i have a 1986 rx7 that i'm planning on converting to a v8. i'm currently helping my brother on his lt1/4l60e conversion into his 88 rx7,(he got a sweeeeeet deal on wrecked 96 TA that he couldn't pass up). so, in the mean time, i have time to decide what direction i want to go... some of it depends on the deals i find when they come along. the car has 4.10 gears, and about a 26" tall rear tire, but i can put a 28" under it, i will eventually go to a live axle with a limited slip or locker.

let me explain what my goals are: a reliable efi street/strip car that i can also take to an autocross or two. probly 50% strip, 40%street, 10% AX. for 1/4 mile performance, i'd like to start in the 12's & work down to the high/mid 10's eventually.
i'll be running no A/C & manual steering, so my only driven accessiries are the water pump(may eventually go electric) & alternator.

engine- i'd like to go LS1 if i can afford it. but i'm considering a LM7 5.3l truck engine as well.(ther're cheap to start with, but have some additional costs)
i know the ls1 is better suited for what i want from every angle, except price.

to use a lm7 i have to use a f-body oil pan, ls1 intake, fuel rails, throttle body, water pump(i think), & alternator bracket. buying mostly used parts for this, what's the average cost?? anything i missed?
how much more does the 5.3 weigh? 75 lbs? how much am i going to be down on power, even running a bigger cam?
i could have the heads shaved to bump compression, how much does porting cost on these usually?
which computer(truck or f-body) is better suited to this type of tuning using one of the tuning programs? i don't have to deal with emissions either.


transmission: i'd like to have a street/strip setup... with overdrive. is the 4l60e suited for this? would i be better off running a 700r4? i'd like it to hold gears when i want to shift manually, but just be an auto still. can i run a trans brake on either? what are the pros & cons of the two? is there something better suited for it?

 

Everything you said is right relating to hardware and engine comparisons but the trans issue is a real problem in a multi-task car.

The cast iron block truck LS is not as important in drag racing, but the additional weight upfront can really screw up a light V8 car for cornering / handling.

Drag racing trans applications are easy, but an automatic is marginal for Auto-X and flat out sucks for roadracing track days. Rear end gears, posi, versus locker, all determine whether your car will be great at one function or the other or just marginal at both.

Important considerations.

 

"The cast iron block truck LS is not as important in drag racing, but the additional weight upfront can really screw up a light V8 car for cornering / handling."

right on the head... i used to have a 88 rx7 with a chevy 350, and damn that thing was a blast in a straight line... but it didnt take the corners all so well. i mean it did have iron heads and block and yada yada... but all that adds up. so just wait and save your money and get a ls1. you wont regret it bud

 

A friend of mine here in Charlotte is finishing up an RX7 with an upgraded LS6/Z06 motor and a Viper six speed manual via a special adapter plate he had made. An AWESOME car in all respects. The six-speed is interesting because it's too low in first for anything other than massive amounts of tire smoke and redline in sixth works out to 277 mph. Yep, he isn't expecting to go that fast, but the key point is that with the six gears he always has a good RPM range to work with, no matter what he's doing. One other item - the car has SO much power, it really doesn't matter what gear is selected.

The 4L60E is supposedly rated for under 400 hp (around 350, I think), so a reasonably stock LS1 would not tax it too much. The problem I see in that tranny is the gear ratios - 3.07/1.66/1.0/.70. Nice first gear but a BIG jump to second, with fourth looking like a cruise gear only. Any autocross runs would be fairly slow (under 60 mph) and maybe you could leave it in first, but if it's a track day, this tranny just doesn't seem like the right tool.

I believe the 4L80E has even worse ratios, not a close ratio box at all. It's stronger, but no improvement for track requirements.

My $0.02,
Mike

 

Check out the RX7. Bob
http://www.exoticperformanceplus.com...Car.php?car=22

 

Dude, don't put an auto in your 7. I couldn't wait for my auto to start dying so I would have an excuse to do the 5 speed swap. Of course I have the torqeless wonder rotary but still. Besides, isn't the auto heavier than the manual? If you do the iron block you will have to think about the extra weight on the tranny as well as beefing up your springs. The LS1 is almost a straight swap weight wise. (you probably allready know all this)
I just hated my 7 with an auto. It was a granny car.

 

thanks for the replies i might have come across my powerplant... 99 LS1/auto camaro, wrecked.
if i get it, i'll have to store it for a while until my brother gets his car on the street. i'll see what pans out this week.

plan is to be street legal, to be able to do some tuning on the street, use it for an occasional night out, and when we head for the drag strip or AX, one is always trailered so if one gets broken, it's not a big problem.

 

go ls1, oh and by the way starting in the 12's is prolly a little slow. if your a halfway competent driver then high 11's shouldnt be a problem at all they fc's come with a 4.10 ring and pinion stock that coupled with the 2900 lbs swapped weight should be high 11's no problem thats just judging by what i've seen 4.10 fbody;s run (12.7 to 12.5 - 700 lbs = 12.0 or 11.8

 

i think i might have found the swap donor...
it's a 99 z28 ls1/auto, 110k+ miles, hit hard in the right side. guy slid it into the end of a guard rail. hit hard enough that the trans tunnel is crunched, the shifter is sitting at about 30* angle pointing toward the drivers side, and is bound up so it won't shift out of drive. dash & console are destroyed, but the airbags didn't deploy. it's been sitting for about 6 weeks in the rain now, so the interior is molding bad.

what's it worth?

my concern is wth it hit so hard will the trans be hurt? what about stresses on the motor?

with 110k+ what are my concerns with the motor? fluids looked OK, oil was dark, but not bad.

 

I ran 11.95 @ 115 mph with a stock 2000 LS1 6-speed with headers and 275/40/17 Nitto DRs. Jesse

 

well really i would go with an ls1 unless you are planning to run boost in the engine. many people feel the the lm7 is much better suited, in stock form, for boost applications. i agree and am planing on using a lm7 because i will be running a turbo off the bat.

 

the debate is over...

i just bought a 99 Z28 camaro, ls1/A4... it's wrecked & has some miles on it, but the price was fair... now i get to tear it all apart!