Cylinder head issues Tahoe 5.3 -02

[Olav]

I might have the common cylinder head problem on my -02 5.3 Tahoe.
I also run LPG so the the issues with valve saets are also consering me.
What alternatives do I have? As i se i can do.

1-Rebuild the heads with new seats and weld the heads, is this alu weldable ?
2- Buy second hand heads from a newer engine, from what year ?
3- Aftermarket heads ?

Anyone have any comments to these solutions ?

Regards

Olav

[Olav]

As it is now i found the water leak, it was not the heads, it was related to the LPG system. Anyway I will look into a set of new heads due to valve and valve seat wear when running on LPG. Look at photos on this link :https://www.facebook.com/photo.php?fbid=237706433082923&set=pb.202483859938514.-2207520000.1396508080.&type=3&theater

What heads to buy for a non modified engine ? I prefer not to rebuild the heads I have since they are most likely Castech heads.


Olav

[Barrrf]

I had Castech heads. I (because I cannot leave anything alone) went with a set of rebuilt 243 heads. Those are the heads found on the Z06 with the sodium filled valves. But when I was done with them they had stainless valves and porting work. I also did a cam swap since I was doing all this work anyways.

Anyways, you can also do 799 heads (same as 243 but without sodium filled valves). They flow much better than the stock 706 heads you probably have and they can be had for cheap even in rebuilt form.

The expense comes in with the rebuild kit depending on what gaskets you choose.

anyways, if you have any questions Im sure I can answer them for you.

[andrewb70]

Olav,

What do other people do that run LPG systems? Isn't there anyone around that can rebuild your heads and install the proper seats and valves to survive with LPG?

Andrew

[Olav]

Olav,

What do other people do that run LPG systems? Isn't there anyone around that can rebuild your heads and install the proper seats and valves to survive with LPG?

Andrew

Cost for rebuilding heads here in Norway is high. Cost for only machining the seats and resurface the valves for 16 pc are $300-350 shim the heads are $200 each. This is average cost if you deliver the heads cleaned and ready for machining. Exstra cost for pressure testing, bead blasting, Valve guide and stem wear/ measuring and so on. Lapping and assembly is also a cost for them who don't can do it themselves. In the end it is more economichal to change them.
Even if I used to work in a machine shop and I get good prices, the cost is high. If I take into consideration that due to wear related to LPG and I probably have to change seats and valves, and the issues With Castech heads the alternative is only new/ reman heads.
If i get a set of good rebuildable heads at fair price I will consider doing that.

[Olav]

I had Castech heads. I (because I cannot leave anything alone) went with a set of rebuilt 243 heads. Those are the heads found on the Z06 with the sodium filled valves. But when I was done with them they had stainless valves and porting work. I also did a cam swap since I was doing all this work anyways.

Anyways, you can also do 799 heads (same as 243 but without sodium filled valves). They flow much better than the stock 706 heads you probably have and they can be had for cheap even in rebuilt form.

The expense comes in with the rebuild kit depending on what gaskets you choose.

anyways, if you have any questions Im sure I can answer them for you.

Thanks, will the 799/ 243 be bolt on ? Then I know what to look for, if I could source a set With 243 heads with low miles that only need cleaning and minor lapping would probably be the best alternative for LPG. I assume that the filled valves are not suited for resurfacing, as Volvo and others that have filled valves.

[Barrrf]

Well sort of bolt on. in order to maintain the proper compression ratio the 799/243 heads need to be milled down .030. If you don't mill them the combustion chamber becomes larger and compression ratio drops resulting in a drop in HP.

The milling is a pretty easy thing to do and shouldn't cost you much even in Norway. Other than that yes they bolt right on. I don't know if the 243 valves can be resurfaced or not. I'll direct that to someone else.

[Olav]

I actually found a set of New 243 LS6 heads here in Norway. Told me he paid $980 for them and I can give him a fair offer. He also have a cam GM 12565308 cam for sale. For this he paid $280 , this is also for sale.
Anyone used this cam in the small 5.3 LM7 engine ?

Regarding milling these heads cost will not blow the budget, I can also consider raising the compression a little since LPG can take higher compression.

[Barrrf]

Olav - LOTS of people do that cam swap because the cam shaft can be had (here in the states anyways) for $100. There is some noticeable gain but it wont leave you screamin or pin you back in your chair.

Regarding milling the heads - if it were me I would still mill .030 and use a thinner-than-stock Cometic or Felpro gasket. This way if for whatever reason it didn't work or function properly you could still go back to the stock thickness (.051") gasket and be back to your normal compression ratio. The problem isn't so much the higher compression as it is clearance. I can tell you that I milled my heads .040 and have a .040 thick gasket and all is well. I don't know that you can go much more than that though.

I cant comment on the LPG side of things but when all of these changes are made I know the computer has to be programmed/tuned properly. You probably already know this though.

[Olav]

Thank you for your answers. The LPG is actually controlled by a additional computer in paralell. This runs a set of sekvensual controlled LPG injektors.
As you say milling is no big issue or cost.

For info:
I will keep the LPG due to the economy. The fule cost is half so costfor repairs is nothing compared to savings. Normally heads last 200' KM's.

Thank you!

[Barrrf]

no problem and good luck!

[Olav]

A quick update, I came over a engine from a totaled -00 GMC Yukon. This is a 6.0 according to title. I can get the 243 heads and cam for $1450 or the 6.0l pullout for $2100. can I use the 6.0 heads on my 5.3 ? And save the shortblock for my Camaro... I will get photos of it later today..

[andrewb70]

The 6.0Lheads should have a casting number 317. The 243 heads are LS6/2 heads. If it has 317 heads they will bolt on a 5,3L but they have larger combustion chambers so it will lower compression. This is a popular swap for people that put a turbo on 5.3L engines.

Andrew

[Barrrf]

What Andrew said. You cant shave them down enough to bring your compression up to the right level without interference issues.

[69cutlassrkt]

Seems like even a lot of turbo guys don't go with the 317s anymore cause the compression is too low for them. Unless it's strictly a drag car or you don't mind it being a dog without the boost. kind of an old school of thought now, the super low compression for boosted motors.