The engine in the Speedtalk link you provided is a a Super Stock engine that operates in the 5500-7500 rpm range . I don't see how the considerations used to determine optimum LSA for that particular engine are applicable to the typical street/strip combo.
Street 360 W/.528" P.S. Cam
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PRH
Well-Known Member
Actually, there was talk of a 6600 converter and a trap rpm of 8800.
So yeh, totally apples to apples with the typical mild street combo.
So yeh, totally apples to apples with the typical mild street combo.
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Same guy who reconfigured and tuned a Street/Strip ford small block making 2 HP per cube on Pump Fuel wrote this:
"A wide LSA with a high flowing port enables a cleaner mixture to be achieved inside the cylinder, the wide LSA reduces exhaust overlap contamination and intake reversion. Provided you can achieve the energy necessary for sufficient vaporization by other methods then wide LSA will gain more power and better emissions from the engine. Better emissions translates into longer engine life and less oil contamination etc.
In terms of cylinder fill it is better to balance the amounts of intake ram which is occuring at the beginning of the intake valve opening against the fill percentage at the valve closing phase. LSA is influential in that. Flow in the port build over time and the intake ram can kick start it or finish it off , I think it is better to edge toward the finishing rather than the start as most intakes have no hope of getting good ram pulses at the start, especially common single planes etc. A wide LSA helps in that regard.
with good droplet condition and good smooth fuel delivery with no dry air pockets a wide LSA cam can rev and power to just as high a rpm as a narow LSA but with the added torque spread of the wide LSA. So the car is a better driver overall. It doesnt seem to benefit a narrow LSA as much by correcting the droplets and fuel curves etc. A narrow LSA allows the piston to pump the exhaust backwards up the intake and you cant stop that with the carby much. So what you can gain from wide LSA is more than how you can fix a narrow one."
Notice he says "with a high flowing port". What is that exactly ? I doubt those words could be used to describe your highly touted 302 castings.
No specs given wider than what?, What works for this type of engine has little to do with average guy builds. and how far off would a Vizard spec'd cam be ? your just assuming it be vastly different.
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Isn't that what every street strip engine has when they swap out the stockers? So your argument is a tight LSA makes the ports flow more?
You mean those severely restricted ports that some how manage to run 10's in a 318?
I've already asked and he isn't prepared to divulge as its a class racer type deal. Maybe head over to SpeedTalk and ask what the normal LSA would be for that class and then realize its much wider in Chads engine?
The average guy believes everything the magazines tell them. Vizard who?
Notice no quotes from Joe Sherman's Racing Engines.More food for thought:
Vizard on 106* LSA vs 112* LSA in a BBC
All 9 pages of it: Here are the opening salvos'
Mike Jones:
"Pretend the story was written by someone you've never heard of.
How does it match what you've seen in the real world.
I've done many dyno tests were we change nothing but LSA, and then move each cam around to where it runs the best. I've come to different conclusions then David."
UDHarold:
"My opinion is that you should buy whatever Dave Vizard recommends, because you probably deserve it.......
Tell your cam man what LSA you want, and he will grind it for you.
This way, your car will run its' fastest.
However, I recommend everywhere from 107 to 118, just depending."
Everyone seems to be arguing a strawman version of Vizards point.
Weaker heads per cid generally needs a tighter lsa.
His point for general aftermarket cams people tend to pick by duration so cam companies run a wider lsa to give a customer an generally acceptable street overlap.
He's generally saying for a given overlap a tighter lsa and less duration would probably give better results for the average street engine.
Not saying DV is the ultimate word on cams, engines etc.. but for novice he's basically the only voice out there and the average dude ain't gonna be led to far astray.
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Here's an interesting quote from Mike again:
"In circle track racing, there are a bunch of classes, where the engine rules are almost identical, but some are limited to lower compression.
These classes run the same size engines, heads, manifold, Carb, and turn the same RPM. The lower the compression the tighter the LSA and ICL needs to be."
Wonder why lower compressions ratios like tighter LSA's......
"In circle track racing, there are a bunch of classes, where the engine rules are almost identical, but some are limited to lower compression.
These classes run the same size engines, heads, manifold, Carb, and turn the same RPM. The lower the compression the tighter the LSA and ICL needs to be."
Wonder why lower compressions ratios like tighter LSA's......
Didn't Hysteric give his specs the other day an eddy head 318 topped off with a 750
DV also states low cr = tighter lsa and vise versa
So is the average street performance engine is running 110-114 lsa, would they generally benefit with more or less lsa? performance wise.
what do consider wide lsa? to me that means 115-120+, middle ground 110-114, anything under 110 is narrow, or simpler 112 is the middle above gets wider, below gets narrower.
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If you uses DV formula for 10.5:1 cr
2.02 408 = 105
2.02 360 = 108
2.02 340 = 109
2.02 318 = 110
1.78 318 = 108
1.88 318 = 109
1.78 273 = 111
1.88 273 = 113
Don't seem to crazly off if looking for high tq:cid seems to me a good ballpark to start from.
110 is close enough probably for most of those without given much maybe the 408.
Main problem I see is going by valve size not port flow, he has stated he picked valve sizes cause most know that over flow numbers.
2.02 408 = 105
2.02 360 = 108
2.02 340 = 109
2.02 318 = 110
1.78 318 = 108
1.88 318 = 109
1.78 273 = 111
1.88 273 = 113
Don't seem to crazly off if looking for high tq:cid seems to me a good ballpark to start from.
110 is close enough probably for most of those without given much maybe the 408.
Main problem I see is going by valve size not port flow, he has stated he picked valve sizes cause most know that over flow numbers.
That works for the basic parameters of a 10.5-1 to gnome and a decently well prepped head. AKA - ported. On or about but closer to under a 300 cfm head but better than a stocker. Giving that the narrow LSA is for the porter head flow on a street engine to aid in extra torque production, it’s a winner.
On higher performing engines, ones with a higher developed intake and exhaust system running much higher compression ratios and big valves that aren’t crippling to the CID of the engine, though on a wedge, that’s always the case, severity is the next issue, the case of a narrower LSA is ridiculous since your ignoring the lower rpm range and operating in a much higher one without care or concern to low rpm output. Mostly because, you’re never there except idling around the pits.
I have no experience how this would work or quite honestly feel on the street. The widest LSA I have used was a 112. I have no notes to compare it against a narrow LSA on the same engine size.
On higher performing engines, ones with a higher developed intake and exhaust system running much higher compression ratios and big valves that aren’t crippling to the CID of the engine, though on a wedge, that’s always the case, severity is the next issue, the case of a narrower LSA is ridiculous since your ignoring the lower rpm range and operating in a much higher one without care or concern to low rpm output. Mostly because, you’re never there except idling around the pits.
I have no experience how this would work or quite honestly feel on the street. The widest LSA I have used was a 112. I have no notes to compare it against a narrow LSA on the same engine size.
Hysteric,
You make these wild claims [ latest in post #23 ]. More power than......what?????????? Where are the numbers for the cam it was compared to????? And the specs?????
I gave an example of an engine making more HP in post #18 of the wider LSA cam making 3.4 hp more [ 3.4 is more hp, right?? ], but dropping 24 ft/lbs through the mid range.
So the Speier cam from Jones used less intake duration but more rocker. Guess what more rocker does! It increases the effective duration...& lift!
And see if you can find ANY comparison dyno tests that Brookshire actually did that tested HIS cams & LSAs.
I could not find any. Would love to see some!
Vizard devotes two pages in his BBC book to LSA correction/optimisation. He tested [ p. 96 ] cams in one engine with 112 to 116 LSA to see the HP difference. Does that sound like he is recommending a tight LSA for that engine??
Nascar engines. Running 9000-10,000 rpm. These rpms are not what your average hot rodder is running & is NOT what Vizard is making recommendations for.
You are just making yourself look stupid.
Oh.....engines had things like cams & pistons in the 1960s....just like they still do in 2023.
You make these wild claims [ latest in post #23 ]. More power than......what?????????? Where are the numbers for the cam it was compared to????? And the specs?????
I gave an example of an engine making more HP in post #18 of the wider LSA cam making 3.4 hp more [ 3.4 is more hp, right?? ], but dropping 24 ft/lbs through the mid range.
So the Speier cam from Jones used less intake duration but more rocker. Guess what more rocker does! It increases the effective duration...& lift!
And see if you can find ANY comparison dyno tests that Brookshire actually did that tested HIS cams & LSAs.
I could not find any. Would love to see some!
Vizard devotes two pages in his BBC book to LSA correction/optimisation. He tested [ p. 96 ] cams in one engine with 112 to 116 LSA to see the HP difference. Does that sound like he is recommending a tight LSA for that engine??
Nascar engines. Running 9000-10,000 rpm. These rpms are not what your average hot rodder is running & is NOT what Vizard is making recommendations for.
You are just making yourself look stupid.
Oh.....engines had things like cams & pistons in the 1960s....just like they still do in 2023.
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Your reading comprehension skills are seriously lacking.
"I have 46 more HP at 7500 than I had."
Hysteric,
Nothing wrong with my comprehension skills. But plenty wrong with your 'logic'. Unless there is cam information posted, there can be no apples-to-apples comparison. Did you miss the bit about 'more' rocker &..... what that does? Did the cam that made 46 hp less have more rocker???
Nothing wrong with my comprehension skills. But plenty wrong with your 'logic'. Unless there is cam information posted, there can be no apples-to-apples comparison. Did you miss the bit about 'more' rocker &..... what that does? Did the cam that made 46 hp less have more rocker???
273,
Thanks for posting that. That was the comparison I was referring to earlier in this thread.
So far, examples for 4 cyl British engines of less than one litre, LS engines & all the way up to 572CI V8 engines all on tight LSA cams: 350 Chev, LS, 468 & 572 making more hp everywhere on tighter LSA cams.
Thanks for posting that. That was the comparison I was referring to earlier in this thread.
So far, examples for 4 cyl British engines of less than one litre, LS engines & all the way up to 572CI V8 engines all on tight LSA cams: 350 Chev, LS, 468 & 572 making more hp everywhere on tighter LSA cams.
I'm sure there's application where lsa wider than 112 have a better power curves but for most of the builds that this site deals with 112 and narrower are probably the better bet.
cookietruck
Well-Known Member
What would happen if one were able to add a half point of compression when they swapped a cam from 108 to 112 lsa?
Or swapped cams with 108 vs 112 lsa but both were installed at 108 or 106…
There are so many damn variables. Seems one could get get quite similar power curves and maybe get some of the advantages of the wider lsa.
Or swapped cams with 108 vs 112 lsa but both were installed at 108 or 106…
There are so many damn variables. Seems one could get get quite similar power curves and maybe get some of the advantages of the wider lsa.
273,
In one of Vizard's articles/testing where he tested different displacements in SB Chevs, the 350 reqd a slightly wider LSA than bigger engines for best power. He does not have a 'fixation' with 106 LSA. All he said was that his testing [ 19,200 dyno tests ] found that cams sold by cam companies in general were on too wide LSAs for best overall power. From that testing emerged a computer program he sells & the 128 rule as a simplified guide for LSA rather than 'pick a cam' out of a catalogue.
In one of Vizard's articles/testing where he tested different displacements in SB Chevs, the 350 reqd a slightly wider LSA than bigger engines for best power. He does not have a 'fixation' with 106 LSA. All he said was that his testing [ 19,200 dyno tests ] found that cams sold by cam companies in general were on too wide LSAs for best overall power. From that testing emerged a computer program he sells & the 128 rule as a simplified guide for LSA rather than 'pick a cam' out of a catalogue.
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Stop asking logical questions.....
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What do you think this would have made had it been a 318 instead of a 360. I know you didn’t like the cam and it would probably be worse in a 318.
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