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let me start this by saying I know how a 350 out performs a 305 through and through, but if your looking for my justification its that i want to have the original block back in my 1986 el camino some day....

onto the question at hand... can a 305 HANDLE the same power before the blocks integrety is in question


i have a 400 sbc in there right now which i love but someday i want to put the 305 back in there... my plan was to stroke it to a 335 with vortec heads and a weiland 142, i figured thatd make good enough power to have some fun and even enjoy some streetable MPG
 

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WFO
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let me start this by saying I know how a 350 out performs a 305 through and through, but if your looking for my justification its that i want to have the original block back in my 1986 el camino some day....

onto the question at hand... can a 305 HANDLE the same power before the blocks integrety is in question


i have a 400 sbc in there right now which i love but someday i want to put the 305 back in there... my plan was to stroke it to a 335 with vortec heads and a weiland 142, i figured thatd make good enough power to have some fun and even enjoy some streetable MPG
There's no inherent weakness in the 305 SBC that would make it any more susceptible to damage than a 350 SBC. It has the same basic bottom end strength; the only real difference is in the bore diameter.

Obviously there are no 4-bolt 305 blocks, but they can be equipped w/splayed 4-bolt caps if you wanted to play it safe. Not really needed in most apps, but the option is there.
 

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The next question is why would you want the original block? The car is worth more with the 400. The 305 will only bring the price of scrap iron. You can build a nice blown roller 305 relatively inexpensively, about the same price as a 350, but there's no logical reason to.

Id put your money into the 400 you have, maybe a fuel injection conversion and some sort of boost.
 

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WV hillbilly
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you can attain 400hp from a 305 fairly easy N/a the limmiting factor is the valve sizes....I do believe you can use 1.94 intake valves so again 400 hp isnt much problem..

305 engines are easy to come by and overlooked for mild performance builds, and as of late dealing with the 350 TPI heads I believe these "dime a dozen" as has been told are a great upgrade for mild performance builds, that is just by a visual inspection of the difference between the two. Id be interested to see what a flat top 305 with these heads would be capable of as the chamber did look smaller than the 305 but then again I have no hard facts just by a glance as I was putting them into storage.
 

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Dave Wilcox has a 400 HP "n/a" 305 in his IROC. It runs pretty strong once it goes above 3,500. He shifts at about 6,800. He doesn't race the car, so "times" are not available. It is, however, srtrong enough to smoke most Mustangs it comes across.

The 1.84" intake valve is used for a simple reason. It allows "full" flow from the intake runner, where, due to the bore size, the 1.94 valve is "shrouded" and flow is inhibited. While the 1.94 valve definitely "fits", it's not a good choice.

I also believe reducing the bore/stroke ratio by stroking it MAY bring a little more low-end power, but will certainly have a negative affect on longevity. If you DO decide to stroke it, use a 6" or 6 1/8" rod. Increasing the rod/stroke ratio will "help" a little.

FWIW

Jim
 

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You could possibly run 1.9" valves as a compromise. Running a longer rod may also be a good approach, run a 6.125" rod and some good forged light weight pistons and you can probably hit 7,000+ rpm. 305 parts are a lot lighter than 350 parts.

Finding a good head may be a problem though.
 

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WV hillbilly
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well if you did bore a 305 .060 i dont see the 1.94's being shrouded much...Then you could use Edelbrock E-Tec 170 heads but the chambers are 70cc so the GM Vortec L31 heads with smaller chambers and the same flow @ .500 lift would be the heads to use...again I dont see much problems making 400 hp... with portwork and milling the heads to achieve a higher CR I dont see much problems making 450+ hp....



found these trick flow heads ^^ http://www.trickflow.com/partdetail.asp?part=TFS-30300001&autoview=sku

from another post on the 283 and for a flat top 305 would be great!
 

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305 power and fuel economy

Please let me know how your 305 performs when you finish it.Im seriously considering a 305 for a pick up.I understand edelbrock makes heads designed for the 305 but I never tried them.Fuel economy is becoming more important than ever now a days. 350 stroke with small bore would make for a perky little mouse.

What are your goals,first economy or first reasonable power? One H.P. per cube would be easy while maintaining decent economy.
 

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Please let me know how your 305 performs when you finish it.Im seriously considering a 305 for a pick up.I understand edelbrock makes heads designed for the 305 but I never tried them.Fuel economy is becoming more important than ever now a days. 350 stroke with small bore would make for a perky little mouse.

What are your goals,first economy or first reasonable power? One H.P. per cube would be easy while maintaining decent economy.
Your economy will not be any better with a 305 vs a 350. If you want economy go with an efi upgrade.
 

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I've never heard of anyone hurting a 305 block. I've also never heard of anyone making a ton of power out of one which is probably why I've never heard of one breaking. They have a glaring flaw in the design. The bores are simply too small. The comment earlier about getting 400hp "fairly easy" out of one would be quite a challenge if you ask me. The amount of good cylinder heads for one is extremely limited. The S/R torquer head comes to mind. I'd like to see the build sheet of the 400hp 305 engine. I like hearing about guys doing more with less, and the oddball builds are always interesting to see.
 

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It wouldn't be that hard, but when you add up the cost it becomes hard to swallow for the typical guy doing a 305. The only part trickier than a 350 would be head selection but that's not too dificult to figure out. If properly ported I suspect a 1.94" valve will still have an advantage even with bore shrouding but its difficult to say for sure. If a machinist wanted to do this on his spare time (ie free machine work) he could probably hit 400hp for less than a grand in parts, provided he had the right core to start with. Otherwise machine work will probably be over half the budget. To get there on the cheap id get a 305 short block with flat top pistons, ported "305 vortec" heads (051 casting maybe?) Taken out to 180cc's or so with the stock sized valve to start with (may need to go larger depending on flow numbers) . Angle mill them all you can (probably only a degree), run a solid flat tappet cam (cost reasons) around 240 duration, an edelbrock tunnelram or ram efi style intake, 1 5/8" long tube headers. You'll have to spend some money on the rotating assembly, stock crank, 6" rods, forged light weight pistons, good balance and balancer, enough to go to 7,000rpm.

That's probably overkill for 400hp but it'd be sure to get there, be very reliable, and make the most out of the stock 305 parts you'd start with.
 

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Boost Retard
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Your economy will not be any better with a 305 vs a 350. If you want economy go with an efi upgrade.
The smaller displacement means more throttle opening at the same load meaning better mpg.

The smaller bore means less distance for the flame front to travel, better detonation control and better efficiency.

I've never heard of anyone hurting a 305 block. I've also never heard of anyone making a ton of power out of one which is probably why I've never heard of one breaking. They have a glaring flaw in the design. The bores are simply too small. The comment earlier about getting 400hp "fairly easy" out of one would be quite a challenge if you ask me. The amount of good cylinder heads for one is extremely limited. The S/R torquer head comes to mind. I'd like to see the build sheet of the 400hp 305 engine. I like hearing about guys doing more with less, and the oddball builds are always interesting to see.
Good small valve heads are the real challenge. you can sink a ton of $ into a stock head and end up with a medeocre head for the same money as just buying a good head that would work well on a larger bore (well, at least around here, machine shop services are $$$, I keep hearing about people posting from other parts of the country with shop charges less than half of what I've seen around here, even compared to some of the prices around here that I can get as a "favor" (I used to work at a speed shop)).

I"m currently working on a 305 project that I've given in and am converting some decent OEM heads (factory aluminum LT1 heads) that I ported to work on an SBC (this ends up being a pain in the butt since the coolant passages are different and there ends up being no _really_ good way to run accessories especially if you want to keep something like AC), which is costing me next to nothing in $ but tons of labor (I just welded the coolant passages in the decks and milled them on my bridgeport, not exactly a normal head surfacing machine which required a lot of tinkering and setup).

As far as actual durability, the original question, I've always figured that it should be the same or better as a comparable 350: for many years they used the same crank casting (with slightly different balance weight configurations), same rods, bearings... the only difference is the smaller bore, which assuming they used the same coolant passage layout should mean .132" thicker cylinder walls (though I've never heard of anyone actually confirming this with a sonic check...). In theory, the thicker cylinder walls should also mean more meat above the block webbing meaning stronger mains and more meat if you convert to 4 bolt mains (just like 400's have less because of their larger bore making some 4 bolt blocks/conversions actually weaker than 2 bolt).
 

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I have a 305 in my Firebrid too, and while I could have swapped it to a 403 easily out of a Trans Am, I decided to keep it matching #'s. But anyways, the 305 can make a good amount of power. Above 300HP though, and you could loose vacuum. Remember, most SBC parts for engines are interchangeable. I would say to go for a nice set of Vortec heads, or maybe swap over to TPI for better gas and power. The 305's problem is that it is an engine that cant breathe or get exhaust out good either, so a nice mild cam would help out too! :thumbup:
 

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My build must be blind luck. I was pretty happy with 220hp or so that i might have been really making. A 305 With stock valve 906 vortecs, angle milled to 60-61cc , A performer cam 420/442, vortec intake performer, 3000 stall from dynamic, 3.73 gear , 28" tire.

Everything was cc personally, and had 8.9:1 compession. It worked. Brake torque fried the tires. It chirped into second. 2800rpm at 65mph with 16 mpg cruise on.

4th of july , it got a kick in the pants. An E force supercharger for vortec heads. Dropped it right on. Fit with room to clear. Added a ton of power. Not even gonna lie with hp numbers I cant imagine.

Other than a wealthy freind with a blown 350. I know nothing about them over the common hotrodder, or what they can do with a mild beginning.

It was $2200 , but well spent and where ever I go from here, Im taking it with me.

The truck was $1900 and The additional 305 build was 600-700.

Cant wait till that next step, and make the jump to hyperspace.

Pic before installation, so people dont think im just talking. I will update my journal when I get things cleaned up. Easy installation.
 

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The smaller displacement means more throttle opening at the same load meaning better mpg.

The smaller bore means less distance for the flame front to travel, better detonation control and better efficiency.



Good small valve heads are the real challenge. you can sink a ton of $ into a stock head and end up with a medeocre head for the same money as just buying a good head that would work well on a larger bore (well, at least around here, machine shop services are $$$, I keep hearing about people posting from other parts of the country with shop charges less than half of what I've seen around here, even compared to some of the prices around here that I can get as a "favor" (I used to work at a speed shop)).

I"m currently working on a 305 project that I've given in and am converting some decent OEM heads (factory aluminum LT1 heads) that I ported to work on an SBC (this ends up being a pain in the butt since the coolant passages are different and there ends up being no _really_ good way to run accessories especially if you want to keep something like AC), which is costing me next to nothing in $ but tons of labor (I just welded the coolant passages in the decks and milled them on my bridgeport, not exactly a normal head surfacing machine which required a lot of tinkering and setup).

As far as actual durability, the original question, I've always figured that it should be the same or better as a comparable 350: for many years they used the same crank casting (with slightly different balance weight configurations), same rods, bearings... the only difference is the smaller bore, which assuming they used the same coolant passage layout should mean .132" thicker cylinder walls (though I've never heard of anyone actually confirming this with a sonic check...). In theory, the thicker cylinder walls should also mean more meat above the block webbing meaning stronger mains and more meat if you convert to 4 bolt mains (just like 400's have less because of their larger bore making some 4 bolt blocks/conversions actually weaker than 2 bolt).
Make sure you check the oil drainback holes on the LT1 head to see if they line up properly. The intake bolt pattern is slightly different as well.
 
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