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Small Block & Big Block Chevy Specific Mouse & Rat Motor Discussion & Conversions

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Old 04-03-2009, 05:43 PM   #1
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Default 305 sbc...

Anyone make any power with one of these? I know it's got a small bore and all, but a turbo or two can make up for a lot...
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Old 04-04-2009, 12:54 AM   #2
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Well, assuming the logic of 1.5 HP per cube, 400 HP is not impossible, but a 350 will make 450. Other than that, boat anchor.
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Old 04-04-2009, 04:19 AM   #3
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With a carefull parts selection you can get 475-480 HP NA engine with daily driver compatibility. However you can make more with a 350 block and the same money like Zone said.
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Old 04-04-2009, 04:22 AM   #4
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If you are going to bother with a rebuild, might as well go with a 350. They use the same accesories and belt routing, so its just a direct drop in replacement. A carbed to carbed motor would require no rewiring, a TBI to TBI swap might require a few wiring projects, but nothing major. Probably the easiest motor upgrade possible.
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Old 04-04-2009, 06:14 AM   #5
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if your "stuck" with a 305 don't be discouraged. Granted like the previous posters said the 350 has alot more opportunities but the 305 can be decent. However you said something about some boost, then of coarse your gonna want a stronger crank and rods and at that point i don't see it being worth it because you could do the same with the 350.

With stock internals, if you have a flat top motor, then your best bet would be to find some 87-92 vortech 305 truck heads with the 55cc combustion chamber. This way it'll make a hair over 11:1, do a little bowl and runner work and set them up with a good set of 130lbs seat pressure springs, go with a mild open plane intake (torker or similar), 600-750 cfm holley, and a pretty hot hydralic cam somewhere between .470-.510 lift. I had a similar combo in a 3rd gen firebird when i was in high school it had a th350/3500 stall and it ran 13.30's on the motor and a 125 shot dipped into the 11's (barely!)..Not saying you'd see that because mine had some great head work done to them.....But all in all, yes a 305 can make some ok power with the right parts. Good luck!!
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Old 04-05-2009, 08:01 PM   #6
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Well, assuming the logic of 1.5 HP per cube, 400 HP is not impossible, but a 350 will make 450. Other than that, boat anchor.
Where'd you get 1.5hp per ci?
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Old 04-06-2009, 01:36 AM   #7
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It is just a basic average for a motor running efficient for 93 octane. It is pretty acurate for the most part. But that is with the better parts in general, nothing mild and getting where old people dont like to DD anything running that lumpy and what not.
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Old 04-06-2009, 01:52 PM   #8
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It is just a basic average for a motor running efficient for 93 octane. It is pretty acurate for the most part. But that is with the better parts in general, nothing mild and getting where old people dont like to DD anything running that lumpy and what not.
That may be true for a NA motor, but not really for a turbo engine. Mod motor guys are making more than 2/ci on pump gas, and even more with a little methanol injection. I'd bet with a good turbo setup, these "boat anchors" would be pretty nasty. Plus the smaller bore may actually be an advantage...
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Old 04-06-2009, 02:43 PM   #9
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Duh...but then there is the fact that a 350 would make 120+ more HP than the 305, so ti is still a waste when it is cheaper to build a 350 no matter how you look at it.
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Old 04-06-2009, 02:55 PM   #10
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That may be true for a NA motor, but not really for a turbo engine. Mod motor guys are making more than 2/ci on pump gas, and even more with a little methanol injection. I'd bet with a good turbo setup, these "boat anchors" would be pretty nasty. Plus the smaller bore may actually be an advantage...
sounds like u got something in the fire there.
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Old 04-06-2009, 08:57 PM   #11
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Duh...but then there is the fact that a 350 would make 120+ more HP than the 305, so ti is still a waste when it is cheaper to build a 350 no matter how you look at it.
That's theory, not fact. It could make more power. The wild card is the bore size, which could upset the displacement difference. For a street car, I don't think there's enough of a difference to call either one a "waste."
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Old 04-06-2009, 08:58 PM   #12
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sounds like u got something in the fire there.
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We'll see. I'm looking for a new project, I just have to pull the trigger.
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Old 04-07-2009, 01:52 AM   #13
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That's theory, not fact. It could make more power. The wild card is the bore size, which could upset the displacement difference. For a street car, I don't think there's enough of a difference to call either one a "waste."
It is simply, bigger bore=unshrouded valves. Not theory, fact. You can get 1000 HP out of a 400 SBC with twin turbos, on pump gas. A 350 cannot do it, but a 350 can make 850 or so on 93 with twins, a 305 is about 750.

And yes, buying more expensive pistons for a 305 when a 350 is cheaper is a waste of money of max power is the concern.

There is a reason a 350 SBC is the most commonly used motor in the WORLD.
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Old 04-07-2009, 09:30 AM   #14
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It is simply, bigger bore=unshrouded valves. Not theory, fact. You can get 1000 HP out of a 400 SBC with twin turbos, on pump gas. A 350 cannot do it, but a 350 can make 850 or so on 93 with twins, a 305 is about 750.
That may be true for a naturally aspirated engine, but a turbo engine is a whole different ballgame. The smaller bore allows a higher knock threshold, so you can run more boost/compression for a given fuel, than a larger bore. You can see this same principle applied in NHRA Top Fuel as well as the Jeg's Engine Masters Challenge. In a turbo setup, boost is the name of the game. Not necessarily good ports/big valves.

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And yes, buying more expensive pistons for a 305 when a 350 is cheaper is a waste of money of max power is the concern.

There is a reason a 350 SBC is the most commonly used motor in the WORLD.
A comparable, quality, dish/reverse dome piston is going to be maybe $200 difference from shelf stock, but for the 305 it will be custom taylored for the application. The right ringpack, compression height, taper/breakover, will all be custom made for the set up. It's worth the extra change if max power is concerned. This is only if you stroke it, though. Staying with the stock stroke, pistons are no problem.
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Old 04-07-2009, 02:06 PM   #15
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Still not going to make the power of a 350, and the point in building a 350 for power is not reasonable to me either when you can build a 383.


Not to mention...the 305 will not make the torque of the bigger engines, TQ wins races.
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Old 04-07-2009, 02:44 PM   #16
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Not to mention...the 305 will not make the torque of the bigger engines, TQ wins races.
A turbo is a TQ multiplier, and is what KCS is intending to use from the sound of things. He can also make 1000 FWHP with a 327 useing pump gas, Inovative Turbo proved that point years ago on a twin turbo setup.
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Old 04-07-2009, 03:15 PM   #17
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Still not going to make the power of a 350, and the point in building a 350 for power is not reasonable to me either when you can build a 383.

Not to mention...the 305 will not make the torque of the bigger engines, TQ wins races.
Sure it will. You think that displacement is the ultimate factor in making power?

You should check out what the mod motor guys are doing with their little 281ci stuff. Even the 2V modulars put a lot of bigger engines to shame....
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Old 04-07-2009, 03:38 PM   #18
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I have a buddy has has one of those weiand blowers on his 305, it's a 1987 LG4 roller 305but that little bastard runs good. It's got the stock internals, worked heads, cam with that weiand roots blower and will put a new mustang GT to shame. It's in a third gen camaro. I don't know what numbers it puts down, my SS will eat it for lunch but for what it is the car will move. I'm sure a person could get some good power out of one, I'd be interested to see a turbo'd 400+ hp 305. Give it a shot!
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Old 04-07-2009, 04:24 PM   #19
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Sure it will. You think that displacement is the ultimate factor in making power?
No, but it is a major player, you dont see 496 BBC motors running with 540s and 565s, just like there is a reason no one uses a 305 for real competition.

You you can make power, bit anything will, there is a saying:

"You can take junk, and make it fast, but in the end all you have is fast junk."

No knocking you all the way, but for christ sake, why would you even want to argue that a 305 can make the power of a 350, bigger cubes, bigger valves...it all come into play. A smaller engine can make as much as a bigger engine, if it spins high enough, but you spin that bigger motor just as high with the proper matched components, you still have more power than the smaller engine. This is of course speaking of the same motor design.(ie:5.0/5.7/6.6:LS1/LS2/LS7:4.6/5.4) So, tell the guys on this site a fucking LS1 will make as much or more power than a LS7 and you will get flames to shit...maybe banned.
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Old 04-07-2009, 04:33 PM   #20
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Depends on what kinda budget your working with. If your pretty tight with money, put the right parts into it and you can have a fun setup. If you got money to burn, with the prices of 350 2 or 4 bolt main blocks, your better off. What do I know though, my post count and itrader isn't that high.
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Old 04-07-2009, 04:33 PM
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