New Member with Big Block questions

[silver69stingray]

New member here, owner of a '69 cortez silver/black convertible, 350/350 non-original motor, factory sidepipes, aftermarket a/c. Hello to all.

Trying to plot out a small block to big block conversion. Have it tentatively narrowed down to the GM 454 w/ aluminum heads, which is the upper limit of what I wanted to spend(about 5,600 plus tax/shipping, and misc.). Wondering if anyone has any suggestions for other big block long block or crate packages that may be better or more affordable. Will not be doing the work myself.

Thanks for any suggestions,
JC

 

[Bob Chadwick]

JC,

I can't comment on the big block itself but make sure you have money budgeted for the springs and other front suspension components associated with the heavier weight of a big block.

And welcome to the CAC.

 

[silver69stingray]

Thanks Bob. I'm figuring in several other things that I'm going to do during the conversion, so I'm expecting it to be a rather large investment. This is one of the reasons I want to make sure I'm making the right choice for the engine itself. As far as the springs go, I've learned that the weight difference between my 350 w/ iron heads and the GM 454 w/ aluminum heads is about 100 lbs.

 

[Billybeau1]

They didnt start putting 454's in until '71. Not that this matters but it would be sweet to find a 427 to make it closer to original. Just my .02

 

[Billybeau1]

Also since the existing motor is non-original, did you check the vin# to see what was in it in the first place?

 

[lnirenberg]

If your going non-original motor, you might consider a small block/large displacement motor for the weight advantage and spend any savings from BBmotor & required suspension mods on a nice tremac 5 spd--a lot of low end grunt helps leverage the ponies and torque of the motor and less wear and tear at highway cruisin' speeds and about the same weight as an OEM 4 spd.

 

[silver69stingray]

Thanks for the input guys. These are all things I've gone through in my head. A 427 would be nice, for sure, but unfortunately GM only makes the 454 crate. Saw some 427 long blocks floating around on ebay and on the websites of other vendors but I'm a little skeptical. If there was a good 427 out there with that I can trust for the same price or less I would take it. I thought about many other options, including supercharging, stroking to 383, and rebuilding the 350, but I am really interested in doing a big block. Plus when I started pricing things out, the labor really started to add up. I was raised-up on a very tame '86 automatic coupe so the sound and feel of a big block is something I want to experience.

Originally the car came with a 350/350 but it's long gone now. If I had the original motor there would be no question that I would just keep it and do a correct resto. But this is not what I was looking for in a car. As far as my long term plans go, I'd like to stay as original as possible and keep the 4 spd.

Also, it already has the big block hood which cuts down significantly on the complexity of the conversion as a whole.

 

[Paranoid]

They didnt start putting 454's in until '71. Just my .02

1970.

I started from scratch with an '87 454 block. Only parts I kept was the crank, connecting rods and balancer, everything else is new. Here's some info from my site: http://temp.corvetteforum.net/c3/themoneypit/index9.shtml Don't know about you, but I wouldn't be able to tell the difference between a 427 & a 454 visually.

Highly recomended.:blue:

 

[Jack]

JC: I'm guessing you're talking about the 440 HP ZZ454 GMPP P/N 12498777. If so, and you want a BBC, I think it's a good choice with good value. This motor uses a 1-piece (one) rear main seal ... meaning it has the late 1-piece-seal crank. Keep in mind those cranks WILL NOT bolt/mate to earlier flywheels ... end of crank is made different ... you'll probably have to get another flywheel if you're gonna run a 4-speed trans. Also, this motor has a pretty stout camshaft ... your 69's headlights/wiper door/HVAC-Astro vent doors need more vacuum than NON C3 ... big cam means small vacuum.
JACK:gap

 

[Billybeau1]

1970.

I stand corrected..... Had a brain cramp

 

[early shark]

Actually as far as weights goes, there is only a 82 lb difference between the 1971's ZQ3 (270hp/350cid) and LS-6 (425hp/454cid). There is only a 20 lb difference between LT-1 and LS-6.

 

[Hib Halverson]

I don't dispute any of the weight information, but what's the source of that?

 

[early shark]

Hib:

This information I garnered from the GM packet sent to me concerning everthing to do with the 1971 Corvette model year.

1971 Corvette specifications by Engineering Product Information Department, Warren, Michigan. Section 3 heading POWER TRAINS, Vehicle Performance Factors, page 4.


Performance weight (pounds) = Curb Weight plus 300 lb (weight of 2 150lb passengers)


Base RPO LT-1 RPO LS-5 RPO LS-6
350 CU IN 350 CU IN 454 CU IN 454 CU IN
270 HP 330 HP 365 HP 425 HP


4spd transmissions

3592lbs 3654lbs 3812lbs 3674lbs

 

[Koop]

New member here, owner of a '69 cortez silver/black convertible, 350/350 non-original motor, factory sidepipes, aftermarket a/c. Hello to all.

Trying to plot out a small block to big block conversion. Have it tentatively narrowed down to the GM 454 w/ aluminum heads, which is the upper limit of what I wanted to spend(about 5,600 plus tax/shipping, and misc.). Wondering if anyone has any suggestions for other big block long block or crate packages that may be better or more affordable. Will not be doing the work myself.

Thanks for any suggestions,
JC

I put in the ZZ383, all of my Vacuum operated systems still work properly and it went in with no modification. I did have to buy deep groove pullies and an intake manifold. The stock quadrajet was rejetted and Thorly Headers went in, electronic ignition conversion, the ignition housing won't bolt right on (you don't need it with the electronic ignition) but I'll get it on there soon enough. I think I'm going to try some steel brake lines as the stock brakes are no longer enough to handle the additional power.

425 Horsepower 460 pounds or torque, it's a monster! It'll beat the snot out of my CTS-V unless there's corners or braking involved.

 

[silver69stingray]

That's great info about the weight difference, especially since the other motor I'm considering is from Precision Engines, 427 ci, 390 hp, and about 2 grand less than the GM motor, 1 year unlimited mile warranty, and with iron not aluminum heads. What I like about it, besides the price, is that it's both factory correct displacement and hp for a base big block in '69. Not that big of a deal but it does influence my decision a little. As far as springs, with the GM 454 with aluminum heads I've heard that some guys get away with stock SB springs, but with this other motor I'll have to upgrade.

 

[Vettehead Mikey]

I think I'm going to try some steel brake lines as the stock brakes are no longer enough to handle the additional power.

Huh? The original brake lines are already steel.

 

[Paranoid]

That's great info about the weight difference, especially since the other motor I'm considering is from Precision Engines, 427 ci, 390 hp, and about 2 grand less than the GM motor, 1 year unlimited mile warranty, and with iron not aluminum heads. What I like about it, besides the price, is that it's both factory correct displacement and hp for a base big block in '69. Not that big of a deal but it does influence my decision a little. As far as springs, with the GM 454 with aluminum heads I've heard that some guys get away with stock SB springs, but with this other motor I'll have to upgrade.

You can put any HP/TQ stickers you want on any BB.. I saw a C1 with a 454 installed and the owner had the huge valve covers re-worked to incorporate 327 labels etc.

Funny thing, people walking by, believed it. :L Is that really a 327? :W

 

[Koop]

Huh? The original brake lines are already steel.

I thought there were some short sections of rubber...I guess that won't fly then.

 

[Vettehead Mikey]

I thought there were some short sections of rubber...I guess that won't fly then.

There are short flex lines that go from the frame to the wheels to allow for suspension movement, but there is no advantage to using anything else. These rubber lines do not reduce or modify braking force in any way. Remember that GM put the same brakes on all Corvettes, including the 500+ HP L88. The stock config. is still the best around

 

[Koop]

There are short flex lines that go from the frame to the wheels to allow for suspension movement, but there is no advantage to using anything else. These rubber lines do not reduce or modify braking force in any way. Remember that GM put the same brakes on all Corvettes, including the 500+ HP L88. The stock config. is still the best around

Thanks for the info,

I called my mechanic and informed him that "I need more brakes on this sled". I think a 15-20%% increase would get me to safe, he told me there are some new pads that just came out and he tried them and had great results on another customers car with the same complaint. I don't want any big visual mods, I like the car to look pretty much stock.

We will see.