so i got a question for you engine gurus out there.. im tearing down a 350 with good rotating assembly and have a guy who works with me and has a 84 T/A that is in great shape but hes a fu*kin idiot and ran it with a blown fan relay... so long story short he beat the rings to death and it is getting poor compression... would it b worth it or even possible to bore the 305 out to a 4.0" bore and drop in the rotating assembly.. i know some ppl use worked 305 heads to get higher compression... so what are your thoughts..

The 305 has a 3.736" bore. You'd have to bore it .264"..........NO WAY!

4" bore is a 1/4" over stock. No way, not gonna happen.

Don't do it!

even if you do, the crank has the right stroke but is is a totally different casting than a 350. Balancing would be necessary and it ends up being more costly than rebuilding a standard 350 to begin with!

go to a junkyard and get a 350 block and spend the money on the machine work for that block

Mike

350 block are too cheap to go with a 305. You can get complete cores for as low as $50 around here. Sometimes FREE!!!

the 305 rotating assy is a lighter bobweight as well. you can use the 350 parts with a 305 crank,, but i'd recommend balancing it to match. there's a cut on the counterweights that i.d.'s the 305 crank,, but they are the same casting # as the 350,, so be careful. no,, the block won't make it. the thickest part of the major or minor thrust walls are only about .220 thick on average. won't be much left.
andy

thanks guys thats what i was expecting... im just considering on how cheap i can get it goin again and get that T/A in to a home where it will b taken care of

Don't count out the 305 though. As bad as everyone bashes them, they are half decent and respond as well as any other small block to mods. Superchevy did an article a while ago on one and made over 400hp with simple bolt ons,(cam, intake, heads). Yes, there is less potential than a 350 due to displacement size, but that lack of cubic inches also chews up less fuel, making for a economically fun ride. If his rings are shot, I'd just bore it out .030, slap in newer flat top pistons to bump up compression, and you'll be really surprised. Depending on condition, and if you're really cheap, you might be able to get away with a simple hone job and new rings, and run it the way it is. And to answer your question, no, you will be unable to bore it to 4.00 inches, the machine shops will laugh at you.

Don't count out the 305 though. As bad as everyone bashes them, they are half decent and respond as well as any other small block to mods. Superchevy did an article a while ago on one and made over 400hp with simple bolt ons,(cam, intake, heads). Yes, there is less potential than a 350 due to displacement size, but that lack of cubic inches also chews up less fuel, making for a economically fun ride. If his rings are shot, I'd just bore it out .030, slap in newer flat top pistons to bump up compression, and you'll be really surprised. Depending on condition, and if you're really cheap, you might be able to get away with a simple hone job and new rings, and run it the way it is. And to answer your question, no, you will be unable to bore it to 4.00 inches, the machine shops will laugh at you.


I agree...Bashing on a 305 over a 350 is like bashing a 350 over a 383 or 406...Nothing wrong with building a 305 if thats what you got.

takes basically the same amount of fuel to make 400 hp with a 305, a 350, a 383, or a 400. still takes about 1/2 a pound of fuel per horsepower per hour. the 305 at that power level will be LESS street friendly,, that's a given.
andy

Don't count out the 305 though. As bad as everyone bashes them, they are half decent and respond as well as any other small block to mods. Superchevy did an article a while ago on one and made over 400hp with simple bolt ons,(cam, intake, heads). Yes, there is less potential than a 350 due to displacement size, but that lack of cubic inches also chews up less fuel, making for a economically fun ride. If his rings are shot, I'd just bore it out .030, slap in newer flat top pistons to bump up compression, and you'll be really surprised. Depending on condition, and if you're really cheap, you might be able to get away with a simple hone job and new rings, and run it the way it is. And to answer your question, no, you will be unable to bore it to 4.00 inches, the machine shops will laugh at you.

I always thought the 305 and 350 blocks were identical?? block size and all except bigger bore

is it worth boring? prolly not since you can get a 350 used cheap that even runs. But I believe you can do it. Check this out >>> http://www.carsinc.com/mr.bowtie/13067/ I dont agree 100% with this either but seems others say it can be done

I always thought the 305 and 350 blocks were identical?? block size and all except bigger bore

No they are entirely different blocks ,only really share outside dimentions ,if you ever look in through the frost plug holes on the two blocks you can see the difference in size of the internal castings , no where near enough matterial to bore that far

No they are entirely different blocks ,only really share outside dimentions ,if you ever look in through the frost plug holes on the two blocks you can see the difference in size of the internal castings , no where near enough matterial to bore that far

Thanx for the heads up, learned something new today!:happy:

is it worth boring? prolly not since you can get a 350 used cheap that even runs. But I believe you can do it. Check this out >>> http://www.carsinc.com/mr.bowtie/13067/ I dont agree 100% with this either but seems others say it can be done

i've bored a bunch of 307 blocks to 4.00" from 3 7/8". that really thins it out. none of those ever split a cylinder,, but a couple rusted through from the inside. these were for production use,, not performance at all.

that's only .125 over which is .0625 from the wall all the way arround.

i wouldn't try it with a 305 cylinder at 3.736 diameter. that's a full .250 over and taking .125 from the wall all the way arround. a thickwall cylinder sleeve is about .1875 wall thickness and usually cuts into water between the cylinders where the bores are thinner on some blocks.

there was a 262 v-8 block iirc for like 1 or 2 years in the mid 70's as an emissions engine,, that would make it to 4.00" but i wouldn't use it for performance with it that thin.
andy

i've bored a bunch of 307 blocks to 4.00" from 3 7/8". that really thins it out. none of those ever split a cylinder,, but a couple rusted through from the inside. these were for production use,, not performance at all.

that's only .125 over which is .0625 from the wall all the way arround.

i wouldn't try it with a 305 cylinder at 3.736 diameter. that's a full .250 over and taking .125 from the wall all the way arround. a thickwall cylinder sleeve is about .1875 wall thickness and usually cuts into water between the cylinders where the bores are thinner on some blocks.

there was a 262 v-8 block iirc for like 1 or 2 years in the mid 70's as an emissions engine,, that would make it to 4.00" but i wouldn't use it for performance with it that thin.
andy

We used to bore 283 out to 4 inch and make 302 z motors as well once [create some scrap by doing that too , no sonic testers back then] but they were a whole different animal than a 305 , cast iron was cheap when GM madethen and not when they made the 305 .

We used to bore 283 out to 4 inch and make 302 z motors as well once [create some scrap by doing that too , no sonic testers back then] but they were a whole different animal than a 305 , cast iron was cheap when GM madethen and not when they made the 305 .

few of them 283's scrapped too as well. i'm with ya. must have done a hundred + of the 307's back in the 90's when the cores sold for 25$ each for a 30' horse trailer full,, only stacked one layer thick. they almost couldn't give them away!! the shop owner would go to the three neighboring states east of us to haul em' back each month. almost cost him more for fuel to go get em' with the cheap fuel back then!! lol.
andy

there was a 262 v-8 block iirc for like 1 or 2 years in the mid 70's as an emissions engine,, that would make it to 4.00" but i wouldn't use it for performance with it that thin.
andy
The 262 was only 3 5/8" bore, even smaller than the 305. Doubtful if it would bore to 4" without hitting water.

few of them 283's scrapped too as well. i'm with ya. must have done a hundred + of the 307's back in the 90's when the cores sold for 25$ each for a 30' horse trailer full,, only stacked one layer thick. they almost couldn't give them away!! the shop owner would go to the three neighboring states east of us to haul em' back each month. almost cost him more for fuel to go get em' with the cheap fuel back then!! lol.
andy

The guy I appenticed under was building 302 Z motors long before GM ever thought of it , he loved those little screamers , fun piece in a nice light car , I'd still like to do a modern version some day for the right car :) Maybe for that front Porshe that Louch owns :cool:

The 262 was only 3 5/8" bore, even smaller than the 305. Doubtful if it would bore to 4" without hitting water.

ok,, that's the one that we made into standard bore 305's then. i was thinking there was another one that would make 4". let me dig some more. maybe it was just the 307. i've slept a bunch since then!! lol.
andy

A lot of 283s have been bored out to make 301s. Old school trick before the 302 came out.