Vortec 7400 - Chevelle Tech

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post #1 of 7 (permalink) Old Jul 18th, 07, 1:40 PM Thread Starter
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Vortec 7400

I have a few basic question on late 90s 454s and am rather new to big block as most of my experience is with LT1s and LSx motors. Craigslist and some other places have had these motors relatively cheap.

Originally I had thought about buying a ZZ454 or 502 as I wanted a hydraulic roller 1 piece rear main seal BBC. However, the oil consumption and other issues have me thinking I could rebuild a Vortec motor and add some Brodix RacRites, small AFRs etc and be better off.

How much overbore will the Gen Vs take?

I assume the motor mounts are the same as my 396?

Does an externally balance BBC have a neutral balanced flyweel?

Will a flywheel off a LT1 T56 bolt on to a Gen V motor? I want to use the the hydraulic clutch setup and LT1 T56.

I have been lurking on here for years and most of the T56 topics I see are swapped on to 2 piece rear main blocks.


Thanks,

Lamar
93 Corvette Polo Green ZF6 13.4@105 Koni SA, GS Brakes Gone
00 FRC C5 H&C (TEA Stg 2 5.3 truck heads & Futral F11 228/230 112+4), 436rwhp 415rwtq 04 Z06 Suspension, MovIt Brembo Big Reds
70 Chevelle SS396 Green on Green
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post #2 of 7 (permalink) Old Jul 18th, 07, 2:09 PM
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Re: Vortec 7400

Quote:
Originally Posted by 93Polo View Post
I have a few basic question on late 90s 454s and am rather new to big block as most of my experience is with LT1s and LSx motors. Craigslist and some other places have had these motors relatively cheap.

Originally I had thought about buying a ZZ454 or 502 as I wanted a hydraulic roller 1 piece rear main seal BBC. However, the oil consumption and other issues have me thinking I could rebuild a Vortec motor and add some Brodix RacRites, small AFRs etc and be better off.
I have heard--but not verified--that the Vortec 7400 is a very weak block by big-block standards.

Quote:
Originally Posted by 93Polo View Post
How much overbore will the Gen Vs take?
I've heard "no more than .060" but a sonic test would tell that story.

Quote:
Originally Posted by 93Polo View Post
I assume the motor mounts are the same as my 396?
Yup. But no fuel pump boss; and you better check to see if the boss for the clutch cross-shaft has been drilled 'n' tapped.

Quote:
Originally Posted by 93Polo View Post
Does an externally balance BBC have a neutral balanced flyweel?
Nope. In fact, there are two different external-balanced flywheels, one for engines with a forged crank, and one for engines with a cast crank. I don't know if EITHER of these is the same as the old MK IV external-balance flywheel.

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Originally Posted by 93Polo View Post
Will a flywheel off a LT1 T56 bolt on to a Gen V motor? I want to use the the hydraulic clutch setup and LT1 T56.
Nope. Smaller bolt circle on '86 and newer small blocks.
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post #3 of 7 (permalink) Old Jul 18th, 07, 2:14 PM Thread Starter
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Re: Vortec 7400

Thanks for the info

Lamar
93 Corvette Polo Green ZF6 13.4@105 Koni SA, GS Brakes Gone
00 FRC C5 H&C (TEA Stg 2 5.3 truck heads & Futral F11 228/230 112+4), 436rwhp 415rwtq 04 Z06 Suspension, MovIt Brembo Big Reds
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post #4 of 7 (permalink) Old Jul 18th, 07, 2:23 PM
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Re: Vortec 7400

I’m currently building one right now, and I think these blocks are awesome deals. I paid $500 for my long-block (less intake), with 30k original miles. Roller cam, 4 bolt mains, efficient (though not high flowing) heads. I think these things are gold-mines for the price.

Anyhow … typically expect to pay closer to $1000 for a running long block. Up to ~$1500 with intake, PCM harness. And remember just about any time you look at a used motor, not in it’s original vehicle … something is going to be wrong. Very few people pull motors out just for fun. My advice is any used motor should be torn down, with at least rings/bearings replaced. Possibly the oil pump too.

The pistons are out of mine, and quite honestly I still can’t tell if they are low tension rings. I do know a number of these on the road, that have none of the oil-consumption issues the ZZ-motors have. So I think we’re safe there.

Head replacement is an excellent choice, except there’s an issue with the pistons. Stock Vortec’s are flat-top pistons, 9:1 comp, 100cc heads. Most any aftermarket head will knock your compression to nothing! Head replacement is most likely going to need new pistons too.

The heads themselves are questionable for performance. I’ve had my motor since 2000, and have yet to ever find flow numbers. I would suspect them to be very low compared to a performance head. I still have faith they will be able to do ~380-400hp. Long duration cam swaps are advisable.

Overbores are a touchy subject on just about any late-model block. I’d feel comfortable at .030”, but nothing more.

Motor mounts are the same as earlier BBC’s. However … you will most likely have to drill/tap for the 4spd clutch pivot, and there will be not place for a fuel pump. You’ll have to set up an electric fuel pump.

Flywheel for Gen5/6 motors are special. No production 454ci is neutral balanced, and the 1pc real seal requires a different flywheel than older motors.

The flywheel isn’t what you’ll want to be concerned about on a T56/hydraulic swap. You’ll still pick up a Gen6, 11 or 12” flywheel. Where you’ll be concerned with the hydraulic setup is in the pressure plate and throw out bearing.

Oh well, have fun.
Neal
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post #5 of 7 (permalink) Old Jul 18th, 07, 2:56 PM Thread Starter
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Re: Vortec 7400

I was leaning towards a setup along the lines of what this member was plannig.

bbc 461
race rites
compression ~ 10:1
voodoo 60212 hydraulic roller
single plane mpfi manifold
stock gm crank stuff but bal

454 combo hp/tq estimate

I would most likely add some decent aftermarket rods and might go a little bigger on the cam. A BBC chevelle is supposed to lope Yes I do know more cam is not always better. I have read plenty of the 496"+ topic with hydraulic rollers but the little motors do not get as much discussion. My ideal goal would be 550-600 hp which maybe stretching it for a hydraulic roller 454.

I found a few motors like what you have no intake/ecu for $800 in a quick search. I had wanted to run efi most likely a Holley Commander but the verdict is out on that.

The LT1 T56 hydraulics should not be a big deal as plenty of the LS1 swap guys are converting over. I had really thought about a LSx based motor but nothing looks like a BBC. The LS1 and LT1 master cylinders are very close in design and using a factory style flywheel clutch would make for a clean easy swap.

I have posted up on the McLeod forum asking about clutches so I may decide to go with a 2 piece rear main, since I can not directly swap in an entire LT1 clutch system. My last project ran a McLeod twin disk which I loved and handled ~525 flywheel hp in a C5 without a problem. We'll see.

The plan for the car is to take it in more of the power-touring/nice cruiser direction. I do not plan to track the car but handle, brake, and cruise like a newer fbody. It may go down the dragstrip a few times but nothing serious.

Lamar
93 Corvette Polo Green ZF6 13.4@105 Koni SA, GS Brakes Gone
00 FRC C5 H&C (TEA Stg 2 5.3 truck heads & Futral F11 228/230 112+4), 436rwhp 415rwtq 04 Z06 Suspension, MovIt Brembo Big Reds
70 Chevelle SS396 Green on Green

Last edited by 93Polo; Jul 18th, 07 at 3:08 PM.
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post #6 of 7 (permalink) Old Jul 18th, 07, 4:54 PM
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Re: Vortec 7400

93Polo,

Your biggest obstacle for the BBC?t56 swap is the use of the Gen V/VI blocks externally balanced flywheels that have a different balance than the Mk IV. AFAIK, no one makes a flywheel that will allow you to mate it to the LT1 style T56.

I know that jakeshoe posted a BBC/T56 swap using a stock pull type clutch over on http://nastyz28.com/ a few years ago. You could do a search over there. The other alternatives become more expensive:

1) Weir makes an aluminum bell housing / hydraulic clutch actuator that will work with the Mk V/VI, check at http://www.weirhotrodproducts.com/. This will allow you to use the LT1 T56 and the Gen V / VI flywheel and clutch assembly.

2) MacLeod Industries makes bell housing / adapters that can be used with the Gen V/ VI, not cheap though. Check at http://www.mcleodind.com/

3) If you got a good deal on the Mark IV engine and if you could get it internally balanced, both steel and aluminum neutral balanced flywheels are available from different manufacturers to mate an LT1 T56 to a BBC.

I'm sure there are other options available, but the above are a few that I can remember. I will be running a BBC with a LT1 T56 using a Fidanza aluminum flywheel and a SPEC stage 3+ clutch. Just got to get it all bolted together!

John
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post #7 of 7 (permalink) Old Jul 19th, 07, 1:57 PM Thread Starter
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Re: Vortec 7400

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Originally Posted by TD509EFI View Post
93Polo,

Your biggest obstacle for the BBC?t56 swap is the use of the Gen V/VI blocks externally balanced flywheels that have a different balance than the Mk IV. AFAIK, no one makes a flywheel that will allow you to mate it to the LT1 style T56.

I know that jakeshoe posted a BBC/T56 swap using a stock pull type clutch over on http://nastyz28.com/ a few years ago. You could do a search over there. The other alternatives become more expensive:

1) Weir makes an aluminum bell housing / hydraulic clutch actuator that will work with the Mk V/VI, check at http://www.weirhotrodproducts.com/. This will allow you to use the LT1 T56 and the Gen V / VI flywheel and clutch assembly.

2) MacLeod Industries makes bell housing / adapters that can be used with the Gen V/ VI, not cheap though. Check at http://www.mcleodind.com/

3) If you got a good deal on the Mark IV engine and if you could get it internally balanced, both steel and aluminum neutral balanced flywheels are available from different manufacturers to mate an LT1 T56 to a BBC.

I'm sure there are other options available, but the above are a few that I can remember. I will be running a BBC with a LT1 T56 using a Fidanza aluminum flywheel and a SPEC stage 3+ clutch. Just got to get it all bolted together!

John
It looks like McLeod has a twin disk that will work with flywheels for either 1 or 2 piece rear mains externally balanced but I will need a LS1 T56. I have seen the Weir belhousing before but I had rather go with a McLeod steel adapter as I have had an input shaft snap before.

Good luck on your project, sounds like a fun ride.

Lamar
93 Corvette Polo Green ZF6 13.4@105 Koni SA, GS Brakes Gone
00 FRC C5 H&C (TEA Stg 2 5.3 truck heads & Futral F11 228/230 112+4), 436rwhp 415rwtq 04 Z06 Suspension, MovIt Brembo Big Reds
70 Chevelle SS396 Green on Green
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