newbvetteguy

I'm really curious if anyone has messed around with 50 degree valve seat profiles on high-end long-runner SBC builds.


In theory, when paired with some good flowing modern heads, and a modern fast-ramp, high lift cam and lightish valve train, a 50 degree valve seat angle should, IMHO, really help out a long-runner torque monster build.

The 50 degree seats help to increase the average port speed through the heads (as almost all long-runner builds are going to peak at or below 6,000 RPM on a 350 or a 383 most performance 180-200cc heads that flow well are going to have less-than ideal port speeds and getting that speed up and increasing the high lift flow will help with both torque and upper RPM HP; the 50 degree seats help tame bigger cams / cams with more overlap, too so the bottom-end doesn't suffer.

The 50 degree seats supposedly further increase the pressure of the tuned waves, which is particularly useful in a long-runner SBC build.

Anyone who's followed Vizard's "128" SBC Cam LSA selection rule, knows that a closer LSA than usual means more peak torque on an SBC so the extra flow, extra port speed, anti-reversion, wave tuning improvement AND the ability to pick a cam with a 2 degree smaller LSA should all combine to make an already amazing long-runner torque peak even better. -Vizard recommends a 108 LSA for an SBC 350 with a 2.02" intake valve and a 106.5 LSA for an SBC 383 with a 2.02" valve for max torque and power (but fewer RPMs between the peaks). Obviously, the stock ECU people can't get near that and with power vacuum brakes you can't either but you CAN get closer to it with a 50 degree seats than 45 degree seats.


If BadSS is still around and still has my engine saved in his EA / EA Pro files, I'd be curious if you could run another simulation with a 50 degree seat profile and a 107 or 108 LSA "for science".


This SpeedTalk thread that exploded has me thinking that a high-end long-runner SBC probably is near an ideal situation to take advantage of the benefits that 50 degree seats have to offer: http://speedtalk.com/forum/viewtopic.php?f=1&t=53485



Adam

BadSS

Adam, my computer’s power supply with EA Pro has gone out and I haven’t replaced it yet and EA Plus doesn’t have a valve job angle parameter.

I haven’t done a much research on steeper 50-degree valve seat angles – what little I did seem to indicate that there is definitely a few horses to be found there, but the steeper angles could have longevity issues on daily drivers. There’s a former NASCAR engine builder in my area that I have do all my machine work and when I mentioned it to him he didn’t recommend it even for a weekend cruiser. He more or less said the seat angle is just one piece of the puzzle and unless you’re building a competitive engine that needs every ounce of power, he’d advise sticking with a multi-angle 45-degree seat valve job. So, I didn’t think much about it since then.

However, you’ve sparked my interest as it appears you believe that you can run 2-degrees tighter lobe separation with the 50-degree seats as compared to 45-degree seats with similar vacuum or idle quality. I’d be interested in knowing how you came to that conclusion and where there’s any information on the testing that was done - if it's in the speedtalk link, I'll take the time to wade through it. If you really can get away with 2-degrees tighter spread,,,, then I may have to try it on the next build I do and just see how it effects longevity (which can mean different things to different people)

newbvetteguy

No worries about EA Pro and modeling it. I'm not sure it would even model it right. Someone on the SpeedTalk thread tried different valve angles in Dynomation and it appeared to not account for the difference in velocity and just saw the decrease in low lift flow and the increase in high lift flow and modeled it based upon that.


Here's the interesting thing with the 50 degree seats and longevity in terms of street motors: Quite a few serious engine builders have weighed in on that thread and they said that longevity isn't really an issue with steel valves, properly wide seats and decent modern seat materials in a street motor. The race engines are often running really narrow seats, ASTRONOMICALLY HIGH seat pressures, narrow seats, titanium valves, and are running crazy high RPMs with crazy fast ramp solid roller cams. Running like a .060 seat width (especially if the seat is close to the outer edge where it's going to aid cooling more), steel valves, hydraulic rollers with dual lobe profiles that usually decelerate the valves before close, lower spring pressures possible with beehives @ <6,300 RPM and only a max of 6,000-6,000 RPMs, street motors have everything going for them in terms of longevity.



The 50 degree seats reduce the curtain area at low lifts (I posted a table comparing a 2.02" intake valve's curtain area on a 45 degree and a 50 degree angle using an XLS that Rick360 created that accounts for all the valve job angles and widths rather than the generic valve size equation-in that thread on SpeedTalk if you go back a few pages.) and have an anti-reversion effect, in addition to obviously increasing the flow and air velocity at high lifts; it's even more pronounced if combined with a slightly tuliped valve. -The air sticks closer to the valve as it enters the cylinder also reducing the impact of any shrouding. The air VELOCITY at the lower valve lifts is also higher when you look at the CFM / square inch of curtain area so you can slightly further delay the intake close and stuff a bit more air in there if you get a cam maximized for the 50 degree valve seat angle. (Plus the slight increase in wave raming strength.) ---That's why you can either run a closer LSA, OR run with more duration assuming the increase in duration on the intake side doesn't screwn up your intake wave tuning (if it does, just run a closer LSA). -That's also why you see the HP Peak RPM drop in the HotRod article, the 50 degree seat ACTS LIKE a smaller cam, but when you combine it with more duration, you get more HP AND more torque down low.



You'd definitely want as high of a lift as you can get for your duration, which is why I think some of the Mike Jones aggressive intake lobes are PERFECT for this (I've got 227/228 @ 0.050 and 272/280 with 0.600" lift with 1.6 Rockers, so not a bad option, honestly; if I knew then what I knew now I would've waited to order my cam and would've gotten my cam on a 108 LSA or with a few more degrees of duration and probably would've gone with 1.65 ratio rockers.)


I'm really thinking a "top shelf" long-runner SBC may really appreciate a 50 degree valve angle. I was trying to convince Rick360 from the speedtalk thread (who was on the EngineMaster's winning team with his Proifiler 185cc (195cc by the time he was done with them) ported heads and 50 degree seats) to do the 45 vs 50 valve seat dyno test by letting him borrow my heads and put the 50 degree valve seats on them. I volunteered to pay to ship him my heads and cam and pay for the new valves if he did the work but he's got such a huge queue of experiments lined up he said there was no way he'd get it all done and the parts back to me by October when I'll definitely need the heads and cam back... (Hey, if I can get a guy like Rick to do the work to switch to the 50 degree seat angle and touchup the SSR to deal with the faster velocity for the cost of shipping 2 ways, I'd be dumb NOT to.)


My thought is that, ESPECIALLY if someone has a profiler 210cc head on a 6,000 RPM 383 cubic inch SBC (I've got 195cc destined for a 383 and the min CSA is only slightly too big, so no as ideal of a test...) or a 185cc head on a 6,000 RPM 350, the ports can support the extra port speed of the 50 degree seats with the extra flow at high lift and it'll probably improve the average power, AFRs have such fast port speeds and such a small min CSA already I'm afraid the RPM at which they'd stop making power would just drop. I'm thinking I have an ideal enough test for the difference between a 50 and 45 degree angle, especially with the FIRST intake. And if someone is already having their heads rebuilt, they can go with the nice Ferrea valves with the thinned out stem that BigJoe says will gain you 6+ CFM, and make sure the exhaust valve valve job is radiused on the entry and have a bunch of small tweaks done that should pickup some good flow with no additional CSA that == more air flow AND more velocity; there's no way that's going to hurt.

-My hesitation is that a better Ferrea 45 degree valve, and a 4 or 5 angle valve job, and the radiused exhaust could pickup a few CFM, and more velocity for probably way less $$$ and all the questions about whether the 50 would work go away; but that's definitely the safe, boring route and no risk, no fun. A top-shelf, high-velocity header / exhaust system also seems to offer MOST of the benefits of the 50 degree seat angle, in terms of anti-reversion and increasing low end torque and allowing for a bigger cam that lets you make more on the top-end (although a good headers/ exhaust obviously won't make the head flow any more CFM at the higher lifts, it seems to have similar benefits and to be tried and tested....).

Now that Rick can't do it, I'll probably just stick with what I have, but come rebuild time, the 50 degree seats and a different cam are going to be pretty irresistable!



Adam

Orr89RocZ

iTrader: (20)

I wouldnt say that. Lsa doesnt mean anything without a duration attached to it. That would tell you overlap and then decide if its possible to work with brakes.

Stock ecu will run anything you want. My old 383 was on a 109 lsa and 230 deg duration with alot of overlap. Ran fine on stock brakes and ecu.

Your 227/228 sounds like a great tpi cam. Jones did Allen’s custom FIRST tpi project cam, i believe it was a 232/232 on a wide lsa. Made power at 6000-6200+ on 369”. 400+ whp.
Long runners usually need a few more deg intake duration than normal to get the air charge going thru those long runners. Need more time to fill cyl

newbvetteguy

Thanks Orr!

I'm currently @ 56 degrees overlap on a 110 LSA. If I just change to the Vizard-recommended max power / torque LSA of 106.5 for a 383 that's 65 degrees of overlap. --I thought that would be way too much overlap for power brakes, no? (And I've got a pretty aggressive cam with only 272/280 duration seat-to-seat; I'd expect most hydraulic roller cams with 227/228@ 0.050" to have more duration on the seats, which would make the overlap even larger still.


I'm shocked you could use power brakes and especially a stock ECU with 230 degrees @ 0.050" and a 109 LSA.

I think with a stock ECU Mike was going to grind my cam on a 112 LSA, but because of the Holley EFI he put it on a 110 LSA; my understanding is that with like 9/10ths of the car's features running on vacuum (stupid 1979 Corvettes ran EVERYTHING on vacuum: brakes, headlights, transmission load sensing, windshield wipers, the heater controls (for real), cruise control has a vacuum line 110 LSA with this cam was all I could use and safely ensure I was going to have brakes. Maybe at the next rebuild I'll move to hydraulic brakes but right now it's just too much to deal with and I've seen loads of problems with the power steering pump running both Steeroids rack and pinion steering AND hydraboost brakes due to pretty significantly different required pressures and flow rates.


Adam

P.S. I think I randomly stumbled across some Youtube videos of you at the strip with one of your old TPI motors a couple months back.

Orr89RocZ

iTrader: (20)

My cam had 78 deg overlap at the seat durations. 19.5 at the .050 numbers. Brakes worked. Give it a fair amount of timing advance and proper air fuel and 1000 rpm idle which most cams like 800-1000 rpm and it will have a fair amount of vacuum.

I since went hydroboost braking and it is awesome. My 400” motor had 83 deg overlap and it was a turbo deal. 113.5 lsa lol Ran for a short while on stock ecu and then went sequential 24x

newbvetteguy

Wow. Makes me slightly regret being so conservative with the LSA, but great info. Do you have any calculator, software, or rules-of-thumb to use for calculating inches of vacuum for a given combo?

Adam

Orr89RocZ

iTrader: (20)

No just goin by the few combos i’ve had in my hands.

BadSS

Man, do not get hung up on Vizard’s 128 “rule”. It’s a really good approximation/rule based on years of his dyno experiences and will get you really close to an optimized cam for pure power output. I’m not disputing that at all. However, as you alluded to earlier, there are things like power brakes, compression ratios, idle quality, and running moderate gearing and stall speeds that play a huge factor into what combination of duration and lobe spread you “need” to run. Plus, the tighter lobe spreads (other than those with minimal overlap) need a SERIOUS exhaust system (like Vizard’s Zero Loss systems) or you’ll run into some funky peaks and lulls, typically around most street sized stall converters that will play havoc with your 60-ft times.

Also, the tighter lobe spreads are peaky in general with a narrower power band and the power drops off quickly past peak. If you’re running a long tube runner the physics involved boosts midrange torque, so much that a boost on top of an already peaky midrange from the tighter spreads just makes it even harder to hook with a peak on top of a peak and the power at the top of the rpm band drops even faster. Simulations validate this - leaving 20lb/ft in the midrage under the shift recovery point when you already have massive torque from the LTRs,, and picking up 15-20HP at the top of the gear and able to hold it out a couple hundred rpm more is a win-win when it comes to ETs. So you really want to go a little wider on the lobe spread with a LTR set up than you would with a single plane.

I can tell you back in the late 80s through mid 90s, I daily drove a pump gas 406 with a solid roller 288/292 – 256/260 – 106 cam that made 614HP at 6600 RPM in the cell. It had 78-degrees seat overlap and 41-degrees overlap at .050”. I had it idled at 1200rpm and could get one good emergency stop out of the brakes and didn’t have an issue with them in normal driving conditions. I remember once there was some road construction and the guy in front of me in a Suburban kept slamming on the brakes, over and over. I had to keep a lot of distance between us because after that third back to back hard stop, I almost ran into him. Granted, the thing wrapped up like a motorcycle and I wasn’t unhappy with it back then, it’s just I wouldn’t want to run that combo now.

I’m not going to give the new cam specs on my latest build because I want to make sure it’s going to do what I think it will do once I get the ported FIRST installed on the engine (I spec'ed it for the FIRST, not for the single plane intake used for the dyno). However, I will say it has 48-degrees seat overlap and 18-degrees at .050”. Yes, it is a fairly aggressive solid roller with a much wider lobe spread than the other cam. However, it’s not going to be a daily driver, so I was comfortable with running the relatively aggressive lobes. With the same heads, intake (single plane), 850 vs 830 carb, 406 vs 406, and near same compression, the thing made 602.4HP on the dyno at 6100rpm and carried 595HP to 6600 rpm. It also made 499.3lb/ft at 3100rpm and 563.7 lb/ft at 5000. It should pull around 18” vacuum at 800rpm after ECM tuning. This thing is not going to have any problems with the air conditioner, repeated braking, or cruise control. It’s going to run just as fast as the car did before with the single plane, carbed, 106 spread cam, but do it running a fricken TPI and with a smooth idle,,, all with less gear and stall speed to boot – go figure.

So, there’s a lot more to getting something to run the way you want it to run than sticking with one lobe spread and rocking the duration up or down. There is NO WAY, NO HOW, I could have gotten anywhere close to 600HP with the vacuum I wanted on a 104 or 106 “128” spread – I pretty much know for a fact cause I ran “that cam” 25-years ago.

I'm finally recovered enough from all the surgeries AND my mom is healthy as well, so I've started back piddling around with the car again. So if all continues to go well,,, maybe I'll FINALLY get this pig running and on the road in 2018.

I'm not aware of any calculators on the web for vacuum estimates. However, EA Plus and EA Pro both have an estimated vacuum that I typical can meet with a programmable timing curve.