LS 862 head porting - Don Terrill’s Speed-Talk (2024)

LS 862 head porting

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Postby cgarb » Thu Jun 02, 2016 3:25 am

I have a cylinder head job to do for a coworker of mine. He wants some port work, a valve job and his springs set up that came with his cam kit. I haven't done any LS heads to date. Im more of a hobbyist that does my own work and some for close friends. Doing some youtube homework before I get started. Watched a few porting DIY's. Mostly looks pretty straightforward for what I would do to most other stock type head, blend in the seat and guide boss, remove the rocker stud hump, gasket match the exhaust. What about the swirl ramp or wing people are removing in the intake port? GM put that there for a reason... Is it worth removing for a performance application or will it hurt the head by taking it out?

Re: LS 862 head porting

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Postby mag2555 » Thu Jun 02, 2016 7:20 am

Take the wing out of the intake bowl and be dam sure to leave a Venturi in the Exh valve bowl below the seat cuts and if headers will be run be sure to leave the Exh port exit at the flange smaller then the inlet of the header tube , very much so on the floor, in fact do not touch the floor at the flange !

You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!

Re: LS 862 head porting

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Postby V Remian » Thu Jun 02, 2016 7:41 am

If the heads are going on a 5.7-6.0 size motor, my recommendation would be to leave the rocker bolt boss largely intact. Just smooth it a little and keep the intake ports 205-206ccs when finished.

Re: LS 862 head porting

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Postby cgarb » Thu Jun 02, 2016 8:28 am

No. I wasnt going to cut the exhaust floor even If I gasket match. Its not going to get headers, just the stock manifolds. The boy says the gasket matches the manifold port and the head is smaller than the manifold.

Re: LS 862 head porting

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Postby mag2555 » Thu Jun 02, 2016 9:48 am

You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!

Re: LS 862 head porting

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Postby cv67 » Thu Jun 02, 2016 7:16 pm

Ignore what youve seen on youtube dont want to ruin your buddys heads
majority of what you see on there and most forums is bad advice

Re: LS 862 head porting

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Postby Newold1 » Thu Jun 02, 2016 8:40 pm

I have had some reasonable experience with LS heads both the earlier cathedral port heads like the 862 casting and the later LS2, LS# and L92 and LS7 castings. The 862 casting with bigger valves and good port work is one of the best early LS cathedral port heads. I am not very supportive of semi-novice hand head porting of almost any cylinder head especially the LS series heads in that in today's performance parts and shops world the availability of some well designed and performing CNC head programs. a lot of these already done heads are very reasonable now in cost. It's really a better direction in my opinion to use some of the professional LS head CNC shops around the country and secure a set of either already assembled or bare, ready to assemble version of a great flowing 862 casting than to take a stock set, spend a lot of money on good porting tools and bits, a proper flow bench with velocity mapping measuring system and try to re-invent the wheel, possibly mess up a good core set and ultimately end up with a set of ports on those heads that will most likely not even come close to the great port engineered sets that are cnc'd and already proven and uniform in port size, port and bowl shapes, chamber shapes and volume. It's kind of like asking one's self "It can't be that difficult to perform brain surgery, so I am going to give it a novice try! EEK! Dead or damaged patient! JMO

The Older I Get, The Dumber I Get

Re: LS 862 head porting

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Postby V Remian » Thu Jun 02, 2016 10:52 pm

Thank God there are people like Newold1 posting on these boards to tell you what an unworthy moron you are for even daring to pick up a grinder.

Re: LS 862 head porting

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Postby jcisworthy » Fri Jun 03, 2016 5:24 am

Re: LS 862 head porting

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Postby mag2555 » Fri Jun 03, 2016 7:05 am

The stock intake air flow level of some 223 @.550 lift of that casting is enough to support 430 hp, is your buddy looking to make more than that, if not I would not touch the casting!

You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!

Re: LS 862 head porting

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Postby ctk30 » Fri Jun 03, 2016 8:32 am

k1ob.com

Re: LS 862 head porting

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Postby Newold1 » Fri Jun 03, 2016 10:46 am

I was certainly not trying to say anyone is a moron for trying their hand at porting. If I offended anyone I apologize! What I was trying to point out as someone with a fair amount of cylinder head experience was that unless a few things exist with respect to hand porting a set of LS cylinder heads, it may be wiser to look at the alternatives. If you have a set and you don't mind loosing them to a porting mistake then have at it. Nothing wrong with learning by doing, I do that myself all the time on certain thins and I DO MAKE MISTAKES! What's sometimes is important in learning is to try and listen and consider what an expert in an area may teach you as part of that learning. I in no way consider myself an expert! I just have learned "That the older I get, the Dumber I get! What is meant by that is that when I was young I thought I knew almost everything, now that I am older I have learned that there is SO MUCH I DON"T KNOW!
A lot of the experts in cylinder heads have taken many raw cylinder head examples and cut them in many cross sections to see what metal is where. Unless you've done that with a set you plan to grind out you may create some unusable holes and thin coolant wall sections. Then you put these heads that according to a good flow bench test do very well on that nice new $6K - $10K engine you've created only to find it damaged or grenaded from coolant in oil or cylinder. GM has done a great job with the LS cylinder heads. They are precision pressure cast pieces that tend to have awesome consistency in the casting.
As I said in the first post, just look around the industry and you may find some great bargains in expertly machined and flow proven LS cylinder heads that MAY BE a better value than your own learning curve?
In any event HAVE FUN and BE SAFE! BEST of LUCK! JMO

The Older I Get, The Dumber I Get

Re: LS 862 head porting

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Postby ap72 » Fri Jun 03, 2016 11:31 am

LOL, according to the post count I'm an "expert." The only thing I'm an expert at is asking questions.

Re: LS 862 head porting

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Postby pamotorman » Fri Jun 03, 2016 11:48 am

Re: LS 862 head porting

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Postby cgarb » Fri Jun 03, 2016 11:48 am

Well, I guess Im sorry I asked for help, I didnt know cylinder head porting was such a controversial subject.