Does anyone have experience with Chevy 305s in first gen birds? I want to increase the horsepower on mine with a college student's budget. I have a factory 165 hp (aluminum intake) engine, and I read that these make about 220 without smog stuff and with headers, but otherwise stock. It is completely stock and runs clean. It came out of an 85 El Camino.
Here is what I have laying around, but any recommendations would be appreciated: Holley 670cfm Street Avenger Edelbrock performer intake Weiand X-cellerator intake. 1-5/8 to 3 inch Hooker headers
It's a 4-speed with an open-rear and no exhaust system. Most of the above parts were stripped off the cracked 383 that originally came with the car.
The biggest problem is the small bore. That really limits the valve size and head selection. That being said, it is a SBC and there are ways to make even a 305 run well.
I was hoping to avoid any machine work, since this motor is just to keep it moving while I find/build a better engine, like a 350 or 383. How much would something like that cost? I have the old 882 heads, but the block and rotating assembly already went to the scrapper.
Put the Holley carb, edelbrock intake, and headers from the 383 on it. Intall a 2.5" dual exhaust with x-pipe, dual mufflers, and full tailpipes on it (Magnaflow, Pypes, and RamAirRestorations make very good systems). Avoid Flowmaster, many like the sound (although others complain of actually being too loud, and droning at cruise) - their mufflers make lots of noise, but they are still restrictive. There are much better choices than Flowmasters out there.
Tune, tune tune! Buy every book on Holley carburetors that you can find. Understand every circuit of the carburetor and how to calibrate it. Learn the in-and-outs of ignition timing - there's some good info. on here actually if you do a search - then recurve the distributor.
That's about all you should bother with until you can afford a better engine.
The Performer intake is ideal for a "performance" 305. Not too big... The Wieand is among the better doorstops on the market... It's a genuine imitation imitation Torker (Holley Street Dominator is the "original" imitation Torker).
The 670 carb may be a tad on the "big" side for the little small block. An Edelbrock 550 might be a better choice. As a "Street Avenger", does that mean it has vacuum secondary? If so, it will be okay. If you could find one of those old "little" Q-Jets from the '67 326 HO, now THAT would be the ticket.
350 heads on a 305 will do exactly what TOHcan says, reduce compression to a woeful point. Also note that no 305 (including the "HO) came with intake valves larger than 1.84". The smaller bore is the reason. Just like the Pontiac, valve "shrouding" is a real issue here.
A cam would really be called for to make all the external mods "work". I like the Comp XE grinds, but a conservative approach (cams, not politics) is better for such an engine. The XE250H or 255DEH ("Dual Energy") would be my choice.
Once you've gotten this thing going the way you want it, and start saving for the new engine, I'll donate a 400 block to make it a Pontiac! It takes a WHOLE LOT of 383 Chevy to equal 400 Pontiac... (:-
As I dont know much about engines, carbs but have gotten good advice from several people....I think "practicality" is important... I learned on my Replica Austin Healey I had that the previous owner put too much of a carb on the 302 in it...we changed it , downsized the carb from a Holley 650 (forget the size we used), got much better performance, was faster , plus got 19 mpg instead of the 12 previous....it had so much carb that it didnt use all of it ,but leaked unused gas into the oil, thinning it out and wearing down the bearings! and as I got my Firebird with a 400, there was an old Holley 650 on it that was in bad shape , only 2 barrels worked...my buddy helping me told me to get another carb...I asked "which one is best for this car"? his reply was "the one you or someone you know is familiar with and likes to work on" so I asked "which one do you prefer to work on"? He said Holley , so that was my choice...
The Holley has vacuum secondaries, so I was told that it would only draw what it needs. I heard great things about Q-jets, but the Holley is in hand, so that should do for now. Thanks for all this information and encouragement. This should be a interesting project, and a bigger engine will definitely be a priority in the future. Out of curiosity, do most of you guys still use points? I have the computer HEI from the 305, but no computer, so no advance. Right now I am using the points from the 383. With an engine this small with low rpm, would there be any benefit in using the HEI? Thanks again for all this great info.
Save your money and keep it running as is. Put that money saved for a poncho mill, or a bigger displacement SBC if so desired. IMO you'll be happier with the Pontiac power. I use to be a bow tie guy 'till I got behind the wheel of a GTO.
You can use any Chevy V8 distributor, so a pre-computer unit will "drop in". Performance will improve significantly, just getting the advance "curve" to work properly. We use the Petronix conversion "kit" for points-type distributors today. HEI is very good up to 6,000 RPM. Beyond that, it has its "problems", moreso in the Chevy than the Pontiac due to the "long" shaft ("deflection").
