pump gas or race gas?
okay here is how race gas or regular gas really works per say. Octane is the rating of the fuels resistance to combustion. 93 is harder to burn than 87 and so on. When you get up to about 10.5 to one compression or about 155 pounds of cylinder pressure you need more octane to keep the intake charge from combusting just from the pressure and not from the spark plug. This is predetonation and can cause very big problem. HP has nothing to do with what octane that you will need. This is why when you run bigger turbos or lots of nitrous it is reccomended that you at least run a race gas pump gas mix, or take lots of timing out of it. This guy you talk about is full of it and I hope you tell him that. As far as the LS series engine it is the most technologically advanced of the chevy sb engines so i would go with it.
Also the engine in my sign is a forged 408 iron block, I have $12000+ in it after building it myself from the ground up to what you see on the engine stand as pictured. That does not count the price of the stuff I already had like the headers, and accessory drive. I reused the water pump ($300) and had the alternator and starter rebuilt locally ($300+ for each if I would have replaced them). LS engines are not cheep to build. You can build a 408 for alot less then I have in mine. I built mine to handle 1200+hp with lots of boost. But still once you add in tuning, accessory drive parts, injectors, oil pump, heck the head gaskets on these things are $250. The oil pan alone was $650. I think you will be better off finding a car with an engine in it first, then drop it out and start your build.
When i called Wiseco about making a set of custom nitrous pistons for my LS1, i told them i wanted to run the most compression and stil be pump gas friendly. They told me that i could run as much as 12:1 and be safe on pump gas!!!! I'd imagine ud have to have a good tune though. I've had alot of old time drag racers that are running old style SB chevy's try to tell me that i had to run race fuel if my compression exceeds 11:1 because that's the way it worked out for them. Of course that's like comparing apples to peaches. The motors aren't even in the same category. Good luck with ur build.
thanks guys for the info and tips. so Texas WS6 you think i would definately come out cheaper going with the forged 347 build vs the 408 stroker build? i am not wanting to go for a setup like yours 1000+hp engine, i am wanting 500-550rwhp mark for now. maybe one day i will go with a 408 but thats in the very distant future. so i think to just get the 500-550 mark the forged 347 will be enough for me and will be cheaper than the 408 stroker.
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True it might be a bit cheaper getting the whole 346/t56 combo used. But you could sale the stock SB and still have all the accessories for the 408...
But coonass, I'm not trying to tell you that what you doing is wrong, I'm just trying to show you some other way and possibility for a build.
The way I see it;
- buy the engine with everything on it for 2200$
- Sell the stock SB instead of getting it rebuilt so; you get 1500$ for the stock SB, you keep the 1400$ for the 347 forged kit and the 500$ for machining. Brings you to a total of 3400$+ for the 408, which cost +-3800$.
- so you have a forged 408 with all the accessories for the same price or very close to it.
I know what I'm talking about, I went the exact same route(getting a 347 SB rebuilt) and in the end it did cost me more than getting an assembled 408 SB.
Good luck with your choice, and share your results!!
But coonass, I'm not trying to tell you that what you doing is wrong, I'm just trying to show you some other way and possibility for a build.
The way I see it;
- buy the engine with everything on it for 2200$
- Sell the stock SB instead of getting it rebuilt so; you get 1500$ for the stock SB, you keep the 1400$ for the 347 forged kit and the 500$ for machining. Brings you to a total of 3400$+ for the 408, which cost +-3800$.
- so you have a forged 408 with all the accessories for the same price or very close to it.
I know what I'm talking about, I went the exact same route(getting a 347 SB rebuilt) and in the end it did cost me more than getting an assembled 408 SB.
Good luck with your choice, and share your results!!
Joined: Apr 2006
Posts: 3,909
Likes: 1,158
From: Grand Rapids, Michigan
My .02: You don't need anything but a set of rod bolts in that shortblock. You think you need forged pistons and better rods to spray 125HP? There are hundreds, if not THOUSANDS of people who have sprayed that much or more to their stock shortblocks and never had a problem. Save your money for a good set of heads and leave the bottom end alone, aside from a cam.
For 500-550rwhp you do not need to go forged anything. The rods in the LS are PM forged rods which are very strong. The crank is not forged but it is a nodular iron cast shaft which believe it or not is a very stout part. The pistons are not forged but they are hypereutectic pistons. Great pistons as long as you stay away from detonation. The blocks are way stronger then the old SBC. 6 bolt mains, "Y" block style! Very nice! The thing that I do not like about the LS is the head bolts on the stock stuff. I am glad they went to 6 bolt heads for the LSX stuff. As far as the compression ratio on pump fuel goes, it is really not the engine design alone that makes that possible, also the technology in the computing system (PCM) and its sensors, something the older engines did not have the luxury of benefiting from.
11:1 compression is what the factory LS7 has and it makes 505hp stock, runs on pump gas, and get 30+mpg, all this with the EPA bull cr@p on it.
As far as strength of the stock stuff, didn't I read some were that GM was running a few LS2's in Bush Racing to cut the cost of the engines down? Maybe a NASCAR/Bush fan (fanatic) will know more about that then me.
11:1 compression is what the factory LS7 has and it makes 505hp stock, runs on pump gas, and get 30+mpg, all this with the EPA bull cr@p on it.
As far as strength of the stock stuff, didn't I read some were that GM was running a few LS2's in Bush Racing to cut the cost of the engines down? Maybe a NASCAR/Bush fan (fanatic) will know more about that then me.
Last edited by Texas_WS6; Jul 3, 2009 at 12:03 PM. Reason: Spelling
My .02: You don't need anything but a set of rod bolts in that shortblock. You think you need forged pistons and better rods to spray 125HP? There are hundreds, if not THOUSANDS of people who have sprayed that much or more to their stock shortblocks and never had a problem. Save your money for a good set of heads and leave the bottom end alone, aside from a cam.
I ran a 150 shot on mine for 4 years. I put the juice to it as soon as it came out of warrenty at 36000 miles. I am the original owner of mine. Anyway, I used it on my stock 346 cam only until I finished my 408. I dropped the engine out it had 88,000+ miles on it, and only God knows how many juiced passes. I am talking juiced off the line, juiced it a few times going threw Houston (not advisable) racing Lambo's and what not. Same thing in Dallas, and San Antonio. 200 shot would be the max I would advice anyone to run on a stock bottom end.
There are a lot of things that will determine how long the engine will last.
Tuning being one of them. Bad tune and n2o dont mix well for engine longevity even if it is forged.
There are a lot of things to look at when you talk about money and what engine to go with. If your going to run boost or n2o then a 347 can be built stout to make good power, but if your not going to be boosting it right away and are looking for more driving down the street power than cubic inches is what you need to think about. More cubes makes more power ( all things being equal).
Then you have the block material argument which comes into play for power adders. Iron is more durable than aluminum.
Budget and application determine the build. How much power are you looking to make?
Tuning being one of them. Bad tune and n2o dont mix well for engine longevity even if it is forged.
There are a lot of things to look at when you talk about money and what engine to go with. If your going to run boost or n2o then a 347 can be built stout to make good power, but if your not going to be boosting it right away and are looking for more driving down the street power than cubic inches is what you need to think about. More cubes makes more power ( all things being equal).
Then you have the block material argument which comes into play for power adders. Iron is more durable than aluminum.
Budget and application determine the build. How much power are you looking to make?
99blancoss, you have made a good point about needing bigger cubes for street power. maybe one day i will do a 402 stroker engine, if i was to go with a bigger engine then it would be the aluminum 402 stroker engine, but for now all i am wanting is 500-550rwhp, just to learn on the engine, and be able to get use to that kinda power. and then once i am tired of it i will upgrade to something else, but money is an issue for me so i gotta take things slow. but if i went with a 402 stroker engine i would try for the 800+ hp range, so if someone could show me how much it would cost for a 800+ hp 402 stroker then i might consider doing it.
