I have a 71 350 270HP corvette. My brother-in-law has located a 396 and a 427 (L34 and L36, I think) that are in good condition. We (my brother-in-law and myself) are going to do a frame-off this winter on the car. What will be involved on swapping in a big block? I don't know witch one we will end up with yet. It depends on price and who will give up the motor. We will be lowering the compression, swapping the cam, and switching the intake to make it fit. I read in the Edelbrock catalog that the Torquer II will fit under the stock hood. My car has a TH400 and A/C. We looked last night and the car already has a 4 core radiator (A/C?) so we are thinking that we will need to replace the springs and worry about the intake clearence and brackets for the alternator, P/S, and A/C. Is there anything else that we will need to think about? I am planning to leave the 350 in the garage if I ever decide to sell (NOT!!). John is the head body man at a Ford dealership and has re-built at least four C3 vettes so I should be in good hands. I appreciate any input. P.S. Merry Christmas!!

 

P.S. I had a 1965 L37 396/425HP vette motor tracked down but the guy sold it this weekend before I could call him! Darn It! Rectangular ports, solid lifters, 780 Holley! Major bummer! Would have had problems getting the intake under the hood anyway. I do have a '69 302DZ motor located for $500 bucks! I might pick that up for fun! Don't know what I would put it in though.

 

Please, anybody? I know that the 454 came in the 71 vettes, so we shouldn't have any problems with engine mounts, but is there anything that is going to sneek up and bite us in the butt? Any input would be appreciated.

 

I think you may be looking at motor mount change, but since your doing restoration it won't be any big deal, as you should replace them even if you kept the 350. Other then that, I think you'll only be looking at changing the obvious things, like alternater brackets, and belts and hoses...I dunno about the tranny mating...I don't see why it wouldn't....Maybe bence will chime in, he is doing a BB swap, and is pretty well in it I think and knows what is involved.

Daniel

 

Thanks Daniel. Does anybody know if you need to change the springs? My springs are in good condition and if I can spend more on the engine.... Anyway, I will hopefully know witch engine I will be getting next week. I will be happy to have a big-block in the family!

 

Hey Josh, I am doing the same thing to my 71 this winter. I looked for a while and found a good 454 generation IV motor, built in 78 for GM trucks. It should be a real monster, four bolt mains, it has Merlin heads and Crane cam. My friend who works on vettes told me that the motor would be no problem to install. We are going with new motor mounts and new brackets for power steering and alternator. I have a Lakewood bellhousing that should be a perfect fit. The other items we are going to check over are the Muncie 4 speed and replace all of the driveline yokes and install a new rear sway bar, and new springs up front. The only other thing to do is hold on when I hit the gas!!! Good luck!

 

the springs...I dunno, perhaps. If you want to try to do it with the stock springs, and don't mind the work, do the car with those springs, and drop it down off the stands, then see how you like the stance. If you went with aluminum heads and intake, I'd say your ride height will be about the same. If you went with iron stuff, then it may be lower, but by how much I don't know. Anyway, you may find you like the lower stance....who knows.

Daniel

 

Thanks Daniel and Tom. Tom, have you looked at hood clearance issues yet? I have looked at a couple of different intake manifolds but the only thing that says that it will clear for sure is the Edelbrock torquer II for oval port heads. I wish that I could have gotten that 396/425 motor. Would have been cool to have a real vette motor in my vette! I will still make just as much power with the oval port motors with the cam that I am looking at (Comp. Cams Extreme Energy 268 Hydro), but the rectangular port heads would have been cool.

 

Having done a frame off resto on the car if you are worrying about the cost of a set of front springs you are going to be in for a surprise. redo the whole front suspension while you are there and put in a set of big block springs. Plan on twice the time and 3 times what you think you are going to spend and you will be close. I'm not trying to downplay it but a true frame off you should do front and rear suspension brake lines fuel lines and everything else while you are there. You should have no problem installing a big block in there. I'd go for the 427 more cubes more power. :cheers:

 

Planning on spending lots of bread. Just want to get an idea of what parts to order. I hope that I get the 427 too, but we will see! My wife is going to drive this car quite a bit, so maybe the 396 is the better choice after all. Ha,Ha! She had a 86 5.0 HO mustang when we met, so I told her that the 71 will have about 200 more HP and have alot less weight. I think that she is a little scared! She works for the local prosecuting attourneys office so at least we don't have to worry to much about tickets! If I check the numbers on those big-blocks and come back with anything good, I will let you know. Thanks for all the info you guys and Merry Christmas!

 

I ran your engine through desktop dyno (I am just having too much fun with this software) and came back with 475HP@6500RPM and 428LB@5000. I guessed that you had raised the compression to 9.5:1. Sounds like a monster!


[Modified by compuvette, 11:15 PM 12/25/2001]

 

Josh, I have a big block(LT-1) style hood now, so with my intake it should be ok for clearance. If not the L-88 style would be an awesome addition!!

 

Tom, came back with 450HP@5500RPM and 460LB@4500RPM with your combo. I assumed that you were running 9.5:1 compression as well. I plan on keeping the stock hood at this point. I can squeze the BB in there as long as I use the right manifold and air cleaner. Thanks for all your input guys. I can't wait to get that engine and start putting everything together!

 

I don't think the prev owner changed the springs in my vette, but like Dan said, aluminum intake and heads puts you close to the average sb weight.
Go with the 427 if you can. More potential, easier to find parts, and "it just sounds cooler". :yesnod:

 

motor mounts are the same for small and big blocks.

 

The assembly manual, not sure of the real name, has all of the different configurations in it. You do need the heavier springs for the extra engine weight. It lists all the brackets and layouts needed. It would be nice to have but not neccesary. You didn't mention it but I'm sure you know, the exhaust manifold.
I had a BB in mine with the stock hood and it cleared, I later added a BB scoop to the hood. Don't know the manifold its low and aluminum.
Also figure on hidden costs. Not just valve covers but nice glitzy valve covers, things like that.

The oval heads are good for the street, low torque. Thats why they made them. I would go with the 427 even if it means not getting the engine right now. Your doing a frame off - you have plenty of time to get an engine. Don't rush yourself because there are 2 right now.

On the engine program before you start believing what it pukes out. Punch in known engines into it and see what it says, then punch something, just one thing up on it- a large cam. Then compare what it says. It falls down in some areas but is still usefull if you know what it isn't capable of.

To my understanding a Vette engine was always high performance. Besides the usual stuff the cranks were whacked, if they rang they were hi po. If they thunked-cracked, they went into the Lo po motors.