Hypothetical cam question...how would it run?

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Re: Hypothetical cam question...how would it run?

Post by CGT » Fri May 11, 2018 2:26 pm

I think the OP's cam would run fine in that application. As far as the EMC talk goes. There isn't a (perfect) centerline through that whole rpm range, it's essentially variable. Every 1000rpm's or so could prefer a different centerline. With the cam and lobes fixed, you just end up where something scores best. The final cam is unlikely to have been better everywhere through that range, on "one" centerline.

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Re: Hypothetical cam question...how would it run?

Post by Headguy » Fri May 11, 2018 2:38 pm

CGT wrote:
Fri May 11, 2018 2:26 pm
I think the OP's cam would run fine in that application. As far as the EMC talk goes. There isn't a (perfect) centerline through that whole rpm range, it's essentially variable. Every 1000rpm's or so could prefer a different centerline. With the cam and lobes fixed, you just end up where something scores best. The final cam is unlikely to have been better everywhere through that range, on "one" centerline.
Will it run, yes. Will it idle against the converter, probably.

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Re: Hypothetical cam question...how would it run?

Post by CGT » Fri May 11, 2018 3:33 pm

Headguy wrote:
Fri May 11, 2018 2:38 pm
CGT wrote:
Fri May 11, 2018 2:26 pm
I think the OP's cam would run fine in that application. As far as the EMC talk goes. There isn't a (perfect) centerline through that whole rpm range, it's essentially variable. Every 1000rpm's or so could prefer a different centerline. With the cam and lobes fixed, you just end up where something scores best. The final cam is unlikely to have been better everywhere through that range, on "one" centerline.
Will it run, yes. Will it idle against the converter, probably.
Im not saying its what I'd do, but it really isn't a tremendous amount of overlap, IVC isn't really that early for a tow/utility vehicle. It'll be done early for sure, but that's how that kind of thing is supposed to be...trading efficiency in one area for another.

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Re: Hypothetical cam question...how would it run?

Post by CGT » Fri May 11, 2018 3:48 pm

If your block has late model provisions, Gm part# 14097395 Camshaft, and Gm part#12499225 lifter set would run circles around anything you mentioned, and affordably at that. Gm part# 12499224 Spring kit, Comp cams 787-16 Retainer kit as well.
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Re: Hypothetical cam question...how would it run?

Post by Walter R. Malik » Fri May 11, 2018 6:29 pm

Many years ago the NSX Acura and a different vehicle which Mitsubishi manufactured which I can't remember, (made a similar vehicle for Chrysler Corporation), used double overhead, small cams with variable cam timing.
At about 1,200 RPM the double overhead cams would change from minimum overlap, (to keep the idle smoother), to full overlap position at every other running possibility for maximum internal EGR, minimize parasitic losses due to higher manifold vacuum and having earlier intake valve closing.

Basically, those "Street Rod" series cams from Lazer Cams were simply always in the max overlap position.

EDIT:
I went and looked it up ... that Mitsubishi car was the 3000GT and they manufactured the "Stealth" version for Chrysler.
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Re: Hypothetical cam question...how would it run?

Post by joe 90 » Fri May 11, 2018 7:11 pm

Walter R. Malik wrote:
Fri May 11, 2018 6:29 pm
Many years ago the NSX Acura and a different vehicle which Mitsubishi manufactured which I can't remember, (made a similar vehicle for Chrysler Corporation), used double overhead, small cams with variable cam timing.
At about 1,200 RPM the double overhead cams would change from minimum overlap, (to keep the idle smoother), to full overlap position at every other running possibility for maximum internal EGR, minimize parasitic losses due to higher manifold vacuum and having earlier intake valve closing.

Basically, those "Street Rod" series cams from Lazer Cams were simply always in the max overlap position.

EDIT:
I went and looked it up ... that Mitsubishi car was the 3000GT and they manufactured the "Stealth" version for Chrysler.
You're talking about the original VTEC (Honda) and original MIVEC (Mitsubishi) systems which had long cams with lots of overlap . They switch over (from shorter less lift lobes)at about 4000RPM. It's not VVT.
It was never offered as an option for the 3000GT / Stealth although at least 2 of them have been built in the southern hemisphere using heads and other parts from the Diamante 30M / Pajero evo.
You're looking at about 55 deg overlap on the small lobes and about 90 deg overlap with the big lobes (over 300 deg duration), that's at working lash.

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Re: Hypothetical cam question...how would it run?

Post by ptuomov » Fri May 11, 2018 7:35 pm

Porsche 968 variocam moves the intake camshaft angle. At idle, the intake is retarded and overlap reduced for smooth idle and good emissions. At mid range rpm, intake is advanced for high overlap and more torque. At high rpms, the intake cam is again retarded to late IVC and resulting better high-rpm cylinder filling. Exhaust timing doesn’t change.
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Re: Hypothetical cam question...how would it run?

Post by Walter R. Malik » Fri May 11, 2018 8:46 pm

joe 90 wrote:
Fri May 11, 2018 7:11 pm

You're talking about the original VTEC (Honda) and original MIVEC (Mitsubishi) systems which had long cams with lots of overlap . They switch over (from shorter less lift lobes)at about 4000RPM. It's not VVT.
It was never offered as an option for the 3000GT / Stealth although at least 2 of them have been built in the southern hemisphere using heads and other parts from the Diamante 30M / Pajero evo.
You're looking at about 55 deg overlap on the small lobes and about 90 deg overlap with the big lobes (over 300 deg duration), that's at working lash.
And, what exactly does whatever vehicle have to do with what the OP was asking about ...?

OK ... you wish to nit-pick about which vehicles had these working systems but, that makes no difference at all for this.

The Mitsubishi MIVEC system IS, (by Mitsubishi's own definition), "Variable Valve Timing" which idles at minimum overlap then switches to maximum overlap at just over 1,200 RPM and slowly returns to minimum overlap as the RPM increases allowing more overlap with sooner intake valve closing and later exhaust valve opening at lower RPM ...

I probably should not have mentioned the Acura NSX engine as an example here but, I really was not sure till now.
The Honda/Acura VTEC system was not exactly varying the camshaft timing but, they used two separate intake lobes on one camshaft with their system for different reasoning than Mitsubishi.

The engine control offerings available were different in Japan and America from both companies.
They are different designed systems which allowed different valve timing; (even different valve lift with VTEC) ... whatever that particular model vehicle is immaterial to the engine effects .

It seems, you are not able see the forest because the trees are in the way.
Either that, or you just get off on making corrections for things which don't matter simply because you want everyone here to imagine how smart you are.

OK, you're smart ... now, I hope you do feel better .
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Re: Hypothetical cam question...how would it run?

Post by Walter R. Malik » Fri May 11, 2018 11:12 pm

joe 90 wrote:
Fri May 11, 2018 7:11 pm

You're talking about the original VTEC (Honda) and original MIVEC (Mitsubishi) systems which had long cams with lots of overlap . They switch over (from shorter less lift lobes)at about 4000RPM. It's not VVT.
It was never offered as an option for the 3000GT / Stealth although at least 2 of them have been built in the southern hemisphere using heads and other parts from the Diamante 30M / Pajero evo.
You're looking at about 55 deg overlap on the small lobes and about 90 deg overlap with the big lobes (over 300 deg duration), that's at working lash.
That electronic / hydraulic VTCE (?) system with variable sprockets was developed separate from the MITEC or the VTEC systems happening. Probably even in the late 80's.
Might not have even been Mitsubishi or Honda who developed it, (I thought I read an SAE report that it was but maybe not), however, that actually doesn't matter who; only that it moves the cams phasing.
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Re: Hypothetical cam question...how would it run?

Post by GARY C » Sat May 12, 2018 2:31 am

travis wrote:
Thu May 10, 2018 10:40 am
Totally hypothetical build at this point, but something I am very curious about.

Basic 8.5-1 smog era 350-ish size engine, smog heads with nothing more that a little port cleanup and a good valve job, basic stock iron or performer type dual plane, small tube full length headers with a decent exhaust system.

I’ve built a million engines like this...mild daily driver or utilitarian use vehicle stuff, using mostly comp cams 252-268 high energy (or similar from other companies), depending on gearing. For a 3.40 geared pickup I would normally use the 268. The result is always predictable, and they will run on cat pee if needed, even with an aggressive spark curve. DCR is in the very low 7’s. They run decent with little maintenance.

Now, change the 268 cam (218@.050, 110 lsa, 106 ica), with a custom ground 256@.006 cam, on a 104 lsa/100 ica...how does the characteristics change? Fuel economy, idle quality, power range, off idle throttle response, etc. Overlap at .006” is still 48*, but the ivc point happens 12* sooner (48 vs 60). Shorter, but harder hitting low end torque? Falls on its face at 4000 rpms? DCR increases to 7.5-7.6 range, so still should be no issues with pump fuel. What about idle vacuum?

I’m thinking an application like my buddies early 80’s ford van with a 351w and 2.75 gears could benefit from something like this, but then again this is well outside of any normal cam specs, so I dunno. If it was something magical then someone would offer something similar off the shelf.

Thoughts?
Here is a simple idle vac calculator to give you a ball park.
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Re: Hypothetical cam question...how would it run?

Post by joe 90 » Sat May 12, 2018 5:38 am

Walter R. Malik wrote:
Fri May 11, 2018 8:46 pm
joe 90 wrote:
Fri May 11, 2018 7:11 pm

You're talking about the original VTEC (Honda) and original MIVEC (Mitsubishi) systems which had long cams with lots of overlap . They switch over (from shorter less lift lobes)at about 4000RPM. It's not VVT.
It was never offered as an option for the 3000GT / Stealth although at least 2 of them have been built in the southern hemisphere using heads and other parts from the Diamante 30M / Pajero evo.
You're looking at about 55 deg overlap on the small lobes and about 90 deg overlap with the big lobes (over 300 deg duration), that's at working lash.
And, what exactly does whatever vehicle have to do with what the OP was asking about ...?

OK ... you wish to nit-pick about which vehicles had these working systems but, that makes no difference at all for this.

The Mitsubishi MIVEC system IS, (by Mitsubishi's own definition), "Variable Valve Timing" which idles at minimum overlap then switches to maximum overlap at just over 1,200 RPM and slowly returns to minimum overlap as the RPM increases allowing more overlap with sooner intake valve closing and later exhaust valve opening at lower RPM ...

I probably should not have mentioned the Acura NSX engine as an example here but, I really was not sure till now.
The Honda/Acura VTEC system was not exactly varying the camshaft timing but, they used two separate intake lobes on one camshaft with their system for different reasoning than Mitsubishi.

The engine control offerings available were different in Japan and America from both companies.
They are different designed systems which allowed different valve timing; (even different valve lift with VTEC) ... whatever that particular model vehicle is immaterial to the engine effects .

It seems, you are not able see the forest because the trees are in the way.
Either that, or you just get off on making corrections for things which don't matter simply because you want everyone here to imagine how smart you are.

OK, you're smart ... now, I hope you do feel better .

I'm just correcting the inaccuracies that you posted...it's the interweb. Clowns cut and paste things they've got no idea about, next thing you know it's fact when the only fact is that you made it all up.

The original VTEC and MIVEC systems didn't use variable pulleys.
The first time Mitsubishi used a variable pulley was with the EVO 9 in 2005.On the intake cam only and VVT only.
A variable intake cam is used by lots of OEMs these days.

The original mivec system was made in the mid '90s. 2 different cam profiles, switching over about 4000 RPM.
Lots of overlap and duration works well in the correct situation but not really at low RPM.

Mitsubishi built a 3rd totally different system which only was seen on the 3.8 eclipse and some Pajeros. Again no variable pulley but a switchable cam lobe but only on the intake cam.......that's what you'll be getting mixed up with.

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Re: Hypothetical cam question...how would it run?

Post by Walter R. Malik » Sat May 12, 2018 10:42 am

joe 90 wrote:
Sat May 12, 2018 5:38 am


I'm just correcting the inaccuracies that you posted...it's the interweb. Clowns cut and paste things they've got no idea about, next thing you know it's fact when the only fact is that you made it all up.

The original VTEC and MIVEC systems didn't use variable pulleys.
The first time Mitsubishi used a variable pulley was with the EVO 9 in 2005. On the intake cam only and VVT only.
A variable intake cam is used by lots of OEMs these days.
A simple sentence saying it was not Honda or Mitsubishi and, maybe someone else ... would have done what you say by correcting the inaccuracies; without all the rest.
It was almost 30 years ago and every SAE report is not totally committed to memory.
Like I later wrote, maybe it was not even Honda or Mitsubish however, there was a system from a Japanese company which had a camshaft phasing system like this in the late 80's. (Somebody PM'd me that it was Nissan but, I have not verified that).

The point I was making merely was that this type valve timing has been done in production and the engine/vehicle did not drive like a light switch.
Pertaining to the OP's hypothetical question, the early "Street Rod" camshafts from Lazer Cams did not drive like a light switch, either.
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Re: Hypothetical cam question...how would it run?

Post by jeff swisher » Sat May 12, 2018 11:10 am

Travis on to your question.

I have built just about what you are thinking of building.
This will be a long read as i want to add all the info I can.

1984 6000 lb Ford E150 with AOD and 355 gears, 302+.030 with flat top keith blacks and stock rebuilder cam, I ported the small valve 1982 heads and ported the iron 2 barrel intake and ported the exhaust manifolds and ran 3" single exhaust.
That factory cam was tiny like 374" lift it was a dual pattern ..but lift was under 400" .
I advanced it 4 degrees and got ok power and MPG was 15 with tuned 2 barrel motorcraft .

I tried various other carbs from AFB's to Q jets with secondaries disconnected and once dialed in they all had the same power and within 1/2 MPG.

I upped the stakes and installed a 260H on a 110 LSA I got 16.7 mpg on low average and 18 MPG every now and then.
Power was up a tick and when pulling my boat to the lake i would still get 16.7 MPG or better.

Timing was quick 18 initial and 35 total all in by 2000 rpm.. I ran 87 octane.
No vacuum advance..I tried it but it would not gain any MPG and tip in was pinging because vacuum was still high enough for hill climbing that advance was still being added by vacuum.
Now OD was not used although the trans had it.. I tried OD and MPG suffered and the little 302 would not pull 2000 rpm going down the highway without loosing power and downshifting so R's were 2700-3100 most of the time on the highway. and got that MPG.

Now we get into the SBC with odd cam like you are thinking about.

I had my cam guy grind me a 268H off the comp master but put it on a 106LSA for a 350 I was putting together for an old 47 dodge truck I have.
I used 601 305 heads I bowl ported and opened the pushrod pinch stock 1.84-1.50 valves.

That cam closed the intake I think 2 degrees sooner than the 260H.
Cranking pressure is high 225 psi. timing is also quick 18 initial and 35-38 total. 38 total vs 35 only resulted in 3HP loss at the wheels.
All in by 2200rpm.

MPG was 12 to 14.. 14 if I really drove for MPG.
AFR was spot on .. 15.0 idle and 14.5 at part throttle cruise and 13.5 full throttle. RPM intake . Lakester headers Homemade.

Now the MPG was killing me and i had a thought.
I wanted a cam ground on a 112 LSA but i liked my low end TQ from the early closing intake valve.

I had my cam grinder build me a cam with the same lobes and close the intake side just like the 106LSA cam but push the exhaust the other way and make it a 112LSA.

I was rewarded with 18 MPG and vacuum only changes 2" at idle.. Small runner heads help in that department. 170-175cc is where they usually come in at.
Now back onto the wheel dyno.. It made max HP at 5700 rpm with both cams and max TQ was 4500-4700 rpm.

But from the way I had this cam made Power past the peak 5700rpm dropped off like a stone on the 112LSA deal.
By 6500rpm the 112 lsa was down more than 45 HP.

No big deal as it actually was running the same ET as before but Top speed blasts suffered with the 112 lsa ..No longer could I run 150MPH.

Not that i need to run 150 :)

So what i got from tighter LSA was a brutal power curve with more overlap that carried power pretty well up top but MPG suffered.


Now I wanted to get 20+ MPG
I thought I got this.. so close just 2 MPG more all i need is a 260H ground on a 112 and i will not open the pushrod pinch on this other set of 601 heads I have.

So i ported the heads just the same except I did not touch the intake entry at all and had the 260H ground on the 112 LSA and put it together.
Brutal TQ out of the hole just like the 268H build but out of steam about 5000 rpm.

Perfect should get better MPG.
6 months of tuning and driving probably 20,000 miles and best MPG was 14.
WHAT happened.
Cranking pressure was 215 psi just a bit less than the earlier closing 268H.

I think it was the big turn at the pushrod pinch.. my air had to turn and maybe atomization of the fuel suffered.
Yea different short block with Hypereutectic pistons H345NP .. the 268H engine had the cast pistons 345NP.
Same rings used , E251K

Oh well. stuck the 268H engine back in and I always open the push rod pinch now.

Have fun with those numbers.

PS. my buddy had a 351HO ford van just like my 302 van and we raced my 302 vs his 351HO Yes I tuned his 351 and it ran better than it did from the factory.
But my 302 would beat it pretty bad. in a drag race .. put the heavy trailer behind them and the 351 would win.

Pulled a 351HO from a truck and stuck a 350 chevy in it and it felt like you dropped a big block in there from all the extra power.

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Re: Hypothetical cam question...how would it run?

Post by GARY C » Sat May 12, 2018 8:31 pm

Jeff, just curious, what ICL or ICLines did you run between your 106 and 112 test?

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Re: Hypothetical cam question...how would it run?

Post by jeff swisher » Sun May 13, 2018 8:49 am

Both were 102 ICL.
I liked the MPG increase so much that i almost want to try 117 LSA
I am sure doing it the way I had him do it the upper end power would be horrible.
And then in the back of my mind i think dual pattern grind may be an advantage here.

But I stop where i am at and enjoy driving the thing.

Here is a crappy video with the cam ground on a 106LSA watch the tachometer swing to 7000 rpm
I had to make that video to show naysayers that 305 heads do not quit flowing air at 4500rpm.
Where some people come up with that nonsense.

https://www.youtube.com/watch?v=hivG7qlPTZA I had 325 gears in it at that time.

When i switched to 456 gears and 4500 stall for giggles first time I got on it the engine swung to 7200rpm and floated the valves just a wee bit.
I have 80 psi seat pressure on that build.

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