700 rpm on the highway, i would look more at the 3.73's unless it is going to be used more at the track than driven at the street, and from your post it doesn't sound that way


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Vacuum will be Plenty. The cam I pointed out only has 218 duration @.050,, a rather mild cam. For small cubic inches or for those that don`t want to get crazy it`s the ideal cam, it has a lopey idle, but it still has plenty of low end torque, but if the truck has 4.56 gears low end won`t be a problem anyways.
Make sure you have a X pipe installed in the exhaust system also.

well thank you for your help on that cam, oh and for the rear gears maybe i wont go with the 4:56 maybe the 4:11 or the 3:73,

but keep in mind its just a weekend hot rod but she might want to drive it to work sometimes that means a few highway miles so i should just go with the 3:73 but i heard that some had that gearing from the factory? is that true,

plus its going to be lowered 3" front, 5" back so will i have room for the x pipes cause i found this muffler that has 2 inlets then crosses pipes inside the muffler like a x pipe the has 2 outlets. the pipes will turnout infront of the rear tires.

I would also use the 3.73 gear, it`s more highway friendley. Some of the trucks in those years did come with 3.73`s, you maybe able to get a book on that model and look up the axle code and find the ratio. Or you can pop the rear diff cover, rotate the ring gear until you find 2 numbers stamped side by side such as 41 11. Divide them and you have your ratio. The muffler your referring to I`ve looked into before and it seems like a good idea, however, I`m not sure how your mother feels about loud exhausts, that`s why I recommended turbo mufflers, they are quieter but have a real deep tone. Even if you lower it yes you still should have room for the X pipe. The X design muffler will be fairly loud but yeah they sound mean.

well she wants a mean sounding hot rod but i dont think she wants it as loud as me.

I don`t know what kind of internet connection you have, but if you have DSL or the like, you can go to YouTube and down load many video links of different mufflers, there are several on there that are on the Flo X muffler.
You can also go to the manufactuers web site and down load sound clips of different mufflers.

to find out the rear gears you can also (this is the jack leg way, but it works) put the car in neutral jack up the rear end, put a mark or peice of elc trap on the driveshaft and spin the tire, this is also a way to find out if it is posi, spin the tire 1 full rotation watching how many times the driveshaft turns, if it turns about 3 3/4 times then you should have 3.73's

Hot street truck low budget 307 =
flat top pistons
Small combustion chamber high compression cylinder heads Home porting is a big ++
eg #416 305 heads with bigger 1.94x 1.6" valves
wg #601 305 heads " " " "
eg 305 (081) or 350(083_ tpi heads
eg 64cc camel backs
eg 906-062 OEM vortecs.
reguardless of which head you use you want a finished chamber volume around 56cc (milling)
thin .015" head gasket
Summit #174001 valvesprings, locks,retainers,seals set. (install at 1.70")

dual plane hi rise manifold 750 carb
long tube 1.5" headers 2.5" dual exhaust.

Isky #201278 cam installed "degreeed in" advanced on 100-102 in C/L

minimum 4.56:1 gears. It's a little CID motor, don't skimp on the gear.
manual trans or 3500-4000 stall for auto.

You'll get the desired effect you are looking for.

adapted OEM Throttle idle speed (anti desieling) solenoid for the A/C
Possible electric auxillary vacuum pump +vacuum resevior for P/B's

optional 125HP "powershot" nitrous.
Be ware of extreme grin on face when you punch it.

most 307 with 3 speed were 3.73 ratio axle standard

90% chance that its 3.73, unless the sticker on the glovebox says something different

auto trans would be 3.07 with a v-8 in this year.

if you get me the stamping code off the pass side axle tube housing i can look it up real quick





TDA, TDH, TPF, and TPM are 3.73 in 1970, if its the original axle anyways.

good luck!

well if it is a 3.73 then i will just do a rear end over haul but for the motor im thinking of going with world s/r torquer 305 heads from world. or gm perfromance heads but are the gm heads good cause they are way cheaper.

and as for the intake im going to rum a edelbrock rpm air gap.
holley 750dp
im still looking for the right cam but i have listened to all the cam help

Thanks, you should have told me I was wasting my breath.

If you plan to use 4:56 gears, make sure you get very large dia. tires to affectively drop the overall gear ratio two around 3:70 to 3:90. It will make the truck sit high and look cool.

If you want to use a very tall tire , use a even higher gear ratio.

This little CID motor with the cam I outlined, needs rpm.
(gear ratio). If you under gear it it will be a slug to drive.
The engines torque curve is shifted up significantly, requiring a healthy rear gear ratio.
A cammed up motor (especially a small ci motor) wants to run in a higher rpm range.

For this engine in this vehicle you want a gear+rear tire combo that results in a 60MPH cruise rpm of 3200 to 3600rpm.
A high perf engine wants to rev. If you build it as described it will cruise quite nicely at 60mph at around 3200-3600rpm and be lots of fun to drive.

RPM@60 = 60 x336 / tire diameter x gear ratio

4.56's and a 26" to 28" tall tires is just right. If you select a taller tire, up the gear ratio accordingly.
(eg: 32" tall tire, use a 5.13:1 gear)

If you want good results using the cool sounding Isky 278 Mega cam in this motor/truck, don't wimp out on the compression ratio or rear gear ratio.
Its all in the overall combo.

I mean like new bearings and seals kinda over haul im not going to switch gears.