Hey guys, I'm just starting an LS6 build as a couple of you may know from the tag team forum. I got a lot of good info from that thread but I wanted to come in here and introduce myself and see if you guys might share some knowledge with me. Currently I have a 1970 Chevelle SS, with a NOM 396 350HP engine out of a 1971 Chevelle SS. Recently I scored a 4 bolt main 512 block at a swap meet for only $200, and now I am in the acquiring parts stage of the build. I originally wanted to keep this build 100% original, using the factory cam and compression, but as some members pointed out to me, the compression would be way to high for street use, and there are more streetable cams out there. So now I'm planning on just keeping the build mostly original with some internal upgrades to match the performance of the original LS6 while using pump gas, and keeping the original look under the hood. I picked up a set of GM dimple rods that should be on there way right now after doing a bit of research showing thats what the LS6 came with, and there are claims that they are comparable to other steel aftermarket rods that are on the market today. So my first of many questions for you guys is Do I have to use a 454 4.000" crank with these rods, or can I use a 496 4.250" with out issue?
Vinnie Vegas Official LS6 build question thread.
vinnievega
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Hey guys, I'm just starting an LS6 build as a couple of you may know from the tag team forum. I got a lot of good info from that thread but I wanted to come in here and introduce myself and see if you guys might share some knowledge with me. Currently I have a 1970 Chevelle SS, with a NOM 396 350HP engine out of a 1971 Chevelle SS. Recently I scored a 4 bolt main 512 block at a swap meet for only $200, and now I am in the acquiring parts stage of the build. I originally wanted to keep this build 100% original, using the factory cam and compression, but as some members pointed out to me, the compression would be way to high for street use, and there are more streetable cams out there. So now I'm planning on just keeping the build mostly original with some internal upgrades to match the performance of the original LS6 while using pump gas, and keeping the original look under the hood. I picked up a set of GM dimple rods that should be on there way right now after doing a bit of research showing thats what the LS6 came with, and there are claims that they are comparable to other steel aftermarket rods that are on the market today. So my first of many questions for you guys is Do I have to use a 454 4.000" crank with these rods, or can I use a 496 4.250" with out issue?
Vinnie ,stop buying stuff until you get a plan.
As discussed ,there are better cams than the old LS6 grind -never said more streetable.
There's also better rods that you could have gotten that would cost you less in the long run.
Your dimple rods will likely need resizing and new/better bolts.
By the time that's done you could have had some new I beam rods complete with ARP hardware for less cost.
Slow down and breathe.
Not much point in using OEM type internals as no one's going to see them so use quality components and build a better LS6.
You can retain the original look with any BBC so that shouldn't prevent you from building something better than GM did 40+ years ago.
Even a 496 can be built and still keep the "original look under the hood".
As discussed ,there are better cams than the old LS6 grind -never said more streetable.
There's also better rods that you could have gotten that would cost you less in the long run.
Your dimple rods will likely need resizing and new/better bolts.
By the time that's done you could have had some new I beam rods complete with ARP hardware for less cost.
Slow down and breathe.
Not much point in using OEM type internals as no one's going to see them so use quality components and build a better LS6.
You can retain the original look with any BBC so that shouldn't prevent you from building something better than GM did 40+ years ago.
Even a 496 can be built and still keep the "original look under the hood".
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Yea I understand, but these have already been machined with new aftermarket bolts, and I got them for $200. These rods sell for $500 untouched. Even if I turn around and sell these I'm ahead of the game and I know that. If I can get an original steel GM 4.000" crank that's what I'll use, but I have been finding a lot of 4.250" as well. My real question is If I find a score on a good 4.250 crank can I still use it with the rods that I know will work with a 4.000" crank.
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Thanks, if he has a set of 291 heads he'd like to part with that would be great.
Yes get a plan before ya fire up the credit card. Food for thought here.
If you go with a stock crank there are stock TRW forged GM pistons that come in at 9.1 to 1. They were used in 1971 Corvette LS motors. I have a set in my engine and the thing is very very accommodating on pump gas. When I bought the carte engine (GM P/N 366250) I took it right home and pulled the larger slugs out because I wanted no issues with the crap gas we are forced to run. My engine is a Gen IV engine running 118 CC Iron Rectangle heads that produce 10.2 to 1 with the large dome pistons GM sold in the 366250 crate engine package.
If you are going to buy heads think oval port or "Rovals" like the Eddy 110 CC heads. You can get the stock exterior look because the brackets will cover most of the Eddy logo on the front of the head. Some guys actually fill it with RTV then paint it orange. Outta the box the Eddys come with the same valve sizes as the LS6 heads (2.19 / 1.88), offer much more responsive street perf due to port size and they raise the compression to about 9.5 or so with those 1971 LS6 Corvette pistons. Essentially the lower compression pistons are "shaved" LS6 11.0 to 1 slugs so unless you go nuts on the cam the 9.1 1971 Vette pistons should work with any cam that will work with the 11.00 LS6 slugs.
Don't run out and do anything before ya get a plan!!
The 4.250 cranks are commonly used with .250 longer 6.385 rods. The dimples are 6.135, and while pretty strong... most consider the dimple a heavy rod... as in weight. the 291 head you mention is also considered BIG on a mild 454ci engine with it's 325cc rectangle ports. You may be better off to stroke it to get more cubes if your dead set on using those heads, or atleast give cstraub a call. I think i saw him make a post about a custom cam for those type of heads ( might have been the open chamber 990's though)that worked well. Another thing i'd do if i were you is take that block to a decent machine shop and have them look it over. 200 bucks sound way cheap for a 512 block from a swap meet. See whatcha got before spending anymore cash. If it checks out, then choose your heads and build to them imo.
sell the rods to some Vette guy or something. buy a steel 4.25 crank that's cut with big counterweights for 6.385 rods, a decent one like a Scat. Buy a set of 6.385 H beam rods, decent ones like Scat or similar. buy a set of forged flattop modern lightweight pistons for the long rods, like JE sportsman or similar. If you buy this stuff right you won't need the damper and flywheel with the big counterweights, the engine will be internally balanced. Buy the pistons for the next oversize of the block, don't try to use the existing cylinder surfaces. Buy closed chamber heads that will give you around 9:1 if you're stuck on the factory iron heads. at 496 size you can use the rectangle port heads and still get good street performance although you'd really be better off with oval port for a street engine even at 496 cu in.
You can build this engine to look externally just like an original LS-6 but it will have much more power and torque and do everything better than an LS-6, original or re-pro.
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Revised: skip the CC heads, use OC heads like the 049, oval port. use the commonly available small dome pistons, 10 or 12cc. This will get you right into the 9.5:1 area, perfect for iron headed street BB with a good cam.
You can build this engine to look externally just like an original LS-6 but it will have much more power and torque and do everything better than an LS-6, original or re-pro.
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Revised: skip the CC heads, use OC heads like the 049, oval port. use the commonly available small dome pistons, 10 or 12cc. This will get you right into the 9.5:1 area, perfect for iron headed street BB with a good cam.
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this is sounding way to costly here. This is a show car, not a race car lol. Is there a rotating assembly that I can buy all of this one shot for a fairly good price after I know the situation with the block?
Depends on what fairly good price is, if you don't need forged rotating assembly get cast steel probably 1000 for a cast steel setup from scat and 2000 for forged. I got a 445 block that was cracked were the head bolt went in the front part of the block water passage way.
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I think I can put together a GM forged set up cheaper than $1000 using the rods I have. Even if I got a brand new crank from GM. ( I work for a GM dealership so I get parts 10% over cost)
Yeah your not going to be balancing i take it? the set i was talking about comes balanced from scat with flexplate balancer and rings bearings. But really upto you if you want to just have a 454 and nothing fancy then your call just giving you options.
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If i went with a GM crank I'd have to go externally balanced. I'm thinking the way to go is keeping the internals as close to original as I can, just lower compression on the pistons, and a stepped up roller cam / roller rocker set up. That should put me at over 450HP, which is plenty and it wont hurt my wallet as much to add value to my car.
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Many years ago a friend of mine used ti be crew chief for Ken Veney on Veneys Vega of BB/FC fame. That would be back in the late 70's. Your signature makes me think of those days.
keep the stock 454 crank
stock 3/8 rods is all you need with ARP rod bolts.
use the .095 tall domed forged Speed Pro pistons
get the 291 heads and low rise 3963569 intake
nothing wrong with using an LS6 camshaft or an exact blueprint replacement.
Heck,you don't even need roller rocker arms.
Keep it simple
stock 3/8 rods is all you need with ARP rod bolts.
use the .095 tall domed forged Speed Pro pistons
get the 291 heads and low rise 3963569 intake
nothing wrong with using an LS6 camshaft or an exact blueprint replacement.
Heck,you don't even need roller rocker arms.
Keep it simple
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I've got factory 7/16" rods with SPS bolts. I've never heard of SPS but the company looks like its specializes in airplane fasteners. If anyone here has heard of them I'll use them, otherwise I will be picking up a set of ARP. What compression ratio would I be running with a .095 dome and the stock 291's (keeping in mind any set I pick up will probably need to be milled a little bit)
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Well I'm glad I can take you back to those days. My name is actually a nick name given to me based off of pulp fictions Vincent Vega.
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SPS has been around a long time as has Pioneer.
http://www.spstech.com/business_groups/engineered.html
anywhere from 9.5 to 1 up to 10.5 to 1 depending on what head gasket,final cc size,and piston to deck clearance.
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