Chevyluver57

I have a 1986 el Camino and have a opportunity to purchase a 5.3 or a 6.0 for the same price both are a carb setup The 5.3 is around 375hp and the 6.0 is maybe 450hp
I was wondering what would be the better choice as far as gas Milage and ease of installation. I plan on using the 200r4 that's already in my car but just rebuild it to handle the extra power.
Will a 6.0 and a 5.3 install the same I hear there is clearance issues with the acpump
Thanks for the help and input

LS1 pwrd NOVA

iTrader: (2)

Same install, Basically they are the exact same externally just internals are different.
If your looking for fuel economy the 5.3 may do better but the 6.0 May not be that bad either. It's all on your tuning with the carb and your right foot.

Chevyluver57

My engine builder said 24ishmpg with the 5.3 and my best guess with the 6.0 with a light car like a El Camino would be around 18 at the best.
It sounds like what you're saying is I need to choose between gas Milage and horsepower. Thanks for your help
And if you know anything about transmissions would there be a big price difference between building my transmission or 375hp as opposed to 450hp?
And if you have any expirance or knowledge relating to the actual install in a installation in my 86 el Camino anything would be appreciated
Just a 19 year old kid looking to expand my knowledge of cars..

murphinator

iTrader: (2)

What mods are in both engines will effect the economy as well. Both 5.3/375 and 6.0/450 sound more than just cam... 327ci to 366ci is not in itself going to drop from 24 mpg to 18 at best , your only talking around 10% change in cubic inches and coming up with 25% drop in economy ?

Both 375 & 450 would be in the minor upgrade category for a 2004r I am thinking as that has always been the go to transmission in the grand national & t type ( came in them stock) you may want to poke around turbobuick.com there should be plenty of info on building those trannys and what parts are needed at what power level - those guys have been modding that trans exclusively for 30 years now.

MonmouthCtyLS7

iTrader: (6)

Try a search this question literally pops up every other day.

Chevyluver57

I'll have to contact my builder and see what kindof of Milage the 6.0 will have 18 is just my best guess. And I will definitely look into turbobuick really trying to see what the project is going to end up costing me and any problems I will potentially run into. Thanks for the advice.

murphinator

iTrader: (2)

I poked around over there this morning and about $1800 will do a stage 1 500hp capable trans from a reputable builder that specializes in 200r4 another 400-500 gets you to a unit capable of 750 hp

RPM WS6

iTrader: (3)

I can't see how the gas mileage would be much different between the two at steady cruise/light acceleration type driving, certainly not 6mpg assuming all else equal with the gears/trans and tuning. As mentioned above, the displacement difference isn't that big and you aren't feeding fuel to that extra 75hp when you're cruising along at ~2000rpm in OD at light throttle. If you plan to drive at WOT all the time, then there might be a noticeable difference.

Lastly, you didn't specify whether your MPG estimates were for city, expressway or mixed. I wouldn't expect 24-ish MPG from either engine driving around town with an auto trans (also assuming a properly matched higher stall speed.)

Chevyluver57

I was quoted $900 for a a 400hp trans without a stall from a family friend that has a shop.
So that sounds about rights I was thinking no more than $1500 all said and done bolted up to the motor ready to go.

Chevyluver57

he said that would be a "good average" with normal driving, so I'm assuming he means both.

RPM WS6

iTrader: (3)

Again, for the reasons already stated, I can't see how there would be a 6mpg difference under averaged normal driving conditions between those two engines.

panic

I agree, 6 mpg loss is too much.
The larger engine has higher vacuum at any load condition, will upshift sooner at the same level of acceleration, and pull a higher intermediate transmission gear.
All the systems pumping losses (oil pump, converter pump, valve springs) are same/same.
You'll regret the 5.3 the moment you try to pass someone at cruising speed.
I've been driving 50 years, and never thought my motor was too big.

Chevyluver57

I am leaning towards the 6.0 at the moment still have a lot of research to get done. Still not sure about if I have to use a different fuel pump or fan assembly to cool a 6.0 compared to my 305 I have in there now. I'm very new to post 1990 motors and just want to get everything done in 3 weeks instead of the entire muscle car season

Chevyluver57

This is also my daily driver in the summer so I really really want to maintain the drivability of the car

LS1 pwrd NOVA

iTrader: (2)

My pure stock ws6, auto with 3.23 gears got 23mpg going around 72mph for 200 miles on 87 octane with lots of hills here n there. So I'm guessing that's what most engines will do around 5.7 size. Maybe a smaller engine will do better but too small engine like a 4.8 can be a turd on the highway in a truck 16/18 highway mpg. But a truck vs a car is a big diff in every aspect.

RPM WS6

iTrader: (3)

In this regard, an El Camino isn't really like a typical truck. It does have some extra drag from the tail gate (assuming open bed) but otherwise the aerodynamics of the front and overall weight are closer to a car. It also wouldn't have the larger drag of truck sized tires or a 4x4 system.

Final drive ratio, state of tune and trans type will all play a bigger role in highway MPG than a displacement difference in the range of 5.3-6.0L. Having said that, I agree that too small of an engine might get worse average MPG as you'll have to push said engine harder (more rpm, more load) under normal acceleration.

Chevyluver57

First of thank thank you for referring to my el Camino as a truck
And I do have a tonneau cover on my car right now. What do you get around town in your car? 17-19ish?
Defiantly won't be going smaller than a 5.3

AronZ28

iTrader: (2)

What sort of cam do these engines have in them? I'd buy the one that's going to be a bit more street friendly, unless you plan to tear it up on the strip 24/7, then definitely go with the 6.0 in that case. Either way, this will be a night/day difference vs that 305 slug that came in your El Camino.

NJmooch

How I would pick, in order of importance:

1. Is one of the engines all aluminum? If so, pick that one. If both are, see #2.
2. Find out what cylinder heads are on both engines, pick the engine with the better flowing heads.
3. Do you have any plans on forced induction in the future, if so the 5.3 would be my choice.

Good luck, and enjoy your truck.