243 Heads on 5.3 - PerformanceTrucks.net Forums
Click here to visit LS1Tech
Click here to visit Performance Trucks
Click here to visit Mod Motor Tech
Click here to visit Modern Hemi

PerformanceTrucks.net Forums  

Go Back   PerformanceTrucks.net Forums > GENERAL MOTORS SPECIFIC FORUMS > GM Engine & Exhaust Performance



243 Heads on 5.3

Reply
 
LinkBack Thread Tools Search this Thread
Old 04-07-2009, 07:58 PM   #1
Teching In
iTrader: ( 2 )
 
EZDOESIT's Avatar
 
Join Date: May 2008
Posts: 9
Default 243 Heads on 5.3

I know this mod has been beaten to death, but I need some clarification.

I have a GMC 99 Stepside with a 5.3l engine, Radix 112 Magnacharger w/3.0 pulley, Dynatech longtube headers, stock heads (LS6 cam and yellow behive springs).

I have a set of LS6 243 heads, which I would like to install, but I'm not sure how much to mill off the decks. Since I have a supercharger, do I want to mill less than the .030" than what's been suggested in the forum?

Is this mod a good idea or a waste of time and money, not enough bang for the buck??

Any expert advice would be appreciated. Thanks.
EZDOESIT is offline   Reply With Quote
Old 04-10-2009, 11:00 PM   #2
11 Second Truck Club
iTrader: ( 48 )
 
fastrt's Avatar
 
Join Date: Jul 2007
Location: Midlothian, Texas
Posts: 1,986
Default

lower compresson, you can run more boost, 243's flow better than stock by far, and you would have a ls6 top end. I would run them as is.
__________________

2006 RCSB Silverado 347ci LS1
12.56@106 N/A...SOLD!!

2008 G8 GT....SOLD!!

2004 GMC 2500HD LLY/Allison 4WD.
2012 Chevy Cruze Silver RS...AKA Zippy.
fastrt is offline   Reply With Quote
Old 08-06-2009, 02:53 AM   #3
On The Tree
iTrader: ( 7 )
 
trenz68's Avatar
 
Join Date: May 2009
Location: Baytown Tx
Posts: 145
Default

i would like to know also
trenz68 is offline   Reply With Quote
Old 08-06-2009, 09:34 AM   #4
Teching In
 
Join Date: Jun 2009
Posts: 28
Default

Agree with fastrt. However, depending on their age/condition you may want to mill .010" just to true them up.
04Crew is offline   Reply With Quote
Old 08-06-2009, 11:27 AM   #5
12 Second Club
iTrader: ( 13 )
 
Join Date: Feb 2005
Location: Gateway International Raceway
Posts: 1,574
Send a message via Yahoo to ExceSSive
Default

What CC are the stock heads...the LS6 heads are 64cc making 10.5:1 on a 5.7L. I am sure you know if the 5.3 heads have bigger chambers or by milling them you make the LS6 heads smaller then you are bumping up compression. I do agree if they have many miles on a slight mill to true them up is a good thing.
__________________
00 Suburban 5.3L, 120k and going (for sale).
02 SS HKE 408, VR Ported FAST92, Moser, Performabuilt, etc (SOLD)
2011 GMC Yukon
ExceSSive is offline   Reply With Quote
Old 08-07-2009, 08:30 AM   #6
Teching In
 
Join Date: Jun 2009
Posts: 28
Default

All heads will vary slightly but I think that stock 5.3's are about 61 and the LS6 (243) heads are 64 or 65. I think that head volume will decrease 1 cc for every .005" of milling. Even with a slight mill, the LS6 heads would still be 63 cc or so which would decrease his compression ratio slightly. He can play around with head gasket size if he wants to fine tune it.

*disclaimer, number noted above are off the top of my head (and therefore approximate). If you wany exact numbers, do you own search.
04Crew is offline   Reply With Quote
Old 08-22-2009, 01:11 AM   #7
On The Tree
iTrader: ( 7 )
 
trenz68's Avatar
 
Join Date: May 2009
Location: Baytown Tx
Posts: 145
Default

so are 234s left alone the best for a 5.3 with a radix.
trenz68 is offline   Reply With Quote
Old 08-22-2009, 01:17 AM   #8
2nd fastest 5.3 ECSB
iTrader: ( 14 )
 
trever1t's Avatar
 
Join Date: Oct 2005
Location: NorCal
Posts: 26,691
Send a message via MSN to trever1t
Default

It is only my opinion, but I have seen the radix perform very well on cars and trucks running at or just under 10:1 compression. Putting the 243's on a stock LM7 will drop CR, sure you can run more boost and maybe better peak HP but at the cost of your power out of boost. I'd set them up to at least keep the stock CR. Just my observations/opinion.
__________________
2005 SIERRA 11.34@119.81 THE SILVER BULLET
626/762 RWHP/TQ
My other ride is a '91 Electraglide custom.
trever1t is offline   Reply With Quote
Old 08-22-2009, 02:51 AM   #9
On The Tree
iTrader: ( 7 )
 
trenz68's Avatar
 
Join Date: May 2009
Location: Baytown Tx
Posts: 145
Default

ya im wanting to stay close to the same compression. i have a 5.3 with stock 706 heads, gt2-3 cam with a radix. Just wanting some opinion on installing stock 243 (ls6) heads will help out any or just go with aftermarket ls6 heads?
trenz68 is offline   Reply With Quote
Old 08-23-2009, 07:58 AM   #10
TECH Addict
iTrader: ( 4 )
 
SweetS10V8's Avatar
 
Join Date: Jun 2004
Location: Michigan
Posts: 2,584
Default

If your going to use #243 heads dont mill them, OEM or aftermarket if your going boosted.
__________________
Quote:
Originally Posted by John Lingenfelter
The world's best cam combined with a poor set of heads will produce an engine that's a dog. But bolt on a set of great heads even with a poor cam, and that engine will still make great power.
SweetS10V8 is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Turbo 2007 NNBS Silverado RCSB chopperloco Trucks and SUV Classifieds 11 01-30-2016 12:29 PM
Looking into a newer truck with 4wd cams 98 silverado GMT 900 Trucks General Discussion 7 07-31-2015 07:36 AM
another cam thread steves86ta GM Engine & Exhaust Performance 5 07-28-2015 10:21 AM
Custom ground 4.8/5.3 cam 06 4.8 GM Parts Classifieds 2 07-15-2015 07:17 PM
Lets talk Valve Springs. Experts please come in. 07NBSChevy GM Engine & Exhaust Performance 20 07-08-2015 07:27 PM


Tags
01, 07, 243, 53, 53l, 706, headers, heads, lm7, ls6, magnacharger, mill, milling, silverado, supercharger

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -5. The time now is 11:06 AM.



PerformanceTrucks.net and InternetBrands, Inc. are not affiliated with the Ford Motor Company