396 in a 81 vette

J

jayhawkvett

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Jul 2, 2010
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Location
kansas
I`m looking for any help i can get.I have a 81 vette and i resently bought a 396 325hp with a fresh rebuild.I have lots of questions,but just a few for now.I have 350turbo in the car now which i`m going to have rebuilt and use with the 396.Would it be best to pull both engine and trans. together or no?Also does anyone know if the big block mounts will bolt up to the same holes in the frame as the 350? thanks for reading, and any advise you guys may have.
 
I alwyas pull them together, I hate getting to those bellhousing bolts with it all in the car.

It will all bolt up.
 
jayhawkvett said:
I`m looking for any help i can get.I have a 81 vette and i resently bought a 396 325hp with a fresh rebuild.I have lots of questions,but just a few for now.I have 350turbo in the car now which i`m going to have rebuilt and use with the 396.Would it be best to pull both engine and trans. together or no?Also does anyone know if the big block mounts will bolt up to the same holes in the frame as the 350? thanks for reading, and any advise you guys may have.
Click to expand...

The stock tranny is a 350C. You may not like that if that is what you are going to use..
 
C = lockup converter. Still a TH350, just w/ added lockup

400 is not a guarantee either, I killed 2nd gear w/ a 355 in my truck..it's still going strong in 1st -> 3rd though....gotta give it that. Been like that for a couple of years and thousands of miles :D
 
The motor mounts off of the 350 will bolt onto the 396 and then you can drop it onto the mounts from there ... no problems .... are you going to use headers ... i have used hookers and you have to dent one tube to clear the power steering gear box... now the accessory brackets and pulleys are a pain ... my suggestion is order a march serpentine kit and use a alternator off of a 88 or newer gm truck ... especially if you are going to keep the air conditioning ... also you may have to do some glass work on the AC plenum ... not sure about this one ... my 79 has no air conditioning. I used a non lock up th350 behind a healthy 427 for a lot of years and never had a problem ... i recommend installing a transgo shift kit if your trans is in good shape .... don't cheap out on a lock up converter ... i learned that the hard way ... buy a good!!! lock up 2500 stall converter .. that way you have some room to play with cams, if your 396 has the stock 325hp cam in it --- change it now, its boring and a 268 or 270 comp cam will wake that engine up nicely ... and last but least talk to gtr1999 (Gary) about rear ends. You will break that before you brake the transmission.
 
Thanks for the help

I do plan on using headers.it is the stock cam and i have a call into the guy that built the engine reguarding the bigger cam. thanks.
 
Also what intake manifold are you going to be using? ... What hood are you using? ... you might run into trouble there ... I used an old TM2-R, holley 850 with a LT1/L88 air cleaner on a stock 79 hood .. I think the 80 hood is a little lower yet .... you should be ok with the stock iron low 396 manifold .. but watch for this ... you might be looking for a hood also.
 
also in regaurds to changing the cam there is a issue with the cam bearing on early 396's. You should check this on your engine before you install your motor ... i have seen a non groved cam and bearing in a early 396 ... lifters always rattled was the first tell tale ... I always check this on 396s now ... some engine builders just don't know ... you will need new valve springs if you chnage the cam ... I always put new valve springs on a new build anyway ... but some people are just plain cheap and they reuse old spings.

http://www.hotrodders.com/forum/396-cam-bearing-140206.html
 
I did a big block conversion on my 81. Everything fits, though it is a little tight with the headers particularly next to the steering box. I used Headman coated full size (long tube) headers. I also used an aluminum radiator with dual electric fans, and here in Florida, it keeps the engine right at about 200 degrees with the AC running, and in traffic. I used a serpentine belt drive system that was adapted from a chevy V6, (BBshark was a GREAT help on that!) so everything lined up really well.

I'm running a GM Performance intake, you can find low profile intakes, but to get the most out of your engine build, you may find it a challange without going to an intake that's too tall for the stock hood. Using the stock hood has been done before, there's some info on this sight I remember seeing. I went with an L88 style hood for the clearance and because I really like the way it looks.

I decided to run the factory Q-Jet electronic carb (I like Q-jets and decided to use the original set up cause sometimes I'm too stubborn to know better!) and computer controlled HEI. As a side note, it worked really well until a few weeks ago when the carb started really giving me problems, troubleshooting showed the issue to be the ECM, so now I'm waiting for one of those.

I put a 2004r trans behind because I like the gear ratios in that trans better than the 700, but either if built right would be good choice. There are modification for each that would have to be done, the 200 can use the same drive shaft, but needs a different or significantly modified cross memeber, the 700 needs a shorter drive shaft and the cross member needs to be modified too.

I swapped the rear end to an iron unit (the original 81 is aluminum and anyone on this site will tell you it's not if but likely when it'd fail with a big block) and had to change the half shafts, strut rods, mounting brackets and drive shaft.

All in, it's a good conversion, there's a post in the projects section for it (http://www.vettemod.com/forum/showthread.php?t=4310) but be prepared, it's not cheap! Like my wife said "If you'd been spent that kind of time and money supporting the unwed mothers at the local strip club, we'd really have a problem!!"

Good luck with your project!!
 
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