So, why all the new interest in ported 5.3 Truck Heads?
10-16-2002, 07:39 AM
#1
TECH Fanatic
Thread Starter
So, why all the new interest in ported 5.3 Truck Heads? Well, I know they have smaller combustion chambers. That in itself will yield maybe somewhere around 11.0 to 1 CR
But with the best pump gas being between 91 octane in Phoenix and many other high altitude areas to maybe 93 octane in the majority of low altitude areas, I can't see where anyone would really need a CR of 11 to 1 or greater.
Hell, mill a set of your stock 5.7 heads .035", and your going to get approx 10.7 to 1 CR
That certainly is enough for 93 octane pump gas.
I keep hearing of folks getting audible pinging and knock retard in there stock 10.1 CR engines. What do you think 11.0 to 1 will do in your daily driver in the heat of the summertime?
Another thing, I may be wrong, but don't the 5.3 truck heads have smaller valves than the 5.7? Just more cost to upgrade since it will require new valve seats. Will a 5.3 head accept a 2.02"/1.57" set of valves like the 5.7 engine with no change to the valve seats (like the 5.7)?
One last thing, I have never heard that the stock ports on the 5.3 were any better flowing than the stock 5.7 LS1 heads.
So, is it the 11 to 1 CR without any milling that so many folks are opting for the 5.3 heads? If so, I think there might be better money spent on just porting/milling your stock 5.7 LS1 heads.
I'm not trying to step on anyone's feet here...
Please correct me if I am wrong... <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
Ron,
Oh ya... One other question; Don't the 5.3 heads require some extra machining in the combustion chambers do to more valve shrouding when used on the larger bore 5.7 engines, since it was never designed in the first place for the 5.7?
Seems like an awfull lot of work just to get the CR up a little better than the 5.7 heads.
Again, please correct me if my info is for ****.
______________________________________________
<small>[ October 16, 2002, 07:54 AM: Message edited by: Kimchee and Rice ]</small>
But with the best pump gas being between 91 octane in Phoenix and many other high altitude areas to maybe 93 octane in the majority of low altitude areas, I can't see where anyone would really need a CR of 11 to 1 or greater.
Hell, mill a set of your stock 5.7 heads .035", and your going to get approx 10.7 to 1 CR
That certainly is enough for 93 octane pump gas.
I keep hearing of folks getting audible pinging and knock retard in there stock 10.1 CR engines. What do you think 11.0 to 1 will do in your daily driver in the heat of the summertime?
Another thing, I may be wrong, but don't the 5.3 truck heads have smaller valves than the 5.7? Just more cost to upgrade since it will require new valve seats. Will a 5.3 head accept a 2.02"/1.57" set of valves like the 5.7 engine with no change to the valve seats (like the 5.7)?
One last thing, I have never heard that the stock ports on the 5.3 were any better flowing than the stock 5.7 LS1 heads.
So, is it the 11 to 1 CR without any milling that so many folks are opting for the 5.3 heads? If so, I think there might be better money spent on just porting/milling your stock 5.7 LS1 heads.
I'm not trying to step on anyone's feet here...
Please correct me if I am wrong... <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
Ron,
Oh ya... One other question; Don't the 5.3 heads require some extra machining in the combustion chambers do to more valve shrouding when used on the larger bore 5.7 engines, since it was never designed in the first place for the 5.7?
Seems like an awfull lot of work just to get the CR up a little better than the 5.7 heads.
Again, please correct me if my info is for ****.
______________________________________________
<small>[ October 16, 2002, 07:54 AM: Message edited by: Kimchee and Rice ]</small>
10-16-2002, 08:27 AM
#2
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Re: So, why all the new interest in ported 5.3 Truck Heads? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>Hell, mill a set of your stock 5.7 heads .035", and your going to get approx 10.7 to 1 CR
That certainly is enough for 93 octane pump gas.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">For most people, 10.7:1 would be enough. You can easily run 93 octane without any problems, assuming your tuning is in order. This is what a majority of the people are doing. The people opting for the 5.3l heads are just looking to squeeze a little more hp/tq out of their setup.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>I keep hearing of folks getting audible pinging and knock retard in there stock 10.1 CR engines. What do you think 11.0 to 1 will do in your daily driver in the heat of the summertime?</strong> </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">When most people add a set of ported heads to their car, they are also upgrading to a larger cam with more overlap. This will bleed off quite a bit of the cylinder pressure added with the extra compression.
My car was one of those who pinged audibly on 93 octane with the stock heads/cam, with no tuning or ported MAF in the car. Once I added a cam and then heads later down the road, the pinging went away, even though I was running a little over 11:1 compression.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>Another thing, I may be wrong, but don't the 5.3 truck heads have smaller valves than the 5.7? Just more cost to upgrade since it will require new valve seats. Will a 5.3 head accept a 2.02"/1.57" set of valves like the 5.7 engine with no change to the valve seats (like the 5.7)?</strong> </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yes, the 5.3l heads come with 1.89/1.55 valves. However, upgrading to the 2.02/1.57 does not require you to change out the seats.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>One last thing, I have never heard that the stock ports on the 5.3 were any better flowing than the stock 5.7 LS1 heads.</strong> </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">In stock form, the 5.3l heads flow less on the intake and just ever so slightly better on the exhaust. Once ported, these differences are hardly noticeable (assuming the heads have the same valve size).
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>So, is it the 11 to 1 CR without any milling that so many folks are opting for the 5.3 heads? If so, I think there might be better money spent on just porting/milling your stock 5.7 LS1 heads.</strong> </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">It usually does not cost anymore money to "upgrade" to the 5.3l heads. Most people just sell their stock heads and purchase a 5.3l set from a junk yard or Valvegod to turn in as a core. Some shops even take 5.7l heads for cores on 5.3l heads. It just all depends on the shop.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>Oh ya... One other question; Don't the 5.3 heads require some extra machining in the combustion chambers do to more valve shrouding when used on the larger bore 5.7 engines, since it was never designed in the first place for the 5.7?</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif"></strong>
Yes, this is correct.
That certainly is enough for 93 octane pump gas.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">For most people, 10.7:1 would be enough. You can easily run 93 octane without any problems, assuming your tuning is in order. This is what a majority of the people are doing. The people opting for the 5.3l heads are just looking to squeeze a little more hp/tq out of their setup.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>I keep hearing of folks getting audible pinging and knock retard in there stock 10.1 CR engines. What do you think 11.0 to 1 will do in your daily driver in the heat of the summertime?</strong> </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">When most people add a set of ported heads to their car, they are also upgrading to a larger cam with more overlap. This will bleed off quite a bit of the cylinder pressure added with the extra compression.
My car was one of those who pinged audibly on 93 octane with the stock heads/cam, with no tuning or ported MAF in the car. Once I added a cam and then heads later down the road, the pinging went away, even though I was running a little over 11:1 compression.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>Another thing, I may be wrong, but don't the 5.3 truck heads have smaller valves than the 5.7? Just more cost to upgrade since it will require new valve seats. Will a 5.3 head accept a 2.02"/1.57" set of valves like the 5.7 engine with no change to the valve seats (like the 5.7)?</strong> </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yes, the 5.3l heads come with 1.89/1.55 valves. However, upgrading to the 2.02/1.57 does not require you to change out the seats.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>One last thing, I have never heard that the stock ports on the 5.3 were any better flowing than the stock 5.7 LS1 heads.</strong> </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">In stock form, the 5.3l heads flow less on the intake and just ever so slightly better on the exhaust. Once ported, these differences are hardly noticeable (assuming the heads have the same valve size).
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>So, is it the 11 to 1 CR without any milling that so many folks are opting for the 5.3 heads? If so, I think there might be better money spent on just porting/milling your stock 5.7 LS1 heads.</strong> </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">It usually does not cost anymore money to "upgrade" to the 5.3l heads. Most people just sell their stock heads and purchase a 5.3l set from a junk yard or Valvegod to turn in as a core. Some shops even take 5.7l heads for cores on 5.3l heads. It just all depends on the shop.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>Oh ya... One other question; Don't the 5.3 heads require some extra machining in the combustion chambers do to more valve shrouding when used on the larger bore 5.7 engines, since it was never designed in the first place for the 5.7?</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif"></strong>
Yes, this is correct.
10-16-2002, 08:35 AM
#3
TECH Fanatic
Thread Starter
Re: So, why all the new interest in ported 5.3 Truck Heads? Jason.... Your a world of info! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Seriously, thanks for the info. I still think I will stick with the regular ported / milled 5.7s
Have ya had a chance to check that TR-220 base circle yet for me? I'm still buggin you about it <img border="0" title="" alt="[Razz]" src="gr_tounge.gif" />
Ron,
Seriously, thanks for the info. I still think I will stick with the regular ported / milled 5.7s
Have ya had a chance to check that TR-220 base circle yet for me? I'm still buggin you about it <img border="0" title="" alt="[Razz]" src="gr_tounge.gif" />
Ron,
