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#21
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#22
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Thanks.. It had a HXL series profile on the intake. Definitely aggressive.
The exhaust side had a RZ roller in it. That is much less aggressive, about the same as the Bullet, probably even a touch gentler. It would be interesting to see the velocity chart like Stan show between the two. |
#23
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Yes, there is a good reason for Intake cam lift above max flow as long as the port doesn't backup. If we ignore the effects of wave tuning. And just look at piston flow demand. The point of max piston flow demand is around 73-77 degrees ATDC depending on stroke rod ratio. So what is your cam lift and head flow there? Stan PS Let me add about Exhaust. One thing almost never talked about is what is your exhaust valve lift ABDC.
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm Last edited by Stan Weiss; 07-02-2023 at 11:55 AM. |
#24
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Related ?
"Unlike a hemi or a typical 4-valve-per-cylinder type head, a parallel (or nearly so) 2-valve cylinder head typically continues to flow more air up to lift values equal to as much as 0.35-0.4 times the valve diameter. The reason for this is that there is a flow pattern transition period that takes place at a lift value of about 0.25 of the valves' diameter. When this point is passed, if the port has been modified to support flow in this lift region, the valve efficiency actually starts to increase. This is the reason why a 2-valve engine responds to high lift." David Vizard .
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE |
#25
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Let Stan do what he does and see how they stack up. |
#26
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#27
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I don't have any lobe lift data for any of those lobes. There is not enough information on the cam cards for me to do what I want. So I went to the Comp Cams Lobe Master Listing I have looking for 0.200" duration and the other number are a tiny amount different. The Exhaust is the same. On the other cam card do you know if those are Bullet or UD lobes? Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#28
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I believe new cam is a UD lobe. He was looking for a proven safe lobe but something larger than the UD .4176 lobe I ran for years. I will double check with Tim. Thanks for the information. |
#29
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE |
#30
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I don't know if there is a "proven safe lobe" to run in a stock block even with a brace in it. Keep in mind with the spring pressures required to control the valve action with these solid roller cams it's like having 16 fat guys standing on your pushrods. The side-loading is extreme with solid roller cams at the spring pressures we run on them aggressive profiles or not......IMHO.
Here I built ONE stock 455 block engine with a solid roller cam for full race duty and it last 11 runs before the lifter bores caved in and took out the entire engine. Prior to that deal we had rebuilt and "upgraded" that engine half a dozen times. It came here first time with flat top SD pistons on stock rods topped with #48 heads and a Comp 292 Magnum cam in it. That engine BARELY busted the car into the 11's so the owner wanted some changes made to it. The heads went to KRE for porting and they supplied a 260/260@ .050" flat solid for it. Added Crower rods and kept the SD pistons but put lighter pins in them. That put the car solidly into the 10's, but after a few years the owner wanted more so we went to a set of 330cfm early Edelbrock round port heads and a solid roller cam. That cam was 264/264 on a 110LSA but not overly aggressive. It really didn't run much faster than the flat solid cam so the owner opted for a larger solid roller cam 276/284 with over .700" lift. I did NOT like the change and insisted on a lifter bore brace, but it didn't help. We lost the lifter bores after 11 runs and took out the entire engine. It wouldn't have mattered anyhow as the power level was exceeding the capabilities of the block. I found a couple of main cap dowel pins in the oil pan last time it was apart so the writing was on the wall before the lifter bores caved in. We replaced that engine with a KRE 505 with High Port heads and it has survived nearly 20 years of HARD use with one set of springs and rod bearings rolled into it. We also had to upgrade to Crower Enduro rockers and 13 out of 15 of the Scorpion rockers were cracked. Hard lesson learned with pushing the limits of the stock blocks. If I were still in the engine building business we'd very quickly go to an aftermarket block with that sort of engine. No solid rollers with PAC springs and super high compression would end up in a stock block for any reason, even if it was for drag racing purposes where it's only loaded 9 seconds at a couple dozen times a month. I'd just build an aftermarket block from the start and sleep a lot better at night.......
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
The Following User Says Thank You to Cliff R For This Useful Post: | ||
#31
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It would suck if it broke. I do have a IA2 with 80% of the stuff already bought. What brace did you run ? That cam was bigger than anything I would try in a stock block. No PAC springs either but anything can happen. I tried to sell the block but no one jumped so I put it together with a few upgrades. Not even going to try getting it into the 9s. I was temped to just run the same UD cam I ran for years and years. This cam is just a tad bigger. But IA2s exist for a reason. |
#32
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Thank you Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#33
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Troy,
Since I don't have real lobe lift data for either of these cams this just a guess on my part. This is the 2 intake lobes. Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#34
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Troy,
Again since I don't have real lobe lift data for either of these cams this just a guess on my part. This is the 2 exhaust lobes and they are almost the same Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#35
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Last edited by Gach; 07-03-2023 at 12:01 PM. |
#36
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And if desired one can order and use solid roller cams that do not need a ton of spring pressure and have ramp designs that are easy on valve springs.
.
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE |
#37
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Thats what I did.
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#38
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The UltraDyne .4176 lobe mentioned in your post number 28 is a fine example.
Tim at Bullet Racing Cams said years ago they used to run it with a typical Small Block Chevy valvetrain mass with around 190 lbs seat pressure, in a Big Block Chevy at around 220 lbs. And I'm not talking about in a Pontiac High Port head with large 2.200-inch diameter intake valves that are 6.200" long ! ! Inadequate oiling, excessive spring pressures and the hammering effect associated with VALVE LASH play a significant part in the failure of the roller, needle bearings and axle. BUT very important, the lack of adequate valve spring pressure to control the valves is a potential KILLER. .
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE Last edited by Steve C.; 07-03-2023 at 12:09 PM. |
#39
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Interesting. How some people want to make all SRT lobes the same. They are not. Some will want more or less spring pressure than other ones. Interesting to watch a spin tron test and see most of the valve train problems go away when the springs are change to ones with less over the nose pressure.
Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#40
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