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  1. #181
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by hq308 View Post
    The reason 1:1 works with EFI is because it's not relying on the incoming airflow to pull fuel into the intake. That's not to say it won't work with a carb, it just might need a bit of tweaking to make it work.
    Just looked at Sniper CFM rating and Holley rate them as 800cfm. So if upgrading to Sniper from something like a 650 or 750 carb you go to an injection system that monitors and adjust afr and opens more throttle to the engine or saying another way, making available at a faster rate more cfm of air/fuel to the engine. I'm wondering if that could be one reason they are raved about when put on a high performance street engine, that the engine gets more air it wants at lower throttle positions, especially accelerating. I have however read elsewhere some people prefer swapping to a progressive linkage. Maybe their driving style is like I described earlier and they like rolling into the secondary's when possible or a smaller engine ci.

    Did you have a Sniper or the like on your 308 at one stage? How did it go?

  2. #182
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    hi

    Air flow changes direction easier than air/fuel combo.
    Also it is mainly about throttle response MPI has better response than a carby so car makers increase the air only side sizing without/ or little cost to the throttle response . One reason when efi engine is designed right all will work well .

    Not designed correctly and the gain would only be 20hp on a 500hp 400chev . Efi gains in other areas also so if considering ,needs to be looked at as a whole system approach .
    Edelbrock has done at least 1or 2 examples online . That was a Proflow system on a chev but the the inlet ports let it down at only 1205 sizing .

  3. #183
    Not the Kingswood! hq308's Avatar
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    Quote Originally Posted by BasicQ View Post
    Just looked at Sniper CFM rating and Holley rate them as 800cfm. So if upgrading to Sniper from something like a 650 or 750 carb you go to an injection system that monitors and adjust afr and opens more throttle to the engine or saying another way, making available at a faster rate more cfm of air/fuel to the engine. I'm wondering if that could be one reason they are raved about when put on a high performance street engine, that the engine gets more air it wants at lower throttle positions, especially accelerating. I have however read elsewhere some people prefer swapping to a progressive linkage. Maybe their driving style is like I described earlier and they like rolling into the secondary's when possible or a smaller engine ci.

    Did you have a Sniper or the like on your 308 at one stage? How did it go?
    I had a Fitech on mine, it's not a bad thing but it was never really totally happy with my 106LC cam. I never really had any major issues with it, it worked quite well considering the lack of idle vacuum. I switched back to the carb because I got bored and wanted to play with a carb again. The carb is a bit of a bitsa, it started out as a 4777 650 which I changed the main body to a 750 HP conversion body and I drilled out the primary IFRs for 6/32 set screws. I never did a back to back but the carb was 3 mph faster than what I had previously run with the Fitech.

  4. #184
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by hq308 View Post
    ........my 106LC cam.
    How is the 106 cam? Did you previously have a wider lobe sep for comparison?

    I’ve never had one at 106 and that lobe sep seems very common with the more drag racing oriented cams, especially sbc. I’ve been thinking of a cam upgrade and 106LC comes up a lot for the usage I’m intending it for for shelf grinds

  5. #185
    Not the Kingswood! hq308's Avatar
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    Quote Originally Posted by BasicQ View Post
    How is the 106 cam? Did you previously have a wider lobe sep for comparison?

    I’ve never had one at 106 and that lobe sep seems very common with the more drag racing oriented cams, especially sbc. I’ve been thinking of a cam upgrade and 106LC comes up a lot for the usage I’m intending it for for shelf grinds
    This is the only cam I've had with the VN heads so don't really have a fair comparison. I previously had a hyd FT with the early heads that was on 110, the 106 is a SFT. Oddly enough both combos had a similar idle vacuum (5-6") but the solid has more lift & duration along with the 106lc and has a more aggressive sounding idle.

  6. #186
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by hq308 View Post
    This is the only cam I've had with the VN heads so don't really have a fair comparison. I previously had a hyd FT with the early heads that was on 110, the 106 is a SFT. Oddly enough both combos had a similar idle vacuum (5-6") but the solid has more lift & duration along with the 106lc and has a more aggressive sounding idle.
    Interesting with the vacuum between cams. All in the combo I guess. So the 106 lsa isnít a problem in traffic?

    Iím considering going from 110 lsa to 106 lsa with the same lobes (244* int, 252* exh). Iím curious if someone has done similar for a back to back comparison and pros/cons. I understand the rough idle and low vacuum bit going from 28* to 36* overlap but not the overall drivability and potential quarter mile difference.
    110 lsa is 2500 - 6800rpm
    106 lsa is 3200 - 6800rpm

    Another option I am considering is going to a 248* @.050Ē int lobe and 250* exh on a 108 lsa. That would give the same intake closing point but 4* earlier opening and an exhaust that opens 3* later and closes 1* later than my current cam. My thoughts are this will give me a bit more tq and hp over a similar rpm range as the current cam.


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  7. #187
    Not the Kingswood! hq308's Avatar
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    Quote Originally Posted by BasicQ View Post
    Interesting with the vacuum between cams. All in the combo I guess. So the 106 lsa isn’t a problem in traffic?

    I’m considering going from 110 lsa to 106 lsa with the same lobes (244* int, 252* exh). I’m curious if someone has done similar for a back to back comparison and pros/cons. I understand the rough idle and low vacuum bit going from 28* to 36* overlap but not the overall drivability and potential quarter mile difference.
    110 lsa is 2500 - 6800rpm
    106 lsa is 3200 - 6800rpm

    Another option I am considering is going to a 248* @.050” int lobe and 250* exh on a 108 lsa. That would give the same intake closing point but 4* earlier opening and an exhaust that opens 3* later and closes 1* later than my current cam. My thoughts are this will give me a bit more tq and hp over a similar rpm range as the current cam.


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    Apart from "pig rooting" at the lights it drives like a normal car, I've driven it to work (~30km each way) on the odd occasion without any issues.

  8. #188
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    I would take D. Vizard's advice on cams. 19,000+ dyno tests, including a stint at Crane cams under contract. When I find somebody with more cam tests under their belt, then I will listen to them.....

    DV uses the 128 rule to determine LSA. A lot of 'experts' [ ignorant in my opinion ] claim that LSA is not the first parameter that should be selected. More on that later. What DV says which makes eminent sense to me is: if you want a smoother idle, you do NOT go to a wider LSA. You reduce duration.
    Piston speed is very important in determining air flow into the engine. You would want piston speed to be at it's highest, or close to it, at or near max valve lift.
    LSA tells you where the valves are at max lift in crank degrees. If you have a cam ground on a 106 LSA & installed with 106 ICL & 106 ECL, then the intake valve is at max lift at 106* ATDC & max exh lift is at 106 BTDC.

    I have noticed in the last 20 yrs more & more cams being ground on tighter LSAs. New knowledge. Isky was ahead of the pack decades ago, with tight LSA cams in the 70s.

    BMC, with their Mini 850 & Cooper engines were ahead of the pack also. All of the factory cams, from mild to wild were ground on 107.5 LSA, with some later bigger cams on 102.5. Six aftermarket cams from Kent were on 106 LSA, even with smooth idle, from 256* to 310* duration. Less duration, sound familiar?

  9. #189
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    I think the smaller the LSA the narrower the rev range but can make more power. I heard somewhere Brock had LSA in the high 90's. Had to be skilled to keep that on the boil. My old camtech solid was 107 and it was good. New cam is 110 which was suggested as the car is manual and would help a little with low speed driveability.

  10. #190
    Do you ever leave? EH179's Avatar
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    The 106 lobe narrows the useable rev range as suggested, but also has a faster acceleration rate, making it peak sooner.
    In a stalled auto, the lower rev range is of no concern to most.

    Install this cam 6* advanced and you now have it @ 100 cl.

  11. #191
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by GtoGeoff View Post
    I would take D. Vizard's advice on cams. 19,000+ dyno tests, including a stint at Crane cams under contract. When I find somebody with more cam tests under their belt, then I will listen to them.....

    DV uses the 128 rule to determine LSA......
    I have Vizard’s How to Build Horsepower and recently re-read his two chapters on camshafts ‘Real Camshaft Science’. I also read some of his 128 stuff online including a fifty odd page thread on SpeedTalk (half of which guys were arguing if it could be used for computer simulation). His 128 rule is based on a sbc with 10.5:1 compression.
    Correct me if I am wrong but doesn’t he talk of choosing degrees of overlap and then with the 128 formula a lsa and from those two duration will fall into place? He discusses the importance and function of overlap which is informative and I agree but then gives an almost ambiguous chart for choosing an overlap. I I were to choose #3 on his chart I would be choosing somewhere between 50-70* overlap. He then talks of lsa (which he calls lca) and where’s and why-fors of that which again is great info. Gives the formula and chart to select for the ci per cylinder. SBC 383 ends up at close enough to 108. But then there are caveats like higher compression has to widen ‘x’ for every point increase in lsa and conversely lower for lower than 10.5:1 compression.
    This all left me in a big ballpark I already knew I was in. I have the utmost respect for Mr D Vizard and his knowledge and experience in the performance industry but the whole magic 128 think I felt left me feeling back where I was but with a little more insight on overlap and lsa.

    Maybe you could shed more light on it Geoff?

  12. #192
    Senior Member BasicQ's Avatar
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    Quote Originally Posted by EH179 View Post
    The 106 lobe narrows the useable rev range as suggested, but also has a faster acceleration rate, making it peak sooner.
    In a stalled auto, the lower rev range is of no concern to most.

    Install this cam 6* advanced and you now have it @ 100 cl.

    Higher peak torque over a narrower band? Would it be a lower torque band than a 110 lsa?

  13. #193
    Do you ever leave? EH179's Avatar
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    Quote Originally Posted by BasicQ View Post
    Higher peak torque over a narrower band? Would it be a lower torque band than a 110 lsa?
    All else being equal...Yes to both.

    In doing so, the cranking compression and cylinder pressure usually increases too, so detonation is not far away.

    The piston chases the exhaust valve home, so PTV clearance needs to be rechecked when swapping cams too.

    Just a few things there to keep in mind, but overall, many Drag racers give the nod to a 106 and tighter lobe cam.

  14. #194
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    Basic,
    The Green overlap chart was incorrect, a printing error. It was corrected on ST, I printed out the corrected version.

    DV later stated that the 128 rule was good for most parallel valve engines, certainly better than taking a guess. He used correction factors for increased CR etc. 131.5 was used for the BB Chev.

    Many cam companies have identical grinds for different brand engines. Unlikely that the cam that works best in a 350 Chev is going to be best in a 351 C, with bigger valves & ports. I doubt any of these cam companies actually dyno test each cam, in every brand of engine, changing things like LSA or ICL to see what produces max HP &/or tq.

    I have heard the furphy many times that tight LSA cams give a narrower power range or peak earlier, etc etc. They might...sometimes....but it is not a categorical rule & there are many exceptions. There are two examples in DVs BBC book. 107 v 112 LSA cams, two different size big blocks. 107 made more hp/tq everywhere. He says had a 104-5 LSA been used, the difference would have been even greater.
    Another test. Identical Isky cams except for LSA, 106, 108, 110. 262/266 @ 050 in a 357 Chev. 106 made more hp & tq everywhere except for peak hp. It made 580 hp v 583 for the 110. It lost 3 hp....but the 106 was up 23 ft/lbs on average tq through to 7000 rpm. I know which one I would be using...

    Probably the best example is Jon Kaase's 403 Ford engine that won the 2008 EMC competition. Cam had a 98 LSA, 92 ICL. It put to bed all the claims about tight LSA: narrow range, goes over a cliff etc. It had a very broad tq curve 478 f/lbs to 617 from 2500 to 5200. It made 663 hp @ 6000. Did it go over a cliff? Nope, dropped a mere 11 hp between 6000 & 6500. Cam was not that big either, SFT, 246/238 @ 050. notice it has less exh duration....

  15. #195
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    Engine bay all tidy and resprayed, new serpentine belt system from CVF Racing installed (hell of a nice system...if only I could post pics). Air con unit installed. Started crimp hydraulic hoses over the weekend but am short 2 fittings, so waiting for those to arrive. New stereo and amp/speakers arrive this week also. Pretty happy with progress os far, albeit slower than planned
    Chris

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    Daily driver - 1961 Buick Bubbletop - not much horsepower, but smiles for miles

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