243's on a 5.3, is porting a must for big hp?
 

So ive had stock 243's on my previous 406 ci , with pt 8847, made about 1000 wheel hp. Id like to make about 1100 wheel hp on the 5.3. My question is, will the stock 243's be ok, or should i port them. Being a smaller cube engine, if i port them will it be lagier, cheers

kinda going thru the same thing. im just gonna get some dart as cast 225 w big valves over porting the set of 243 I have. used stock heads before w good results. but mathwise it don't make (cent$) to run ported stock castings. atleast imo
the 225 dart as cast are right next to the 243 in flow and have a thicker deck.
0.02$

Pushing air through a larger free-flowing orifice will speed up velocity and efficiency. You'll make more power with less boost with a ported head. Hard to say how much, but if you have the means to have the heads ported for little or no cost, or it's in your budget, by all means go for it.

If you're not on a time crunch, $50 worth of carbide die grinder bits, sandpaper rolls, some WD40, and a few beers will be worth it if aftermarket heads aren't in the budget.

For a hundred, just twist the knob a little bit and keep an eye on the tune....That what all the turbo truck guys tell me.

Ok, yeah i have access to a machine shop, i will port them, i actually thought that if you make the ports bigger, you lose velcocity?

I think stock ones would be fine

I hate reading "just turn the boost up a little" as an answer to every question like this. If that were the case, everyone would be running $150 4.8's pushing 80 psi and making the same 1200 whp.

"Is an LS6 intake going to show any gains?" "IDK... just turn up the boost"
"Will ported/aftermarket heads show and gains?" "IDK... just turn up the boost"
"Will headers be better than logs?" "IDK... just turn up the boost"

It comes down to balancing budget, time, and HP goals. If the heads are sitting on the bench, to me, it makes no sense to leave them stock... clean them up at the very least... but that's just me.

ding ding ding lol. Obviously porting the 243's is gonna show some power. Will it be worth the cost? who knows. But Im the same as above. My 706's were just sitting there from my 5.3L so I decided at bare minimum to clean the castings up with a white wheel then valve lap them. More or less to get some of the bumps out and clean the carbon off of them. Am I expecting big gains? not really

You could just turn the boost up. But why bother putting more pressure in the motor when you could maybe make the same HP at a lower level with ported heads. I'm going to assume at that power level you are probably already close to pushing the limit of a 4 bolt head anyways. So adding more boost may not help.

I say at minimum hit them with a white wheel or some sand paper wheels if money is tight, if not have someone do a good 5 angle valve job and port, but if you are gonna bother investing that much you are probably better off selling them 400-700ish depending on valvetrain and investing in a head with a 3/4" deck or thicker.

Jay

Thats not correct... Pushing air through a larger free flowing orifice drops velocity and increases flow. That’s why throwing a huge aftermarket runner head on a 5.3 is a bad idea. The port velocity will be garbage.

Assuming you match the top end of the engine properly to the turbo, 15-16lbs of boost should roughly double the NA crank hp. If your turbo has enough flow for a head port job then porting the heads will obviously make more power. The OP will have to run quite a bit more boost to be at the same power level as the 408. Then add even more to hit the new goal. I’d bet an NA 5.3 won't make much over 400whp with a decent cam and 243’s NA. So the OP is probably looking at 30+psi to hit his goal. Break out the methanol and good luck to you!

It’s more of a time/effort thing IMO. Most of the people asking these questions that I've seen are running 500-600hp if they are lucky. If you can make enough power to blow the short block with boost alone, why would you spend money/time/effort on things like porting, aftermarket intakes, manifolds…etc.

If your going “all out” or class racing I can see reason to do all of the above.

I agree a cleanup can’t hurt much. From what I’ve seen a lot of DIY guys have the bigger is better mentality. They will hog out a head to the point where they are doing more damage than good, basically destroying a perfectly good head. As with most things, If you don’t know what your doing… its best left alone.

Not sure what your budget is but if your reaching for another 100+ I'd get a set of AFRs or Trick Flows and be done, provided you have a good rotating assembly. Good luck

Forcefed. Thanks for making this statement. I couldn't agree more. The bigger is better mentality does not always apply when it comes to cylinder heads.
Most people on here don't know me from Adam. My background consists of mostly NHRA stock and super stock cars. In super stock we are allowed to port but the heads must retain stock runner volumes. Which basically means we are allowed to reshape the ports whatever we remove has to be filled in somewhere else. So port design and velocity is of the up most importance. It's always fun for us to put peoples home done hogged out big valve heads on the flow bench and then put a set of super stock heads with stock valve size and small runners and watch them put up as good or better numbers in most cases. Glad to see this site has similarly minded people.

As to the OP head work isn't going to hurt and will help get you towards your ultimate goal as long as it's approached the correct way. Will you be able to achieve your ultimate goal I couldn't answer as I don't have any experience in this situation. But good luck.

Rick

Thanks fellas, much appreciated. Yes im definetly on a budget.
Ive ported a couple of heads for friends in the past, mainly just cleaning up around where the valves come through, taking the humps off. I dont really want to take away from wall thickness too.

Some decent tutorials about what you should and shouldn't remove on a cathedral LS head on youtube. Just search "How To LS1 DIY Head Porting" He's got a few good videos.

But when it comes down to budget and price per hp, porting heads costs money for an unknown amount of power increase while "turning a knob" is free.

If you have the ability to make more power by either spending $1000 on some heads or simply turning a knob...which one would you chose? That's why most people's answers to those questions are as you put it "who cares just turn up the boost". And that's why people spend thousands of dollars turbocharging their car...for the convenience of "turning up the boost" when they want a few more horses as apposed to having to go through all the trouble of getting heads ported for example.

If you're trying to squeeze out EVERY SINGLE horse out of an engine then yes porting the heads or getting a different intake will help. But when looking for just an extra kick (eg. 20 more hp) it's silly to not just turn up the boost in a matter of seconds if you can vs. taking off the heads, shipping them out, spending $1000 on a port job and then waiting weeks for those to come back in.

You'll make more power with less boost with a ported head.http://finanziellede.de/6ce1.jpg

Who said anything about spending $1000 on PnP heads?? I made the argument that if the heads are already on the bench, you're not out much other than time to do a mild DIY PnP (clean up the castings, streamline the valve guide bosses, knock down the rocker bolt bosses, blend the valve seats, and possibly lap the valves). That will net a good hp/$, as well as let you make the same power at lower (safer) boost.

Yep, thats what ill do, thanks again, and for the yt link.

With the OP’s goals I think he needs every bit of help he can get. Personally I’d send the 243’s out for a nice CNC port job over entry level aftermarket heads with oversized runners for a 5.3.

For most it depends totally on the setup and power goal. Boost isn’t unsafe. Less boost isn’t “safer” IF you know what you’re doing. If I build a turbo car I want turbo do the majority of the work. All these “built” motors running 10-12lbs of boost seem counterproductive. If you went through all the time and effort to add a turbo, use the turbo to make the power. It’s the most cost effective route by far.

A nice DIY port job will easily take 4-5 hours of labor in per head. Plus the rotary tools, sanding rolls etc. I’ve done it. I thought it was boring, messy, and time consuming. Personally if I can reach my power goal without going through 9-10 hours of misery for a marginal amount of gain, I will! If you’re not racing where every hundredth of a second counts it’s something most can skip. If you have tons of free time and enjoy repetitive messy work, go for the port job! Heck I’ll let you do mine! ;)

Yea, I see what you mean... 8 extra hours of time in the shop on a build that most likely is taking months for basically free HP sounds like a terrible idea. :eyes: