Is a 2.00 intake valve too big for the 5.3 liter engine. The combustion chamber will be unshrouded for the valve and the head will be milled 15-20 thou.

 

I say it will be, velocity is the name of the game not just total flow. You have ~3.78" bore...that's small. Most badass SBF heads run 1.9-2.02" and they have a 4" bore to give you an idea...the production heads ran between a 1.78-1.84" intake on them too.

That's my opinion and there's gonna be a lot of them but unless you're needing some serious airflow I'd stick to that stock 1.89"...

 

I thought I seen something somewhere in one of these threads that it was better on our 5.3s to go to at least 2.00 intake valves... All of the sponsers that I have talked to about heads (FMS,Absolute Speed, TEA) said to go with the stock size LS1 Valves.

 

Yeah, its kind of confusing. HitmanX has said it time and time again. I have probably called futral 3 times, each time Allen stated that the 2 inch valves wouldnt hurt, he suggested the 2 inch valves once and the 1.94's once. From what I hear, the 1.94's arent available for the ls1 heads and putting a lt1 valve in there is a big no no. I have called, TEA, and Thunder racing also, stating that I have the 5.3 liter engine and that this will be going on a truck, each time I was told the 2 inch valves. (I know nothing about this) I just need someone to explain the process to me and I am sure others want to know too.

 

You would be amazed how well a backcut 1.89" intake valve will flow.The port and valve preparation is much more important to head flow than a .11" increase in valve size.The smaller valve will make more power than a 2.00" intake valve that loses port velocity due to a shrouded condition.

 

Yeah, he told me about the 1.94s, but I don't know where to get them. Then when I asked him about the 2.00s he said that would be fine, but not any bigger.

Hitman X & whitt: do ya'll know if they make 1.94s?

 

I Pm'd Futral and a guy from TEA. Maybe they will come on and explain the theory to us.

 

Whitt hit it right on.

Are you telling the head porters these 5.3 heads are going back on a 5.3? I'm not a head porter or anything but basic theory on valve sizing to bore size tells me that you're going to kill velocity with a valve that big. I gave some i.e.'s for valve sizing on motors with a 4" bore let alone this 3.78" in the 5.3.

And no, I don't know if there is a 1.94" intake valve for the LS1 based motors. Besides that, the install for larger valve requires cutting the valve seat, buying the valves, etc. It's gonna cost more for no gains I'd think.

 

Ok guys,hope this helps....If you are JUST doing a valvejob,a 1.89" intake valve is the best choice. Now if you are doing a good port\polish and shape the chamber properly a 2.00" valve is the better choice. We feel anything bigger then a 2.00" on a stock 5.3l bore will flow better,but hurts power.

 

This is nothing against you Hitmanx. I feel that you are one of the most knowledgeable people on here among others. After calling everyone and hearing this and that, then reading this and that on here,all of it can cause confusion in the mind of someone that doesn't understand what is totally going on.