Gains from a Multiangle valve job
i prefer a 5 angle 70 60 45 30 15, instead of the air having to step by the seat it gently flows by it. in sbc's i ran .2 seconds quicker just by doing a 5 angle and laping in the valves.
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Can anyone explain why "longevity" becomes a concern with a multiangle valve job? I don't think I've ever heard that before.
Also, can the LS1 Heads (241, 853, etc.) reap similar rewards from a valve job and bowl work. I picked up a set of 241's for next to nothing with the intention to start working them over, but everyone skips over them for 243 castings. I know they are better than LS1 heads....
Sorry if that wanders too far
Also, can the LS1 Heads (241, 853, etc.) reap similar rewards from a valve job and bowl work. I picked up a set of 241's for next to nothing with the intention to start working them over, but everyone skips over them for 243 castings. I know they are better than LS1 heads....
Sorry if that wanders too far
with any ls series heads, they can pick up quite a bit of power from any type of porting. the reason people think they dont last as long with a 5 angle is the seat surface. but with this new fangled thing called fuel injection it doesnt matter as much.
i do it for a living, kind of need to know this.
i do it for a living, kind of need to know this.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
The trick is to get the right angles for desired transition into the bowl area. It is not a matter of X Y Z angles work best. It is a matter if X Y Z work best in corrolation to the bowl work done. (and that takes mundo experience)
Over 50% of flow increase in a head porting is gained at the valve seat into the bowl area. That is why a good casting such as 243s shine so much with a proper valve job/bowl work and untouched runners.
Take for exemple a mass produced CNC 243. They will flow well and produce Ok results. But why aren't they stellar and why some other port jobs are much ore expensive to yield better results? Well the difference is the handywork on the VJ/bowl area (with a bit of attention to the short radius
)
Over 50% of flow increase in a head porting is gained at the valve seat into the bowl area. That is why a good casting such as 243s shine so much with a proper valve job/bowl work and untouched runners.
Take for exemple a mass produced CNC 243. They will flow well and produce Ok results. But why aren't they stellar and why some other port jobs are much ore expensive to yield better results? Well the difference is the handywork on the VJ/bowl area (with a bit of attention to the short radius
) Last edited by PREDATOR-Z; Aug 27, 2009 at 03:12 AM.
Dont the 241 and 243 castings come with factory 3 angle valve jobs? I know when we were cleaning up and milling my heads putting the engine back together it already had a 3 angle valve job.... I may be mistaken but I know mine had them and they are stock.... just like the rest of the car..... was. In that case it would be a case of either going 5 angle or getting the valve job and bowl blending precise as Predator stated above.
Most shops, in my experience, use a pretty standard 30-45-60 degree valvejob and call it their "competition" valvejob. It's probably better than stock, depending how far they take the seat diameter out to, but it's far from being good. Their 5 angles may just add a 15 on the top and a 70-75 in the bowl. Usually this helps, but a good 3 angle valvejob will usually kill it. A good 3 angle valvejob is going to have some R&D behind it, and usually isn't the same for every type of head.
As far as longevity is concerned, it's mostly in the seat area. Stock valvejobs from the OEM usually have the seat diameter a couple thousandths of an inch smaller than the diameter of the valve. This gives more area for the seat to wear and is easier on the valve. Example, on a 2.00" LS1 valve, the seat diameter is only about 1.95" or so. You can see it when you lap a stock low mile valvejob and the ring is just under the edge of the valve seat face.
Also, use a steeper seat angle than a 45, and it will start to cost you longevity. The upper echelons of drag racing use much steeper angles like 55 and 60 degrees, and coupled with the huge spring pressures they run, valvejobs wear out quickly. It'll cost you on a streetcar as well.
As far as longevity is concerned, it's mostly in the seat area. Stock valvejobs from the OEM usually have the seat diameter a couple thousandths of an inch smaller than the diameter of the valve. This gives more area for the seat to wear and is easier on the valve. Example, on a 2.00" LS1 valve, the seat diameter is only about 1.95" or so. You can see it when you lap a stock low mile valvejob and the ring is just under the edge of the valve seat face.
Also, use a steeper seat angle than a 45, and it will start to cost you longevity. The upper echelons of drag racing use much steeper angles like 55 and 60 degrees, and coupled with the huge spring pressures they run, valvejobs wear out quickly. It'll cost you on a streetcar as well.
Can anyone explain why "longevity" becomes a concern with a multiangle valve job? I don't think I've ever heard that before.
Also, can the LS1 Heads (241, 853, etc.) reap similar rewards from a valve job and bowl work. I picked up a set of 241's for next to nothing with the intention to start working them over, but everyone skips over them for 243 castings. I know they are better than LS1 heads....
Sorry if that wanders too far
Also, can the LS1 Heads (241, 853, etc.) reap similar rewards from a valve job and bowl work. I picked up a set of 241's for next to nothing with the intention to start working them over, but everyone skips over them for 243 castings. I know they are better than LS1 heads....
Sorry if that wanders too far
I'm pretty sure SAM had their black Camaro in the low 10's naturally aspirated before the 500ci motor went in. I'm pretty sure it was just a 370ci iron block with 853's. I don't remember the MPH.
the reason for the 70 60 45 30 15 , is the 70degree is almost like a back cut into the head (like a small porting job) it blends the port and the seat together, now the x-tra 15 is to remove a sharp spot out of the cylender (sharp spots create hot spots). as i stated, i have tested my theory more than one time. on average i ran .2 quicker. the reason alote of machinists go with a 3 angle is time. time is money. those extra 2 angles are well worth the hassle. its just like porting, u want smooth transitions not sharp ones.