Thread: sbc 350

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I have a chevy 350 bored 80 over. the temp runs at 190 degrees but i want to put a bigger cam in it but i need to tips on the cam becaues i dont want to go to big

Welcome to the forum.You can't bore a 350 to .080 over. Cam choices are dictated by compression ratios. We would need alot more details about your engine,trans,rear end,tire sizes,and wt of your vehicle before we could help you with a cam choice.

why cant you bore a 350 .080 over? seen it been there done that. just like you "cant" bore a 283 .125-.155 over been there done that to. works fine. taken proper precautions.

what is the compression ratio?
what heads do you have?
what gears and converter do you currently have?

Originally Posted by gassersrule_196

why cant you bore a 350 .080 over? seen it been there done that. just like you "cant" bore a 283 .125-.155 over been there done that to. works fine. taken proper precautions.

what is the compression ratio?
what heads do you have?
what gears and converter do you currently have?

Precautions??. And what would those be??.

My64,
Welcome to CHR! From what I see, SBC 350's from '68 to '74 were simply the old 327CI blocks with a longer stroke, and the 327's didn't have a lot of "extra" meat in the cylinder castings for boring. In 1975 the 350 got a new block, and those built from '75 on were beefier than their predecessor's, so you might get by with a heavy bore, but why? Like Gasser says, it's a lot like the old 283's, you're pretty safe with a 0.060" bore on a post '75 block, and you might do just fine with a 0.080" bore but you might also "hit water", or thin a wall to the point that you need a sleeve to save the block. Worse, you might thin a wall just enough to be a problem, and not know it until you're chasing water in your oil, or worse. At least that's my understanding.

You'd be safer sticking with a 0.030" (355CI) or even 0.040" (357CI) bore, and chase your power needs in the heads and valve train. Share a bit more about what this is going to be dropped into, and people can jump aboard and give you a lot of good advice.

older blocks most all the time are thicker 327 had a 4.000 bore same as a 350 some engine can go to 080to 125 in bbc alot less sbc i never cut a 283 out to 4.000 bore i look at the ones i had in the shop 060 would be max the older block pre 59 may work better if you feel the need to make a 302. cutting them to a bore 4.000 had to do with the core shift at time engine was built .read the front of most makers that sell pistons books over size there on guaranty every one will bore past to or past 080 . less you have 20 core blocks and start sonic checking them you may not like what you see i done some most 350 and 283 like to be no more then 040. past that i going to do a sonic check

The cheaper reman's coming out of places like Autozone are those horror stories of .080. Certainly not blocks I would want to stress much. Some leaking water right out of the crate.

So being in a bad mood,I go back to what I said in the first place,the guidelines of you can't bore a 350 .080. Even if you have seen something doesn't make it right.

Now I was/am hoping the O/P made a mistake in his post. Guess we'll have to wait for him to post again.

those precaustions would be, checking for core shift, magnufluxing it among others.

have you personally built one to these specs, to be able make this assumption?

Originally Posted by pat mccarthy

older blocks most all the time are thicker 327 had a 4.000 bore same as a 350 some engine can go to 080to 125 in bbc alot less sbc i never cut a 283 out to 4.000 bore i look at the ones i had in the shop 060 would be max the older block pre 59 may work better if you feel the need to make a 302. cutting them to a bore 4.000 had to do with the core shift at time engine was built .read the front of most makers that sell pistons over size there on guaranty every one will bore past to or past 080 . less you have 20 core blocks and start sonic checking them you may not like what you see i done some most 350 and 283 like to be no more then 040. past that i going to do a sonic check

Thanks for clarifying, Pat. My info about the pre/post '75 blocks came from some "Ask a Mechanic" place from a guy who claimed to be a 30+ year chevy master mechanic, but I'd rather trust your experience ten times over. I have no doubt that Scooter successfully punched a 350 out 0.080", and from what we know (one post) My64 has one already done to that extreme, too, and his question is not about his bore, but about cam recommendations.

Seems we've all (me included ) gotten a bit off track on a new guy's question, IMO. I hope he checks back in and is not too turned off by all of the negative responses.

Originally Posted by gassersrule_196

those precaustions would be, checking for core shift, magnufluxing it among others.

have you personally built one to these specs, to be able make this assumption?

Yeah-this is my first rodeo...........

No matter how you say it-bad advise is still bad.

well he apparently already did it!!!!!!!!!!!!!! so instead of telling the guy what a roach he has, why dont we answer his question????

Well,while we WAIT for him to reply if what he posted is really what he has,then if that is the case,I wouldn't recommend him to stress a THIN wall block like that.
As easy as it is to get a 350 block and cheap,there isn't a single reason to build a .080 block.Just isn't logical.Opps-there is my suggestion!!!.

Originally Posted by gassersrule_196

those precaustions would be, checking for core shift, magnufluxing it among others.

have you personally built one to these specs, to be able make this assumption?

i have a magnuflux set up dry and wet . and two other ways to check for cracks that.s not going to tell you $hit if the walls are to thin . i own a sonic checker that will tell you if the walls are to thin any thing other then that your guessing

Originally Posted by rspears

Thanks for clarifying, Pat. My info about the pre/post '75 blocks came from some "Ask a Mechanic" place from a guy who claimed to be a 30+ year chevy master mechanic, but I'd rather trust your experience ten times over. I have no doubt that Scooter successfully punched a 350 out 0.080", and from what we know (one post) My64 has one already done to that extreme, too, and his question is not about his bore, but about cam recommendations.

Seems we've all (me included ) gotten a bit off track on a new guy's question, IMO. I hope he checks back in and is not too turned off by all of the negative responses.

i done some 283 s and know guys have bored then to 4.000 . but very few will stand up to that . i had a 1960 i did last year and a 1959 this year . look at both for the hell of it to see if they were meaty enough for it .NO just another one of them deal were can it be done? or should it be done .feel lucky.. your talking about a block that.s been kicking around for 50+ years . 350 block or any blocks i see come in any thing past mild 70s is not thicker . one of the big piston company.s was closing down here in Mi they would sell 080 over cast piston for less then$4.00 a piston and 50. abox .they only had 080 overs when i found out. i asked my buddy that has been at the machine shop game for 40 years i asked him what block 350 he knew of would he bore that big and last ? None .funny thing about the 080 overs . one of the bigger warehouse i deal with were was trying to sell me 080 350 piston for a hell of a good deal... thats been 6 years ago .i told them were they pick them up from i think there still try to unload them. most of the time we check blocks with soft plugs out and used a welding rod grab the inner and outer wall you used your thumb and first finger for a mic .grab it here and there.. Hey by god i think bore it to 100 but there is alot you can not see .that is were the sonic check tells the rest of the story

this is why i said, "and other precautions"