I can get a set of 5.3 heads for a very good price. They only have 3,000miles on them. Is this worth doing? Will they go well with the mods that i have? What gains might i see? Pros and cons would be great. Thanks all

 

anyone?

 

I am not sure but I THINK 5.3 heads have larger chambers which lower compression ratio.I THINK they are best used in FI applications.But here's a TTT for you...

 

I heard the LQ9 heads from the 6.0L have some good flow numbers and will bolt right up to the LS1,it'll raise your compression to 10:1 though,so if you don't want to do that you can use the LQ4 6.0L heads & that'll give you 9.4:1 but get the'00 or later heads that are aluminum cause '99 and older are cast iron.Source: Super Chevy magazine,May 2004

 

It's the other way around.

The 5.3 heads have smaller CCs...so the CR goes up. Unmilled 5.3 heads will bring your CR up to about 10.8:1.

Stock CR is 10.1:1.

If you can get a good deal on them, go for it. I'd spend a little money though and have them ported...if you don't port them, you're just wasting your time. Also, you're going to want a cam to go along with the heads. Swapping heads and keeping the stock cam is also a waste of time, IMO.

 

Cool, I can get a set for 90 bucks, is that a good deal? Also what would be a good cam to go along with the heads? I drive the car about 5,000 miles a year. And i drive it like it was ment to be drivin.

Holla if ya here me

 

If there's nothing wrong with them, $90 is a steal.

If I were you, I'd give TEA or Absolute Speed a call about the porting. Both have good reputations and their prices are very good.

About the cam, my two choices would probably be MTI or Thunder Racing. Give them a call and tell them what heads you're going with and what you want from the cam. Lopey idle or smooth, high RPM power or low(er), emissions "friendly" or not, etc...
MTI and TR also have very good rep's and some pretty knowledgeable LS1 people working there so they should be able to give you some good options.

Last, a lot of the guys over on ls1tech.com have H/C setups. Ask some of those guys what cam(s) are working well with the 5.3 heads.

 

Keep in mind that 5.3 truck heads have smaller valves too. So putting them on just for the compression ratio increase will probably be a waste of time.
Now if you have them ported and have larger valves installed with the appropriate springs and a good cam..................

 

combustion chamber sizes are 64.45cc for the LS1 and 61.15cc for the LM7 head.
valve sizes are: 2.00 intake and 1.55 exhaust (LS1) 1.89 intake and 1.55 exhaust (LM7)

according to gmhtp:

what you need to know: These small combustion chamber truck heads offer no advantage over an LS1 head except the combustion chamber. This along with milling of the deck surface, will allow a slightly higher compression ratio to be achieved. Because of the smaller intake valves installed in these heads, a valve upgrade is practically manditory.

 

CHEVY QC so if i were to get these have them ported and polished, have new valves put in and alos some bigger springs, along with a cam it would be a good idea? Sorry guys im kinda a noob when it comes to heads.

Thanks

 

I live in houston.. am down the street from MTI and I would never go there.. I suggest Thunder Racing for you cam..

Just thought I would throw that your way ( MTI has upset alot of locals...)

I any case, if you do the heads and cam, let us know what it does.. get some track or dyno numbers..

 

i'd certainly look into it. there are a few companies selling re-worked 5.3 heads. i'd look into seeing all what they do to them.

 

First if the heads are in good shape $90.00 is a great deal. Now as for the upgrade to just an 5.3L heads untouched it is not worth the effort as the stock valves(intake) are much smaller the stock 5.7L heads. The heads will raise the compression to about 10.9:1 since the heads are used they need to be milled a bit to resurface deck. Now as fas as the port work goes for 1300.00(using your heads) and shipping costs we can set those up on a stage 1 level. ported and polished, 2.00 and 1.55 valves, 26918 springs, ti retainers, new lock and seals, hot tanked & inspected, milled and assembled.

 

cool, a vendor that's familier. what kind of numbers have you guys found from the swap?

 

we have never done just a straight swap using un-touched 5.3L heads as the benefits of increased compression are negated by the loss of air flow on the intake due to the smaller intake valve.

one of the major advantages of the 5.3L heads is that you don't have to mill them to raise compression so you can use a higher lift cam and not have piston to valve interference. once ported and polished with a 2.00 or 2.02 the 5.3L heads can flow as well at the ported 5.7L heads