Fast Freddy

what was done by the factory to increase the power from a 91 to a 95 and how much do the parts cost to upgrade a 91 to 95 factory parts?

can a 700R4 or 4L60E auto trans be swapped into the car and what kind of shifter do you use?

pushrod-v8

Cylinder heads and camshaft timing and yes you can convert to an automatic transmission.

Fast Freddy

thanks 4 the info

FASTAZU

Post over n the http://www.zr1.net/forum/index.php one of our members has a ZR-1 converted to auto.

http://zr1netregistry.com/Marketplace/BuyersGuide.aspx

Crabs

As mentioned by pushrod V-8 the major differences are in valve timing, the heads and the intake area.
Another difference between the 91-95 was in '93 the block went from 2 bolt mains to 4 bolt mains (not that this affects the power any but it is a difference).

As far as cost, figure on $11-15k.
http://www.dragtimes.com/parts/1993-...147529061.html

It would cost far less to simply port/polish the top end of the '91 and a few other mods will get you well into the mid 400hp range without replacing the engine or breaking your budget.

As far as swapping the transmission, there have been a handful of ZR1's converted to Automatic using a standard shifter and console insert out of an automatic C4, but the big question is, WHY?

ZR1's really weren't designed to be drag cars if that is your goal, although they will turn very good times for a car of that vintage and weight.
The IRS becomes a weak link with lots of breakage if power is upped into the 600hp range. If you really hook up well on drag slicks you will be buying lots of axle hubs and rear end parts.

'Crabs

Fast Freddy

thanks 4 the info

That 4 bolt main versus 2 bolt main detail is a BIG one. as far as the top end goes i would just port the cylinder heads and put Bigger cams in, etc. a Bigger ci motor would be nice though and i would think whoever does those builds would prefer to have a 4 bolt main block. how much would a 4 bolt main block cost??

The auto would be nice to have in traffic up in Phoenix. i would not be racing this car.... it would just be another street car for me like my current vette

USAZR1

The bottom end on an LT5 is not anything like a SBC. So,not a big difference in strength between a 2 bolt & 4 bolt block. Both are pretty stout.

Fast Freddy

^^^^ - that is good to know

Crabs

If I were going to twin turbo or NOS a LT5 and money was no object I'd probably want a 4 bolt bottom end.
Otherwise, there are stroked 415ci LT5 with 2 bolt bottom ends producing north of 600hp that seem to do just fine.

'Crabs

Paul Workman

As stated, the 2 vs. 4 bolt comparison of the SBC does NOT apply to the LT5 in the same way.

The main caps are molded into an aluminum cradle that secures the caps, and the cradle too is subsequently bolted to the block around the periphery.

In addition to 415s, there are some 427 and 441 LT5s with the two-bolt mains that are making 700+ hp.

As for the 30 hp increase between 92 and 93, in addition to cam timing, the amount of taper in the head intake runners was opened from aprox 32.5mm (my 90/91 heads) to about 34mm at the small end (near the valve guide).

It's NO secret the LT5 in factory form is starving for air,evident by the near 100 rwhp that can be had by porting and headers alone; keeping the stock TB and cams! The point is, careful DIY porting erases any performance distinctions across the 90-95 MYs, AND all this performance comes without loosing any WOT midrange torque OR sacrificing any drivability! (Welcome to DOHC!) But, I digress...

scottfab

That is what I have been hearing over the years.
However, there is one advantage of the 4 bolt.
You get to say your engine is "4 bolt"
ooooooo cool.

Graybeard ZR1

But even coooler, is knowing that it doesn't matter

Anthony F

The world speed endurance records were done with a 2 bolt, I think it's good enough.

Rkreigh

Marc did a presentation and the 4 bolt design has smaller bolts and is only about 5% stronger. but since the 2 bolt will withstand almost anything up to 700 hp or more, it's really just "bragging rights"

that said, the later engines do have a bit better head flow, and cams and some other improvements in how the intake and injector housings line up, better designed injector housings (got rid of the big bump for the injectors) ect.

I like the 93-95 injectors too. they are alchy tolerant and don't break down with the "drunk" gas we run.

any of the lt5s are built like an anvil. super durable and very smooth.

Aaron71771

[QUOTE=Fast Freddy;1586430341 as far as the top end goes i would just port the cylinder heads and put Bigger cams in, etc. a Bigger ci motor would be nice though and i would think whoever does those builds would prefer to have a 4 bolt main block. how much would a 4 bolt main block cost??

[/QUOTE]

Porting, new cams, a bigger CI - your getting north of 25K for a turn key motor. Sure you want to go through with this with an LT5? You can build an LT1/LT4 to make lots of power for lots less $$$.

A 600hp ZR-1 is the stuff dreams are made of - but the price is pretty steep.

5abivt

Im curious to know why the change to 4 bolt ? Clearly there was a reason for it...

Dominic Sorresso

You're not getting 600hp out of an LT-1/4 motor without more cubes and an idle of ~900rpm. There are stock block LT-5s running 560chp.
A 380CID LT-5 is pretty inexpensive and would get you to 600chp w a civilized idle and mpg. Power and torque peak rims will also be significantly more elevated on the LT-5 w stock valve train.