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I see where he was going with that...Broadly - For a race car running in a narrow RPM range where the only consideration is the torque curve that you are riding while you are between the gear shifts, the lobe separation angles can be tuned to the crank stroke to maximize peak torque. We could also take advantage of the overlap on a free flowing exhaust. That said...On a street car, where the restriction of the exhaust limits the beneficial effect of cam overlap, the wider lobe separation angles generally reduce overlap and provide a wider, but lower peak torque curve (desirable) and potentially a better idle. Can't forget how duration effects overlap but apples to apples this is kind of how it works as far as I know. Extra exhaust timing from a dual pattern cam helps the restrictive exhaust work better too.
Awesome explanation.
Vizard of course assumes a “properly” designed non-restrictive exhaust, but that doesn’t mean that street cars can’t have nonrestrictive exhausts. (Vizard’s “zero loss” system using wave termination boxes as a great example.)
I’m very visual so the relationship between duration and LSA driving overlap is way easier for me to remember than valve event timing. -Just stare down the end of a cam and that part makes sense: as the durations get bigger between the exhaust and intake lobes, with the same LSA, the lobes get “fatter” at the bottom and, when staring down the end you can see that they physically overlap more. If you could actually grab the lobe centers and pull them further apart you’ll eventually pull them far enough apart that they don’t overlap anymore. (Obviously overlap is actually concerned with the valve events but the visual construct helps it make sense, IMO. And when you model valve events in many programs it physically shows you the overlap in a way that is easy to mentally transfer to looking at a cam down the end.)
I see where he was going with that...Broadly - For a race car running in a narrow RPM range where the only consideration is the torque curve that you are riding while you are between the gear shifts, the lobe separation angles can be tuned to the crank stroke to maximize peak torque. We could also take advantage of the overlap on a free flowing exhaust. That said...On a street car, where the restriction of the exhaust limits the beneficial effect of cam overlap, the wider lobe separation angles generally reduce overlap and provide a wider, but lower peak torque curve (desirable) and potentially a better idle. Can't forget how duration effects overlap but apples to apples this is kind of how it works as far as I know. Extra exhaust timing from a dual pattern cam helps the restrictive exhaust work better too.
Awesome explanation.
Vizard of course assumes a “properly” designed non-restrictive exhaust, but that doesn’t mean that street cars can’t have nonrestrictive exhausts. (Vizard’s “zero loss” system using wave termination boxes as a great example.)
I’m very visual so the relationship between duration and LSA driving overlap is way easier for me to remember than valve event timing. -Just stare down the end of a cam and that part makes sense: as the durations get bigger between the exhaust and intake lobes, with the same LSA, the lobes get “fatter” at the bottom and, when staring down the end you can see that they physically overlap more. If you could actually grab the lobe centers and pull them further apart you’ll eventually pull them far enough apart that they don’t overlap anymore. (Obviously overlap is actually concerned with the valve events but the visual construct helps it make sense, IMO. And when you model valve events in many programs it physically shows you the overlap in a way that is easy to mentally transfer to looking at a cam down the end.)
Blocking the bypass is a good idea, just remember to us high pressure oil filters. Like Wix or K&N. I also use Morroso top end oil restrictors I did drill them out to increase the flow somewhat
Blocking the bypass is a good idea, just remember to us high pressure oil filters. Like Wix or K&N. I also use Morroso top end oil restrictors I did drill them out to increase the flow somewhat
I do have a good stock of Wix filters already on the shelf. Some 10W-30 and some 20W-50 Valvoline VR-1 cases piled up next to them.
I already know how you like that Crane cam. Its the 3rd time for me to use it.
Last edited by stingr69; Feb 14, 2019 at 01:27 PM.
When blocking the oil filter bypass.....make SURE you run a high flow element like the the Fram HP4 or HP8 (short).
And before we go Fram slamming......the HP series of filters are made on their own and the $14 price tag confirms that.
I use a high flow Wix Racing unit but next oil change it will get changed out for the HP8.
When blocking the oil filter bypass.....make SURE you run a high flow element like the the Fram HP4 or HP8 (short).
And before we go Fram slamming......the HP series of filters are made on their own and the $14 price tag confirms that.
I use a high flow Wix Racing unit but next oil change it will get changed out for the HP8.
Jebby
Jebby,
I looked at the Wix Racing filters but the very high flow rates with less desirable micron ratings make me think they will not stop smaller particles.
The standard Wix filter "51069" is rated to flow 9-11 GPM (plenty) and stops a 21 micron particle size. Adequate flow and good filtration.
The Wix Racing filter "51069R" has a much greater 28 GPM flow rating but a worse 61 micron particle size rating. You get higher flow rating that you will never need by not filtering out the small dirt particles. Seems like a judgement call to make there.
Fram has me on the fence...Lots of Hater-Aid on that brand. They do have cardboard end caps on the more basic filters but they are glued to PAPER elements. Seems like we worry a lot about the cardboard but paper is even weaker.. I dunno? That's why we get choices I guess.
That 60 psi oil pressure you have spreads out over a paper filter that probably has near 200 sq inches. So there is hardly any pressure on 1 sq in of filter element (1/3 psi?). Yeah you probably couldn't even tear wet tissue paper with that little paper. The micron rating on the other hand is extremely important. I would want as fine as possible in my new LS6 engine I just spent way too much on. Anyone know of a comparison of oil filter micron ratings? And no I didn't even google it yet....
I just talked with the speed/machine shop helping me put my 496 together and he agreed with the need to plug or remove the oil filter by-pass.
They sell a billet piece that replaces the pot metal OEM bypass.
I ordered one for my big block and it will be here next week.
Last edited by OldCarBum; Feb 15, 2019 at 07:46 PM.
Those Oberg filters are pretty sexy. Love the "tattle tail" warning system. Reusable elements...easy to service even between oil changes. Tag along is cool.
UPDATE - The molly rings were ordered as "file fit" so they do not come pre-gapped. From my experience, the pre-gapped ring sets can run pretty large gaps. I didn't want to do that so I ordered a set of "file fit" rings. They are basically .005" over bore sized rings with tighter gaps. The ends will butt or close to it when installed "out of the box". I filed the ring ends to get the gaps where they needed to be and dressed the sharp burrs before installing them on the pistons. All the pistons are now installed and the oil pump was next.
Low mileage used GM oil pump. No significant wear.
This is a good time to drive out the roll pin and remove the original oil pump pressure regulator spring. It needs to be removed before the pickup can be brazed to the pump anyway. The only difference between a stock GM pump and a high pressure Z/28 pump is the oil pressure spring. You can buy the spring for about $6 and install it yourself. Melling changed their oil pump castings in the early 1990's so the standard pumps are thinner and not as strong as stock castings. You can buy their higher performance models with thicker stronger castings and higher pressure or volume but they are not cheap. Unless you have made some significant changes to the oiling system, you do not need a high volume pump. All you need is 10 PSI for every 1000 RPM and forget about it. The "White Stripe" GM oil pressure spring provides 70 PSI at high RPM in an otherwise stock pump so it should be enough for most any streetable build.
DO NOT forget to install the drive shaft before you install the oil pan. (not that I would ever do that -LOL)
A wad of aluminum foil on the pick up to check the distance to the bottom of the pan.
We were shooting for 3/8" clearance between the bottom of the oil pan and the pick up. The test fit of the oil pan looks like it is just right.
Still need to add the windage tray before we put the pan on next.
You forgot the last part, getting hauled in for st racing lol
i had my license pulled 4 times in little rock ark, twice for a year twice for 6 months. When i would apear before judge butler we knew each other well.... He would simply say... Jim what im i going to do with you... Thats only what they caught me with.... I was so bad i would not be exagerating much by saying if a cop car pulled up beside me i would race them.... Ya looking back on it i could do without all those court apperences.
Last edited by Little Mouse; Feb 21, 2019 at 01:26 PM.
Why did you use the neoprene collar instead of the IS55 piece with the steel collar pinned on it?
Jebby
I already had the shaft and the collar so they were free.
Why do we need a steel collar? There is no load or wear happening on that part. The white collar holds the shaft in place if I turn the engine upside down before the distributor is installed. Just an assembly aid for the most part.
Low mileage used GM oil pump. No significant wear.
DO NOT forget to install the drive shaft before you install the oil pan. (not that I would ever do that -LOL).
It does & did happen just in last few weeks HERE AT CF …
......builder posted pic w/ pump installed but with NO shaft. Another hawkeye spotted it and tipped builder before pan silicone cured.
I already had the shaft and the collar so they were free.
Why do we need a steel collar? There is no load or wear happening on that part. The white collar holds the shaft in place if I turn the engine upside down before the distributor is installed. Just an assembly aid for the most part.
Because at 5000 rpm.....a std. volume oil pump requires 4-5 horsepower to turn (as much as the average lawn mower produces TOTAL).....and the hole that it goes through is sloppy so the neoprene collar is the only thing keeping the shaft from walking off the pump drive......and as an added bonus.....after about few thousand heat cycles, this part becomes brittle. I believe that an engine that is designed to rev over 5000 on occasion should have the steel collar shaft.....it is just an engine builder staple at $11 a piece. You can do build it how you see fit but I would change this out. You are all over it by removing the bypass spring for brazing and installing the Z-28 spring, brazing on the pickup and checking for pickup height.....but leave this part stock.
Just an observation and am not bashing in any way......
BTW.....for $6 more dollars you can use a stud to hold on the oil pump and for free you can chamfer the oil port on the main cap for less turbulence at high RPM. I love the stud because it leaves NO way to pull the threads out of the main cap when torquing the bolt....which on old stuff I have seen many times.
Jebby
Last edited by Jebbysan; Feb 21, 2019 at 03:43 PM.
