318z28

lookin to swap over some 5.3 heads to my 2000 ls1 but was lookin for a little feedback on some specs on the heads and maybe someone else on here thats done that swap and how they like it...

how much compression bump do you get from the head swap and would it be ok with my stock cam, what are the combustion chamber and int/exh runner sizes on the 5.3 heads and can you use the same head gaskets and what year 5.3L truck would be the best to pull the heads off of if it makes any difference??? thanks

318z28

post has been up here for a month and a half and no responses... thanks alot for all your help everyone...

5.3LJimmy

iTrader: (10)

LS1 Head / 5.3 Head
Chamber cc: 66.7 / 61
Intake runner: 200 / 200
Exhaust runner: 70 / 70
Intake Valve: 2.0" / 1.89"
Exhaust Valve: 1.55" / 1.55"
Int Flow @.600": 227cfm / 226cfm
Exh Flow @.600": 178cfm / 174cfm
Comp Ratio: 10.1:1 / 10.8:1


BTW: It's not worth it to swap a stock 5.3 head over the stock LS1. I just spent 15 minutes of my time using google to find this info and to post it here. Thanks for your patience.

El_TransAm98

iTrader: (1)

it waste unless u port them atlest u will see a difference...

318z28

thanks for the help, yea i was plannin on portin and polishin them before they ever got put on the car but they r goin to be temporary heads anyways until i get the ones i want because u can pick them up so cheap

08 silverado z28

So since the 4.8 is the same engine would those be the same heads? Even on a 2008 4.8?

TooLateVTEC

iTrader: (2)

Porting isnt as important as upgrading the intake valve size. Just look at what 5.3Jimmy posted and look at the valve sizes.

Im still trying to figure out why you would want to go through all the work for half a point in compression for a stock camshaft? Thats going to net you maybe 10HP lol.

Gotta love the people that come on here and ask a question that any search engine can find out in 30 seconds and make a smart *** post about not getting any help.

Have fun on your quest for 10HP.

5.3LJimmy

iTrader: (10)

Your 2008 4.8 will have either the 799 or 243 casting(more commonly known as LS6 castings).

Sales2@Texas-speed

iTrader: (5)

OP: You posted late in the evening on a Friday night....this place is always slower on the weekends and unless you bump the post on Monday, it's not that uncommon for them to go unseen or unreplied to by the masses.

I'd agree, don't throw them on stock....you'll be disappointed in the performance gains if you don't port them first!

318z28

yea gotta love smartasses like urself too mr toolatevtec, im just lookin for a little feedback and doin my research and i havent researched much on it until yesterday so i think im doin just fine and the ones im lookin for are the 243 castings off a 05-07 silverado or sierra, bout to order an ls6 cam along with it

LS-1Z28

iTrader: (6)

the gains from an ls6 cam will be marginal as well

make it worth while

318z28

im not lookin to throw a monstrous head and cam package on it right now just something mild

Midnight02

iTrader: (8)

If you're goinng through the trouble of heads and a cam swap, don't waste your time with the LS6 cam. Go with a very mild 224/224 cam and match it with a set of properly ported and polished 5.3 heads and then you'll actually notice a major power increase after the tune.

TooLateVTEC

iTrader: (2)

243's and 5.3 truck heads are different.

Watch the classified section and you can find 243's in there quite often for sale used which will save you some money.

passionforracing69

ok so I have a stock ls1 and an extra 5.3l truck engine.. so basically what I am getting from this thread is that if you port and polish the heads it will bump compression and give a small gain in hp but to really see some good gains you need a good cam with it correct? what would you guys recommend?

King Nothing

iTrader: (9)

it's proven 243's outflow 5.3 heads, the only plus to havin 5.3 heads is it up's your compression big woop. have a better flowing head or a head that doesn't flow that good but bumps your compression a little depending on what you do yeah i'll go with the one the flows better . . . . oh wait i did do that lol good luck with your build OP

JonCR96Z

iTrader: (33)

For the sake of keeping the confusion down, instead of refering to them as 5.3 heads you should say 706s or 862s. 243s (LS6 castings) have been on some 5.3 engines since 2005 and all 07+ 5.3s and 4.8s have 243s/799s.

An 706/862 heads has relatively the same runners as an LS1 head but with a smaller intake valve and smaller combustion chamber. Essentially anything you do to the 706/862 heads you could also do to the LS1 heads, but you'd have slightly more compression with the 706/862s. Unless you're panning on spending a good amount of money you're probably not gonna end up with a heads that's much better, if any, than a 243/799.

If you just want more compression you could just go with a thinner gasket and/or shave the head some. It still wouldn't be worth doing for that alone and switching to unmodified 706/862 heads is more likely to hurt your power than help it.

And even if you put an AFR or Trickflow head on your car you're not gonna see that much gain on the stock cam. Switching the cam usually makes more power than just switching the heads. Even if it's a small cam. Hence the reason there are no "head only" lists on here.

Mr Bowtie

are there 5.3 /4.8 heads that one should stay away from ?

JonCR96Z

iTrader: (33)

Yes, if you are going to get a set of old 5.3 heads. Then you should try to get the 862s.

The 706 from Castech are bad about cracking through to the water jacket around the head bolt holes.

They also have a logo over the intake runners that you can use to distinguis. them.


In this pic 1 is the logo and 2 is where they leak at.




Another pic of the logo.




Other heads have this logo as well but only the 5.3 heads were affected. Here it is on some 243s.

passionforracing69

Hey man thanks for the info it's good to see some guys on here that are actually about helping some of us EFI and LS-newbies. I'm not a noob to performance or chevy engines but I have never been able to play with these engines before and I love them except the limited clearance. Like I said earlier I already have the extra set of heads but from you guys have told me so far is that it's too much work for not enough gain. Once again thanks for the info bud....