Hey guys, first time poster.

Planning out a little project at the moment and was wondering if anyone has a 4.8/5.3 head around and would be able to measure the diameter of the combustion chamber or even the valve spacing.

Looking at the possibility of sleeving a 5.3 block to meet class regulations regarding capacity - so just checking to see what clearance I have before going down that path.

Thanks team

 

You mean the dimension at the widest point? Combustion chambers are not round, so no diameter. Also, the valve spacing is the same for all cathedral heads.
What capacity is required by the class you're contemplating?

 

Yeah talking about the measurement at its widest point - I should have chosen my wording better!

Think I seen somewhere else on the forum that the valve spacing for the cathedral port LS1 is 1.91"

4.5l or 275ci is max capacity permitted - by the looks sleeving alone isnt going to be able to take it back that far so an offset ground crank might be the go or a combonation of the two.

 

Not sure about valve spacing.

Found this on the internetz

Can't post the link because we aren't supposed to post non sponsor links but in the hot rod article it says it measures 3.756 across. And they put this picture in there.

The article is called "Surprising HP Numbers From Our Stock LS Cylinder Head Test". Copy and paste that into google and you should find the article easily.


If I had to bet I would say the offset grind is what'll do the trick, I don't think you'll be able to get the sleeve or piston size you need to reduce the bore size enough to meet your requirement.

If you don't already know the 4.8 and 5.3 use the same bore but the 4.8 crank is smaller so you would want to start with a 4.8 crank. It's a 3.268" vs 3.622". Looks like you can go as high as 3.06 with a 3.78 bore and have a 274.72. Not sure if they can take that much off that isn't really my field.

This is a tough one. A gen 5 4.3 would be sweet though for requirements and having late model tech

I don't have a head to check or I would measure it, I have dial calipers etc, but no heads laying around.

 

This stuff always blows my mind, why do people have certain classes that require you to spend WAY more money to have LESS power?
I dont understand

 

I agree, but to each their own.

 

Yeah its just one of those things unfortunately - original rules were probably written up 40 years ago with other motors in mind.
Thanks for the help guys.