Does a LSX cathedral port head, 243 casting in this instance, have a specific cut angle? different than modular ford, sbc, etc.
I do not know if shops in my area are familiar with the LSX cathedral port head and wish to ensure they know what to do. I am in Miami and some places promise the world. Best to be prepared.

 

Are you talking about the seat cut into the valve? Or the head of the valve in relation to the stem? Cause the seat will have a specific angle to match that of the seat cut into the cylinder head. As far as the head of the vale in relation to the stem, should be just straight.

 

When I call a machine shop and ask them if they do 3angle valve job on LS heads and they respond yes and I followup with what angles do you use so I know they are for LS heads and not other engines.
Not the std SBC 30-45-60

 

In my experience, the best shops do testing to see which valve angles are ideal. Typically they do not share the specific details of the valve angles used. The best LS valve jobs are typically 4 angle or 5 angle VJ's.

Likewise depending on goals & cam selection the VJ can be customized to favor the mid-lift flow or peak high lift flow.

If the shop shares all the specific details of their VJ angles, from a performance point of view you will be paying for at best a 2nd or 3rd or 4th rate VJ.

Really nailing the VJ also requires taking the intake & exhaust port profile into consideration plus the chamber design etc. If the 243 head has port work there isn't a cookie cutter list of perfect angles to check for that will best work in every case.

For best results, I suggest considering and contacting, TEA, Land Speed Cylinder Head, Frankenstein, Mamo Motorsports or other top notch vendor for cylinder head work.

 

Hate to break it to ya, but...

LS1/LS6 Engine Dimensions & Clearances

 

hahahaha. Thanks man. I knew the heads came from the factory 3angle. Thought it was rough work vs. what a shop being paid $$ would do.
Much appreciate. I searched the old threads and saw a few combos. Not that one.

 

Yeah, the factory valve job leaves a lot to be desired. A good shop can use a 30-45-60 profile, add a 70 or 75 bowl cut, and get decent results. I use a couple profiles I learned about from when I went to SAM. I won’t just hand them out, but you can find where Greg Good recommends them in a thread over on Speedtalk.com.

 

I posted there yesterday as well. Received good info

 

I would bet those bowl cuts make a nice difference.

 

I'm newer to cut angles, but I didn't think any were specific to any engine. I thought angles have been updated over the years a couple times and or different trains of thought on the angles and they apply to all engines.

Secondly, I keep getting throw by bowl blending/cut. It seems some guys refer to that as chamber side work, and some refer to it as work behind the valve, blending the seat to port. What is the right way to say these two different things?


Edit: had no idea they came with a 3 angle. That's interesting.

To add to this, someone added pics of 799 and 243 pics recently. Looked like the 799's were not blended or cut, and the 243 had a bowl cut...

 

Nearly all factory heads come with a 3-angle cut. Even the old traditional SBC.

There also used to be some debate as to whether cutting the valve and the seat at slightly different angles on the sealing surface (the 45°), like 45° on one and 46° on the other, helped them seal better. Iunno.

Seems like the more angles, the better, almost regardless of the details. In fact if it was possible to make a smooth curve cut, maybe that would be better. Again, iunno.

I would also suspect that the "better" motors, Vette GTO CTS-V & F body, would come with more attention to detail in a general way than the trucks. Which might maybe include different seat cutting. Iunno. Even if the casting # (799, 243, whatever) was the same. Kinda like they put the different valves in certain ones.

 

More seems to be better. Just didn't realize it was common to come with a 3. And yeah I agree the 243's would likely be finished out better. But I think later they may have put the bowl cut on other heads as well. If I recall correctly I saw that 706's have it as well. But then someone else posted up a 799 with a bowl cut. So seems like it was also all over the place.

 

Thanks everyone, I found a good shop. Keeping the LS6 intake and cam has .561" lift so do not see need for extensive work on the heads. Recall reading years ago the majority of gains are in the valve and bowl area

 

Yeah do a 4-5 angle intake seat cut, blend the valve seats in, and you'll have a damn good head. Back cut the intake for the low to mid lift

I've noticed a lot of head programs are radiusing the exhaust valve too. But your major gains should be from the valve job and blend.

A bump in compression while they're off is always a good plan too.

 

Is 280-290cfm @.600" lift realistic if you have the above work performed by someone competent on 243/799 castings? Seems like all you would need to make ~500 or so crank HP on the cheap.

 

You could make 500 at the crank with stock 243's and a cam and a decent intake manifold, including the ls6 intake. LS6's were rated at 405 and we all know they would dyno higher on the engine dyno, throw a cam in there you should see 500. Stock LS1 with **** 853 heads made 400 on the engine dyno many years back supposedly with a LS6 intake. Made 480 with a cam. With stock LS6 heads 500 should be easy.

I've never seen someone flow a 243 with the above mentioned work so I'm not sure, but out of the box the 243's are around 250 cfm if I recall correctlly. I got curious about numbers with just valve work and did a small amount of searching. Didn't see a lot but came across this thread. My time go cut short boss is over my shoulder so I couldn't read more, at a glance looked to be decent info in here with links to other threads with more info on flow with valve job
https://ls1tech.com/forums/generatio...valve-job.html

 

​​​​​​Nice, looking through that thread it appears 280cfm would be doable. 👍
I'm piecing together parts for a top end rebuild, going from ls6 intake/241 heads to Fast 78/799 heads + ATI balancer and a few other various bits so realistically I should be up over 500 with any kind of work to the heads but I'm drawn between fully porting the head with bigger valves or putting that money into another area.

 

I wouldn't do larger valves unless you go larger bore, shrouding is already a small issue, larger valves cause more shrouding if chamber size stays the same

I'd focus on allowing the valves they have to flow as well as possible



Good bang for buck here too
http://www.improvedracing.com/crank-...kit-p-433.html

 

Cheers mate, I'd been looking at just the crank scraper on its own but not the windage tray kit. Strongly considering this as I want to pull the motor and replace the leaky sump gasket anyway so any 'while I'm in there' mods like that which can free up a few HP sound pretty good to me.

 

So a larger valve head will make less power on the same bore size as one with a smaller valve?