305 is like Rodney Dangerfield; don't get no respect! 
4.8 to 305
Thread Starter
Teching In
Joined: Mar 2013
Posts: 10
Likes: 0
From: Sewell, NJ
4.8 to 305 Hi guys, I picked up a 4.8 to go into my 86 Monte Carlo, and I want to bore it out to a 305, pretty much just so that I can say its still got a 305. To get there, I need 3.855 pistons. I've read on here that you can go up to a 3.903 and still be okay on an iron block, so I should be safe. Problem is, Anyone have a clue were I might get pistons and rings? This is a budget build, but if I got to go custom, so be it.
Also ,will I have enough diameter to safely run stock LS1 heads? Or can I up size to stock valves?
Thanks in advance guys
Also ,will I have enough diameter to safely run stock LS1 heads? Or can I up size to stock valves?
Thanks in advance guys
Last edited by LE5CAV; Feb 21, 2016 at 09:37 PM.
10 Second Club
Joined: Jan 2010
Posts: 2,317
Likes: 20
From: Hurley, VA
From a performance stand point you'd be better off with a 5.3 or 5.7 but LS1 stock pistons are 3.898 and would be the cheapest option. Not sure on the cubic inch but custom pistons will cost a fortune and you'll probably be waiting forever on them. Just seems like alot of time and money just to say its a 305.
if claiming it has a 305 is so important just run a 4.8 or a 5.3 or 6.0 and lie
the jig would be up the first anyone runs your "305" anyway, no need to spend a fortune to achieve the same end result
the jig would be up the first anyone runs your "305" anyway, no need to spend a fortune to achieve the same end result
Thread Starter
Teching In
Joined: Mar 2013
Posts: 10
Likes: 0
From: Sewell, NJ
if claiming it has a 305 is so important just run a 4.8 or a 5.3 or 6.0 and lie
It may be misleading saying its a 305 even though it is a modern version, but it isn't a lie, that may be splitting hairs, but it's still honest
the jig would be up the first anyone runs your "305" anyway, no need to spend a fortune to achieve the same end result
It may be misleading saying its a 305 even though it is a modern version, but it isn't a lie, that may be splitting hairs, but it's still honest
the jig would be up the first anyone runs your "305" anyway, no need to spend a fortune to achieve the same end result
From a performance stand point you'd be better off with a 5.3 or 5.7 but LS1 stock pistons are 3.898 and would be the cheapest option. Not sure on the cubic inch but custom pistons will cost a fortune and you'll probably be waiting forever on them. Just seems like alot of time and money just to say its a 305.
Contacted Ross Racing and Arias Pistons about 3.855 pistons. Once the designs are finalled, I could have them with in 4 days from Ross, or 1 week from from Arias. Cost between $600 and $1200 per set depending on specs.
Last edited by LE5CAV; Feb 22, 2016 at 03:44 PM.
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Staging Lane
Joined: Dec 2014
Posts: 97
Likes: 0
From: Mobile, AL
Who said the LS1 doesn't rev high or fast? I have a simple solution: torque converter. With the proper set up the LS1 will rev past 7000 RPM's safely. Pretty sure a 4.8 will see the same limitations. Not trying to argue though. It is your car.
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Brett Foote Unless you are really ready to spend some time and money your custom "305" ls will run into the same RPM redline limits as any other Gen III or IV. Things have changed to a degree in how true the assumption that short stroke automatically equals quick revs and high rpm. The 4.8 is a short stroke 5.3 and there is not any benefit to it outside of being cheaper in the junkyard. Stick a low lash solid roller in whatever cubic inch you want and I bet it will rev faster and have the potential to rev higher than whatever short stroke hydraulic roller engine you can easily build.
There is nothing really sleeper about an LS engine unless whoever you are dealing with is clueless. If anyone sees it, it doesn't matter what cubic inch you claim it is...people will know an LS engine is going to make at least decent power even stock. If they don't see it you're still not accomplishing anything at the end of the day whether they get beat by a 293ci LS or a 305ci LS.
The more correct analogy here would be talking about spending a lot more money to build a 402 big block as you could spend on a 396, 427, or 454 big block just for the sake of wanting to say "it's a 402".
Just really depends on how much you want to spend and how much power you want to sacrifice just to say "it's a 305" to a stranger. I know guys with 396 badges on their 540ci cars...once the clocks light up no one is fooled by the badge any more.
There is nothing really sleeper about an LS engine unless whoever you are dealing with is clueless. If anyone sees it, it doesn't matter what cubic inch you claim it is...people will know an LS engine is going to make at least decent power even stock. If they don't see it you're still not accomplishing anything at the end of the day whether they get beat by a 293ci LS or a 305ci LS.
The more correct analogy here would be talking about spending a lot more money to build a 402 big block as you could spend on a 396, 427, or 454 big block just for the sake of wanting to say "it's a 402".
Just really depends on how much you want to spend and how much power you want to sacrifice just to say "it's a 305" to a stranger. I know guys with 396 badges on their 540ci cars...once the clocks light up no one is fooled by the badge any more.
TECH Resident
Joined: Jun 2009
Posts: 856
Likes: 2
From: Elizabeth City NC
This thread is a bit much, just swap the car and be done with it. Who cares what you have under the hood 305 or not.
And a fast high revving motor? Have you driven a ls powered vehicle? They are fast high revving.
And a fast high revving motor? Have you driven a ls powered vehicle? They are fast high revving.
TECH Resident
Joined: Apr 2014
Posts: 985
Likes: 12
Hi guys, I picked up a 4.8 to go into my 86 Monte Carlo, and I want to bore it out to a 305, pretty much just so that I can say its still got a 305. To get there, I need 3.855 pistons. I've read on here that you can go up to a 3.903 and still be okay on an iron block, so I should be safe. Problem is, Anyone have a clue were I might get pistons and rings? This is a budget build, but if I got to go custom, so be it.
Also ,will I have enough diameter to safely run stock LS1 heads? Or can I up size to stock valves?
Thanks in advance guys
Also ,will I have enough diameter to safely run stock LS1 heads? Or can I up size to stock valves?
Thanks in advance guys
This is not Burger King, you don't get it your way, you get it our way or you don't get it at all.
Thread Starter
Teching In
Joined: Mar 2013
Posts: 10
Likes: 0
From: Sewell, NJ
Check out Race Tec pistons. They have 2 lines of pistons, Race Tec and Auto Tec. Auto Tec uses a lesser quality material and and would be more than you would need probly. Ive had 2 custom sets from them and price is very good. Plenty of info about them if you search.
Thread Starter
Teching In
Joined: Mar 2013
Posts: 10
Likes: 0
From: Sewell, NJ
Thanks, I checked with Ross Racing and Arias Pistons so far, prices between $600-$1200 depending on specs
TECH Addict
Joined: Jul 2013
Posts: 2,189
Likes: 123
From: Portland, Oregon
Get the custom pistons and bore the block. Nay-sayers be damned. You are still going up in displacement, that is usually considered a good thing. You get the 4.8L's nice rod ratio. And forged pistons cost what forged pistons cost, custom size doesn't add that much to the price, so whatever you want, just do it. People run 241/243's on 4.8/5.3 motors all the time, even without overboring it, so you can run just about any cathedral port heads you want. I would use the WCCH stage two 5.3 heads, with the 1.95/1.57 valves, and enjoy the smaller valves being unshrouded by the slightly larger 3.855" bore. Should be a fun car.
TECH Addict
Joined: Jul 2013
Posts: 2,189
Likes: 123
From: Portland, Oregon
The overall ~250 peak isn't huge, but the ~75% exhaust to intake flow is what makes them real nice. It is 82% at .600", and that is huge. And they are only going to flow better on the larger 3.855" bore.
A single pattern cam, like a 224/224 or 228/228, should do really well. Probably shoot for .605" - .610" lift, and you will be in business.
A single pattern cam, like a 224/224 or 228/228, should do really well. Probably shoot for .605" - .610" lift, and you will be in business.
