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Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by JayG, May 31, 2000.
How can I get more power out of my 305 engine??
Rebuild it ? Add a Supercharger, or Turbocharger ?
Advance the timming, run some High Octane fuel, and a good shot of NOS ?
Blow it up.This will give you excuse too build a different motor.Just kidding.Couldn't help my self.
305's will respond to the same performance goodies that liven up a 350. Headers, intakes, cams, exhaust, etc. The same parts on a 350 will make more power than on a 305, but they will perk up a 305. Replacing the 305 with a bigger engine to begin with works fine also!
HarryH3 - '75 K5
Mine was getting sluggish and I just did a simple tune-up on it and that juiced it up!
Man. It depends on how much more power you need. Why don't you do a cat-back exhaust, K&N air filter, and an ignition upgrade. And save the rest of your money to build a 350 if thats not enough. You can get much more power with a 350.
Chevy good...Ford bad
what exactly consistes of a cat back exhuast...
well if you dont have to have your emissions checked you can pull the smog pump..
i know when i got mine the a/c needed recharged, i decided against it, so i pulled the a/c belt, and then pulled the smog belt while i was at it, its quite surprising how much power you take back and put to the wheels...
that was my first and only upgrade before my engine locked up...
i do believe someones signature on this site is "never rebuild a 305", and i completely agree, save your cash for a 350 or bigger...
new pipe, muffler, and on some systems, tips, that installs after the cat.
I've been researching this lately. I actually plan on rebuilding my old 305 and putting it in place of my 350. Then I'll rebuild my 350 and put it back in place of the 305. It's a good thing motor swaps only take 6 or 7 hours.
Anyway here's what I'd do and the order I'd do them. #5 has two parts because you can choose one or another.
1. Tune your carburetor. Get some DR rods for the secondaries.
2. Edelbrock 2101 intake. Good for ten horses or so unless you've got a crappy equalized dual plane intake then it's worth more.
3. Headers. Good for just about ten horses. Find 1.5" primaries if you can because otherwise you'll sacrifice some low end torque.
4. 2" open spacer under the carburetor. This slowly generates horsepower but it doesn't break the 5hp mark until 3500 rpm. If you've got room, stick it in there. It's only $20. Worst case scenario is that you'll lose some bottom end torque and you'll have a $20 piece of phenolic plastic that would go great on that 400SBC powered Camaro you've been dreaming about.
5a. Find some 58cc heads if you don't already have them (I've never heard of them being in a truck or blazer). Get them machined for 1.94 intake valves instead of stock 1.84. This should bring your compression ratio up above 8:1. If you can, find a set that you can mill some material off so you can get the compression up a little higher yet.
5b. Camshaft. It seems that 108° works the best. I don't know anything more than that--I'm still researching.
6. Rebuild. Stick some higher compression pistons in it. Port the heads.
After both #5s and a rebuild you're supposed to be able to squeak 250hp@5,000rpm with a properly tuned carburetor.
Most 305s had between 7.5:1 and 8.0:1 compression ratios. If you take that up to 9.5:1 you'll see around a 5% horsepower increase. You figure 2-3% per point of compression increase.
All truck 305's are 9.2:1 stock AFAIK, and the HO car ones (SS) were as well.
First give your motor a compression test, if they are with in ten percent of each other go with the mods. Best bag for the dollar, Dynomax ceramic coated 1.5 3/4 length headers WLK-86118 219.95 (I love them on my truck), Custom 2 1/4 y pipe that dumps into a single three inch exhaust with a 70 series muffler, summit cam&lifters SUM-K1102 $71.95, Edelbrock EPS manifold EDL-2701 129.95, Edelbrock EPS carburetor EDL-1406 244.95. 86' carbs are all right as long as they're fully functional, do you know if both soleniods work. Edelbrock is just two easy to work with. I run a Q-jet built by Jet Performance hopping for better MPG and it runs good and same MPG but I had better throttle response with my EDL. Then again the Q-jet is easier to start.
According to DD 2000, my 260 HP 305 would make more torque as a 350, but no additional power without a bigger cam and better cylinder heads.
loudnowlouder - what do you mean by "pulled the a/c belt"? i've got a bum a/c compressor, can i just pull it out and add some power?
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