I don't know if it is even worth it but I am going to change the cam in my 2007 lq4 and was wondering if it was worth putting 243 heads on. What kind of horsepower would you see. I know the compression would go up some, not sure how much. Thanx

 

I think that would be a great move as the 243s will pick you up a decent bump in compression which will help quite a bit with driving this motor on the street. The heads flow right about the same but the compression bump is more then enough of a reason to do the swap in my opinion.

 

argueably the best set of heads you can put on an LQ4.

 

John what do these heads flow stock, 317 and 243. What kind of power do you usually pick up?

 

243 on a 6.0 youre looking at close to the same compression as an ls2 since ls2's are 6.0 with 243 heads, some are 799 but the same. 317 and 243's flow the same. stock 6.0 with 243's youre going from 310 or what ever the stock numbers are plus 30 maybe 40. just guessing here. add a nice cam for good torque to compliment the truck intake (depending on vehicle it will be in) and you're looking at a very strong street motor that can pull almost anything. 6.0 with ls6 style intake, get a cam with good mid to high range power and be a good street performer upwards of 400+. a buddy of mine has a 6.0 with stage 2 ported 243's, tr224, and 85mm typhoon intake, and that thing was stupid fast for a lsx swapped s-10 rod. he ended up toasting a rod bearing, and now has a 5.3 with a ls6 intake and an "old man cam" not sure what the specs are but pulls nicely.

 

I've read there was a combustion chamber design difference between 243's and 317's as well.

I did the 243's, but have no basis for comparrison since I never ran it with the 317's.

 

well that may be true since truck engines are labeled vortec, which means that when the air charge is being brought into the cylinder it creates a tornado effect to get a more efficient combustion. pretty much the same thing happens on ls series (1/6) heads. i know that the combustion chamber design on those series of heads creates a swirl effect. i dont see much difference between car style heads or truck style heads.

 

No offence but I don't see any way you could get 30hp swapping from a stock set of 317s to a stock set of 243s. If you're talking ported 243s then sure but the small bump in compression isn't worth that much HP. It WILL help tame a bigger cam in the LQ4 than you could run before though.

 

I wouldn't expect much more then 5-15rwhp by bolting on these heads, not from flow but from a compression bump. 317 and 243 heads flow the same which is usually around 260-270 cfm at .600". You will definitely notice the power increase because the over responsiveness and low end power are going to change because of the added compression. LQ4 motors have a valve relief in them so they will be around 10.2:1 with those heads on them. Much better then before either way you look at it. Also, vortec does not mean there is a tornado effect on the incoming air charge.

 

a couple things, i truly thought it would be more then 15 increase going from 70cc chamber to 63 and way more then 10.2. hell, 243's on a ls1 is up around 10.8 is it not, so i thought it was at least 10:1 on a stock lq. not much difference from lq4 to lq9 other then pistons and a couple points in compression and slightly more aggressive timing. and i honestly thought vortec means what i stated above which, as the above poster pointed out, it does not so plz clarify. i apologize for giving bad info, so plz educate.

 

243s on an LS1 would put you at 10.5:1 which is what a stock LS6 motor is. LQ4 motors have a dish in the piston so they don't make as much compression. The LQ9 will be right up at 11.0:1 with a 243 head on it but that is because they have a flat top piston. A ported 243 might pick up 20-30 no problem but I don't think you can pick up that much power from a half point in compression.

On the original 4.3l v6 "Vortec" GM claimed that they had the technology to create a vortex inside the combustion chamber. Now a days it is just used as a marketing tool to help sell motors. I have a hard time believing it every created a vortex in the combustion chamber, but at this point its neither here nor there in my opinion.

 

ah, ok. thanx for the clarification

 

Hi John,

i'm running your 233/239 cam in my lq4. ( Last weekend we ran 161mph at Maxton).

If i swapped 317 for 243 heads, how much i can mill them ?

Fred

 

A.I. 243's pick up about 50rwhp on an LQ engine assuming all the other supporting mods are in line.

 

Dang I never knew the 317s had a bigger chamber than the 243s. I had read they were basically the same. I've got an LQ4 but it's the early style with iron heads so I've been trying to decide what heads I want. Was trying to find a cheap set of 317s since they are cheaper than 243s.

I think I'm going to go with L92s and an LS3 intake. LS3 intakes are as cheap as LS6s and the heads will only be a little more, but that combo will make more power than 243s with an LS6 intake.

 

I paid $319 each for new assembled LS2 heads (got 243 catings) about a year ago.

 

I have a question... If one were to purchase a short block LQ4, what would be the result of 241 LS1 heads on it? Would that be a huge power killer compared to the 317s?

 

From the data I have, the 243's flow about 5% better than the 317's in stock form. When you have porting done by AI or somone then the ports are all CNC'd the same so they would flow the same (obviously), according to an AI post.

If you look at the pocket area of the head near the valve guide stem you will see where the swirl (vortec) is suppose to be enhanced. It is my understanding that the heads are designed to help the air (I can't recall which side for certain) move faster along one side of the valve and "swirl" into the chamber for a little better "mix". Hence the term Vortec. I believe most porters remove most of the casting by the valve guide in an effort to increase flow which likely results in a notable reduction in "swirl" (which is better for low end power...emissions).

 

That's pretty good, can you still get them new? I've been looking at LS3/L92 stuff on ebay and with all the LS3 Vettes and Camaros being modified there are a lot of low mileage take off heads and intakes at cheap prices.

 

You cannot mill them very far without fly-cutting pistons. I've heard .030 is the max unless your camshift lift is pretty high.