Wanting a streetable 425+ crank h.p. from my 305...tell me how.
04-04-2009, 09:04 PM
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Wanting a streetable 425+ crank h.p. from my 305...tell me how. Just recently picked up a '85 S10 with a low miles stock 305 crate motor and a th350. I've had 7 people in the past week ask me why not a 350? I planned on keeping the motor simple until this repetitive question started getting under my skin. Now I'm feeling like I need to compensate and I don't have the money for a Viper or a Porsche.
Is 425 crank realistic with a 305 while still keeping it streetable? Tell me how to do it. This is my first non-ls1 motor so I'm plain dumb on a good ole sbc.
I'd like to stay stock cubes, under 6500 rpms, carbed, naturally aspirated and to feed it off the pump. No race gas, boosteses, spray or fuel injection.
Is 425 crank realistic with a 305 while still keeping it streetable? Tell me how to do it. This is my first non-ls1 motor so I'm plain dumb on a good ole sbc.
I'd like to stay stock cubes, under 6500 rpms, carbed, naturally aspirated and to feed it off the pump. No race gas, boosteses, spray or fuel injection.
04-04-2009, 09:23 PM
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You are going to have to go with a turbo or s/c with a nice big cam and n2o. I dont know of a way to make a 305 stay a 305 and be able to pull 425 out of it???
04-05-2009, 12:10 AM
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305 vortec heads, slugs that will make over 10 to 1 compression and a roller cam with about 224/230 duration @.050 with 500 lift on a 110 LSA. Decent headers and a performer RPM intake. Good for a little over 400 HP, but the extra money on GOOD pistons cost more than a set for a 350.
04-05-2009, 03:15 AM
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Scat makes a good rotating assembly that strokes the 305 to a 339 with a .060" over bore size. It consists of a cast steel lightweight crank (51 lbs.), 4340 forged I-beam rod, Keith Black Forged piston's, rings, and bearings for about $1,000. You will be looking at around $500 in machine work. I would look for a pair of ZZ4/L98 aluminum heads and have them ported. I would use a 2"/1.55" valve for or out of a LS1 for better flow and reduced valve weight. I would then use a dual valve spring combo from Patriot Performance for a hyd roller cam. I agree with Zone on the cam size, here is a link for the cam & lifter kit from Comp http://store.summitracing.com/partde...8&autoview=sku . I would use a set of 1.6 ratio full body roller rockers as well. I like the RPM Air-gap intake as well for this kind of build and would use a QuickFuel carb http://store.summitracing.com/partde...5&autoview=sku .
04-05-2009, 07:49 AM
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04-06-2009, 11:55 AM
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While a 305 can make good power, it is handicapped due to the small bore which can't fit 350 (or 400) heads. You would have a power peak of at least 6,000 to squeeze 425hp out of a 305.
I would suggest a 350 with heads and a cam, which can easily get you to 425hp at a lower peak rpm with more TQ.
I would suggest a 350 with heads and a cam, which can easily get you to 425hp at a lower peak rpm with more TQ.
04-06-2009, 01:48 PM
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Scat makes a good rotating assembly that strokes the 305 to a 339 with a .060" over bore size. It consists of a cast steel lightweight crank (51 lbs.), 4340 forged I-beam rod, Keith Black Forged piston's, rings, and bearings for about $1,000. You will be looking at around $500 in machine work. I would look for a pair of ZZ4/L98 aluminum heads and have them ported. I would use a 2"/1.55" valve for or out of a LS1 for better flow and reduced valve weight. I would then use a dual valve spring combo from Patriot Performance for a hyd roller cam. I agree with Zone on the cam size, here is a link for the cam & lifter kit from Comp http://store.summitracing.com/partde...8&autoview=sku . I would use a set of 1.6 ratio full body roller rockers as well. I like the RPM Air-gap intake as well for this kind of build and would use a QuickFuel carb http://store.summitracing.com/partde...5&autoview=sku .
04-06-2009, 11:03 PM
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Carb
Holley Double pumper 650 CFM
Intake mani
RPM Air-Gap (1500 - 6500 RPM)
Cam
Performer RPM # 7102
ENGINE: CHEVY 283-400 V8
RPM RANGE: 1500-6500
Duration at 0.006" Lift: Intake: 308° Exhaust: 318°
Duration at 0.050" Lift: Intake: 234° Exhaust: 244°
Lift at Cam: Intake: 0.325" Exhaust: 0.340"
Lift at Valve: Intake: 0.488" Exhaust: 0.510"
Heads
VICTOR JR. 23° HEADS BARE OR WITH VALVES ONLY
64cc 215cc 2.08"/1.60" #77569* #77579*
I have near the same in my 350 witch is now a 385 and it made about 415. look in to "Power packages" they normally show dynos.
Holley Double pumper 650 CFM
Intake mani
RPM Air-Gap (1500 - 6500 RPM)
Cam
Performer RPM # 7102
ENGINE: CHEVY 283-400 V8
RPM RANGE: 1500-6500
Duration at 0.006" Lift: Intake: 308° Exhaust: 318°
Duration at 0.050" Lift: Intake: 234° Exhaust: 244°
Lift at Cam: Intake: 0.325" Exhaust: 0.340"
Lift at Valve: Intake: 0.488" Exhaust: 0.510"
Heads
VICTOR JR. 23° HEADS BARE OR WITH VALVES ONLY
64cc 215cc 2.08"/1.60" #77569* #77579*
I have near the same in my 350 witch is now a 385 and it made about 415. look in to "Power packages" they normally show dynos.
04-07-2009, 03:30 AM
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i already posted in the other 305 thread how to make one run on a tight budget...here it is, i don't know what hp numbers it'll make, i just know et's...
agreed that "why not a 350" question is annoying!!
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!!
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!!
agreed that "why not a 350" question is annoying!!
Last edited by dedon500rt; 04-07-2009 at 03:38 AM.
04-13-2009, 12:22 AM
#15
04-13-2009, 10:00 AM
#16
there's a guy on TGO that had some bowl blended L98 aluminum heads, and a decent sized solid flat tappet in a .030 over 305 that ran mid 12s and he street drove it all the time. may want to check that out
04-14-2009, 10:21 AM
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Yeah Matt's car ran hard... He takes the time to make his car work though.
05-12-2009, 03:27 PM
#19
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High flow heads, cam that's pretty radical, Carb spacer and forge it...then blow it! That's my philosophy to make 425rwhp with a 305. Of course, if you're in the mood to just throw money around....I'll take some.
But seriously, I would recommend getting either a 383 or a even a forged 350 bored .030 over to make it a 355. That's what I'm doing.
But seriously, I would recommend getting either a 383 or a even a forged 350 bored .030 over to make it a 355. That's what I'm doing.
05-12-2009, 03:29 PM
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2 weeks ago we took a 305 out, and stuffed a 350 stroker in my friends 81 Cutlass..305's are good for boat anchors only. SO SORRY..do not waste your money and time. NOPE. 