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Necoa #: 10070
Location: 5(NC,SC)
Joined: Aug 29, 2007
Posts: 103
Year: 1981
Model: El Camino
Posted: Wed Jul 02, 2008 6:25 pm Post subject:
Not that this will turn a 305 into a tire fryer but you mentioned that you have a 650 carb. That's a bit too much carb for a 305 no matter what cam/ heads you have.
Here's some idea's to toss around:
1) Though you didn't mention what kind of carb it is, make sure that the secondaries are not coming in too soon. The 305 was never known for stump pulling torque however a decent daily driver. If they are opening too soon, this will KILL whatever power your car would make coming out of the hole.
2) Consider replacing the carb with a smaller one? A 600cfm Edelbrock or Holley is still a bit large on a generally stock 305. Consider even the 500cfm Edelbrock. It'll provide crisper throttle response compared to a 650 and potentially improving low speed torque.
Also keep in mind that original torque converters are pretty tight and do not allow the engine to get anywhere near peak torque from a standing start. The downside to a higher stall speed is crappier city mileage as the car will always be "on the converter" around town. Not to mention the significant heat that is created from the slippage. aka potential tranny failure.
Just a few thing to ponder. I hope some of this might help.
I myself had a 2.41 geared 305 powered car in high school. Off the line it could match the acceleration of a Nissan P/U, though once I got to about 35mph, it would run door to door with Corvettes of that time (late 80's-early 90's). It created a nickname for me then, it was "roll stomper"...well there was "bondo bandit" too, but that conversation belongs in another section of this forum
Necoa #: 5673
Location: 2(CT,MA,ME,NH,RI,VT)
Joined: Jun 26, 2005
Posts: 850
Year: 1970
Model: El Camino
Posted: Fri Jul 04, 2008 6:31 am Post subject:
All the things discussed above are definitely performance factors (Timing, carb adjustment and size, engine displacement, cam choice, rear end ratio, tranny, etc) but none make a bigger difference to performance than the ring and pinion ratio and secondly the converter stall speed.
If you want reasonable MPG, stay with a smallish engine, stock converter and keep the R&P ratio between the 2.41:1 you have now and 3.08:1 . (I had a modified 327 in a 68 Camaro with a 2.73 open R&P and it was a pig off the line).
If you want performance, and fuel cost is less important, then I'd dump the 2.41 R&P for at least a 3.73 (posi preferred), a higher stall converter (say around 2200-2500 is still reasonably streetable) and consider using a later model tranny with a lower 1st gear and an overdrive.
There are all kinds of driveline combos, of course, but I think you'll get your biggest "bang" out of a R&P and converter stall speed upgrade (they're the two things I didn't do in my Camaro). The LAST thing I'd ever do is upgrade the engine and leave the stock drivetrain.
Be forewarned though, your mileage is going to plummet by about 40% or more. This could (will likely) be one of those "Pay me now" AND ALSO "Pay me later" decisions.
All the best.... _________________ 70 Elky (Non-SS) 454CID, TH700-R4
69 Chev C-10 Pickup (recently Upgraded to 454) w/TH400
29 Model A (Recently Sold).
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