Thread: Squeezing Power from a SBC

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I was just wondering if anyone has any tuning tricks/tips for a stock 305 sbc with a rochester qjet (the late 70s high flow 700-750cfm model) and a TH350.

I'm just trying to find little foolproof ways to open a few extra horses from this stock motor till i can afford some good aftermarket parts.

The upgrades are
1. Open element air filter
2. Soon to be running HEI (went BACK to points from HEI)
3. 700-750cfm Qjet (instead of the 83' ecm controlled carb)
4. Dynomax Blackjack full length headers.

Thanks
Dallas

Just a suggestion which is really a question to other Forum members: What would adding 1.6 ratio rockers do to a stock 305? I note both Speedway and Summit have 1.6 roller-tip rockers for about $90. The lesser friction of the roller tips might free up a few HP and the 1.6 ratio ought to provide a little more cam duration as well as lift.

Don Shillady
Retired Scientist/teen rodder

If you don't have a carb yet, 600 CFM is enough up to 6800 RPM.
I don't think that motor can rev anywhere near that limit.

Bert

I've got a 700cfm Rochester Quadrajet. Dunno if you were aware but the later 70s model BIG BLOCK q-jets flowed between 700-750cfm. I grabbed mine from a big block caddy, a late 70s non computer controlled carb. It works pretty nicely. Without any tuning (besides adjusting the idle) the thing runs very nicely, no hesitation, no sputtering, no noticable "flat" spots. It pulls good and hard, and will probably do better with HEI upgrade. Anyone want to buy a brand new OER distributor w/ blue streak cap and rotor and duralast wires? lol.

I am also planning on gettting a set of heads from the junkyard and getting them magnafluxed, checked for cracks/warpage, shaved, ported and polished and then i'll rebuild THEM and install them along with a new intake manifold and a nice black crinkle dressup kit lol.

So i'm wondering,
do any certain year/model heads FLOW better than other years?
I know vortecs and alum heads are the big rage, but I want to keep cast iron on them. I know fuelies are good, but i don't know what to look for to distinguish them from regular heads.

Any tips are VERY VERY GREATLY appreciated.

Dallas , from TN, now in Orlando, FL.
70 Nova - 83' 305, ??' TH350, Fulllength Headers, 750cfm Qjet.
68 Dart - 318 bottom end, 273 topend, Factory A/C & P/S.

I would be careful swapping heads from other SBC such as 350 or 400 because I believe the 305 bore is only 3.75" while the 350s are 4.00" and I believe the 400s are 4.125" diameter. This means that the valves from a 350 or 400 will hit the sides of the 305 cylinder wall! You need to look for a 305 HO heads or buy Edelbrock 305 heads.

Don Shillady
Tetired Scientist/teen rodder

good point. I'll look into some part interchanges and some valve sizes/clearances etc etc. I surely don't wanna get any problems from them lol.

Thanks for that, i didn't even think of it!

Dallas

set of headers a curve kit for dist good set of spark plug and wires dual plane aluminum intake and if you do not drive it in the cold plug the cross over in the intake good for 10 hp they say. and a good rv cam do some bowl work on the heads back cut the valves and a good 3 angle or more valve job. this is what i would do

WAITT!!!! Just to let you in on a secret (not really) but edelbrock is really expensive stuff...They are pretty good but there are better heads for the money...World Products makes a good head that I've run on a 305 before..the S/R heads.

Edelbrock makes a really good intake manifold for the money. For not very much money you can put more cam into it. Headers are always a must have. You can also regain some HP by stripping accessories...A/C is one. You will also notice a big difference in your launch and just all around cruising if you were to change your rear end gears...with a 305, mechanical advantage needs to be used to its max.

http://streetmachinesoftablerock.com...opic.php?t=435

Already got headers. Dynomax Blackjack full length. I drive the car in FL...so where is this crossover? lol.

Accessory wise, there are none, the ONLY thing driven (externally wise) by the crank is the alternator. No P/S, no A/C no AIR pump, only the alt. Good throttle response. hehe

I was thinking a 3way swirl valve job, some good porting and polishing, the carb i'm running is 700+cfm.

Edelbrock heads won't be on my car. lol. Either World or GM performance.

The edelbrock intake is coming at the same time as heads and the black crinkle dress up kit...with crane gold rockers, new SS valves and some machining.

Hmm...I blocked off the EGR too. and what about this distributor curve? What does this do? I got the typical vacuum advance, running 4degrees advance timing.


Dallas

yeah, gears are in the list too, probably 3.42s or so..4.11s are a bit low for my 3 600mile (round trip 100miles each way, 3x a month) drives a month lol. So 3.4x's should work decently.

It's a pretty stout 305. i'll give it that much.


How about exhaust? Currently my headers dump RIGHT into a set of Turbo Mufflers, and it ends there right under the tranny crossmember,

With open headers the topend is crazy but the low end is weak , with the mufflers it's looses some top end, but is compensated nicely with bottom end,...should i run my exhaust more?

Do 305s feed off backpressure or are they allergic to it? lol.

I'm thinking they feed off it...like a leech. if i want torque. heh

I was shocked at the difference an intakes makes. I switched a factory 4 barrel intake for a 2101 performer on a very mild small block. No other changes. It was a seat of the pants difference.

The carb was quadrajet and it still had exhaust manifolds.