SS 5.3 ls combo
 

I was thinking of building a 5.3 LS rated at 305 for a super stock GT combination. It looks like I can use the 243 or 799 heads which I think can have flow numbers better than 300. My question is if this is a good combo to build and is the Throttle body large enough to support over 650 hp. I was thinking of putting it in a Nova for GT/GA at 3400lbs.
Any thoughts would be appreciated.

Henry Sliwinski
5774 SS/HA

Re: SS 5.3 ls combo
 

What RWD car was the 5.3 LS installed in from the factory? And where is the 5.3 listed at 305 horsepower?

Re: SS 5.3 ls combo
 

I don't think there are any RWD cars but I was looking at the 2007 impala engine. Since aftermarket blocks are allowed could it not be used?

Re: SS 5.3 ls combo
 

I don't think there are any RWD cars but I was looking at the 2007 impala engine. Since aftermarket blocks are allowed could it not be used? Sorry it is rated at 303 hp.

Re: SS 5.3 ls combo
 

I've been wondering about this combination..

Re: SS 5.3 ls combo
 

Don't know about the block situation. But the heads flow great. We've had a couple sets on the bench that we've done flow over 300cfm @.700 without getting really crazy with them with the stock size valves. Could be a pretty interesting combination I think.

Rick

Re: SS 5.3 ls combo
 

Removed

Re: SS 5.3 ls combo
 

I think the aftermarket block would be my choice on this build. and the heads have great potential. I am just not sure if the throttle body can support the airflow demands. Maybe a sheet metal intake can overcome the throttle body size. I would like to see the motor make between 680 to 700 hp. I think the heads can support that, the question is the other components. I think peak power may be in the 7800- 7900 range.

Re: SS 5.3 ls combo
 

If you are talking 300@28'', if throttle body and intake don't cut back air flow, I calculate around 611 HP @ 8759 rpm, this is calculated using superflow's formulas for HP and peak rpm for HP based on airflow and cubic inch.

Mike Taylor 3601

Re: SS 5.3 ls combo
 

Thanks Mike, I forgot about those calculations. I have used those in the past and I have found that you may have to multiply the horsepower by the volumetric efficiency to get close to real world numbers. The rpm side was usually close. I didn't think with the longer stroke of the 5.3 that it would need to rpm that high.

Re: SS 5.3 ls combo
 

You're kidding, right?

Re: SS 5.3 ls combo
 

Those formulas make real world numbers on the superflow I use,stock configuration heads using stock valve locations and angles about 99% of time will make within 5 hp of formula.
When you get into raised runners,18 degrees etc, spread ports,big chief style etc. then they make more than calculated.
LS engines I don't have any dyno info on them,don't know if will just make calculation or more.
I always check head on flow bench when I know I will run a engine on dyno,so I know what hp to expect.
as example a small block i had heads went 275 @ 25'' calculates 594 made it made 596.

Mike Taylor 3601

Re: SS 5.3 ls combo
 

Mike,
I have found the LS heads make more power than the formulas for traditional heads. More like RR and spread port heads. I have a fudge factor when doing LS engine models. I believe his concerns with the T-Body air flow are justified, but not as important as with traditional heads. I've never done a carb or injected restricted LS engine. The closest I done to a restricted one is a 5.7 bracket deal with a good 750.

Re: SS 5.3 ls combo
 

I thought LS may make a little more than formulas, with their valve angle and location.
I had fudge factor for big chief it was around +9% power over formula.
Mike Taylor 3601

Re: SS 5.3 ls combo
 

Thanks everyone for the replies. I appreciate the knowledge sharing and helpful insight.