Castech heads have been leaking antifreeze into the heads (oil) of a 2004 5.3L for over a year now. Leak has been very slow. No milk on the dip stick. Sludge in the oil filler cap. Heads seem to be weeping oil in the back too. Eats a gallon of antifreeze every 1000 miles. Engine has 160k on it. No oil pressure problems yet.

Questions:

• Do I replace the engine or only the heads?
• Best deal on replacement heads?
• Best deal on replacement engine (I don't do junkyard pulls)?
• Would larger valve heads make a noticeable difference with the factory cam?
• What are the largest valves that will fit in a 5.3L?
• What's the highest compression people have been running on 87 octane in an LS1?

 

Drop the idea of bigger valves.
If you refuse the junkyard idea maybe price a new GM engine with no worries.

Drop the compression idea on 87 octane too.

 

You can probably find some 862's on Craigslist, but keep an eye out for that Castech logo so you don't end up in the same situation later on. If you just swap that out and change your oil, I'd think you would be fine.

You can use 2.02"/1.60" valves in a 5.3L with the stock seats, but with such a small engine and factory cam, it may not be worth it unless you plan on having a valvejob cut anyways.

 

The most important question, is the engine likely shot?

 

2.0 valve is the largest you can go with the bore size of the 5.3. The bigger valve might make 862s flow about 5%-10% better IMO. You have to get a price on the valve job and decide if it is worth it to you. Stock LS1 intake valves are that size so you could find some cheap used LS1 valves to use. Another option would be to find some LS1 heads and have them milled down to reach stock 5.3 compression ratio. Stock LS1 heads have much larger combustion chambers than early 5.3 heads - by about 10cc. But if you are sticking with a stock cam, you could have LS1 heads(which would cost you $100-$150 depending on condition and the seller) milled .030 or so for under $100 and likely be just fine for piston to valve clearance...and have the bigger intake valve. The stock 5.3 intake is a bit restrictive at high RPMs so don't expect it to breathe fire, but it would breathe a little better.

I *think* Castech heads are 706 casting number and 862s should all be devoid of the cracking/leaking problems. Someone please verify. I've gotten nice sets of 862 heads on eBay for $100- $150 shipped. I've got a set of 12K mile 853(LS1) heads in the box ready to go that I don't plan to use if you decide to go that route..but 862s would bolt right on.

If the problems are because of the heads, the short block could be just fine. How does it run?

Good luck!

 

I'm currently considering the stage 2.5 heads PRC heads from TSP or the ported heads from SDParts. I'd prefer heads with a 1.6 exhaust valve, no less than a 2.00 intake.

I wouldn't mind something less than $1100 for the pair.

 

Ah. I gathered that we were looking at factory-type parts since you indicated stock cam. If you're interested in aftermarket stuff, you will be quite happy with either of those you mentioned. You would likely want a cam and exhaust to get the most out of ported heads though it isn't entirely necessary. The factory intake will be restrictive above 5000RPM as well but depending on your cam choice, that may not be a problem.

 

That engine has a lot of miles on it and I'd start to wonder about the bearings especially if water got it there. It sounds like the OP has driven it a lot after the problem started.

 

Seems like a waste to replace with stock parts. considering I'm not doing the work and I have to pay ~$800 in labor for the swap. Not really planning to run the Z71 4x4 above 5000 much. Considered higher ratio rockers.

Considering the bearings' prolonged exposure to glycol, I'm not sure a new cam would break in without failing. At the moment, I don't even know how long the bottom end will hold together.

 

Its a hard thing. Now, even with the cracked heads it runs well with good oil pressure. Wonder if the Mobil One made any difference.

Conflicted.

 

It would be foolish to do ported heads and all with a stock cam.
The intake was fine on 6.0l engines and better than LS1 intakes coupled with you low rev intentions don't let anyone talk you into thinking twice about it.

 

Using confrontational words like "foolish" is a poor substitute for facts. Give me a link to non-ported heads with 2.00 intakes that aren't ported and I'll consider them.

My only realistic options so far:

https://sdparts.com/details/scoggin-...center/sd8926c

https://www.texas-speed.com/p-4345-p...-outright.aspx

If you have something better/cheaper, reply with a link.

 

You have the option just to have the valve job cut for larger valves without actually purchasing the porting service along with it. Advanced Induction (AI) used to do this, but your local machine shop should be able to do it for a couple hundred dollars. It would be best if they had a nice valve job profile for the heads too, rather than the old trusty (and OEM) 30-45-60 degree profile.

If you're planning on using the stock cam, you could also just slap on a set of 243/799 heads and have the deck milled for about the same price or less. They come with 2.00" intake valves from the factory.

 

I don't want to use a stock cam. I just doubt the engine can tolerate a cam swap. Got any links to new unported heads? The ones I've found cost as much as the SDParts heads.

 

Anyone had any luck with Castech heads just using stop leak in the antifreeze? I suspect the expansion/contraction of the aluminum won't allow it to work.

 

What would be the point of using bigger valves on stock seats? Don't you need a larger seat to increase flow?

 

You can use the stock seat, but you have to machine it for the larger valve.

 

If you think "foolish" is confrontational then an Internet forum is the wrong place to be. Sounds like you want blind validation of your ideas.

You want more performance but are refusing the some of the best things you could do like a cam.
Hell if you want more low speed power a junkyard lq4 would be the cheapest easiest option, not screwing around with heads on a 5.3 that has burned gallons of antifreeze.

 

You likely won't find new old stock heads cheap unless you get lucky.

As I mentioned I have a set of 12K mile 853 takeoffs(LS1, 2" valve) you can have for $120+shipping(probably $40 or so shipping). They are CLEAN. About as close as you will get, I think. Other than that, find yourself a set of good used 862s. Or the LQ4 route mentioned above is easy and still cheaper than a set of ported heads for a used long block.

Hell, you're right in Houston. I'm in Baton Rouge. I have a fantastic 5.3 with about 80K miles on it with 862s, etc. Will make you a heck of a deal on it if you come pick it up. Could even meet you somewhere. Pulled a head off only to get a broken exhaust manifold bolt fixed up(commonly break off in LS motors) and then found an LS2 in the mean time and putting that in. Can still see the cross-hatching in the cylinders of the motor and will give you at least another 100K miles of good service. Was going to wait until I finished the swap and clean it up and put it up for sale but if you want it you can get it tomorrow.

Send me a PM with your phone number if you are interested.

Good luck.

Chris

 

I was being nice. You are a jerk. Don't bother chiming in and wasting your time and mine. If you knew half of what you claim to know, you wouldn't be so insecure about it. Congrats, you made a caprice go fast. Now go away.