i have an 86 z28
350 at ..040 over = 356 4 bolt main
forged bottom end..crank-rods-pistions
aluminum heads off a 90 vette
crane cams 510/512 lift 284/284 duration
edelbrock rpm manifold
rochester quadrajet 4bbl
mechanical fuel pump
stock distributor w/ hyperchip coil, cap rotor

5 speed manual
2.73 rearend

i run a 12.9 @ 109.4mphs

i want faster....i can beat many street cars..but its not fast enough, there are a couple 10 and 11 sec cars in my area and id like to beat them. what can i do? i will do anything except change the rear. any recommendations welcome.

 

i forgot exhaust

headman headers 1 5/8 primary
3in collector

3in downpipe

3in dynomax catback exhaust

3in highflow cat....emissions suck

no AC...No Smog (does pass w/o, just run lean)

10.8 total compression

 

what are your objections to changing the rear if I may ask?

 

Agreed. You need more gear and Nitrous and you can run low 12's. You will need to pack some serious heat to run in the 10's and 11's. You will need 450 to 500 at the wheels to see 11's. On your 356 that will take a serious spray and or some serious boost from an adder.

 

I would also recomend some gears
am not sure exactly which ones my guess would be something along the lines of 3.42 maybe but your 2.73 are not going to cut it


also might want to see if you can rework the heads a little (not hog them out) just to see if you can improve air flow while keeping velocity up there

also this might get moved

but what is it you have against the rear end?

 

I bet he'd pick up a few tenths if he got rid of that "rochester quadrajet 4bbl" and slapped him a nice Demon 650 on it.

 

get some drag radials, with a trap speed like that you should be running about 12.4 . My dad has those trap speeds and runs a 12.39- 12.41 at 110 .

 

i forgot , what about doin sfcs. and new suspemsion pieces, that might help pick up some extra tenths with you did drag springs ans lca;s and relo brackets. and mayeb a better torque arm.

 

kinda hope he already has sfcs runnin those kinda times, otherwise he prolly has some stress cracks and or body twistin goin on...

 

What's been done to your qjet so far? If it's pretty stock then you should consider seeking out a good carb guy and getting a race prepped carb adjusted to match your engine. A stock qjet isn't a good race piece for many reasons. They can be modified to work fine but it does take a lot of work. If this hasn't been done already, you can probably find a very significant performance gain by swapping around some induction pieces. I'm also assuming you are running a spacer to adapt the spreadbore to your intake. Is that right?

 

You are leaving several tenths on the table by not changing the rear end. Go to at least a 3.42 gear or 3.73 since you have overdrive. That cam is way too big for that grandma gear you have.

 

the replies are great.

i do have sub frame connectors, and new shocks and struts

i do want to change the rear...but the parents wont let me so thats y im avoiding it.

that also rules out spray. the drag radials however i like.

i do have a 1in moroso spacer, but it is square bore...its a spacer thats it...

the carb is jetted for the origional motor which was a 305....it has been rebuilt, but i had it rebuilt to go on a 305

also i had the machine shop port my heads when i was havin the motor built, but not polished, i was told not too...it would swirl the mixtures allowing better combustion....

also the cam i have, was recommended by crane cams for my application, my rearend and my 5 speed manual trany..... it is a cam meant for 4x4..so the low end torque is insane!!!!


any other replied are welcomed

 

why will the parents not allow you to change the rear?

they let you port the heads

if they are worried about gas mileage
you shouldn't go down that much by gears as long as you stay somehwhat conservative (ie no 4.88)

 

i cant change the rear...because im told by the rentz that its not necessary and why change something thats not broke... also, when i was building my engine neither of my parents are car literate so it was easy, and they didnt ask too many questions..
can u see my problem? i need a solution fast...i need more go power....help

 

Tell them that it is broke or break it. Probably one-legged anyway right? Do something to break it and get some 3.42's maybe with posi. You sound like you have lots of money to throw around so just do it and i agree to go with some other carb more specific to your application.

 

eh simple fix


break it
then it needs fixed



but just tell them that is the fun of owning a car to make and change it to fit what you want


have they ever upgraded a TV or radio?
the old one wasn't broke was it?
or traded in a car for something else?
the old car wasn't broke was it?


and with cars sometimes you never know but by getting gears I have heard of some gaining gas mileage a little just because the motor is at a more efficient point

 

Gears, heads if you're looking for 10's, ditch the q-jet, get a holley (or some variation) with manual secondaries, bigger cam will help (it's roller right?). You're going to need spray or a lot of cam (and other stuff) to make it in the 10's.

As far as the rearend goes, break it, or remove something from it to make it seem like it's broken... lol

 

shouldn't be 2 hard to break, just beat the living **** out of it.. these little *** rears break like twigs, especially with a 5 speed.. just try not to break the 5 speed thats the tricky part...

 

A set of ET drags will work too, they're sticky.... Couple launches with those puppies and bye-bye rearend (and possibly tranny and driveshaft). But that would give you an excuse to upgrade to a TKO and a good shaft...

 

yup should be able to blow up that tranny n rear pretty ez with some good sticky tires

 

LOL you guys are horrible. Thats whack how you cant replace it. Id do it anyway. Its your money right....If its theirs I can see their point fo sure.

Nate

 

Sounds to me like Step 1 for you is to take responsibility for yourself, move out of your parents' house, and set your own rules about what can and can't be done to your car.

 

I know how ya feel. i can't swap something until it breaks. its will all come in time. if u wanna blow that rear end up. theres a few tricks to doing it. 1- weld the spider gears ogether. and then drain al the fluid. go do some dounts and a few days later she should go if not sooner. mine did.



but only do this if you have disk brakes in the rear. i had drums and didn't know about the c-clips.

no there a 4th gen rear end w/ 3.42's

i went from running a 14.9ish to 14.6ish
w/ some suspeion goodies i am know running a 14.4 w/ stock exhaust and 245 radials pulling 1.9 60' times



as for you. have that carb retuned for your 350 and get some 3.73's and a posi. that should drop ya into the 12.3 area

 

is that a 4th gen rear or is the rim not bolted to the car? i didnt realize they stuck out that far if it is.. defently gotta get new rims b4 i start that swap.. that just looks plain silly!

 

no, they aren't bolted up, you can see the rotor.

 

Uh, no. If you look closely, you can see the brake shoes still on the end of the axle. That picture illustrates what happens when a c-clip rear-end breaks..... The axles dont really wanna stay on anymmore...... Ooooops. Ouch.

 

correct. thats my car. the c-clip broke. and its a drum rear. that is the shoes you can see. and the rim is bolted on to the axle. It just happens to be that axle isn't really being held in place right. thanks to a broken C-clip

 

oh

 

If you need to kill the rear end, just drain the oil out and drive it.
I'd stay off the freeway and close to the house however.

 

ah cant see it on my puter, guess its the monitor it just looks black to me..

 

I've done this, at this point, the car is indriveable. Drain the oil, and do some donuts or something then drive for a few days. After this, you get a nice growl, and then some clunks. Now you're ready to take your parents for a ride so they will think you're crazy if you drive it around like that!!!

 

if you want them to thinks its broken just unbolt the rear sway bar let it drag on the ground it'll look broken.

 

if your car needs more gear, swap a T56 in, then put some nice gears... i wouldnt go any higher then 4.10s but i really liked driving with 4.10s.... and gas miliage isnt affected since the RPMs are as low or lower in 6th... and in the city, the gas miliage is based on how yuo drive.. just like before.


best of both worlds.. welcome to the modern age of overdrive.

 

if i do change the rear, id like to think that the car could be capable of low 12s or high 11s. but im gettin the feeling that many of you believe that my 356, doesnt have the go power??? is this a true statement? if so, im gunna need a little more help, and im gunna kick my engine builders A$%!!!! he told me that the block would put out between 360-380 HP... i thought that was plenty, seeing how the stock engine which was a lg4 had only 185, and was capable of 14.7 in the quarter in show room appearence...

 

eh, at best, mid 12s...

the lower the number, the harder it gets to drop a tenth.

whats your 60'? if its really bad, the gears/posi will help you out there...

 

ok heres an idea.
get a new carb like a 750 holley, and getca 125 N20 Kit. your also going to need some new tires(drag radials) and some gears. (3.55:1)

 

honestly, i woul dsuggest getting a holley or a demon carb (650 is fine), upgrade that manifold to a victor jr, and get some gear in the car...

you'll get better top end out of the car, seems how you have a decent sized cam as well, you would do fine with the victor... you'll lose some bottom end (the gears will help bring that back) but once you get that top ened power, your gonna be bootin yourself in the *** as to why you didn't go that route to begin with...

fist step would be to chaneg thew gear stho...

 

I'm just going to repeat what everyone else said basically. There was really no point in keeping the Q-Jet if you changed the manifold and you definitely need some gear. I'm running 4.10's with a posi. If I were you I'd go 3.73's with a posi. Oh, and a good way to not kill your car and still convince your parents is to tell them that the bearings on your rear are shot and need to be replaced or further damage could occur and while your in there you might as well change the gears and slap in a posi. If your parents aren't convinced I'll tell you what I did. Slide a floor jack under your tranny and jack it up a little. Just enough to break the tranny mount. This will cause the stick to shoot up in the car when you accelerate hard. Again say the bearings in the rear are shot so the gears are forcing your driveshaft forward and making the stick jump. In the case you'll need to change the tranny mount, I suggest going with a poly mount. Then you can get your gears.

 

thats not gonan drop him into the 11's. he runs a 12.9 right now. w/ a nice gear like 3.73's. that might put him into the 12.5ish area. w/ a posi and tires a low 12 is possible. then get a 750 holley and a 125 N20. that wil put him nicly into the 11's.

 

Matched parts make all of the difference in the world! Like everyone said, a new rear end, some suspension upgrades, a new intake (get a high rise dual plane...Holley makes a good one that is fairly inexpensive), a demon/holley carb and a tuning kit.

Oh, and in the mean time, autozone sells a spacer that will fit on a qjet...it's like 20 bucks and is an inch tall.

 

Does that spacer match the Q-Jet to a square bore manifold.

 

Does that spacer match the Q-Jet to a square bore manifold.

 

If you've got all this money why not EFI? You could get holley's 950 4bbl TBI setup and keep all of your carb parts. Throw on that Victor or a Team G you wont lose the bottem end because its not vaccum operated. Just a thought, if you're going to be switching out the quadrajet anyway. Only problem would probally be tuning.
my $.02

-chuck

 

I'm not sure if you said this, but whats your 60ft?

 

i dont have a 60' time, but ill check my slip to double check....just gotta find it now...

 

60' is 1.98

 

Yep, your gears are KILLING YOU. That and probably your tires. I would listen to everyone here. What you need to do is take a sample of your rear gear oil and show them it, adn tell them that it's too late for the gears. Say your going to get stock replacements and a posi to help you in rainy weather. Just my .02 Good luck!

 

lol --- i read every post reply to this guys post --- great info and please do get better gears , and having the qjet on that motor is just rediculous, enjoy what you paid for... spend a bit more for a nice carb

GL! and have fun

 

Gears Gears Gears, good *** man. Four simple steps. Step one pull rear diff cover off. Step two rip Spider gears out. Step three smash the hell out of the gears with hammer. Step four show to parents. These simple steps will not only give you the ability to do the gears but you will need a good Posi to help your self-made Spider problem. O and get rid of the Quadrajet, if you want a nice replacement go for the Edelbrock performer. A lot nice to deal with on a daily bassis than a Holley.