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Topic: Big Block swap help

in Forum: C3 Engines

Big Block swap help

Posted: 5/2/04 5:04pm Message 1 of 9
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HOUSTON, TX - USA
Joined: 11/15/2002
Posts: 296
Vette(s): 1976 L-48 coupe
I am considering an engine swap on a '76. SBC 350 out, BBC 454 in. What are some of the items I need to be aware of concerning mounting, exhaust, starter, water pump, etc? What items are interchangeable?
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Big Block swap help

Posted: 5/2/04 8:43pm Message 2 of 9
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Hot Springs, AR - USA
Joined: 4/24/2004
Posts: 3236
Vette(s): 69 Conv #'s match 427, TKO-600/.64, 3.36HD-Posi, HT, T/T, PS, PB, PW, SP, Leather, Comp XE264HR & Roller Rockers & Lifters, Air-Gap RPM intake, Holley St Av 770 VS, MSD 6AL+Dist+Blaster SS, K&N, Jet-Hot Hooker Side-Pipes, Steeroids, Al Rad, Spal Fans
Ive never swapped a SBC for BBC in a vette. Your direct engine accessories will need to be replaced. (exhaust manifolds, water pump, intake etc) but you can keep your distributor as it is the same in BBC as SBC. make sure you use a correct "corvette" oil pan. get the gm ls7 pan from gmpartsdirect (part #14091356). be sure to get the windage tray studs too if your block doesnt already have them.

also be prepared to have NO room under the hood..

in fact you need to be very mindful of intake/carb clearance. without a BB hood ... there isnt much room for a carb and a decent intake.


Big Block swap help

Posted: 5/2/04 8:46pm Message 3 of 9
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Hot Springs, AR - USA
Joined: 4/24/2004
Posts: 3236
Vette(s): 69 Conv #'s match 427, TKO-600/.64, 3.36HD-Posi, HT, T/T, PS, PB, PW, SP, Leather, Comp XE264HR & Roller Rockers & Lifters, Air-Gap RPM intake, Holley St Av 770 VS, MSD 6AL+Dist+Blaster SS, K&N, Jet-Hot Hooker Side-Pipes, Steeroids, Al Rad, Spal Fans
also... the radiator needs to be beefed up


Big Block swap help

Posted: 5/2/04 8:48pm Message 4 of 9
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Hot Springs, AR - USA
Joined: 4/24/2004
Posts: 3236
Vette(s): 69 Conv #'s match 427, TKO-600/.64, 3.36HD-Posi, HT, T/T, PS, PB, PW, SP, Leather, Comp XE264HR & Roller Rockers & Lifters, Air-Gap RPM intake, Holley St Av 770 VS, MSD 6AL+Dist+Blaster SS, K&N, Jet-Hot Hooker Side-Pipes, Steeroids, Al Rad, Spal Fans
and stay away from "universal" brackets for alternator and power stering.. try to get "real" brackets for a earlier model vette


Big Block swap help

Posted: 5/2/04 8:54pm Message 5 of 9
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MEDINA, OH - USA
Joined: 1/30/2003
Posts: 111
Vette(s): 1977 dark red,buckskin int. 355small block ,built
Owen; what happened to the blower motor??


Big Block swap help

Posted: 5/3/04 5:05am Message 6 of 9
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Frederick, MD - USA
Joined: 9/8/2003
Posts: 3398
Vette(s): 1969 convertible L71 427/435 4-speed black interior
You'll likely need to replace the front coil springs with those rated for the heavier engine, as well as front and rear sway bars like factory big block cars did.


Big Block swap help

Posted: 5/3/04 5:57am Message 7 of 9
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HOUSTON, TX - USA
Joined: 11/15/2002
Posts: 296
Vette(s): 1976 L-48 coupe
Thanks for the input. I am having problems with the blown 350. I suspect a cracked block but won't know until later this week. I have a fresh 454 available and am considering a swap if the sbc is trashed...

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Big Block swap help

Posted: 5/3/04 7:12am Message 8 of 9
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Joined: 6/16/2003
Posts: 252
I would stay away from the BBC in a Vette unless you are just dying to have one. 1) W/ SBC the weight distribution is very close to 50/50 2)Unless you mod the hood you have to use an intake that is practically a valley 3) Cooling is much more an issue than a SB car 4)Pulleys and brackets are not cheap for this swap. 5) Probably have to change front springs. 6) Harder to work on than a SB. 7) Have you priced exhaust manifolds? $500+ for good repros or use headers

I would swap in late model fuel injection. Lot more bang for your buck. TPI is easy (that's what I have), LT1 is not bad, LS1/6 is more difficult, but not impossible. See www.corvettefaq.com The TPI can use existing exhaust, accessories, etc.


Re: Big Block swap help

Posted: 12/7/18 12:04pm Message 9 of 9
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chesterfield, MI - USA
Joined: 2/16/2015
Posts: 34
Vette(s): 1979 L48 Auto red on red 1971 Coupe 350 auto 1970 454 4-speed Coupe sold 1977 350 auto sold
I am also converting my 1971 Coupe from 350 auto to 454(468) 4-speed. Mine is a project car I bought without an engine or trans so my expenditure will be close to just restoring her with the 350 auto or darn close. Anyways, nobody has mentioned drive line issues such as trans slip yoke, differential yokes(3) and half shafts. I have 454 half shafts already but now have to contemplate issues with small block standard yokes and drive shaft(s) I have a 4-speed drive shaft so I think thats fine and my input yoke on the differential is fine. My Muncie M21 I have is a 27 spline output and I have a yoke for that, GM standard slip yoke, but wonder if I have to go beefier on that. I do plan on heavy duty u-joints all around. This 454 has been bored .60 over and I want to use a cam just 2 steps over a stock 70 LS5 spec. Holly 750 and performer intake. I wouldn't think my horsepower and torque will end up crazy or even close. I hoping for around 425 h.p. and 450 ft/lbs.


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