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tired 305, what would you do?


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#1 MATT

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Posted 14 September 2008 - 09:37 AM

hello, thanks for admitting me to the forum group.
i've been an avanti owner for over 10 years now.

my 1981 Avanti II, factory black, factory loaded, very nice condition, all stock.... but a tired, sluggish, 305... what would you do?
if it was a stock 327 like earlier/later years, i'd just rebuild it... but can't see do'n that to a 305

my father offered me a nice 500ci Cadillac engine with everything.....
know anyone that has fit one in an Avanti II?
would any major modifications have to be done?
read hear that a 700-R4 should be no problem (stuck one in my conestoga a while back with a fresh stude 289)

thanks! glad to find AOAI!

#2 MikeValent

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Posted 14 September 2008 - 12:03 PM

Why not go with a 350 crate engine since it's really the same block dimensions, same mounting points and all that? A prior owner of my 3771 installed a Paxton SN2000 which does improve power quite a bit, but a good 350 (or 383) would give the same or better result with less complexity.

#3 Ernie

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Posted 14 September 2008 - 05:25 PM

I agree with Mike.

#4 Gunslinger

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Posted 14 September 2008 - 06:07 PM

I agree wholeheartedly. A crate engine is far more cost effective than rebuilding your 305 or installing a Caddy engine. The engineering headaches alone would likely drive the cost of such a conversion into the stratosphere.

With a crate engine you have many, many options regarding power levels. From GM Performance alone you can go from a 350 260hp version up to a 383 stroker, with several versions in between. That doesn't even include all the other crate engine builders out there.

You can get a Vortech supercharger kit made for the small block Chevy if you like that idea, or, as I did with my '70, go with electronic fuel injection mated to a GM Performance 350HO 330hp crate engine...or simply go with a carburetor, of which you have options of Edelbrock, Holley or Demon that will all give excellent performance based on your needs. Barry Grant even makes a "Six-Shooter" system...an intake with three 2-barrel carbs mounted and all the linkages. That would give some real "WOW" factor to any car.

Crate is definitely the way to go.

#5 theGman

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Posted 14 September 2008 - 08:04 PM

Or you can do what I am being tempted to do.....install a more modern 350 with 4 spd auto trans. I specificallly have a LT-1 in my '95 Fleetwood. It is fuel injected, has the electronic overdrive automatic.
Car runs perfect; has 114K on it. I've read somewhere that others have done this in Avantis; need new fuel lines, pump, etc. plus a number of other items, but this is a standard type upgrade into a lot of cars.

Just something to think about, since you'll end up with a modern fuel injected motor with all those advantages, and there are a lot of engines of this basic type out there.

I'm sure I'll run into problems, like right now I'm trying to figure out if I need a different radiator, since the coolant flows backwards, etc. but the problems should be worth the better performance and mileage.
Many internet sites describe this transplant.

Paul

By the way, I have an '81 with a Jasper crate motor in it, and Edelbrock carb, about 25K. Runs great; I'm probably nuts for thinking of this upgrade, but it is a long winter!

Edited by theGman, 14 September 2008 - 08:05 PM.


#6 Twnchgr

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Posted 16 September 2008 - 09:56 PM

would any major modifications have to be done?
read hear that a 700-R4 should be no problem (stuck one in my conestoga a while back with a fresh stude 289)

thanks! glad to find AOAI!
[/quote]

Hi Matt,
In my 88 LSC. After my 305 died. OD'D on NOS and Boost.lol Replaced it with a 350 as has been suggested.The crate engine is the easest way to go.Everything just bolts right up.I used a comp cam for a 305 FI. 212/218 @.050 114 LC &.442 lift. Elebrock Preformer intake to keep it Calif. smog clean. Makes a mountian of torque.pulls like a freight train. Also installed a 700R4. The extra low first gear keeps it perky out of the hole.The OD gives you gas milage . Hyper tech also makes a chip for it. Will also make the car more respondsive.
Karl

#7 IndyJimW

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Posted 17 September 2008 - 03:10 PM

I'm sure I'll run into problems, like right now I'm trying to figure out if I need a different radiator, since the coolant flows backwards, etc. but the problems should be worth the better performance and mileage.

The coolant flows backward INSIDE the engine, still comes in the waterpump and out the thermostat housing.

Jim Wood

#8 ernier

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Posted 17 September 2008 - 09:35 PM

I agree on the crate motor, lots of choices and price ranges. The Cadillac sounds sexy but has little or no benefit over a Chevy engine and instead of being back on the road in a couple of weekends you could end up with a never ending project.

A couple of thoughts on transmissions though...if your 81 is a 3 speed but with a high ( numerically low ) rear gear you might consider just leaving the existing trans in there and upgrading with a shift kit and modified governor. If you must go overdrive after having experienced both the 700 (formerly in my 64 ) and the 200, presently in my 64 I vote for the 200. If you have a TH 350 in there now the driveshaft length is the same you would just need to fab a mount further back on the frame to mount the 200. TV Cable set up on either of those transmissions is a BIG issue and your current carburetor may not work with either trans. The gear spacing on the 200 is better and while the 1st gear grunt on the 700 is fun it doesn't last very long. I have had lots of issues with my overdrive conversions and if I had an Avanti II with a rear gear 3.36 or below I would beef the current 3 speed and drive.

ErnieR












hello, thanks for admitting me to the forum group.
i've been an avanti owner for over 10 years now.

my 1981 Avanti II, factory black, factory loaded, very nice condition, all stock.... but a tired, sluggish, 305... what would you do?
if it was a stock 327 like earlier/later years, i'd just rebuild it... but can't see do'n that to a 305

my father offered me a nice 500ci Cadillac engine with everything.....
know anyone that has fit one in an Avanti II?
would any major modifications have to be done?
read hear that a 700-R4 should be no problem (stuck one in my conestoga a while back with a fresh stude 289)

thanks! glad to find AOAI!






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