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Old 03-07-2011, 12:26 PM
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chevy 305 performance

well im thinking of getting a 87 s-10 with a 86 monte carlo 305 in it. it was converted to carb. im not needing something to run 12's with at the track or anything but i would like to change the heads, maybe bore it, and just squeeze a little more power out of it. before i get the truck i want to know around the horses i might be looking at with a set of heads, boring it out, and maybe putting some flat top pistons in it. it already has headers, and as i stated before he put a new intake and a 4 barrel carb. im on a budget and dont want to buy a 350 i just want to pull this one and rebuild it and put in a couple performance parts. thanks

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Old 03-07-2011, 12:48 PM
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Quote:
Originally Posted by bigd_ok87
well im thinking of getting a 87 s-10 with a 86 monte carlo 305 in it. it was converted to carb. im not needing something to run 12's with at the track or anything but i would like to change the heads, maybe bore it, and just squeeze a little more power out of it. before i get the truck i want to know around the horses i might be looking at with a set of heads, boring it out, and maybe putting some flat top pistons in it. it already has headers, and as i stated before he put a new intake and a 4 barrel carb. im on a budget and dont want to buy a 350 i just want to pull this one and rebuild it and put in a couple performance parts. thanks
Whoa, a budget and you think rebuilding a 305 will be less expensive than just getting a 350. You need to carefully run the numbers. From a rebuilding cost stand point a 305 box of parts is the same cost as a 350 box of parts. The only difference would be the cores. They also run about the same. For dollar spent, there is a lot more capability from starting with a 350, which if you pick the right model you don't need to squeeze a little more out of it with boring and heads.

Then comes the cost of rebuilding, this needs the numbers run against buying say a new bottom of the line Goodwrench 350, these will deliver about 230 horse out of the box and it has a warranty for about 2000 bucks. Rebuilding the 305 with new heads and couple hot rod parts will start pushing that real hard with no effort at all.

So I'd recommend sweeping the rebuild cost optimism away and start doing some hard knocks cost estimating before getting on this road.

Bogie
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Old 03-07-2011, 01:50 PM
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if this 305 is that worn out that it needs to be rebored with new pistons etc, build a 350.

If its got the factory fla t top pistons the cylinder walls are any way half decent just hone and re-ring end bearing it to freshen it up..

You most likely already have the best factory 305 heads on your 305.
Check the head casting number. The HO heads end in 4416 and have 1.84x 1.50" valves.

If your heads are the low perf 450-434 castings or... with small 1.72x 1.50 valves ditch them and dig up a set of the 416's and get to work on them.

More power comes from home porting these. More compression ratio comes from milling the 416 heads down as far as the edge of the intake valve seat edge (51CC finished) and reinstaliing with a thin .015" felpro 1094 head gasket. (factory dished 305 pistons)
if your 305 has the factory flat top pistons just knock .030" off the heads, hone port them and install with the thin gasket.
You can drill and roll pin the stock rocker studs if you are worried about them pulling out.

062 or 906 vortec heads and a vortec manifold would be fun too. Keep cam lift under .460" to keep it simple and low cost..with stock vortec head valvetrain.

You can mill them down a bit too to get the cr up.

If you want to run a stock torque converter keep the cam duration modest.

212 or less. a 208-216 or 204-214 .420-.442 or a 211-221 .442-.465 cam is plenty. Single pattern cams work just as good (or better) too.

Check the Isky online cam catalog.

A Bigger cam than these will need a high stall converter. if you do burp the wallet for a high stall get a 10" "3500 stall" . You will only realize about 2800-3000 real stall speed behind a 305CID motor as the 305 is shorter on torque than a 350. If you buy a converter rated at less than "3500 stall" for your 305 you will waste your money and come up short on stall and off the line perf with a cam bigger than what I recomended.

Again if you don't want to get into buying a high stall, don't get nuts with the cam duration.

Keep the lift under .480" for stock valvetrain. replace the stock valve springs with hi perf stock diameter and shim them correctly for max rpm performance. cammed up motors need to rev.

A performer RPM manifold and 750cfm carb is not too big.

Higher ratio rear gears (4.10's) make it fun to drive and go fast.

Bolting on a holley weiand 142 blower would be fun, fun , fun. Low compression ratio is key.

Last edited by F-BIRD'88; 03-07-2011 at 02:16 PM.
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Old 03-07-2011, 07:50 PM
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new heads will run about the same price as buying a used 350 from a junkyard or off craigslist. if the 305 is running ok. install you a performer cam and keep rolling. the best thing to do to a 305 to notice performance is installing a set of gears in your rearend. save all that money you have for heads and pistons for stuff around the 305, like gears, tranny, exhaust, and electrical components
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Old 03-08-2011, 10:37 AM
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i started down this same road about a year ago when i decided to fix up my 86 parts camaro. the cylinders were in good shape so i did as F-Bird 88 said and honed the cylinders and reringed it and but new bearings in it. mine didn't have the 4416 heads so i found a set on the internet for 75.00 and i bought a rebuild kit for them for about 120.00, i since i didn't want to spend 400.00 getting them ported i decided to do it my self, but first i bought a book to help me (Chevy SB cylinder heads, by Graham Hansen) i did a mild port job on the areas that the book mentioned were for the best imporvment, and put the heads back togther. i used a cheap single pattern cam 204 @ 050 260 advertised and .427", i used cheap long slot 1.5 rocker on the intake and 1.6 rockers on the exhuast. a edelbrock performer intake and the stock Q-jet carb (rebuilt) as set of el-cheapo headman headers, HEI distributor and true 2.5" duals. as for the 700r4 i decided to order a rebuild kit from Monster transmissions and a 1800 stall (first trans rebuild that i did my self) and then i found a used "posi" carrier out of a 88 iroc and bought 3.73's.

since i did everything my self and i was very budget conscience i ended up having around 3000.00 into everything. the car runs great, is very strong up to about 5000rpm (not much after that) i still get about 18mpg and i would estimate that it makes about 280hp/320tq (give or take a bit). it's nothing comaired to my other camaro but it's still a pretty fun car to drive around. not to mention i've been offered more money to sell it than i have into it.
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Old 04-15-2011, 12:30 AM
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Coming from somebody who also has a 305, I found out it's not really worth it. The bore/stroke ratio isnt really good for performance. The cylinders are too small to throw any good set of heads on there or go much bigger than a 600cfm carb. At first I considered rebuilding my 305 until I found out that the rebuild kits, re-ring kits, and rotating assemblys for a 350 were dramatically cheaper than the 305. And the stroke in a 305 is the same as the 350 crank so you get way more bang for your buck with a 350. So it's not only a better idea for performance but if your on a budget like me, a 350 is a much better option.
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