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1/29/14 5:17pm - Original Message: 'changing up an '81''
RedVetteinprogress
Former Member
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West Bend, WI - USA

Vette(s):
1985 silver coupe & 1975 red coupe

Joined: 3/18/2010
Posts: 46
I'd like to know what you guys think about this plan for my '81 car. I would like to make the car a better over the road cruiser but can't spend ton's of green on it. I want to replace the worn out 350 with a 290HP, 350CI GM crate motor and install a 700R4 transmission for lower RPM's. The rear end gear ratio is supposed to be 2:87. What do you guys think about this combination and what problems could I run into. Thanks for any help you can give me. Darrell

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1/29/14 5:30pm - Reply: 'Re: changing up an '81''
dads2vette Lifetime Member
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Ash Fork, AZ - USA

Vette(s):
1981 Red Interior White exterior

Joined: 4/18/2007
Posts: 1038
Darell,
I replaced my motor with a crate 325 hp, 350 tq engine.  I still have the turbo 350 auto tranny but intend on replacing it with the 700r4 next year possibly, depending on what kind of mileage I get with it this summer.  I have about 7000 miles of road trip planned so far.  So to answer your question, you sound like an incredibly brilliant and insightful individual.Big smile

...and now for some dissenting opinions LOL


____________________________________
Dave C..........My mantra: I can not be bought!!      Long and short term leases available.
In the words of Zora Arkus-Duntov "Is your seat belt fastened? Alright, Let's go"


Yeah, I know, Shut up Dave.
Lifetime Member #192


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1/29/14 6:19pm - Reply: 'Re: changing up an '81''
jimiam
Former Member
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Memphis, TN - USA

Vette(s):
1981 Red 1993 Black Rose

Joined: 2/16/2007
Posts: 134
I look forward to reading the replies about this from those in the know. To me it would seem almost counter productive to install the 290hp engine with the intention of also dropping the RPMs. The term "worn out" can mean different things to different people as can the word "cruising". Sometimes that "worn out" engine can provide some really good cruising with the right suspension upgrade.  (curious)

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1/29/14 8:44pm - Reply: 'Re: changing up an '81''
dads2vette Lifetime Member
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Ash Fork, AZ - USA

Vette(s):
1981 Red Interior White exterior

Joined: 4/18/2007
Posts: 1038
Jim is right about the suspension.  Before I purchased my 81 I had restored a couple of first generation camaros.  They ran great but they had the original kidney breaking suspensions.  With this car I replaced the front suspension with new parts from Vette performance and brakes.  Everything that went back in was not only better performing but also gave it a more comfortable ride.  The consequence of new technology.  I kept the original rear composite leaf spring after having it inspected and much debate.  I rebuilt the trailing arms. 

____________________________________
Dave C..........My mantra: I can not be bought!!      Long and short term leases available.
In the words of Zora Arkus-Duntov "Is your seat belt fastened? Alright, Let's go"


Yeah, I know, Shut up Dave.
Lifetime Member #192


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1/29/14 9:42pm - Reply: 'Re: changing up an '81''
Case75
Former Member
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, - Canada

Vette(s):
1975 Corvette 383 stroker w/Patriot 190 heads, Eagle stroker kit, Comp 279TH7 cam, DUI distributor, Edelbrock 7116 intake, Edelbrock 1806 carb, Hedman Hedders, TH400 w/TCI Breakaway 2400 stall, Transgo 1-2 shift kit.

Joined: 6/19/2012
Posts: 230

I would just go with the Goodwrench 195hp 350. It is in all essence an L48 except with 4 bolt mains right down to the camshaft and heads. I've seen this engine built up to over 400hp gross so lots of potential in it. The GM Performance 290hp you are looking at is the same engine but with the L82 cam for a lot more money. Pretty expensive camshaft.

http://www.summitracing.com/int/parts/nal-10067353/overview/


http://www.summitracing.com/int/parts/nal-12499529/overview/

Good story here on the Goodwrench 350:

http://www.chevyhiperformance.com/techarticles/46320_gm_350_crate_engine_build/

http://www.chevyhiperformance.com/techarticles/46326_gm_350_crate_engine_build_ii/

http://www.chevyhiperformance.com/techarticles/46359_gm_350_crate_engine_build_iii/

http://www.chevyhiperformance.com/techarticles/46364_gm_350_crate_engine_build_iv/

http://www.chevyhiperformance.com/techarticles/46370_gm_350_crate_engine_build_v/

http://www.chevyhiperformance.com/techarticles/46438_gm_350_crate_engine_build_vi/

http://www.chevyhiperformance.com/techarticles/46461_gm_350_crate_engine_build_vii/

http://www.chevyhiperformance.com/techarticles/46467_gm_350_crate_engine_build_viii/











|UPDATED|1/29/2014 7:42:38 PM (AZT)|/UPDATED|


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Build Date: May 7, 1975. 383 w/267 RWHP/310 RWTQ
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1/29/14 10:54pm - Reply: 'Re: changing up an '81''
eldredjames Lifetime Member
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Temple City, CA - USA

Vette(s):
1969 Daytona Yellow. 350 / Automatic.

Joined: 10/3/2010
Posts: 361
Man, I hate it when summitracing links take over your browser and you can't go back!

I have a GM ZZ4 350ci with 355HP.  Runs great but I'd gladly swap some of that HP for a better ride.


|UPDATED|1/29/2014 8:54:33 PM (AZT)|/UPDATED|


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1/30/14 12:25am - Reply: 'Re: changing up an '81''
daveo76
Standard Member
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 831
I rebuilt my original L48 and did all the work I could myself and still probably did not save any money over going the crate motor route.  Especially if I had gone the base Goodwrench way that Greg suggests.  (I never really considered that as a viable option back then, but in hindsight it seems like it could be a good idea).  I had fun and learned a lot doing it the way I did, but it's not for everyone.  I did that and the front suspension over a time period of almost 2 years.  Rear suspension I did a few years previous -- when I had to pull the rear-end to get it rebuilt.  It's never ending.....

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1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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1/30/14 8:28pm - Reply: 'Re: changing up an '81''
tonytheroofer
Former Member
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Rochester, NY - USA

Vette(s):
1980 L- 82 fully restored and upgraded.

Joined: 6/12/2012
Posts: 95
With such a low rear gear set it may be trouble swapping to a O/D transmission . I say that because if you hit 4th gear and lock up at 45 mph you will have an rpm of 1100 and that motor will struggle to maintain speed or accelerate up from it.

As you sit now at 45 you are turning 1500 to 1600 rpm at 60 your at 2000 rpm. All perfectly good rpm ranges and what us guys with tall gears hope for in O/D . I run a 3.92 rear gear and am at 2100 at 60mph which is a perfect rpm to drive with. 

Also you have a carb , if you go and look the O/D transmissions where mated to fuel injected cars and the reason is ,as motor load changes the FI adjusts a/f ratios .. A carb can not do that and you will end up with a car that bucks and shudders as you try to gain speed normally.

PLUS you should have a 350c ,,, That has a lock up torque converter which also will drop rpm at cruse speeds. 

So if it was my car and I had no aspirations for a lot more hp and stouter rear gears i would put a fresh TH350C back in her ... 


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1980 , ZZ430 , 3.92 rear , 700R4 2400 stall NEW EZ EFI 
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1/30/14 8:47pm - Reply: 'Re: changing up an '81''
dads2vette Lifetime Member
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Ash Fork, AZ - USA

Vette(s):
1981 Red Interior White exterior

Joined: 4/18/2007
Posts: 1038
Great info Tony

____________________________________
Dave C..........My mantra: I can not be bought!!      Long and short term leases available.
In the words of Zora Arkus-Duntov "Is your seat belt fastened? Alright, Let's go"


Yeah, I know, Shut up Dave.
Lifetime Member #192


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1/31/14 10:17pm - Reply: 'Re: changing up an '81''
KDADDY79
Former Member
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Dutchess County, NY - USA

Vette(s):
White '79 Corvette. It's a driver.

Joined: 8/27/2007
Posts: 2484
I have a '79 with the L-48 and a 700-R4. The rear end is stock. I have true dual exhaust, too.
I like the 700-R4 in it, but I wish I had more motor to go with it. (Maybe when the kids graduate college!)
I don't experience a bogging down when driving at highway speeds. I know it's not making much power at low RPM's, but mine runs out smooth at the low highway RPMs.
What I really like is the downshift from O/D to 3rd. at highway speeds.
This gets the tired old L-48 to making about as much power as it can on the highway. Fun to drive!
I'd say go with your plans and enjoy the ride.
You'll need to plan on some exhaust work, too. The 700-R4 is a bit wider and the exhaust needs to be modified some.

Kevin


|UPDATED|1/31/2014 8:17:26 PM (AZT)|/UPDATED|


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1/31/14 10:52pm - Reply: 'Re: changing up an '81''
dyoes
Former Member
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Zachary, LA - USA

Vette(s):
1974 L-48 Auto. Just your basic Vette. GM crate motor w/vortec heads and intake. Crane cam. Scorpion rockers, Edelbrock carb. Lots of parts still in boxes... :(

Joined: 1/27/2013
Posts: 201
A 700R4 has a final drive of .7:1, compared to the TH 350/400 of 1:1.  With an rear end ratio of 2.87:1, a 700R4 may be a bit tall.  There is an engine rpm calculator at powerblock.com.  Using 285/50R15 tires, you'd be turning 1300 rpm at 55mph.  With that rear end, I'd keep the three-speed and spend the money on engine!!  Just my two cents... 

Has anyone here done the 700R4 or 2004R conversion?  If so, how did you handle the torque converter lockup?

http://www.powerblocktv.com/resources/


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"Let them that don't want none have memories of not gettin' any."
- Brother Dave Gardner

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2/1/14 11:02am - Reply: 'Re: changing up an '81''
tonytheroofer
Former Member
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Rochester, NY - USA

Vette(s):
1980 L- 82 fully restored and upgraded.

Joined: 6/12/2012
Posts: 95
Lock up is pretty easy , you can buy a B&M controller , or use a toggle switch like i do because I only want lock up at highway speeds .

|UPDATED|2/1/2014 9:02:02 AM (AZT)|/UPDATED|


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1980 , ZZ430 , 3.92 rear , 700R4 2400 stall NEW EZ EFI 
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2/1/14 2:56pm - Reply: 'Re: changing up an '81''
dads2vette Lifetime Member
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Ash Fork, AZ - USA

Vette(s):
1981 Red Interior White exterior

Joined: 4/18/2007
Posts: 1038
link to a members swap




|UPDATED|2/1/2014 12:56:18 PM (AZT)|/UPDATED|


____________________________________
Dave C..........My mantra: I can not be bought!!      Long and short term leases available.
In the words of Zora Arkus-Duntov "Is your seat belt fastened? Alright, Let's go"


Yeah, I know, Shut up Dave.
Lifetime Member #192


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