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Future big block swap?

Ed's 1970

Well-known member
Joined
Sep 17, 2006
Messages
87
Location
SoCal
Corvette
1970 Stingray coupe
Hello everyone,
I was thinking about swapping out the small block in my car with a built 540 big block gen VI motor (4.25 stroke, 4.50" bore), as my car is just a weekend hobby and not a daily driver. I am planning on using a gm bowtie block and all forged bottom end, hydraulic roller cam, mild aluminum heads. I am looking at 550-600 horse and tons of torque. Can the C3 handle the torque and what about the rest of the drivetrain. Is the big block too heavy for this car? It should be a bit lighter with aluminum heads. I did notice they sell an ZL1 aluminum block (it's only like 100 lbs), but it is over 4 grand just for the block. I am really intrigued with the big block lately, I don't know why. I really love my C3 btw, this car has great lines!
Thanks & Happy Holidays,
Ed
 

LVMYVT76

Well-known member
Joined
Apr 21, 2006
Messages
664
Location
springfield, mo
Corvette
1976 medium blue
Well they used to put big blocks in these cars, with steel heads. You might have to change the front springs to heavier springs. You should check all the welds on the frame to see if they have cracks, since you are putting alot more horse power in. I would be more worried about transmission and rear-end with the added horsepower.
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
The weak link in the driveline with big horsepower is the half-shafts and U-joints, especially with slicks; stock-size tires are an excellent safety valve to avoid driveline and underbody damage. :)



:beer
 

zachh

Well-known member
Joined
Aug 1, 2005
Messages
221
Location
virginia beach, va
Corvette
1979 black 'n' silver L82 1978 Trans Am Y88
I know a fella who put a 600 cu. in his 69, has a wieand blower also. He runs the stock driveshaft, 4-speed transmission, and rear end. He did have to put tougher springs in the front, but you can't even tell the difference.

Happy Holidays
zachh
 

Ed's 1970

Well-known member
Joined
Sep 17, 2006
Messages
87
Location
SoCal
Corvette
1970 Stingray coupe
TZ racer has done an incredible amount of work on that car! It kind of scares me about the time and money required at that level.

The 383 small block would be my other option. The big block itself is not all that much money, but everything else around it. There are so many things with this car, suspension, frame, exhaust, bushings, etc. It is a mechanically complex vehicle IMO. I can see the costs of this buildup skyrocketing.

Perhaps I should wait until I retire in about 14 years to work on this car. Hopefully there will be some gasoline left.
 
C

crebo

Guest
The big block swap definitely starts to add up. I went through it about 2 years ago. I had most of my work done in a shop in Costa Mesa, California. It was the bracketry and a few other mods that started to kill me. I ended up getting a L-88 cowl for the hood, new springs and shocks. I had to get a A/C compressor bracket fabricated. During that time I also changed my transmission. I purchased a 700R4 from Bow Tie Overdrives in Hesperia, Ca. All seems to be well so far.
Chris
 
V

vmrod

Guest
I too would vote for a souped up small block in leiu of a big block. These days, you can really trick out a 350 for a fair price. Also, if using the same engine, you can always advertise that the 'numbers match'.
 

Ed's 1970

Well-known member
Joined
Sep 17, 2006
Messages
87
Location
SoCal
Corvette
1970 Stingray coupe
Well you guys, I did some research on the big block parts. They are not all that much more than the small block parts, except the block and especially the heads. The heads are basically twice as much. I can build a 540 stroker big block for about $8500 in parts. This includes a GM gen VI bowtie block, good heads, roller cam, water pump, oil pump, oil pan, carb, manifold, valve covers. It doesn't include any of the brackets, pulleys, cooling system, suspension, or exhaust.

The small block fits better, I know that for sure. But, you can't beat the power or finesse of a big-block chevy. It is kind of like comparing a V6 with a V8. A 540 engine is 65% bigger than a 350. The engine I have in it now is not the original, but a factory replacement CE block. It probably is a 4-bolt main, forged crank and pistons. Good base for a 383 or 396.

I figure I will make this decision when the car chassis is restored hopefully sometime in the next couple of years. The frame has some moderate surface rust on it but looks fixable to me. The shell and birdcage appear to be in excellent condition.

If I restore the frame & suspension and put a new 540 in this thing, how much do you think it will be worth?
 

fine69

Well-known member
Joined
Dec 12, 2004
Messages
975
Location
Maryland / D.C.
Corvette
'69 Convertible Vette; '72 Z28 Camaro Rally Sport
"... I figure I will make this decision when the car chassis is restored hopefully sometime in the next couple of years..."

Ed,

That's a good idea to wait a couple of years.

If I remember correctly, you just got your Stingray this past Fall, right? My advice -- You should enjoy it and drive it for a while first (get used to the waves!)

It's easy to get over-zealous about restoring these cars. I did a full engine, tranny and front end restore -- took a brief respite --- and am now in the midst of restoring and replacing the interior, windshield, dash and electrical. I barely had a chance to enjoy the car over the past year or so, and I really should have waited on this particular phase of the restoration.

Ralph
:w
 

Jack

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Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Ed:
Once you're sure you're ready for a hi-po motor ... you have many options ... and exponentially more opinions of what's best. I'm a fan of conventional small block 400-based motors. However, I'm convinced that big-inch LSx motors are the future ... so is GM. GM just debuted their latest aftermarket LSX block at the PRI show a week ago ... ready for 4.25" bore & 4.5" stroke ... that's about 511" from what GM currently refers to as their "small block". BTW, World products offers similar LSx-based block & heads ... I think world calls theirs "warhawk LSx" ... also room for BIG inches ... also VERY light. FYI, even the tamest OE LS1 heads will outflow most any conventional sbc head ... even the hi$ AFR stuff. Also, a 427" LSx-based motor (ie LS7) is what powers the latest 505hp Z06 production vette. Anything LSx-based is MUCH, MUCH lighter & more compact than any of the BBC stuff. Suggest for no more than another $3K-$4K above your 540 plan ... you could build an injected big-inch LSX that'd probably walk away from the 540 while having superior driveability. BTW ... the GM rep who announced the big-inch LSX block at PRI said bare block should retail for between $2000 & $2500 with availability in late March 2007.
 

Ed's 1970

Well-known member
Joined
Sep 17, 2006
Messages
87
Location
SoCal
Corvette
1970 Stingray coupe
Hi u guys,
I think I am sold on the big block, gen VI. This is the same type of block used for the 572. I want to keep it simple with a carb and not fuel injection (for now). I believe the large big block will not be stressed like a small block at higher power levels and be more durable. The only downside is it takes more fuel and is about 100 lbs heavier, that's okay the big torque curve will take care of that extra weight no problemo!

They've done test of small block vs big block with equal displacments, like 454, and the small block won due to less reciprocating weight and less friction. But, the big block has way more potential for power if the cubes go up beyond 454, like 496, 540 or 572 whereas the small block has been maxed out. Jack I like the LS engines, I have one in my truck, the 345 horse LQ9. It runs great, I just wanted to have something different for the corvette.

I have the bottom end pretty much figured out. The top end there are so many choices. Rectangular or oval port Edelbrock, dart, gm, afr heads. The cam not too aggressive, a hydraulic roller cam with good to fair idle characteristics. Any suggestions on the heads and cam? Looking for about 550-600 horse and 600 tq with about a 9.5-10.0 compression ratio. I was thinking about getting the zz502 cam, it's 224/234 with 527/544 lift. I may use the newer beehive springs, heard they work great. Intake manifold, edelbrock rpm air-gap. Carb either holly HP or speed demon 850 cfm. I can always easily change out the manifold for a single plane if the dual plane ain't enough.

Thanks and happy new year!
 

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