Starting 350 V8 upgrade on 72 240Z-have questions

[Guest mondolog]

Upon studying what info. there is on the web about this conversion, I am seeing serious fabrication needed to the stock 240Z frame and undercarriage. My 240 still has solid front frame rails with no rust. Alabama car with only 80,000 original miles. Motor was missing, so I have decided to go to the chevy V8 conversion.

I plan on making mine a streetable car that I can also take to the dragstrip on Saturday night if I feel like it.

Can you guys give me any tips or actual usable info. as to how much and what kind of frame strengthening I will need to do to run a 355 V8 small block pushing about 325-350 HP with a turbo 350 auto tranny?

I plan to give the stock rear suspension a try before going to something different there also.

I was hoping to make some subframe connectors and get by with that plus possibly a 6 point rollcage.

Any help is appreciated, and I will try and document my progress with as many pics and details as possible as I go. I plan to do my own fabrication and work, so I plan to take my time and research this as much as possible before diving in head first, so to speak.

[strotter]

Although beefing up any part of the Z suspension and frame is a good idea, none is really necessary with a mild buildup like you're describing. Once you get up into the 425+ hp range, then it's time to think of subframe reinforcement as pretty much necessary, though a lot of guys don't bother. Why? Because the chassis can handle the horsepower in a straight line just fine; however, it's a noticeably flexible car as soon as you turn the wheel, v8 or no. Also, it's an old car, so any help it can get is desirable.

 

The weak spot, for higher-horsepower buildups, is the differential and/or half-shafts. There are a number of simple, easy-to-implement fixes possible (do a search here for "R200" and "half shaft"), and there are limited-slip units fairly easily installed. Also CV-type half-shafts. Again, not something you need to worry about with your setup, but not a bad project either.

 

It sounds to me like you haven't read the "JTR" book. Get it, read it, know it, love it. It will almost certainly answer most of your questions.

 

http://www.jagsthatrun.com/Pages/Datsun_Z_V-8.html

 

Also, you are *not* going to want to use a T350. Ratios are wrong for what rearends are available. Consider one of the newer OD autos, or a T-5 or T56 if you like manuals.

[Guest coolmesser]

yeah, what that guy said:

 

1. get the JTR book. best 40 bucks you'll spend

2. don't use the 350 tranny. do not. don't do it. did I mention don't?

3. go with the T-56 or the 700r4

4. while it is tried and true that you don't have to, I would still work on the back brakes and suspension. You'll find that the radiator will need a swappin', you'll need new headers, and you may need new fuel delivery.

[280zwitha383]

If you already have the 350 turbo throw it in there and forget what everyone else thinks about it. It's not ideal but it's not as hideous as some would have you think. On the other hand, if you don't have a transmission yet then I would agree, the 700-R4 is decent. If I had to do it again I would buy a 200-4R because of the closer gearing ratio between 1st and 2nd. IMO the 200-4R is the way to go with automatics in these cars.

[Guest mondolog]

My reasoning behind going with the turbo 350 tranny is twofold. One is that I already have it, and two is that I have a mechanic that can build it with all race parts and shift kit for $200.00 and has an excellent reputation in the local drag race community for his work.

On the beefing up of the frame under the 240, it looks like I will be doing the full blown 2x2 tubing from front to rear, since I just discovered late last night that the front subframe rails are both badly rusted out on the very bottoms of both front rails. Floorpans are also gone, so I guess my first part of the conversion has now been lined out for me. Its probably best anyways, since I may decide to go to more HP/Torque later on after I get the car back on the road. I thought I would try it mild first, since I would like to keep the car usable for an everyday driver also.

I have had many bad reports on 700r4's and auto overdrive tranny's holding up to higher HP engines, plus it costs much more to have one built, and the lock in converter deal bothers me too.

I have access to both 350 turbo trannys and 2 speed Powerglides. Which would be best from these two choices to start with in my project and still be able to drive it on the street with the stock 240 gears?

[Mikelly]

Something to consider is that a lot of these hipo failures with 700R4s have a lot to do with who set them up in the beginning. A lot of documentation has gone into correcting the TC Cable issue so most failures can be fixed before they become failures... Another thing to consider is that The Zcar is much lighter than most of the applications the 700R4 is being used in... I had a 700R4 in a low rider Full sized GMC truck with a cam and some boltons. We regularly towed well beyond the rating of the vehicle with no added coolers or work to the tranny and that truck was traded in at 290K+ miles on it. The tranny was the only thing that didn't require work.

 

A T-350 trans is going to push 55mph up in the 3K+ RPM cruising range depending on tire size.

 

Mike

[Guest mondolog]

I think I will try to find a 700R4 tranny in place of the TH350. I think I have one in an 85 Astro Van behind a 4.3L V6 engine. It was still in good shape when I parked the van from broke rings in the motor.

Has anyone found a type of radiator interchange that works well in these 240 conversions? I would rather shop my local junkyards and not pay out $300.00 or so dollars for the new ones offered for these swaps.

Also, are there any stock chevy manifolds that will work instead of going to the block hugger headers?

I am mounting my motor directly above the factory Z perches, which I believe is the more rearward mounting point for these conversions.

[Pop N Wood]

The stock radiator will work if you have it recored to a 3 row core. A number of members have run sucessfully that way. Saves the trouble of fashioning new mounts. Only real draw back is weight when compared to an aluminum unit.

[strotter]

"Has anyone found a type of radiator interchange that works well in these 240 conversions? I would rather shop my local junkyards and not pay out $300.00 or so dollars for the new ones offered for these swaps."

 

JTR manual, Ch. 12 "Cooling" including pgs 12-4, 12-6.

 

"Also, are there any stock chevy manifolds that will work instead of going to the block hugger headers?"

 

JTR manual, Ch. 14 "Exhaust" including pgs 14-1, 14-4, 14-7.

 

"I am mounting my motor directly above the factory Z perches, which I believe is the more rearward mounting point for these conversions."

 

JTR manual, Ch. 2 "Brackets and Motor Mounts", all.

 

Dude, we recommend people get the JTR manual to make *their* lives easier, not ours.

[Tim240z]

I think I will try to find a 700R4 tranny in place of the TH350. I think I have one in an 85 Astro Van behind a 4.3L V6 engine.

 

Those early 700s are notoriously weak, even behind the 6 in the van. Those are good vans, but suffered from the weak tranny. Just FYI....

[Guest z-ster]

Ok i've been reading and now iam wanting....what all do I need to change to make this 350 small block chevy work in my 78 280z 2+2..DO I really need to change tranny, drivshaft?? I know iam new but please give me some insight...

[Tim240z]

Ok i've been reading and now iam wanting....what all do I need to change to make this 350 small block chevy work in my 78 280z 2+2..DO I really need to change tranny, drivshaft?? I know iam new but please give me some insight...

 

Read some of the posts/suggestions above

[Here comes trouble]

Get the JTR Mamual.. It is essential anf if you are serious about a Hybrid Z it will be your most important expenditure . I have milled flanges cast iron GM "Rams Horns" which are now more expensive and harder to find than Summitts cheapo block huggers

[RPMS]

Ok i've been reading and now iam wanting....what all do I need to change to make this 350 small block chevy work in my 78 280z 2+2..DO I really need to change tranny, drivshaft?? I know iam new but please give me some insight...

 

Yes, you will need to change the transmission and driveshaft. There's no way on God's green earth that the stock Nissan transmission will bolt up to an American V8.

 

Aside from being a very good reference tool, the JTR book is interesting reading, too.