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302 GMC engine
#1339779 Mon Dec 30 2019 11:52 PM
Joined: Apr 2018
Posts: 5
N
New Guy
I have started down the modernization road with my GMC 302, without the 'extreme' part. The engine is rebuilt with a bump in compression, lighter pistons, balanced assembly, mild cam, mild head porting, and full flow oiling conversion.
The modern part is the addition of HEI, and a FiTech EFI system on the factory 2 barrel (military) manifold. This will be backed up by a T5 overdrive manual transmission, and a 3:38 diff, and all of this under a '53 GMC panel truck.
As it is yet to run, I can't say how it will perform, but I expect a world of difference from stock!
The goal was to make this set up be as smooth, reliable, economical, and powerful as possible without the very specialized work you are planning on doing. I plan to drive the heck out of this truck, and reliability is paramount!

I collect vintage motorcycles, and sell insurance for vintage vehicles, so this truck will transport me to shows all over the West Coast, serving as my transportation, as well as a way to haul my bikes and booth to shows. Looking forward to it!

Last edited by Tiny; Tue Dec 31 2019 01:12 AM.

Nick Dounias
Re: 302 GMC engine
ndounias #1339792 Tue Dec 31 2019 01:14 AM
Joined: Aug 2005
Posts: 9,152
Master Gabster
This was piggybacked on a swap meet thread. Had nothing to do with the thread.


Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.
Re: 302 GMC engine
ndounias #1339795 Tue Dec 31 2019 01:30 AM
Joined: Nov 2012
Posts: 137
B
Shop Shark
Sounds cool! Let us know how she performs!

Re: 302 GMC engine
ndounias #1339798 Tue Dec 31 2019 01:40 AM
Joined: Mar 2010
Posts: 9,451
5
Master Gabster
I suspect that you will spend very little time in 5th gear/overdrive with the 3.38 rear gears. What size tires are you going to run? Shorter tires will make overdrive more usable.
If you haven't selected your T-5 yet, I would suggest the .86 to 1 version. This would work better with your 3.38 gears than the .72 to 1 T-5.
Carl

Re: 302 GMC engine
ndounias #1339813 Tue Dec 31 2019 02:36 AM
Joined: Jun 2001
Posts: 732
T
Bondo Artiste
I don’t have experience with the 3:38 gears, I do have experience with the 3:55z

I’m running a 302, with Pertronix, dual Zeniths, and a Truckstell .73 overdrive, with Patrick’s 3:55 gears, and 16 inch tires. It does very well and I use overdrive often. This set up in the 45 Art Deco GMC does very well. I’m confident your 302 can handle the 3:38 in overdrive. Log some miles for yourself and then adjust if necessary.


Phillip
1927 Chevy Capital 1 Ton truck - basket case
1941 Chevy Suburban - Parts only
1949 GMC Suburban - 10 year project
1945 GMC half ton truck - Driver
1946 Chevy COE - Might restore one day...
1959 GMC Half ton long bed NAPCO

https://photos.google.com/u/1/albums
Re: 302 GMC engine
ndounias #1339862 Tue Dec 31 2019 05:46 PM
Joined: Apr 2005
Posts: 2,623
C
Shop Shark
I am very interested in your FiTech install. We have used the FiTech on a number of V8's including replacing the factory system on LS engines. I've been waiting for a customer to request one and figured we would have to get a 4bbl intake for a 235/261 and then use a four to two barrel adapter. Your 302 is already there. GMC's were often worked hard and were in the 10-12 mpg range and maybe 13 or 14 for an unloaded highway pickup so mileage with the FiTech will be of interest. Keep us posted!


Evan
Re: 302 GMC engine
ndounias #1340033 Wed Jan 01 2020 10:52 PM
Joined: Mar 2010
Posts: 9,451
5
Master Gabster
I missed the part about the FiTech. If that system has the sensors and a computer which will continuously adjust fuel delivery rate efficiently at all RPM, the 3.38 rear gears may not be much of an issue for performance and efficiency. I would suspect that with the 3.38 gears, you will not be able to pull stumps in 1st gear however, but you can't have everything I guess.

Re: 302 GMC engine
ndounias #1340063 Thu Jan 02 2020 03:43 AM
Joined: Apr 2005
Posts: 2,623
C
Shop Shark
With a spiced up 302 and loaded with a bike you will HAVE to have a World Class T5. We have a pile of broken regular T5's from behind V8's with sticky tires. If shifter position is not a factor the WC ones for Mustangs are easier to find and easy to adapt. Seems you allotted sufficient funds for the build so you might check out the TKO 500, a 5sp that will take everything your 302 can dish out.


Evan
Re: 302 GMC engine
ndounias #1340164 Fri Jan 03 2020 12:32 AM
Joined: Aug 2005
Posts: 9,152
Master Gabster
The OP hasn't been on site since the first post. Don't expect a lot from this thread.


Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.
Re: 302 GMC engine
Tiny #1340755 Mon Jan 06 2020 07:52 PM
Joined: Apr 2018
Posts: 5
N
New Guy
Tiny, I am not too familiar with these threads, so if I did something wrong I apologize.
Thanks!


Nick Dounias
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