sciff5

iTrader: (1)

Hey guys I dont post on here much but I am in the process of building an LS1 Rx7. This will be used as a race car and occassionally as a weekend car. It will be completly stripped, hopefully ending up weighing around 2300lbs. Basically I will be trying to extract as much performance from it as humanly possible with no real creature comforts, no dash no headliner no sound deadening material aluminum 10 gal fuel cell. So in continuing this trend with the engine I want to build an engine that puts down power for the cheapest amount of money possible. I am bulding the whole car for around 7k (before modifying the engine) so money is tight. I am looking at heads/cam which produce lots of power for a good price. Because the car is so light I am not worried about losing some low end grunt. I am looking for as much top end hp as possible to get my trap speed as high as possible. Like I said I run it on the street some time and I dont wanna get pulled by a busa or a Liter bike so I am looking to trap 135-140mph, which will prob take around 600whp. I was thinking of a Trex cam and ported ls6 heads. The problems with that setup which I forsee is that the trex cam requires some serious springs. I dont feel like changing springs every time I change my oil.. just more work than I want to deal with but will if I have to. Also I heard the trex cam isnt the best for nitrous and I am deff going to be using Nitrous prob anywhere from 100 shot to 200 shot. So I want to know is there an aggressive cam out there that is very good for use with nitrous and some good heads or porting options to match. Remember price is big in this, thats why prob 150whp is going to be coming from the juice.

Idle is of no real concern, just as long as its idle is reasonable enough that I can learn to keep it from stalling most of the time, If I'm pulling up to the staging area at the strip and the car stalls 3 times getting there, thats not reasonable.

I also have a couple hookups with a local inspection station so the sniffer isnt of concern either.

What do you guys think. How would you get to 600whp on a budget minus just a massive shot of Nitrous, I also dont feel like having to keep a scuba tank of nitrous in my house just to fill up my bottle after every quarter mile run. Or run with a busa.

Smartass6885

iTrader: (3)

i think the TSP MS4 cam and some of TSP's budget LS6 heads would give you around 450rwhp with the right intake and headers and stuff. Then a TNT wet 150 shot to top it off. that will put u right around the 600rwhp mark.

-Blaze

sciff5

iTrader: (1)

What would that cost? What spings do you need to use with the MS4 cam, at what rpm does it make a majority of its power? around red line like the trex cam? and is it nitrous friendly?

sciff5

iTrader: (1)

BTW the RX7s have 4.10 gears out back and I will be using a t56. Just to give you some more info. Ohh yeah and this setup has to run on pump gas. I think thats everything.

Ryan02SS

iTrader: (3)

Anything over 400rwhp in a 2300lb chassis will fly assuming it will hook. The C6 Z is trapping 122-126 at 3000lbs.

sciff5

iTrader: (1)

Yes it will fly and prob be scary even, hooking is not gonna happen..I've accepted it. Thats why I am going for trap speed. And although its prob looked down appon by this forum I want this car to be a highway monster.

With the aluminum fuel cell out back and the sound deadening tar removed I've effectivly removed prob at least 50 lbs from the back end of an already light car. The good news is that if I am going for good ETs the spare tire wheel well is about as far towards the back of the car as possible and its deep, thus very low, I would imagine 50-70lbs of lead shot would help a lot if its hanging 6in or so behind the rear wheels.

Right now the one thing I do have going for me in terms of being able to hook is that I've got 245 nitto 555R's out back which should help some.

sciff5

iTrader: (1)

Any more suggestions?

magius231

iTrader: (8)

lt1dave seems to be able to extract near 500rwhp using Patriot heads and his own cam. Patriot heads are budget heads, so you might want to give him a ring.

Smartass6885

iTrader: (3)

I would run the Comp 921's. but the PRC duals will probably work too. Check out TSP's website for exact prices on everything. They can get you set up with everything you need. I think the cam is designed for strong mid-range and real strong top-end. Probably peak around 6600rpm and shift around 6800. I know the MS3 was good for N2O and heard the MS4 will be also. Any cam will respond good with nitrous. it wont matter unless you are goin with a fully built motor to run a huge like 250 and bigger shot.

sciff5

iTrader: (1)

well the cheapest heads and cam to make around 450whp is really what I'm lookin for. I have seen comparison threads between the ms4 and the trex and most people seem to think the trex is more agressive and better for flat out speed. What if I bought stock LS6 heads and put a trex cam in there. I know used ls6 heads can be had for pretty cheap. How much is porting usually if you have it done by a local performance shop?


I am trying to buy used wherever possible because this is a weekend car. I dont need to rely on it every day and prob 2 or 3 months of the year it wont even touch the streets.

BOWTIE

[QUOTE=sciff5] Like I said I run it on the street some time and I dont wanna get pulled by a busa or a Liter bike so I am looking to trap 135-140mph, which will prob take around 600whp. /QUOTE]
Hate to say it, but if you are only trapping 135-140, you will most likely get walked by most of the newer litre bikes, and just about every Busa. My 1990 ZX11 with just minor bolt ons (pipe, sprocket, jet change {not even a jet kit}), trapped in the high 130's and even an occasional low 140 and was running 10.20's. However, I could run other cars that trapped as fast or faster than I did at the track from a role and they would not have a chance. Now granted if you could get the drag down low enough and keep the car stable enough, you might be able to gear it to catch them after they top out, but that would be well in excess of 175 mph. That is about what mine topped out at with the gear change (would be higher with the stock gearing) but most of the newer big bikes are even faster, even though most are limited at like 186 stock. Of course some of the older Busa's are not limited and have achieved even higher speeds stock while modified ones are doing better than 200 mph on a regular basis. Oh, one last thing, all it takes is a programmer to do away with the limiter on the other bikes as well. Good Luck taming those litre+ bikes from a role. You would be better off trying to put a suspension under your car and taking them in the 1/4 where thaty have to worry about spending time on their backs if they get to aggressive.

sciff5

iTrader: (1)

[QUOTE=BOWTIE]Hopefully they are not more than another 100 shot away. A 250 shot on a progressive controller is as big as I'de go. That would put me around 700whp

orangeapeel

iTrader: (18)

There is nothing wrong with making it a highway monster. You just wont be one with the 4.10 geared rear end. Step down to a 3.42-3.73 and you will have your hwy monster.

bjamick

iTrader: (31)

if you have read up on this yet these are sick cams and are giving anywhere from 60-80HP and powerband starts at 2300 rpm and goes allt he way up to 6500rpm, but the high trap speed is great in all but your 60' is the most important.. if you.ve got 600 whp but cant get but a 2.1 60' then there is something wrong. but you can buy the cam package that comes with the valve springs and pushrods that you need, which were used in testing the cam for $699.99 and TSP are very respectable great products,im looking in to buying this cam for myself also so ive checked all about it. and get like a 114 lsa and it will have a little lope to it and it will make it kind of a sleeper. but this is just my .02

PREDATOR-Z

For $7K it wont happen.

1- because the rear wont hold it
2- you'll need major suspension mods
3- you'll need major safety mods
4- you'll need major braking mods
5- 7K is about a budget motor build

Although your plan is like a nice concept, if that is your budget, you better reconsider.

sciff5

iTrader: (1)

I am building the car with a stock ls1 for 7k. I know I am going to be spending additional money to mod the car, prob twice that but what I was trying to point out was that I am trying to keep the buildup on the engine relativly cheap aka I'm not gonna go spend another 7k on the engine when the whole car is only worth that much.

The rear end on the rx7 will hold hard launches with slicks up till abou 500whp. I am gonna be grannying it off the line and I'm not gonna spray off the line. This should save the rear end from getting screwed up (but if it does I may step it up to a ford 8.8 and then I can change the rear end gearing too). suspension mods I dont need (people actually are getting the best 60's with worn out stock suspension), like I said the purpose of this car is not to get the best ETs possible. The RX7 already has 4 piston calipers which in a small car like the rx7 are plenty. Safety equipment I only need if I am running it at the track but I'm not crazy I'll get a cage at some point.

I cant change out the rear end gearing btw. I am stuck with 4.10s.
But when I asked someone on torquecentral if I could get different rear end gearing for stronger highway performance they said I really dont need it as 4.10s will bring me up to something like 187mph at the top of 5th.

Again I am not going for the best ETs I am going for the best trap speed cause trap speed is usually indicative of HP, and usually the car with the higher trap speed wins from a roll. Even if my car is only running 11.5's it will still smoke pretty much everything on the street from a dig.

PREDATOR-Z

You do not seem to be understanding. Your rear will not hold 500 rwhp. your frame will not hold that much torque either.
RX7 is a tough little car, but there are limitations.
Your brakes will not stop 500 rwhp either.
If you insist on a death machine, be my guest, but as a conscious racer, i just feel compelled to try to make you see that.
Build it wisely, it will improve your chances to build another project in the future and tell your kids about it.

My advice for the setup, TURBO with all the safety goodies and a lot of home fabricating.

Forged 346
6.0 PP heads
Custom cam
turbo hot parts
turbo
etc...
Kazz rear
Built TKO
stage 3/4 clutch
Brake system
Poly suspention
frame braces
Chrome moly cage
etc..

Only then would i step in a rocket like this and strap on.

sciff5

iTrader: (1)

To give you an idea I am building my car very similar to this one.

http://videos.streetfire.net/video/a...3400bea310.htm

The mazda rear end is a tough unit. With automatic cars its survived deep into the 9s. With t56 they are very well known for surviving into the mid 10s. This guy just broke his rear end recently pushing over 600+ wtq and Mickey tompsons. And he broke the ring gear not the LSD, I dont believe anyone has actually broken the LSD. As for frame considerations some 1.5in square tubing welded to the frame rails should take care of that concern. Most of the cars on torquecentral running 400,500,600 whp/tq have no chassis reinforcement which is friggen IMPRESSIVE. My buddy who is well known in miami for his FB RX7(older less ridgid chassis) has a built ford 351 in it. Its boosted, and he runs a 150shot out of the hole, when he launches on the street he does so with MT radials and VHT. He has had no problems with the chassis.

Now is that smart or safe to build a car liek that and reglarly race it every weekend? I would say HELL no. Thats why I will put a cage in the car at least 8pt at some point. Not right away cause money will be tight but I am sure this car is gonna become a wild ride and I know I will feel the need for a cage. The cage would deff be DOM mild steel. Chromoly is really pretty unnessacary in a street car, and unreasonable for what I am trying to do. A chromoly cage would be best because it would save some weight but DOM tubing thats a little thicker can be just as strong. Chromoly is about twice the money per foot as mild steel and needs to be tempered and tig welded instead of mig welded, which also around doubles your labor cost. Making for a cage that prob would end up costing me as much as the LS1 maybe a little more. As for the bushings as I build the car I am also converting to the turbo II rear end which is the one that is significantly stronger. In that process I will be switching from rubber bushings on the rear subframe and differential to a material (forget the name) but its more solid than poly, like a very hard plastic.

Brakes, well it depends on what you consider adaquate. For a 2300-2500lb car 4 piston calipers with vented rotors SS lines high performance fluid and high performance pads (basically what the car comes with stock) is usually considered overkill. It will deff produce more stopping force than the tires can provide grip and much more braking force (proportional to its weight) than any of the camaros (or prob vettes) with stock brakes. So I'm not too worried about braking. I would be more worried about it if I was into hard core road course racing, which I'm not.

Turbo setup, as friggen amazing as it would be to have (I meen thats my real dream right there) Sounds like a lot of money (almost no one has done it in the RX7 community and supposedly clearence for a turbo is at a premium in that engine bay) to design, tune and keep running correctly. I dont have the experience to build a turbo system myself or the experience to tune it, thus it would cost me A LOT of money to have someone do it for me.


Any more suggestions on heads and cam would be great. I hear Slowhawk, Dez Racing is in MA and I hear he does great work so I will prob give him a call when the time is right. I would not rule out the option of a custom grind cam, but right now the Trex and ported LS6 heads looks like the best bet for what I'm trying to accomplish/

Nihilanthic

I'd just like to wiggle in here...

The RX7 chassis is great, the ONLY prob is that theres no longer gear options for the rear end - youre stuck doing either a center section swap (cobra or 4th gen corvette irs pumpkin... I know the C4 vette swap runs $1000 said and done more or less, you just need to broach the stub shafts inside of it to accept the T-II half shafts and cut and reweld the 'wings' on it shorter to bolt to the mounts under the rear of the car) or revving higher becuase your street tires are gonna be in the 26" range and you CAN fit 28" slicks if youre good with your offset.

So, naturally, with a 4.10 out back, and 26-28" tires keeping your gearing short, but very low weight so you run real fast, lots of guys are running out of gear. He doesnt need to make the bulk of his power at higher rpms so much as just keep pulling in it so he can trap in 4th.

6800-7200 rpms is really as far as he needs to go, and I mean as far as redline, not really shift point. I know of a guy with a mostly stock LS1 who shifts at 7100 and has all the top end he needs.

But the one thing is that Im starting to think spending the gee on a C4 vette swap and some proper gearing might be better in the end than valve springs, rod bolts, and a cam swap.... heh heh heh.

Oh, and FYI these cars get high 20-low 30 mpg with a T-56 if they show some right-foot-discipline when driving with the 4.10s and 26" tires as-is, so I could only imagine how some 3.42s or 3.55's would help.

And personally Im seriously thinking of a 6.0 truck block with a LS1 intake/oilpan in a 2nd gen RX7 myself, but as a drag/street/occasional HPDE car. Ive realized that racing rules would put a v8 rx7 into "E-Mod" and other crazy classes, so if I wanna race roundy round seriously Im stuck with a rotary in a RX7... or a Miata or a 240SX. Blah.

At least miatas are easy to park. heh.