Input needed on daily driver sbc truck build

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novadude
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Re: Input needed on daily driver sbc truck build

Post by novadude »

gottago wrote: Mon Oct 15, 2018 12:48 pm

What happens to driveability in regard the subject criteria ( daily driver ) Idle characteristics, fuel mileage, type of fuel required, torque converter specs etc..
I can maybe address this from my own experience.

I have a 270/278, 217/225, 108 LSA hydraulic roller cam in a 9.6:1 355. Idle characteristics and fuel mileage are great. Pulls from ~1200 rpm (manual trans) without lugging the engine, and runs hard up to ~5600-5700 RPM where I shift it. Gets 18-20 mpg at a 3200 rpm cruise speed.

I always bought into the hype that "tight LSA = narrow powerband and bad manners". I'm glad I read DVs book and took the leap of faith to try something different with this build, as I am very happy with the results.
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Re: Input needed on daily driver sbc truck build

Post by gottago »

What heads are you using novadude? Is your cam installed straight up? Do you think that cam would work as well behind an automatic trans?
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Re: Input needed on daily driver sbc truck build

Post by novadude »

Cam is from Howards, and I am using out of the box '062' GM vortecs (new stock truck heads, no the bowtie heads) with a spring swap.

Cam is installed on a 104 ICL per cam card. Running a Q-jet, GM low-rise "performer" style intake, and tri-y headers. Trapped at 108 mph in Chevy II (3350-3400 lb race weight with driver). Not bad for a very mild combo, IMO.

If I was putting in a heavy vehicle with tall gears and a stock torque converter, I might want to go a bit shorter on duration / overlap. Maybe a single pattern in the 212-217 deg @ 0.050 range on a 108 LSA. I would guess it would still run very strong up to 5200-5500 rpm, but maybe pull better from 1500 rpm? I don't think my cam would be "bad" in with a stock converter automatic, I just think the off-idle (1500 rpm stall)could be improved with a different selection.

Just my $0.02 (with no data to support this).
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Re: Input needed on daily driver sbc truck build

Post by gottago »

ND
Gets 18-20 mpg at a 3200 rpm cruise speed.
Just noticed that, pretty impressive especially at 3200 rpm cruise speed but that may be a bit much rpm for daily driver status imo. Guess that depends on how much highway driving you do but for most I think 2200 - 2500 is max for real long distance driving or mainly highway cruising.

Which then gets back to the cure!
If I was putting in a heavy vehicle with tall gears and a stock torque converter, I might want to go a bit shorter on duration / overlap. Maybe a single pattern in the 212-217 deg @ 0.050 range on a 108 LSA. I would guess it would still run very strong up to 5200-5500 rpm, but maybe pull better from 1500 rpm? I don't think my cam would be "bad" in with a stock converter automatic, I just think the off-idle (1500 rpm stall)could be improved with a different selection.
Note your vehicle weight too nd.. 3400 lbs with driver.. Most of us are going to be a fair bit more. Dropping duration but sticking with the 108 lsa as suggested might work for some but you do risk the effect I try to avoid as much as possible. Passing a vehicle on a single lane highway requires a bit of performance just for safety purposes. The less amount of time you spend out in the left lane, the less chance you run of having any sort of accident. I've been in some nasty ones and don't trust any one out there anymore.. The 104 lsa cam I ran at one time had the effect of hitting a wall at a certain speed. There was no more to be had whatsoever when you got there. Imagine passing someone and a transport truck comes around the corner in front of you and you are stuck out there unable to accelerate any faster. The 112 lsa at least had some run out room in that regard, even if it weren't a ball of fire getting up there. That's where the 5000 rpm tractor power like cam on a tight duration lost its luster for me. Reminiscent of Isky's old mile-a-more cam back in the early 1970's. Why isn't anyone using that any more in a daily driver? Same effect.. Great basic off the line, around town, but all done on the entrance ramp before hitting the highway.

D.V. says it is just a matter of getting the absolute correct lsa for the particular combination to get the best of both worlds.. Maybe so, I'm willing to listen. Daily driver definition again.. For me, has to do everything reasonably well with a bit extra on reserve for safety factor alone. Maybe comps common 110 lsa recommendation isn't that far off the mark in this category?
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Re: Input needed on daily driver sbc truck build

Post by novadude »

If David comes back with a cam specification, can you please share all of the parameters that were provided for this selection? I'd be very curious to see the detail, as I think we can learn from it.
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Re: Input needed on daily driver sbc truck build

Post by houser45 »

gottago wrote: Thu Oct 18, 2018 1:06 pm ND
Gets 18-20 mpg at a 3200 rpm cruise speed.
Just noticed that, pretty impressive especially at 3200 rpm cruise speed but that may be a bit much rpm for daily driver status imo. Guess that depends on how much highway driving you do but for most I think 2200 - 2500 is max for real long distance driving or mainly highway cruising.

Which then gets back to the cure!
If I was putting in a heavy vehicle with tall gears and a stock torque converter, I might want to go a bit shorter on duration / overlap. Maybe a single pattern in the 212-217 deg @ 0.050 range on a 108 LSA. I would guess it would still run very strong up to 5200-5500 rpm, but maybe pull better from 1500 rpm? I don't think my cam would be "bad" in with a stock converter automatic, I just think the off-idle (1500 rpm stall)could be improved with a different selection.
Note your vehicle weight too nd.. 3400 lbs with driver.. Most of us are going to be a fair bit more. Dropping duration but sticking with the 108 lsa as suggested might work for some but you do risk the effect I try to avoid as much as possible. Passing a vehicle on a single lane highway requires a bit of performance just for safety purposes. The less amount of time you spend out in the left lane, the less chance you run of having any sort of accident. I've been in some nasty ones and don't trust any one out there anymore.. The 104 lsa cam I ran at one time had the effect of hitting a wall at a certain speed. There was no more to be had whatsoever when you got there. Imagine passing someone and a transport truck comes around the corner in front of you and you are stuck out there unable to accelerate any faster. The 112 lsa at least had some run out room in that regard, even if it weren't a ball of fire getting up there. That's where the 5000 rpm tractor power like cam on a tight duration lost its luster for me. Reminiscent of Isky's old mile-a-more cam back in the early 1970's. Why isn't anyone using that any more in a daily driver? Same effect.. Great basic off the line, around town, but all done on the entrance ramp before hitting the highway.

D.V. says it is just a matter of getting the absolute correct lsa for the particular combination to get the best of both worlds.. Maybe so, I'm willing to listen. Daily driver definition again.. For me, has to do everything reasonably well with a bit extra on reserve for safety factor alone. Maybe comps common 110 lsa recommendation isn't that far off the mark in this category?
No way on the 104 lsa cam hitting a wall. You had something else effecting it. I have 305 inch sprint car flat tappet cam engines on a 104-105 lsa and they pull good clear on up to 8000 rpm.
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Re: Input needed on daily driver sbc truck build

Post by gottago »

The other end of this equation with the 104 lsa was getting a smooth idle. "daily driver" I don't think yours would qualify.. But this is kindof the point with the tighter lsa, in order to get a real nice smooth idle you have to drop duration considerably. By then the upper end fades fast. At least that was my experience.. It was one or the other, not both. Anyone else ever tried to get a 104 lsa cam to idle like a stocker?
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Re: Input needed on daily driver sbc truck build

Post by cjperformance »

gottago wrote: Thu Oct 18, 2018 10:22 pm The other end of this equation with the 104 lsa was getting a smooth idle. "daily driver" I don't think yours would qualify.. But this is kindof the point with the tighter lsa, in order to get a real nice smooth idle you have to drop duration considerably. By then the upper end fades fast. At least that was my experience.. It was one or the other, not both. Anyone else ever tried to get a 104 lsa cam to idle like a stocker?
You got it,, seeing that the overlap window has such a big influence on idle quality for a given ex and in lobe 104 lsa will have more overlap than a 112.
For small lobes and duration a 104 can have a smooth idle and the early ivc will make it responsive and it will have great idle vac. but it will run out of puff earlier than the same lobes on say 110 lsa.
On the other hand if you use say a 110 lsa and want similar or same ivc you must reduce duration or advance the cam, of course affecting all other events.
Now reducing duration to achive a similar ivc will make the 110 fall off earlier as will advancing the 110 to get the same ivc.
So after all that waffle, you have to either pick an lsa then spec lobes/events to give your combo what you want OR pick lobes and put them on an lsa that gives your combo what you want!
Edit- i will just add to that, that i personally dont pick a cam going off of lsa. I pick by .050 and .200 duration, lift, seat to seat and .050 events and lobe centerline,, the lsa is (shock horror) an end result of where the correct events etc are set. I will sometimes do a simple lsa change on a cam i already know/use as a way to slightly tailor for its end use.
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Re: Input needed on daily driver sbc truck build

Post by gottago »

the lsa is (shock horror) an end result of where the correct events etc are set.

for which there is only one correct set of events for any given combo in its desired range, meaning (shock horror) there is only one best lsa ? The one providing best torque and hp right across the desired range, confirmed by dyno of course.. Almost sounds like DV getting up on the wrong side of the bed..

In regard the ivc point for decent idle quality. Is it the same point no matter the lsa? If not, you do not have to drop as much duration with the wider lsa and can therefore run a higher rpm with the same idle. How to determine where that is?? It is rather individual and maybe even age dependent. I seem to be creeping up in lsa as the years creep by..
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Re: Input needed on daily driver sbc truck build

Post by David Vizard »

gottago wrote: Tue Oct 16, 2018 4:19 pm On the way...
What type of cam - hyd or solid flat or roller??
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Re: Input needed on daily driver sbc truck build

Post by cjperformance »

gottago wrote: Fri Oct 19, 2018 2:15 pm
the lsa is (shock horror) an end result of where the correct events etc are set.

for which there is only one correct set of events for any given combo in its desired range, meaning (shock horror) there is only one best lsa ? The one providing best torque and hp right across the desired range, confirmed by dyno of course.. Almost sounds like DV getting up on the wrong side of the bed..

In regard the ivc point for decent idle quality. Is it the same point no matter the lsa? If not, you do not have to drop as much duration with the wider lsa and can therefore run a higher rpm with the same idle. How to determine where that is?? It is rather individual and maybe even age dependent. I seem to be creeping up in lsa as the years creep by..

No i most definitely never would say there were only one correct set of events, there are correct events that will tailor a combo to suit a usage, for a given combo, the cam that gives the sharpest tq curve is not the cam that will provide the best rpm past peak potential. And there are a multitude of other reasons for altered events/lobes, ie, differences in exhaust system shape length is just one, for a combo always running open headers, would you say the cam optimal in that was the same as the cam for a full exhaust, or a boat?
As far as idle quality is concerned, IVC has a big effect on tq produced at idle, not the 'camminess' but ability for the engine to hold idle rpm against load in gear, power steer, aircon etc- earlier ivc will help, later will hinder.
The overlap window has the biggest effect on the 'camminess' you will experience.
If you're liking more lsa then id say this is because you are less caught up in the pose value of the cam/engine sound and more preferring the better idle quality, smoother low end etc?
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Re: Input needed on daily driver sbc truck build

Post by gottago »

DV.. definitely want to go with a hr this time..

re- cjp
there are correct events that will tailor a combo to suit a usage, for a given combo, the cam that gives the sharpest tq curve is not the cam that will provide the best rpm past peak potential.
Ok, I get that.. you may have to give up something somewhere to achieve the desired goal. But by the same token how much and where gets pretty important on a daily driver. Knowing where peak tq and hp is would be a good starting point. Then there is no substitute for experience imo. The more of these combinations one has built and or driven the more feel you get for what does what.

re-
And there are a multitude of other reasons for altered events/lobes, ie, differences in exhaust system shape length is just one, for a combo always running open headers, would you say the cam optimal in that was the same as the cam for a full exhaust, or a boat?

If someone had some experience with and had chosen all of the other parts they knew they wanted to run for a specific usage, would there then not be one set of correct cam events and therefore one best lsa? Maybe its the goal that needs to be defined more accurately in order to find that one best set of events including lsa?

If you're liking more lsa then id say this is because you are less caught up in the pose value of the cam/engine sound and more preferring the better idle quality, smoother low end etc?
For sure, I've got old racer friends who have almost totally lost hearing now. All that noise and stall converter kick, rough idle rocking etc has lost its appeal for me. I'm way more a sleeper sort of driver now. I'd call it wanting a more "spirited daily driver" as opposed a street strip. Make it like a smooth factory idle but add as much in as possible when the pedal goes down further. I stick mainly to na now but have a vortec centrifugal charger and a few favourite turbo's still kicking around should the urge hit again.. However, with age, price and simplicity weigh heavier and the longevity of ones daily driver is also a consideration. I'd love to have a nice dependable "daily driver" parked outside the old folks home when I get there. I'll quietly idle away in the mornings and they'll never know any different and hopefully never take my license away.
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