We’ve recently been refocusing our attention to the 5.3l engines and heads. I did some work on them in back in 2000 and 2001, but the tuning software for the trucks was still in it’s early stages and I was getting more demand from the LS1 folks so I shelved the programs. I recently started testing heads again and thought I’d share some flow data with those on this board. All the testing was done on a Superflow 600 flow bench using a 3.780” test bore diameter. In my baseline testing I picked a stock core that looked centered on the valve seats. Some heads can get pretty core shifted and the flow can vary wildly so I sifted through a number of cores before I made my choice. I tested two intake ports and two exhaust ports. This head was an 862 casting.

Lift___Cyl1Int.____Cyl2Int.____Cyl1Exh.____Cyl2Exh .___Cyl2Exh w/out pipe
.100___65.6_______64.8_______52.4_______54.9______ ___53.0
.150___94.3_______96.5_______75.1_______76.9______ ___74.3
.200___133.3______135.8______100.7______103.2_____ ___99.8
.250___166.3______166.0______118.9______120.7_____ ___115.9
.300___188.9______188.5______133.8______136.5_____ ___129.8
.400___207.9______206.6______160.9______163.6_____ ___153.6
.450___213.8______213.3______167.1______169.4_____ ___162.9
.500___219.2______218.0______175.4______178.4_____ ___165.5
.550___221.1______221.3______182.2______184.7_____ ___171.2
.575___222.2______222.8______185.3______186.8_____ ___173.7
.600___223.4______224.6______187.6______189.8_____ ___175.1
.625___224.3______226.1______189.1______192.3_____ ___176.5
.650___226.7______228.2______191.8______194.0_____ ___177.6

Intake runner volume = 205cc
Exhaust runner volume = 77cc
Combustion chamber volume = 62cc
Test bore dia. = 3.780”
The intake ports were tested with a radius flow plate and cyl. #1&2 exhaust ports were tested with a stub pipe.
I’m impressed with the flow from .100”-.350” lift. No doubt this is one of the reasons why these engines run so well in stock form.
I’ll post some flow specs on ported heads in the near future.


Richard

 

Good data Richard, thanks for posting this up!

 

yes. that is some great information...

 

Flow it with a truck intake manifold attached and I'll do this.
First I've seen on a 3.78'' bore and w/ a stub pipe.

Thanks for the data.

 

how about a cam specifically ground for stock 5.3 heads?

This is great data sheds alot of light on why the 220 range cams with .55x lift seem to fit well with stock heads

Im with sportside Id love to see some numbers with the truck intake attached

 

The TR220 .55'' may work well but, you could squeeze a lot more air into the chamber with more lift. Flow does stall at .55'' but it does not drop off. By adding more 'lift' your effectively adding more duration at higher lift.

If you put a camshaft w/ say the specs... 218* .625''
You've added more lift which in term gives you more duration at say .5''+ where the head seems to gather most of its flow.
AKA... more power if the rest of the cam is setup correctly.

 

Great idea guys. I'll see if I can round one up and then test the same ports with the intake. My guess is that the intake won't hurt the flow between .100"-.350" much. It will slightly hurt the flow from .350"-.500" and will probably hurt flow above .500" a few percent more. Ported heads will be more affected by the intake being in place.


Richard

 

I'll send one out to you for free...
It would be worth it to see the results.

I'd expect to see 90% E-I ratios @ high lift.
Maybe thats why my stock, reverse split camshaft has such a flat torque curve.

 

Richard,

Do you have any flow data on the stock 6.0L head? It's easier if I compare on one bench AND since I have your 5.3 heads...

Thanks for any help.

 

I'll get some fresh flow data on a stock #317 head in the next day or two. I'll post it up later this week. I've got an intake manifold located. It might be a week or two to get it though.......... I'll re test the 5.3l heads and then the 6.0l head with the intake manifold when it gets here.

I'm pretty pleased with the port flow we're seeing on the 5.3l heads with some minor porting and a valve job. A 40cfm increase at .550" lift and an increase in runner volume of only 3cc

Stay tuned,

Richard