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Heads And Intake Question


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so i got through joes first post trying to take in everything, and it really makes the square port design look like the best thing since sliced bread, and also backs up the results that hot rod got in their tests of cylinder heads.

 

but the question i still have is: if the larger valve and runner L92 heads produce a higher and faster cfm rate per square inch and provide more torque and hp, why don't we put 245 intake runners on all our motors using the cathedral ports.

 

 

also when talking about changing the valve angle he says " The additional lateral load on the valve directly affects valve guide life"

 

I would think the straighter the valve the less lateral load there is on it. If it moves straight up and down like a 0 valve angle, there is no side loading right? Also the straighter the valve the more PTV clearance you get. And he never said anything about the aftermarket castings that may have design the runner to work with the shallower valve angle and therefore not creating a sharper drop or angle for the air to flow from the runner and down around the valve.

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So basically what I'm getting at is i want to go with a simple head/intake and cam swap, that doesnt require a lot of custom modifications that will also yield good gains. I would like to switch over to the l92 style heads if possible but dont want to shoot myself in the foot in the upper rpm range if the stock intake manifold is going to hold me back THAT much. IF i buy the l92 style heads im going to build them up before installing them for sure with springs rods and what not, im not going to just throw them on the truck and pray they hold up to a cam swap. Also, what will I have to consider differently in my cam selection with the cathedral heads vs the l92 heads? Im really learning a lot here guys, previous to this i knew very very little about this type of stuff. By far the most helpful thread ive ever started.

 

Zach

 

I'd have to have Steve explain more, but i would think using the l92 heads and then using the l92 truck intake would flow better then reusing the lq9 intake. From what i understand about your plans, the fast intake is out because of price so your left with a proflow intake, TBSS intake swap or reusing the lq9 intake. I would not use the proflow only based on the material and the hp/time i loose from heat soak. I think the l92 uses the 4 bolt 90mm tb right, so it should flow better then the lq9 intake and equal to the tbss intake providing the runners are about the same design.

Edited by shadowsniper3006 (see edit history)
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wow! This is a lot of info!!! What about simply porting a set of stock lq9 heads, getting a more aggressive cam to match, new valves and springs, new rockers, and call it a day?? Is that too optomistic for hoping for some decent gains at a reasonable price? Or is that not even worth the effort. zachm89 you have me thinking about a swap now as well. I don't really want to change the heads if porting them will yield decent results. I also wouldn't want to spend a couple of thousand dollars to do it. So what do you guys think?

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porting/decking the lq9 heads is a very good way to go and very much worth the price/effort, we are just discussing what might produce more hp, yield a better torque curve, get us a better ET and still be cheaper.

 

I had ported lq9 heads...they worked good

Edited by shadowsniper3006 (see edit history)
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When you ported the heads, I would assume that you got a new cam for the new airflow? And assuming that someone were to do this, ported heads with new cam and valves and springs, (because I have no idea) what general price range would someone be looking at spending? I know other things would have to be considered, such as a new tune, new head gaskets, and other small things but just looking at the port job and the big parts is what I am wondering?

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http://www.totalengineairflow.com/products/gmhead/gmls6/

 

here is just one place to get prices from.

 

Cam would be around 400

 

push rods around 160-180

 

head gaskets are depending on GM or aftermarket, but don't fear the stock gm gaskets...they work great

 

lifters can be changed at this points as well, i would do it. Price depends on lifters, ls7 lifters will do for most guys, cts-vr lifters are more expensive but might be better for sustained rpm, morel lifters have a great design for aggressive cam lobes, but will cost two arms and a leg.

 

if memory serves...the stock rockers are good to around 625 lift...i think. But you could replace the stock gm rockers as well for a tad more hp based on friction and it would be better on the valve stem. Around 450 for the yella terra UL, but there are other options as well.

Edited by shadowsniper3006 (see edit history)
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I've read the first page so far and that's about it. I'll give my base opinion on this to start with. The best point with running an L92 port starts with the price. Dollar for dollar it's hard to beat the overall price of the L92's for intake port flow. The L92's aren't really at home all that well with the small bore of the 6.0L, but they do work well. If you use the L92's for what they are really meant for, you will absolutely love them. The best thing with these heads which is what they were designed for is to make big power with a small camshaft. What has been found by myself and many others is that it is very hard to make really big power with L92 as they don't really respond all that well to camshafts over 230 duration. I frequently see them with cams bigger than that, but you'll find that they don't make much of a gain over the same setup with a small cam. For anyone considering running an L92/LS3 port cylinder head I commonly recomend a 6-8 degree split for a naturally aspirated setup and around a 22x/23x duration range. As a comparison stand point an unported 317 cylinder head with a 228/230 cam with a long tube header and a truck intake will make around 390RWHP. The same LQ9 with an unported L92 cylinder head and a 223/231 cam with a long tube header and a truck intake will make around 420RWHP or so. The L92 setup will also have a smoother idle with more vacuum. To make similar power to an unported L92 head you need either a very well ported 243/317 head or an expensive aftermarket head. I'll add to the post in a few. Wife is ready for the hot tub.

 

The short of it basicly is that if you want great drivability and 400-450RWHP, it's hard to beat an L92 port cylinder head with a small cam.

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I'd have to have Steve explain more, but i would think using the l92 heads and then using the l92 truck intake would flow better then reusing the lq9 intake. From what i understand about your plans, the fast intake is out because of price so your left with a proflow intake, TBSS intake swap or reusing the lq9 intake. I would not use the proflow only based on the material and the hp/time i loose from heat soak. I think the l92 uses the 4 bolt 90mm tb right, so it should flow better then the lq9 intake and equal to the tbss intake providing the runners are about the same design.

 

If he goes with the L92 heads he will not be able to use the LQ9 or TBSS intakes. He would have to go with a rectangle port intake like the L92, LS3 or L76. If I remember correct, I did see that there was a modification that can be done to the alt bracket to allow a truck intake and 90mm tb (plug is on opposite side) to be used.

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I've read the first page so far and that's about it. I'll give my base opinion on this to start with. The best point with running an L92 port starts with the price. Dollar for dollar it's hard to beat the overall price of the L92's for intake port flow. The L92's aren't really at home all that well with the small bore of the 6.0L, but they do work well. If you use the L92's for what they are really meant for, you will absolutely love them. The best thing with these heads which is what they were designed for is to make big power with a small camshaft. What has been found by myself and many others is that it is very hard to make really big power with L92 as they don't really respond all that well to camshafts over 230 duration. I frequently see them with cams bigger than that, but you'll find that they don't make much of a gain over the same setup with a small cam. For anyone considering running an L92/LS3 port cylinder head I commonly recomend a 6-8 degree split for a naturally aspirated setup and around a 22x/23x duration range. As a comparison stand point an unported 317 cylinder head with a 228/230 cam with a long tube header and a truck intake will make around 390RWHP. The same LQ9 with an unported L92 cylinder head and a 223/231 cam with a long tube header and a truck intake will make around 420RWHP or so. The L92 setup will also have a smoother idle with more vacuum. To make similar power to an unported L92 head you need either a very well ported 243/317 head or an expensive aftermarket head. I'll add to the post in a few. Wife is ready for the hot tub.

 

The short of it basicly is that if you want great drivability and 400-450RWHP, it's hard to beat an L92 port cylinder head with a small cam.

 

 

Thanks for the real world advice Zippy.

On the cam suggestions, I was told that a large split like you mentioned above with a big lift say .610/.620 does very well for the L92's. Any comments on that? I was also told that you can run a lower LSA because of the valve sizes and have a quality idle.

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I guess overall what I'm getting at is what all would need to be changed if I go with a set of stock L92 heads with upgraded springs, rods and lifters, the stock truck intake manifold and throttle body (which i believe is a 90mm) and also correct me if I'm wrong but someone told me that the motor I'm looking at already has 40lbs injectors? Not entirely sure on that one, just what someone else mentioned. Of course I'm going to go to Zippy for a cam reccommendation when all the other variables are decided but from everything that I've read so far the L92 heads and truck intake are looking like the route that I'm going to go unless someone can talk me out of it. I want this swap to be as simple and easy as possible and still come with gains that are worth the money. Other things I'm planning on swapping out along with the cam are oil pump, ls2 timing set, an possibly a walbro 255 fuel pump and injectors IF the injectors on that motor aren't already 40lbs. Lemme know what you guys think!

Thanks for all the help fellas, you guys are great!

 

Zach

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Yes the injectors are 40# ers. On the connectors I believe they are plug and play but not 100% sure.

I think you will also need an x-link for the tb.

Cut the side of the alt/PS bracket off.

Might have to go with a car style water pump and truck pulley,

If you don't get the whole motor make sure you get the rockers for sure.

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If he goes with the L92 heads he will not be able to use the LQ9 or TBSS intakes. He would have to go with a rectangle port intake like the L92, LS3 or L76. If I remember correct, I did see that there was a modification that can be done to the alt bracket to allow a truck intake and 90mm tb (plug is on opposite side) to be used.

 

 

yeah thats what i was trying to say. if he went this way these are the options and if he went square port these are the options, and between doing the TBSS intake on the cathedral port set up or the l92 truck intake on a square port set up, i think it would be a wash

 

but now i see what zippy said so it looks like the square port heads are just a better choice? which is also opposite what i would have thought so i need to learn more here.

Edited by shadowsniper3006 (see edit history)
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damn zippy you got a hot tub :)

 

 

back to the orginal post...now you have siad your goals were P1 down the road...well my friend if you are thinking about doing a head/cam swap we are doen that road, and I have to say I have seen a few P1's for sale for about the same as you are going to spend to get the L92s on and running.

 

I think zippy nailed it: if you are on a budget and looking for a decent power gain the L92's fit the bill. The discussion gets off topic into the pissing match about cathedral vs square...

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I'm not sure that's the way I would put that joe. He asked for opinions on a set up based on getting a motor for a good price, or other ideas. We all discussed what would be a better set up for the price. It looks as though of he gets the motor for a good price it would be better for his budget and maybe even be an all around better choice.

 

Sent from my SAMSUNG-SGH-I897 using Tapatalk

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yes, I agree.

BUT with out changing his converter I think he should look at FI. I know if I had a different stall my goals would be different...Untill we know the price point his friend is givging him and the parts you could sel to offset costs...there are too many unknowns on budgeting his set-up to match his goals.

 

I think my set up was done for under $2500, but that is no where near what it would cost if I had to buy the misc parts and do it again.

 

I feel if I can dial my set-up in and run a little better number that would be good proof of how good/bad the set-up is, but at the end of the day it's still mostly OE parts...Tom (local and on here) just ran 13.6 which I believe is what a radix truck runs???

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