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so has anyone actually made 500bhp from a v12 pre.he

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XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

so has anyone actually made 500bhp from a v12 pre.he

 
  #21  
Old 05-18-2013, 01:02 PM
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500*
 
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  #22  
Old 05-19-2013, 04:12 AM
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Cal might be worth talking to these guys.

Stew Jones Restorations
 
  #23  
Old 05-19-2013, 09:37 PM
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that guys e type was the inspiration to my motor to be honest
 
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Old 05-20-2013, 12:04 AM
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No need to start a new thread - I'll give you the answer right now: LSx swap.

Anyway, I have no doubt you can reach 500hp, but at what cost? And with what engine characteristics? Just make sure you've thought through those questions and are comfortable with the answers.

How's the build coming, anyway?

Originally Posted by Flint Ironstag View Post
Maybe this warrants a new thread: best method of reaching 400RWHP and maintaining the engine characteristics we love.
 
  #25  
Old 05-20-2013, 09:19 PM
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the build is coming! just waiting on the rods to be machined and then I'll be ordering the custom pistons and rings, and having them expedited to get the car on the road before summer
 
  #26  
Old 05-22-2013, 11:24 AM
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With 6.5l 500hp is doable. The v12 runners are short and favor high RPM. You need to extrude home the intake. You need two 6 cyl ignitions. One coil aint gonna set off a v12 at 6500rpm. Id treat it as two 6cyl and use two of everthing. You are going to need a cam with at least 230 degrees at .05 lift with aggressive ramps and see if they float at 6500rpm. Domestic v8 comparisons dont apply. You have more cylinders and more valve area so the smaller vavles and ports are less an issue. You need to think of your v12 as 2 streigh 6`s. Bmw got 240 hp from a 2 valve 3.5l 6cyl in the 80`s. Research that motor cam and valve sizes, you basicaaly have two of them.
 

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  #27  
Old 05-24-2013, 07:04 PM
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The cam I am using has 254 degrees of lift at .05 I am gonna look into what valve sizes they use
 
  #28  
Old 05-30-2013, 02:15 PM
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Calvin... I think you should take those heads to someone who can flow bench them and see what you're working with. That way you will know what needs to be done. With the flow data you can do some math and make a reasonable assumption on power output. My quick calculations suggest you will need at least 175CFM at 28inches of water at full valve lift to make 500hp.
 
  #29  
Old 05-31-2013, 10:54 AM
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175 CFM , times 12= 2100CFM , thats a lot of air,gonna require some big ports and valves, not counting the inlet manifolds and runners.

you could run 12 TBs, much less 4 TBs, and still wont get that much air thru the engine!

this has been gone over many times, the limiting factor for most 4 stroke engines is the valve area window,(diameter+lift), hoping that shrouding doesnt block flow against the cyl. wall or chamber walls.

when an engine has some restrictive breathing, force feeding it,is a way of over coming some of the problems!

and for anyone who dont believe turbos work?

google, STS turbo systems, READ THE REVIEWS, then make an opinion, about the old fashioned myths of turbo lag, running the pipes under car, cool air coming from the rear of the vehicle, not from under hood(bonnet).

i have been doing turbo systems,all types, since 1979, its easy, believe me its easier to run a pipe under the car than,putting a stroker crank in, (done that also).
 
  #30  
Old 05-31-2013, 11:14 AM
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Darn you guys make me think(not a bad thing tho), my 1st STROKER build, was a 1939 Ford flathead V8, it happened in the year 1953 summer, came across this guy with a 1/4" long stroke crank, bought it and started the cubic inch thing!

never stopped liking cubics, untill 1962, built a 1/2" stroke chevy SMC, but bolted on a 6-71 blower, OMG, what an eye opening experience, rail type drag car went a 7.5sec. at almost 200mph,(198).

OH well, thats ancient history, didnt have any good turbos back then, but todays turbs are Ball bearing,light weight rotating wheels, and computor designed shapes, they are unbelievable power adders.

YES prochargers are good, twin screw blowers are great, all forced induction stuff today is good , but it seems the fastest and most powerfull are turbo engines!

course you could upgrade your fuel to Nitromethane, and enter a new world of totally uncontrolable power! been there done that too, everything is always limited by money.
 
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Old 05-31-2013, 05:00 PM
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I looked at rear mounts for the XJS but running the pipes back to engine not enough room under the car. I love FI my daily driver is an M90 equipped 3.8L and great low end torque. I have had 5 turbo and 3 PD supercharged cars.

The jury is still out on what I will do the 6.0L but FI is almost a definite. I keep switching between Procharger and TT keeping the CR up (9 or 10:1) and running lower boost. The tuners today are running LSX engines up to 12psi on stock CR, admittedly these have knock senors.
 
  #32  
Old 05-31-2013, 07:31 PM
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agreed warrjon, tuning will always be the last careful part of a build.

N/A engines can be off tune a little without hurting them, but forced induction,the higher the boost the more accurate the tune has to be, and it seems that the boost magic really happens around 1 bar, 1 atom., or 15psig in the inlet manifold.

theory says 1 bar could make 100% more power. dont quite work out that way, but close, depending on the system design.
 
  #33  
Old 05-31-2013, 09:02 PM
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I remember reading about a fellow who put dual turbos on a stock 5.3 HE and put it on a track then beat on it. He was surprised how long the engine held up.
 
  #34  
Old 06-01-2013, 12:56 AM
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my buddy is flow benching a bunch of my stuff, im not done porting and polishing the heads yet (although you should.never take heads to a mirror "polish" I still use the term) the intake flows around 135cfm through the worst runner. and I believe he said at 28inches. idrk ill check tomorrow. the oversized liners give the valves a little more room to flow, 3mm to be exact, and I will be going with 43.5mm intake and equally oversized valves in the fall when I do the next stage of my build.
 
  #35  
Old 06-01-2013, 12:59 AM
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the equation in my physics text book is cfm x .43 x #cyl =hp. so with 135x.43 x 12 you get 696hp.

sweet Jesus gents.

I'll see whay the heads flow. I also wanna flow match all the ports aswell
 
  #36  
Old 06-01-2013, 01:14 PM
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You theoretical calculation doesnt not account for so many things including VE. There are other rules of thumb you can use...consider these.

Head flow in direct relation to HP and/ or Tq and also peak RPM - LS1TECH


Peak_HP = Flow_CFM * .257 * Number_of_Cylinders

or 175CFM * .257 * 12 = 539HP.

I'd add in a 10% correction factor for VE, oil pump, combustion chamber inefficiencies on the old Jag v12 so 539 * .90 is 485HP.

The 175 CFM is a big assumption at this point. When you get them flow'd at least you'll know what these heads have to do to perform. If the heads don't flow then the cam, displacement and everything else doesn't matter. 135 CFM isn't gonna make 500hp. on a 6.5L v12 It will get you about 380HP at a low RPM. That's not too shabby....I have a Coupe with 420HP SBC and it's a hoot!
 

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  #37  
Old 06-01-2013, 04:23 PM
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okay, so i have been doing some looking into the port sizes, the intake valve is 1.6 in, and on an estimate compairing it to similarly ported heads, it should be able to flow over 200 cfm. im not worried about the heads. i am worried about the intakes, i put the figures on a calculator, and i got 390hp at 5200 rpm. not bad. but i need to figure out how to open the intake up?

chad bolles said use quad throttles, and he has steered me right so far, so i am pretty ready to believe him.

extrude hone?

any other options?
 
  #38  
Old 06-01-2013, 04:42 PM
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i am thinking i should go with the group A intakes, from v12 sales. these things flow a ton better than the stock ones, aprox 186 cfm when extrude honed.

i cant afford to have them honed just yet, so i adjusted the numbers back down 155, i get 440hp, and 165 i got 470 hp

at 185 i am capable of producing 526 hp.
 
  #39  
Old 06-01-2013, 06:26 PM
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and the beat goes on! sonny&cher 1975.
 
  #40  
Old 06-02-2013, 04:05 AM
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Originally Posted by ronbros View Post
and the beat goes on! sonny&cher 1975.
Damn I remember that song - its on my playlist
 

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