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Old 04-13-2011, 02:13 PM
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A "TRUE"305

I have a 76 305 that i want to make a muscle motor with.I hear people talk about there bad 305 stroked to a 331.
To me its not a 305 anymore. I seen one true 305 muscle motor at a track in northern IA.the bottom half was completely
Stock including pistons,but the upper half was set up real nice & had the right gear/tire combo.It was in a 83 cutlass that he
Drove to & from the track.I wanted to get more info from the guy,but didnt get a chance to,but he was turning times of 13.50s.
The thumpstick was huge or sounded like it anyway.I remember looking in at the tach.& it was pulsing between 1000&1200.that's,
How i want to build my 305.Any clues to a formula like that would be awsome!
Thanks!
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Old 04-13-2011, 02:34 PM
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While I have no problem believing that guy was running those times w/a 305, one of the oldest lies in the book is claiming an engine is smaller than it really is.

Just sayin' is all.
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Old 04-13-2011, 02:40 PM
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Honestly, a stock 96+ vortec 305 could probably get close to those numbers in a light car like a vega with a carb swap, decent exhaust and some deep gears. It wouldn't take much.
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Old 04-13-2011, 02:42 PM
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VERY basically you need enough compression ratio to support the camshaft's duration/overlap and enough valve lift/cylinder head flow to allow the engine to make power in the RPM range you've targeted. Then it's a matter of feeding the heads w/enough air/fuel and exhausting the remains.

Hooking that power up to the track is as important as making the power in the first place, so the vehicle weight, torque converter stall speed, rear gear ratio, tires and suspension/shocks all come into play.

You might want to start by doing a search on this site for 305 builds. There are MANY threads on them.
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Old 04-13-2011, 03:20 PM
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Great tips,thanks!Do some 305s come stock with flat top pistons?I pulled mine apart & the pistons are flat tops?
They have 2 half moon shapes in the tops?
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Old 04-14-2011, 07:46 AM
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Ok guys n gals,my buddy was on his fourm & asked for a wicked combo for a stock bottom half & got a hit from a guy in Cali.that run this combo for his stop light to stop light racer,
Tell me what you think.cam;234/244-488/510 110lobe sep. Intake;Weiand highrise dual plane. Carb;Holley600 vac.secd. Double roller chain,1.6 rockers(not roller).Super Comp.full size headers,
2.5"pipes with FlowMaster 40s(no cats),350 trany with 3200/3500 stall. 488 gears.This is in a 81 impala 2dr. Rear tires are 215/60/15.He said he was on YouTube in 09 running against a 99 camaro 5.7
& beat it by a half car!(1/8mile).Please let me know,i would like to start building soon.
Thanks Again!
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Old 04-14-2011, 08:57 AM
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Quote:
Originally Posted by 305mouse
Do some 305s come stock with flat top pistons?I pulled mine apart & the pistons are flat tops?
They have 2 half moon shapes in the tops?
I think there were a few 305's w/FT pistons (w/four "eyebrow"-type valve reliefs) but most came w/a dish and the four eyebrow reliefs.

Your pistons sound like they're aftermarket if they have just two valve reliefs per piston. If you look closely at the top of a piston you may be able to see a part number and an oversize marking like "020" or "030".


COMMON 305 DISHED PISTON

Quote:
cam;234/244-488/510 110lobe sep.
To use that much cam effectively in a 305 will require heavily modified production 305 heads (ported, 1.94" valves fitted, new valve springs at a minimum), modified Vortec production heads (guide boss shortened and cut for seals, new springs, milled deck) or aftermarket heads. You might also consider the old small chamber "fuelie"-type head- but I wouldn't favor them over the Vortec or aftermarket heads. Any production head can benefit from screw in studs and guideplates. I would choose a cam that had the specs I wanted w/1.5 rockers instead of using 1.6 rockers.
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Old 04-14-2011, 09:34 AM
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Cobalt,ya that pic.you have posted is what mine look like.I thouhgt the 4eyebrows made 2 circls.sorry about that!...Wow,that's alot of work for that cam set up.Well,back to the drawing board.
Darn,my auto tech.teacher must of been right by saying im trying to polish a turd!lol...im not giving up!He told me one time to put 350 rods in it to shorten the stroke? Sound right.What makes a 305ho?
My older sister had a 76-77nova i think it was a ss or rs & had a 305ho.It was a tire burner!
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Old 04-14-2011, 10:04 AM
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Quote:
Originally Posted by 305mouse
Cobalt,ya that pic.you have posted is what mine look like.I thouhgt the 4eyebrows made 2 circls.sorry about that!...Wow,that's alot of work for that cam set up.Well,back to the drawing board.
Darn,my auto tech.teacher must of been right by saying im trying to polish a turd!lol...im not giving up!He told me one time to put 350 rods in it to shorten the stroke? Sound right.What makes a 305ho?
My older sister had a 76-77nova i think it was a ss or rs & had a 305ho.It was a tire burner!
The bottom end of your engine- all the way up to the pistons- is identical to a 350. The pistons of a 305 and the bores in the 305 block (that cannot be bored to the size of a 350, btw- in case you were thinking that way ) are about 1/4" smaller than the 350. The 305's bore is 3.736", the 350's bore is 4.00". BOTH use the same 3.480" stroke crankshaft.

Changing the rod length doesn't have any effect on the engine displacement. The displacement can change two ways- bore and stroke.

The 305 HO engine used more CR and IIRC a bigger cam and had heads w/1.84" intake valves instead of 1.72" intakes used on the lower output 305's. There may have been other differences, you can check on that through google or maybe someone here will chime in.
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Old 04-14-2011, 10:40 AM
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Cool,thanks!You guys really know your stuff! Ive learned more in one day here than 3yrs. Of highschool tech.class.
I will figure something out.
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Old 04-14-2011, 12:14 PM
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Let me run this by you guys he just put it up on our sell it board here at work. 1978 350 mild cam,204/214-420/442.Edelbrock perfomer intake,Holley 600,305 heads,
$400.Would this be a better starting point?
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Old 04-14-2011, 12:45 PM
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Here´s my "TRUE" 305, just before I took it to the junkman.
I´d done the cylinder heads World Products, and a torquey cam,
headers, intake, all MSD ignition but my car was made when this went out and a 355 went in.
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Old 04-14-2011, 06:33 PM
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Quote:
Originally Posted by cobalt327
BOTH use the same 3.480" stroke crankshaft.
True they both have the same stroke but the cranks aren't quite the same. The 305 crankshaft uses smaller counterweights because of the smaller pistons. That's not to say that interchanging cranks wouldn't work, but they're not the same.

Quote:
Originally Posted by 305mouse
Ive learned more in one day here than 3yrs. Of highschool tech.class.
It sounds to me like your school needs to find another auto shop teacher.

Here's an article about a 370+ hp 305 build: http://www.popularhotrodding.com/eng...e_testing.html

Something to consider though is that if you were to build an otherwise identical 350 you're going to end up with over 400hp. That's why fewer people are building small displacement V8s and 383s, 400s, 454s and 500+ ci engines are becoming more and more popular. More cubes from an otherwise identical engine is darn near free horsepower.

Last edited by Blazin72; 04-14-2011 at 06:41 PM.
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Old 04-14-2011, 08:06 PM
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Check out some of the NHRA stock eliminator cars. 305 cu in with cam, head, abd carb restrictions running 11 sec ETs. It's not just the engine that gets you there. It's the chassis , trans, and the engine. Skimp on any of these and you could have a stone.
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Old 04-14-2011, 09:02 PM
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Ya,the more i think about it i might jump on that 350 with 305 heads. My shop teacher was hard to understand,he is a big Mopar guy,infact running a plymouth arrow with a 501 indy motor.
We went to the track as a class & watched him lay down 8.20s(1/4mi.),but cant help me with my sbc?
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