Small Block & Big Block Chevy Specific - 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.

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???

thats really hopeless, its an oversqare engine and will never make respectable power. its wayy cheaper just to build a 350 or 383, 305 is a pos.

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.

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/partdetail.asp?part=CCA%2DK08%2D423%2D8&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/partdetail.asp?autofilter=1&part=QFT%2DSS%2D650&N=700+4294925239+4294839063+4294919007+400990+115&autoview=sku .

I would not waste a dime on a 305. No pun intended

here is an article for ya.

http://www.popularhotrodding.com/enginemasters/articles/chevrolet/0667_phrs_305_chevy_engine_blocks/index.html

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.

thats really hopeless, its an oversqare engine and will never make respectable power. its wayy cheaper just to build a 350 or 383, 305 is a pos.

Most high power NA cars are oversquare, where the bore is larger than the stroke. 425bhp is not unreasonable to ask of a 305.

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/partdetail.asp?part=CCA%2DK08%2D423%2D8&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/partdetail.asp?autofilter=1&part=QFT%2DSS%2D650&N=700+4294925239+4294839063+4294919007+400990+115&autoview=sku .
That's almost exactly what I would do, except I would probably go with a different manifold, LS6 valves, beehive springs, and small diameter Ti retainer. I think he hardest part is getting a good piston for these things. The extra displacement helps too.

Decided to go with a high revving 350 based motor. Deciding how to do it now. Don't want a stroker and have a power goal in mind.

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.

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...

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!!


agreed that "why not a 350" question is annoying!!

Just go 350, it is so much more efficient, you can even tell people it is a 305.:secret2:

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!!


So "why not a 350" ?:punch:

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

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

Yeah Matt's car ran hard... He takes the time to make his car work though.

hey, if you're gonna do more with less it takes time

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. :)

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. :nod:

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.

WTF, since when would 350/400 heads not fit on a SBC? all heads from 283-400 will work on any small block.

when my stroker blew i wanted to drive my car over the summer, so i took a stock 305 we had laying around, threw on a set of dart heads, airgap intake, a .500 lift cam 228 duration iirc with a 600cfm carb and a nice set of headers. that motor was nothing compared to my 383, just was a dog, even with the parts we had in it. i would honestly recommend spending your money on a 350/400. i know you dont like to hear it, but theres a reason behind everyone saying that.

Put a 250 shot of juice on it till it dies, then walk away never looking back...

WTF, since when would 350/400 heads not fit on a SBC? all heads from 283-400 will work on any small block.

They will bolt on, yes. However, if the combined diameter of the intake and exhaust valve are larger than the actual bore, you might run into problems. Even if the valves aren't larger than the cylinder bore the airflow is going to be pretty nasty opening the valve up that close to the cylinder wall.

As touched on before, the biggest limiting factor will be the heads. Even well ported production castings will NOT do the job - not even the Vortec stuff. AFR used to sell a 305 specific 180cc casting that worked VERY well. AFR might be able to build a small chamber small valve 195cc Eliminator head that would make a 305 scream for sure!

In the end no matter what you do, the 305 will cost more to make less power than a similar 350. LMAO at anyone who does the 305 head and cam swap to be satisfied with low 13s - high 12s. My $1800 intake to pan 9:1 350 with just a basic rebuild did better.

Finally, anybody who still runs any of the Torker manifolds on any SBC is out of their mind :nono:

ive used heads with 2.02 intake valves and 1.6 exhaust on a 305 and never had a problem the best bet for a 305 is to use the stock heads because the combustion chambers range from 58cc's-64cc's take them to a machine shop and have them machined for bigger valves and ported i read a article once about a 305 it was called hate my 305 or something they took a low output late 70's 305 with dished pistons left bottom end stock put a set of vortech heads that were around 350 dollars i think i checked out the price once a long time ago and a a cam cant remember what brand or any specs and put a different intake and a demon carb i think and long tubes and produced slightly over 400 hp the article said if it wouldve been a later model 305 H.O with flat tops and a roller motor the #'s wouldve been around 425-450 range all motor which is pretty good for that motor

found the article heres the specs on the heads they used
intake runner volume 180cc
combustion chamber volume 64cc the had the heads milled 0.030 so 60cc heads
intake valve 2.02
exhaust valve 1.60
guide I.D 11/32
guide O.D .530"/.531"
intake port width 1.19"
intake port height 2.00"
exhaust port width 1.35"
exhaust port height 1.35"
the heads came from enginequest
the cam was a COMP XE268H flat-tappet hydraulic 224/230-degrees duration @ 0.050-inch, and 0.477/0.480-inch lift, on a 110 degree lobe separation
and they used comp cams 1.6 steel roller rockers and comp cams beehive style springs