Was wondering what the best bang for buck heads are for ls1. Currently have the stock 853 heads and a head gasket leak. Already replaced the head gaskets and it still leaks so I'm just gonna upgrade heads while I'm at it. Heard the 243s and 5.3 heads are both good but wanted some different opinions. Trying to stay under or around 12-1300.

 

did you resurface the heads when you changed the gaskets?

 

I scraped off all the old gasket left on there making sure to not knick the surface up. hit it with brake cleaner and wiped it down real good on block and head surfaces. I got it pretty damn smooth enough to run my fingernail over it and it wouldn't get caught up on anything. Put it together and it had a leak so I brought it to a mechanic and had him screw with it. I got it back from him and had to call and tell him it still leaks. He said my heads are either cracked or warped so here we are.

 

The 243 heads where the rave back in the day and bolted to the once enfamous LS2 then GM started using them on the 5.3's and now they can be had for cheap. Also look for the 799 casting which is really the same cylinder head.

 

that's your problem then man, when you change head gaskets you need to bring the heads to a machine shop and have them resurface the heads. when you overhead a motor or also known as blow a head gasket, your heads may get slightly warped but the machine shop will correct that for little to no money, alot cheaper then getting new heads. Also you have to make sure to use new head bolts as the bolts are only a 1 time use. I'd pull the heads off and take them to a machine shop unless of course you just want new heads and when you put it together make sure to follow gm torque specs I would change the gaskets again with this process even though you just changed them. In my opinion it's not worth the risk.

 

op didn't resurface the heads when changing the gaskets. There's probably nothing wrong with them that a trip to the machine shop couldn't resolve. thats less then 200 bucks my way

 

When did it become a requirement to resurface a head everytime you install new head gaskets? My post was informative at best and it wasn't put out there to one up anyone but since we're on the subject of warped heads, Do you know if the heads are warped or not? You could lay them down on a piece of flat glass and do the old slide a piece of paper under the head trick to see if they're warped or not and if so then break out some feeler gauges and see just how warped they really are. I would rather do that first than take the time and money to send them to a machine shop. Yes you can get them resurfaced only if they haven't been milled to the point that you can't do anything else with them. Do you even know if they've been milled or not?

For cleaning the surface of the cylinder heads a razor blade scaper, some brake cleaner, emory cloth and a little elbow grease can clean the surface of the cylinder heads. A light coat of Permatex copper spray on each side of the new HG is all that's needed to get a good seal too.

 

I didn't take it like that bro, not counting tally marks here just trying to give op advice. Read his second post he had a mechanic confirm warp or crack and my vote would be warp. Sounds like his vehicle is pretty close to stock if he's asking the difference between the 2 heads. Sounds to me like he probably ran the car hot at some point and blew the gaskst or damaged it enough that it eventually starting showing itself. Also when I blew the gaskets on my turbo silverado I had to get mine resurfaced. I did the copper spray and it still leaked, so I had to pull it back apart and get them cut and now I'm good to go, mine were cut at 30 thousands and I had to go to 40.

 

Are you sure the right gasket was used for the 853 heads? They probably have a notch in the deck surface and require a special gasket for them to seal properly since the fiber gaskets are no longer available for them. Not all MLS gaskets will seal this condition.

https://ls1tech.com/forums/generatio...-ws6store.html

 

Think they have proven many times over now the cheapy truck small valve small chamber heads will make the most power. Not to mention they are usually less than $200 a pair at any junk yard. I routinely pay $100-150 for a pair of 706 heads. They flow less, and have a smaller intake valve. But the tiny 61cc chamber more than makes up for that. Id buy a set of 706’s from the local junk yard or FB marketplace. Put a straight edge across them to ensure they are flat… and run them. Believe it bumps ya up to about 11:1.

As mentioned above… when you take your heads off, confirm if they used the notched head gaskets the 853’s require. Also confirm the notch was in the correct place.

 

Typical forced induction thinking.

The small-valve small-chamber heads will make the most power, IFFF the valve isn't the limit to cylinder fill.

CYLINDER FILL.. That's the key to making power. Power comes from 2 things: one we can call "thermal efficiency", which is, the engine's ability to turn the heat generated from combustion, into useful work (DOMINATED by compression); the other, is how much fuel is burned in each cylinder's cycle, therefore, how much air/fuel can we jam into there. If you're N/A, then the ATMOSPHERE - 14.7 psi give or take - is ALL you can ever access to fill your cyls, apart from limited effects from intake inertia and exhaust scavenging and such as that. If you're boosted (AHEM, forcefed86) then all of that is OUT THE WINDOW, since you can just turn up the boost and drive MORE air/fuel through intake trace restrictions such as small intake valves and crappy manifolds.

Sure, if you can somehow assure that the intake valves aren't The Bottleneck to the engine's overall performance, they yeah, the 706 type heads are FOR YOU. On the other hand, that doesn't fit ALL possible scenarios. IFF (mathematician for "if and only if") something else in your motor is The Bottleneck (the cam, exhaust, whatever) they're GREAT. Butt if the intake valve diameter is The Bottleneck, then opening them up (243 vs 706), can give MUCH greater benefits than the compression bump. All depends on the combo IN TOTAL.

OTOH, for all the rest of us that are N/A, the tradeoff that the small-valve heads present, is a conundrum. Can we make enough MORE power by way of their small chambers (higher compression, therefore higher "thermal efficiency", therefore more of our fuel's chemical energy goes into pushing pistons down instead of going into the cooling system or out into the exhaust); or, can we benefit MORE from simply being able to get MORE molecules of air/fuel (better FLOW) into each cyl? Can be a tough question sometimes. There's no "one size fits all" answer in the N/A world, unlike Boost World. Boost man's opinion might run COMPLETELY counter to the world YOU live in.

IGNORE the "advice" given to you by someone who wants to pleasure his smallest member about what he "knows". Instead, think CAREFULLY about what YOUR motor needs to do, FOR YOU. All of us are different. Some are drag racers, some run spec motors (ASA e.g.) on round tracks, some run on the street, some are rock crawlers, some just want to not get stuck in ruts when we go hunting, some want to haul concrete around construction sites, some want to give our (possibly less technical) family members some pretty-day fun with minimal probability of the car breaking, and so on. It's up to each of us to decide what's most important. Don't get all hung up on "most power" and all that, to the exclusion of ALL OTHER factors (how about, fuel we can buy down at the corner gas station where we live); consider what YOUR vehicle will be used for, on YOUR roads or tracks or whatever, with YOUR driver, on fuel YOU can buy with YOUR money to put in YOUR car. Me, I would tolerate VERY DIFFERENT things if I was building let's say a cruiser for my wife or daughter to cruise her convertible around on pretty Sunday afternoons, as opposed to ... some of those other things. DON'T get all wound up in "most power" if that's not your PRIMARY objective. Whether the car starts up reliably, can pass some things besides a gas station, won't overheat on some sandbar somewhere (yes I was out skiing on the Mississippi River near Memphis on the day it hit its lowest recorded gauge reading until the 21st century), etc. etc. etc. Sure, "more power Scotty" is A Real Good Thing, but there can be more to life sometimes.

So:

What kind of vehicle is this? What do YOU want to use it for? What other modifications, if any, does it have done to it? What doesn't it do now, that you'd like it to? or, what would you like to improve?

 

You are clearly trying way too hard with the cut/paste internet knowledgebase and clear lack of experience. Go ahead and google search the “coefficient of discharge” and “port velocity”. It gives a much more accurate representation of the cyl heads power potential than valve size.

The 706 heads flow really well for a factory head.. They flow enough to still be efficient around 470chp. The OP’s factory ls1 isn’t making that. He clearly just wants his car back together without leaky heads. Arguing about a 1.89” VS a 2.0” intake valve is moronic. We are talking .11”. It’s not worth the time/effort on a setup that hasn’t maxed out the smaller valve yet.

There have been several back-to-back tests where they swap all the OEM heads around on 5.3’s and 6.0’s. Holdner’s are probably the most “Famous”. They clearly show the small valve heads (stock for stock) make the most power. (Yes, more than 243’s.) All NA tests, nothing to do with forced induction.

An engine is just an air pump. If it makes more power NA… its will make more power when you add boost. Suggesting boosted performance is some sort of contrary voodoo compared to NA performance is nonsense. Another clear lack of experience and general knowledge.

The 243’s lose out to the lowly 706s in other ways too. You can sell the over-hyped 243s for $400+ easily and pick up the 706’s for $100 or less in most cases. Most porters actually prefer the 706, as you can shape the ports more efficiently for power and easily add the 2” intake valve. Not to mention you don’t need to mill them to a reasonable performance NA CC size.

Again, its not about having the most power. Whomever has the most $ always wins that game. It’s about spending your money wisely and getting the biggest bang for your buck. Why in the world would anyone pay $400+ for used 243s to make less power than a set of 100$ 706’s? . Has nothing to do with forced induction mentality. Why shave the existing 853 heads you have down for $200+ when you can buy 706’s for half that and make more power?

FWIW I’ve built many NA setups as well. My latest build is a $500 NA JY 5.3. First thing I did was sell the 243’s for $400 (and the accessories I didn’t need) that basically paid for the motor. Then picked up a set of 706’s. Milled those down .100 which net me 13.4:1 compression. It’s a VERY healthy “cam only” SBE NA setup for very little money. A fun street cruiser on E85 with the 6 speed manual as well.

 

Small bore head with a larger 2.0" intake valve and ported to allow for more air flow and milled for more compression. It makes for a beefed up little cylinder head but it's only going to flow so much air therefore it has its limits. To put them on the larger 4" plus bores such as the LS3 or LS7 would rob you of power.

 

A factor to consider if you're thinking of upping compression is the fuel available in your area. Here in the ICT area only 91 is generally available, whereas in KC 93 can readily be found.

Logging my stock LS1 at WOT shows several degrees of KR at the peak of the torque curve on 91. As a result, I backed off the advance in that range. Increased compression would only exacerbate the detonation issue.

 

Should look into ethanol blends at ICT. Ethanol content sensors etc... E50 is some powerful stuff and you don't need a massive fuel system to run it like E85. Very few places have E98 at the pump like we do here. We also blender stations that have 10-20-30% ethanol blends ready to go. E30 is even better than 91. (cheaper too)

 

I don't take my car to the track anymore, so I'm fine with generally available fuels. If the OP is going to use his car the same way, then it would make sense to pay attention compression ratio for practicality.

 

It's crazy some of the places you guys live only have 91, every gas station here sells 93 and just about every racetrac gas station around here sells e85 and we have a few other stores that sell e85. I can literally leave my house and drive 5 minutes down the road to racetrac and get e85

 

I'm in Cali and 91 is as good as it gets. E85 is almost unheard of here too.

 

Whats funny about the ENTIRE ethanol in our fuel “solution” to save our environment BS, is that it never really made its way to Cali, or populated areas of Jersey, etc. At the 10 year anniversary of the introduction of E-fuels, our EPA did a 50 state study in all major cities and found that the air quality was in most cases worse than when it started 10 years prior. In zero cases was it determined that the E-fuels have helped our air quality in America. But with trillions invested, it’s waaaay too late to pull the plug on it. I could keep talking but it would get political and we can’t do that here. That’s for discussion down in Racers Lounge.

 

I'll just say this- E85 exists due to, and for the benefit of, the corn lobby. That's it!