Rebuild 350, 383, big block swap? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

charettesa · 12-03-2013, 05:04 PM

I have 71' C20 with a 350 sb and unknown automatic trans. At its current condition it runs and drives fine but feels weak.

I wanna know what would be the best route. Ive heard that I can make my 350 more powerful as a 383 stroker but I have no idea how to go about this. I plan on taking it to a rebuilder but I want to know as much as possible before I take it in.

Or should I drop in a 454 bbc? If I do that what do I need to change? Trans, engine mounts, ???

I plan on towing and pulling a camper trailer..

**66 C10 383** · 12-04-2013, 12:23 AM

Since you plan on towing I'd say either the 383 or 454.

The 383 is basically the same as a 350 with the exception of a longer stroke crank and pistons with a shorter pin height. The rods can be reused or can be longer (6.0" vs stock 5.7") but that just adds more cost as the longer rods are more expensive as is the shorter pistons.

The 383 may get better fuel mileage when not towing but that's hard to say. Depends on how much weight you will be towing and the number of miles you drive while towing. Is it basically flat land or lots of hills? Also, are you going to be mainly towing or just ocassionaly towing?

Lots of variables here ...

ItsRandy · 12-04-2013, 01:03 AM

Big Block and Th400 or 4l80E. Once you go Big Block you never go back!

suspect · 12-04-2013, 05:05 PM

If your 350 runs fine, why not just upgrade your cam? Quick and easy power increase.

charettesa · 12-04-2013, 05:54 PM

Wow a lot to think about.. I appreciate the insight from everybody.

Also..

How do I figure out what transmission I have? (know stupid question) It is an automatic three speed.

If I go big block will my trans bolt up? If not what would be a good automatic trans to run with a bbc such as 454.

storm9c1 · 12-04-2013, 06:17 PM

Crawl under and look at the pan.

Your choices will be limited if you intend to use a 383 or a BB for towing. TH400 or 4L80E if you want success.
As for whether to go 383 or BB, either one will work pretty well. You will have some chance at economy if you go with a 383 and the proper cam. Plus all of your accessories, mounts and brackets will still work.

GMtrucknut!! · 12-07-2013, 09:09 PM

It should be a 350 turbo trans.

**kwmech** · 12-08-2013, 08:29 PM

3/4 ton could be either a 350 or a 400. Look at the chart above, unless you have a pic of the spid sheet in the glove box

storm9c1 · 12-09-2013, 04:24 PM

Quote:

Originally Posted by kwmech

3/4 ton could be either a 350 or a 400. Look at the chart above, unless you have a pic of the spid sheet in the glove box

...and SPID codes are only good on a known stock truck. After all these years, who knows what's been swapped. Eyes are the right tool for this job.

12-03-2013, 05:04 PM	#1
charettesa Registered User Join Date: Dec 2013 Location: California Posts: 2	Rebuild 350, 383, big block swap? I have 71' C20 with a 350 sb and unknown automatic trans. At its current condition it runs and drives fine but feels weak. I wanna know what would be the best route. Ive heard that I can make my 350 more powerful as a 383 stroker but I have no idea how to go about this. I plan on taking it to a rebuilder but I want to know as much as possible before I take it in. Or should I drop in a 454 bbc? If I do that what do I need to change? Trans, engine mounts, ??? I plan on towing and pulling a camper trailer..

12-04-2013, 12:23 AM	#2
66 C10 383 Senior Member Join Date: Aug 2012 Location: Somewhere In So. IL. Posts: 412	Re: Rebuild 350, 383, big block swap? Since you plan on towing I'd say either the 383 or 454. The 383 is basically the same as a 350 with the exception of a longer stroke crank and pistons with a shorter pin height. The rods can be reused or can be longer (6.0" vs stock 5.7") but that just adds more cost as the longer rods are more expensive as is the shorter pistons. The 383 may get better fuel mileage when not towing but that's hard to say. Depends on how much weight you will be towing and the number of miles you drive while towing. Is it basically flat land or lots of hills? Also, are you going to be mainly towing or just ocassionaly towing? Lots of variables here ... __________________ Doug Old Build Thread - 383/T56 http://www.67-72chevytrucks.com/vboa...d.php?t=540838 Updated Build Thread - Modern Relic - 66 C10 536 Dark Aqua 5.3/4L60E - BTR Stage IV Truck Cam - Vintage Air - Dakota Digital http://67-72chevytrucks.com/vboard/s...d.php?t=778784

12-04-2013, 01:03 AM	#3
ItsRandy Registered User Join Date: Nov 2010 Location: Grand Terrace, Ca. Posts: 1,607	Re: Rebuild 350, 383, big block swap? Big Block and Th400 or 4l80E. Once you go Big Block you never go back!

12-04-2013, 05:05 PM	#4
suspect Registered User Join Date: Jul 2011 Location: oklahoma city Posts: 692	Re: Rebuild 350, 383, big block swap? If your 350 runs fine, why not just upgrade your cam? Quick and easy power increase. __________________ Daniel 68 C10 Build http://67-72chevytrucks.com/vboard/s...d.php?t=503594 Romans 10:13 Everyone who calls on the name of the Lord will be saved.

12-04-2013, 05:54 PM	#5
charettesa Registered User Join Date: Dec 2013 Location: California Posts: 2	Re: Rebuild 350, 383, big block swap? Wow a lot to think about.. I appreciate the insight from everybody. Also.. How do I figure out what transmission I have? (know stupid question) It is an automatic three speed. If I go big block will my trans bolt up? If not what would be a good automatic trans to run with a bbc such as 454.

12-04-2013, 06:17 PM	#6
storm9c1 * That's interesting * Join Date: Oct 2008 Location: Pittsburgh, PA Posts: 2,772	Re: Rebuild 350, 383, big block swap? Crawl under and look at the pan. Your choices will be limited if you intend to use a 383 or a BB for towing. TH400 or 4L80E if you want success. As for whether to go 383 or BB, either one will work pretty well. You will have some chance at economy if you go with a 383 and the proper cam. Plus all of your accessories, mounts and brackets will still work. __________________ Tom Chevy by day... 1969 Chevy C30 Rollback Tow Truck -- 383 stroker, 4L80E 2011 Chevy Caprice PPV 9C3 6.0L 1995 Chevy Caprice 9C1 1994 Chevy Caprice 9C1 #3 1995 Chevy Caprice Wagon #2 1995 Chevy Impala SS Mopar by night... 1969 Dodge Charger 1972 Chrysler Newport 2dr Hardtop (27K miles) Plus others... Last edited by storm9c1; 12-04-2013 at 06:25 PM.

12-07-2013, 09:09 PM	#7
GMtrucknut!! Registered User Join Date: Dec 2011 Location: Attica,indiana Posts: 264	Re: Rebuild 350, 383, big block swap? It should be a 350 turbo trans.

12-08-2013, 08:29 PM	#8
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,634	Re: Rebuild 350, 383, big block swap? 3/4 ton could be either a 350 or a 400. Look at the chart above, unless you have a pic of the spid sheet in the glove box



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