5.3 to lq4 swap questions
03-23-2019, 09:15 PM
#24
TECH Senior Member
03-24-2019, 11:39 AM
#27
TECH Senior Member
03-25-2019, 11:02 AM
#28
Did you see the hot rod dyno test where they tested 243's and 706 heads? They tested others too but those two were the most surprising. Stock form 706's made more power than stock form 243's.
I would like to see the test run again with the 243's milled down to the same chamber size as the 706, but out of the box and slapped on the 706 made more. But there isn't that much difference in chamber size so it wouldn't make a ton of difference, may just even them out.
This is from super chevy, I think hot rod did the same test, can't remember
Last edited by 00pooterSS; 03-25-2019 at 11:11 AM.
03-25-2019, 11:39 AM
#29
TECH Senior Member
Looks like 706's were good to about 46-4700, where the 799's bigger ports allowed it to breathe. That DOES show that you should not count 706 heads very short, though. A good bowl blend and righteous valve job would make a great low and mid range head out of it, great for truck use, or street cruising.
03-25-2019, 12:36 PM
#31
Well long story short I had someone make me an offer I couldn’t refuse on my truck at the same time I found one already built. So I just picked up a Silverado with a fresh lq9 with .025 shaved 799 heads and a btr stage 3 cam with a 4l80e swapped in. The btr is 218/224 with .560 lift roughly. Would I gain anything by switching it out for my fti 220/224 111 lsa .600 lift and come 918 springs? Also they put a stock stall in with a 4l80e flexplate and spacer. Circle D makes a 3000-3200 for the 4l80e I just want to make sure it for the 4l80e flexplate and not the 4l60e. It’s a low millage trans. I’m also debating on doing the transgo hd shift kit at the same time. I see that jakes performance makes a good set up for it so not sure which would be better. From what I’ve read they say .120 on the 1-2 shift. 3rd take the check ball out and 4th .125 for a good shift.
03-25-2019, 01:02 PM
#32
TECH Senior Member
03-25-2019, 01:34 PM
#33
It was a 5.3. Which you also don’t know if bore takes into account the 5.3 heads working better and then compression. The 243’s are on the newer 5.3’s with flattops and they also produce more power
03-25-2019, 02:20 PM
#34
Looks like 706's were good to about 46-4700, where the 799's bigger ports allowed it to breathe. That DOES show that you should not count 706 heads very short, though. A good bowl blend and righteous valve job would make a great low and mid range head out of it, great for truck use, or street cruising.
Look at the chart again, at no point did the blue line (706) go under the red (799). Only met up at times then separated again and pulled away.
03-25-2019, 02:24 PM
#35
5.3
I'm not saying the 706 is a better head, I'm stating it's surprisingly good compared to what we all thought was the be all cathedral head. And it's in some cases, better. But after seeing real world testing I personally will hold my assumptions. Edit: It's also gonna gonna be a WOT vs under the curve thing. There's no doubt at WOT at upper RPM on more cubes the 243 will take over. But what about the other 90% or so of the RPM range and under the curve?
03-25-2019, 05:03 PM
#36
This is what I always wonder about, because a 706/862 head lq4 with TBSS intake, is what I have been wanting to put in my suburban. Seems like it would be the best for torque but...... nobody measures part throttle power
Last edited by Ls7colorado; 03-25-2019 at 06:17 PM.
03-25-2019, 06:02 PM
#37
TECH Senior Member
I magnified it... Yep the colors do not trade places! lol GOT to pay better attention...
03-26-2019, 12:09 PM
#39
very worthwhile build for a truck. I haven’t done the tbss intake yet but plan to do so in the future.