HitchHiker

Hello all,

I'm looking SERIOUSLY at Absolute Speed's H/C deals, they are selling their 5.3 Stage II heads for 1449.00 right now plus refundable core charge, just seems too good to pass up!

Anyways, I'm relatively new to the H/C thing. Can someone give me a general overview of why one would go with 5.3L versus 5.7L versus 6.0L heads? I'm assuming it's mostly to either boost (5.3) or lessen (6.0) compression ratio, but that's probably not all?

The Absolute sale is on thru 4/1 for those interested BTW...Stage I starts at only 889.00, awesome deals.

HitchHiker

TTT

Ed Blown Vert

iTrader: (2)

ttt

SuperZ28

I'd like to know the specific details on each as well...

TTT

Constrictor 98TA

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong> 5.7= stock for us, 67 cc chambers
5.3= stock for truck, 62 cc chambers
6.0= stock for truck, 70 cc chambers
LS6= stock for Z06, 64 cc chambers.

Basically the 5.3's don't require major milling to achieve more compression... </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">To elaborate on what John said, the 6.0L heads have similar flow numbers to LS6 heads, so if max flow is your aim and you don't want to spend the money on LS6 heads, 6.0L heads are a good compromise.

5.3L or 4.8L (theyre the same) heads have a smaller combustion chamber (as John said) which makes obtaining a higher compression ratio easier. I think that putting 5.3L heads unmilled on an otherwise stock 5.7L block, you get a CR of 10.5:1. You can mill them a little to easily get over 11:1 compression ratio without any serious piston to valve clearance problems.

5.3L heads have a smaller intake valve compared to the 5.7L heads, so you would definitely want to get new valves put in before installing them to your engine.

In the end, the 5.7L heads aren't bad by any means. With a .030" mill, you can obtain a 10.8:1 compression ratio, and with a good port, can come within 20-30 CFMs @ high lift of ported LS6/6.0L heads. And remember, CFMs aren't the only thing that makes a car fast...

DailyAluminumBlock

In eveyones honest opinion which head offers the best CFM with good velocity. This is a very broad question and can be interpreted in many ways so any input will be appreciated.

PHANTA-Z

Im curious as well. Come on now, all these whiz-bang experts who've forgotten more about how to make big numbers than we'll ever know, give some low down here. Thanks in advance.

Pro Stock John

iTrader: (34)

5.7= stock for us, 67 cc chambers
5.3= stock for truck, 62 cc chambers
6.0= stock for truck, 70 cc chambers
LS6= stock for Z06, 64 cc chambers.

Basically the 5.3's don't require major milling to achieve more compression...

Pro Stock John

iTrader: (34)

For what application, a stock bore motor?

In the end the LS6 heads will be the best if all the heads have the same porting and same size valves, and if we assume that none of them have been milled for additional compression. The feeling right now is that LS6 heads on a stock cube motor might be worth another 10rwhp.

GoldRamAir

1997+ LS1 66.67 cc 10.1 cr 2.00 intake 1.55 exhaust standard LS1 head and best all round

2001+ LS6 64.45 cc 10.5 cr 2.00 intake 1.55 exhaust d-ported version of the LS1

1999+ LR4,LM4, LM7 61.15cc 9.5cr 1.89 intake 1.55 exhaust 4.8/5.5 truck head small cc but also has small intake valve, needs head milling and valve upgrade

1999-2000 LQ4 (iron)71.06 cc 9.5 cr 2.00 intake 1.55 exhaust 6.0 truck engine good for boost but extremely heavy

2001+ LQ4 71.06 cc 9.4 cr 2.00 intake 1.55 exhaust 6.0 truck engine aluminum version good boost head

2002+ LQ9 71.06 cc 10.0 cr 2.00 intake 1.55 exhaust High performance version of 6.0 engine similar to LS6 best head for high boost applications

GMPP "Gen-III Racing" 65 cc 10.5 cr 2.00 intake 1.55 exhaust GM ported LS6 heads

GMPP "Showroom Stock Racing" 63 cc 10.8 cr 2.00 intake 1.55 exhaust stock LS1 head milled to reduce combustion chamber and raise cr

I hope this helps

Ling_650vette

iTrader: (1)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by GoldRamAir:
<strong> 1997+ LS1 66.67 cc 10.1 cr 2.00 intake 1.55 exhaust standard LS1 head and best all round

2001+ LS6 64.45 cc 10.5 cr 2.00 intake 1.55 exhaust d-ported version of the LS1

1999+ LR4,LM4, LM7 61.15cc 9.5cr 1.89 intake 1.55 exhaust 4.8/5.5 truck head small cc but also has small intake valve, needs head milling and valve upgrade

1999-2000 LQ4 (iron)71.06 cc 9.5 cr 2.00 intake 1.55 exhaust 6.0 truck engine good for boost but extremely heavy

2001+ LQ4 71.06 cc 9.4 cr 2.00 intake 1.55 exhaust 6.0 truck engine aluminum version good boost head

2002+ LQ9 71.06 cc 10.0 cr 2.00 intake 1.55 exhaust High performance version of 6.0 engine similar to LS6 best head for high boost applications

GMPP "Gen-III Racing" 65 cc 10.5 cr 2.00 intake 1.55 exhaust GM ported LS6 heads

GMPP "Showroom Stock Racing" 63 cc 10.8 cr 2.00 intake 1.55 exhaust stock LS1 head milled to reduce combustion chamber and raise cr

I hope this helps </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Straight from GMHTP <img border="0" alt="[USA]" title="" src="graemlins/patriot.gif" /> lol

I was fixin to say GMHTP has an almost complete rundown of Gen III heads (it doesnt mention the aftermarket brands from LPE, MTI, ARE and so on) but it does list the differences between LQ9, LM7, LQ4, LS1 and LS6 heads. And is basically word for word what GoldRamAir said...

zTrackerz

To make it short... If you are on a budget the 5.7 Ls1 heads are the way to go. Get them ported and your set...
If you have the extra money the LS6 are the best for performance. They offer the slightly smaller combustion chambers, for a slight CR increase, also the D shaped exhaust for improved flow.
The 5.3 are ok. These mainly if you want to increase CR without milling, they have smaller valves so you'd need a valve upgrade.
The 6.0 are good for blowers/turbos. The larger combustion chambers are good for the decrease in CR for blower/turbo use....

Boosted LS1

Has anybody modded the LS1 exhausts to D port configuration? Did they flow better? Also is it only the late LS6 heads that have the sodium valves or do the late 6.0 head get them as well?

I'd like truck heads with sodium valves.

ss1le02

iTrader: (4)

What is the biggest lift on a cam you can have if you have milled 5.3 liter heads?

Tin Indian

ss1le02 ...

It's not just high lift that causes piston to valve clearance problems, but duration is a very big factor. I understand that duration plays even a more important role. The 5.3 heads will allow for a larger cam than the 5.7 heads as long as both heads are setup to yield the same CR.

You say "milled" ... Well, it all depends on how much they are milled and the cams lift and cam duration.

There is no simple formula that I am aware of.

Ron,

Tin Indian

ss1le02 ....

What do you fly?

Ed Blown Vert

iTrader: (2)

Is it worth getting the 5.3L heads for the added compression? Or will it make the engine more prone to detonation??

SuperZ28

I think even up to 11.0 CR you'd be fine running 93 octane pump gas....detonation should NOT be a prob with a proper tune.....

<small>[ April 14, 2003, 09:28 AM: Message edited by: SuperZ28 ]</small>

Ed Blown Vert

iTrader: (2)

OK, so any disadvantages??
I am getting ready to order some.