Hello all,

I am new here, just signed up today actually. I have owned a 94 Camaro Z28 for a while now and finally spun a rod bearing my LT1. I am pulling the LT1 and building up a fully forged 383 with ported heads, big hyrdo roller cam, 4000 stall, and carb conversion with a demon 750 cfm carb...

I have sold the chassis of the Z28 to build up the motor, and plan to drop it into a 71-72 Chevelle... I just have a couple of questions for you guys regarding fitment, etc...

Question 1: Which option package came with the stock 12 bolt posi rear? What rear gear ratio came with the 12 bolt?

Question 2: Have any of you ever dropped a gen 2 LT1 into a Chevelle. I am looking to buy a nice set of coated long tube headers, but I am worried that they might not fit quite right. If anyone has dropped in an LT1, which long tube headers did you go with?

Question 3: I believe most (if not all) stock Chevelles came with the TH-350 transmissions. Did they have a different bell housing on the BB vs. SB versions of the car? Also, how long of a tailshaft did they usually have, the 4" or 9"?

Question 4: Closely related to the last question, this is another tranny question. I am going to be putting out about 450ish rwhp with this engine, and in the future I will probably be running a 200ish hp dual stage nitrous kit. What rebuild kit (part numbers would be great) should I get to beef up the stock TH-350's that came in the cars. I def want the 350 over the 400 cause of it's weight and better transfer, and also ease of bolting up in the stock location. Also, I have a 4k stall for the th-350 so it is my horse...

Any help would be greatly appreciated... Thanks for taking time to help out the noob... smile.gif

-Garrett

I can help a little, but not much. A 350 / 400 trans will bolt right up to both a BBC and SBC. The car could be had with 350 / 400 trans depending on the model, Malibu / SS. I THINK that the SS cars all came equipped with the T400/ 12 bolt rears, gear ratio may have been an option. I am fairly sure (here's me thinking again)that the short tail shaft trans for both the 350 and 400 is what your after. Both use the same trans frame cross member, its just located further back on the frame rails mounted in existing factory holes. I am sure somebody will come along shortly with all that info, lots of Guru's around here in that department. If your really gonna run 650 HP thru the trans and flog on it, I would consider a correctly prepped T400. Been there / done that with a propper T350 and fragged it with considerably less power than your forecasting. Better score a good after market drive shaft (Denny's is the kind) with some 1350 yokes and U joints as well. Oh yeah, while your at it plan on going thru the rear end, score a good posi, c clip eliminators, upgrade the stock axels, and upper / lower trailing arms and score the frame braces as well. See what you have started!!!!! You will have to chase that power all the way from front to back. IF you could get it to hook on some slicks, that power level WILL BREAK stock drive train componets. Sounds like a fun project, ENJOY!!!! graemlins/beers.gif

Oh yeah, I got to tell you this.........for what it will cost to turn that LT1 into that stroked fire breathing dragon, you could build a sure enough BIG BLOCK, thats what belongs in these cars :D :D :D

Originally posted by iwannaChevelle:
Hello all,


Question 1: Which option package came with the stock 12 bolt posi rear? What rear gear ratio came with the 12 bolt? The 12 bolt was standard with a big block and could be ordered on any other chevelle. Positraction was also an option.

Question 2: Have any of you ever dropped a gen 2 LT1 into a Chevelle. I am looking to buy a nice set of coated long tube headers, but I am worried that they might not fit quite right. If anyone has dropped in an LT1, which long tube headers did you go with?Direct bolt in, no problems. Jet Hot Hooker headers will do the job for you.

Question 3: I believe most (if not all) stock Chevelles came with the TH-350 transmissions. Did they have a different bell housing on the BB vs. SB versions of the car? Also, how long of a tailshaft did they usually have, the 4" or 9"?The powerglide was actually the standard tranny in most small block chevelles The TH350 was an option as was the TH400. The TH400 was put behind big block cars. Bell housings are identical. Tailshaft was of the short variety.

Question 4: Closely related to the last question, this is another tranny question. I am going to be putting out about 450ish rwhp with this engine, and in the future I will probably be running a 200ish hp dual stage nitrous kit. What rebuild kit (part numbers would be great) should I get to beef up the stock TH-350's that came in the cars. I def want the 350 over the 400 cause of it's weight and better transfer, and also ease of bolting up in the stock location. Also, I have a 4k stall for the th-350 so it is my horse...OK first thing first. The TH400 will hold up much much better than a TH350. 4K stall is way too much converter. I am running 510 HP at the flywheel on my 454 and only running a 2200 stall. The TH400 will bolt up just fine, all you need to do is move the crossmember back. The holes are already in the frame. You will need to have a tranny built to handle that amount of HP. A beefed up stock built tranny will break.

Hope this helps and welcome to the best site on the net graemlins/thumbsup.gif graemlins/thumbsup.gif

Thanks for the great info guys... smile.gif

As to the debate of 350 vs. 400, I'm still not decided. I have seen people running 750ish hp on built th350's with no problem, yet others have fragged with 400hp engines. I think it is all in the quality of the build...

As for the 4k stall. There is a lot more that goes into the stall choice than simply the amount of horsepower. Your BB makes a lot of torque down low, and therefore benefits from a lower stall such as the 2200. My current cam doesn't even start making much power until 3500rpms. The 4k stall will let me power break to about 2800-3000, which is right where I want it to hit the meat of my power. Keep in mind, I'll be spinning up to a 7000rpm redline... :eek:

The only true way to choose a stall is to get on the dyno and find out where the max torque point is... It's hard to do that when you are building the motor though... :D

Again, thanks for the input, and feel free to let me know if you come across any 71-72 chevelle chassis for around $2-3k... Paint can be ****ty, but I prefer that it have very little rust and no holes if at all possible... smile.gif Has to have an interior too... graemlins/waving.gif