351C Timing |
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72FordGTS
Admin Group GTS.org Admin Joined: 06-September-2005 Location: Ontario, Canada Status: Offline Points: 5846 |
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Posted: 19-November-2022 at 9:30AM |
The retarding helps but it seems not enough. From the DCR calculator at 300' it shows: Static compression ratio of 10.4:1. Effective stroke is 2.84 inches. Your dynamic compression ratio is 8.12:1 . Your dynamic cranking pressure is 165.15 PSI. Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 8.06 :1. V/P (Volume to Pressure Index) is 144 Interesting seeing the power curves don't change that much between the cams. What I actually wanted you to try was retarding the Howard's 230245-12 6 degrees instead of 3 degrees as you indicated above. I think that might get your DCR to a safer range and not affect the power curve too much. Runinng the Howard's 230245-12 at 3 degrees retarded seem to get the DCR close, so I thought 6 degrees might be right on the money. Maybe Rock will have a better idea.
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Vince
1972 Ford GTS Sportsroof - Survivor, One Family car GTS.org Admin |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Apparently not the way normal people do..... This is one retarding my cam 8* versus the 235245-12 retarded 3*. Not much difference on paper but the latter has slightly better vol eff. The latter also has an exhaust cycle 14* longer Without dots is the cam I have -8* |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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I had re read your post. I'm likely going to just swap the camshaft but I'm having a lot of fun with the program. I retarded the cam 8* (in the program!). It flipped the cycles on the intake and exhaust. Likely more than obvious to someone who's studied camshafts. If I understand what I'm reading it would likely cause exhaust reversion. The intake closes at 68.3 but the exhaust is closing at 64.3. Most are closing in the mid to late 70's. It does mathematically look better in the program. As it sits 392HP @ 5500 / 426TQ at 4000 8* retard 407HP @ 6000 / 411TQ at 4000 and 4500 |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Didn't even think to check at 8*. 😮
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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72FordGTS
Admin Group GTS.org Admin Joined: 06-September-2005 Location: Ontario, Canada Status: Offline Points: 5846 |
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How does it look if you retard the Howard's cam 6 degrees so it runs 2 degrees retarded? This timing set allows for +- 8 degrees at 2 degree increments: Can you post pics of the power curves?
Edited by 72FordGTS - 15-November-2022 at 6:55AM |
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Vince
1972 Ford GTS Sportsroof - Survivor, One Family car GTS.org Admin |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Not too happy about it now but it is what it is. I'm just as concerned about going too soft as I am too hard. Disappointment is not what I'm looking for in a 17 year project.
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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factor in chain stretch and i think you'll get that 3* you're looking for fairly quickly. me personally i'd target at least that 72* IVC figure i came up with, it'd be a pisser to go through it all and still be on the edge
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72 GT Ute
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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I picked 2 cams so far. One from George and one of the Howard's off the shelf cams 235245-12.
LIFT DUR LCA ICL PSI DCR George's cam 70* IVC .544/.544 .278/.286 114 111 160 7.96 Howard's 67*IVC .576/.600 .278/.282 112 108 166 8.14 230245-12 Howard's -3 70*IVC .576/.600 .278/.282 112 111 160 7.96 230245-12 George's cam 396HP @ 6K 411TQ @ 4.5K Howard's -3 405HP @ 6K 410TQ @ 4.5K Howards -4 405HP @ 6K 408TQ @4.5K These following are my assumptions based on how I understand what I'm looking at. Please feel free to correct if so inclined. Georges cam is 3* advanced 114 LSA / 111 LCA 70* IVC Howard's 230245-12 is 4* advanced 112 LSA / 108 LCA 67* IVC I assume if I install the 230245-12 3* retarded 112 LSA/ 111 LCA 70* IVC If that's the case taking out the whole 4* advance 112LSA/ 112 LCA 71* IVC Basically losing 1-3 ft lbs of torque in a place I'd never miss it. The HP and TQ between Georges cam and a 3* retarded 230245-12 cam are just about identical until you get to 5500 and 6000 rpm where Georges cam falls of by 4HP/4TQ and 9HP/9TQ. Not very important picking one over the other in a street car. I find the lift differences and similar power curves somewhat confusing The previous numbers were based off the Dyno2000 program with a dual plane intake and HP manifolds (they are large compared to most) w/ full exhaust Large tube headers w/ full exhaust 453HP @ 6K 451TQ @ 4.5K Add Single Plane 490HP @ 6K 469TQ @ 5K Drop the exhaust 503HP @ 6K 480TQ @ 5K |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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I did that with the Boss351 cam. Now I'm experimenting......
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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72FordGTS
Admin Group GTS.org Admin Joined: 06-September-2005 Location: Ontario, Canada Status: Offline Points: 5846 |
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I think you are correct about the program making the assumption on the ramp rates of the cam lobes. The hp figures in the program aren't always the most accurate but what it is really useful for is comparing changes from one cam, head or other changes to another and the affect on the power curve etc. I did some stock do some stock engines with the program and got pretty close to the advertised figures (gross SAE numbers).
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Vince
1972 Ford GTS Sportsroof - Survivor, One Family car GTS.org Admin |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Interesting experiment but I have no idea of the math behind it.
In the dyno2000 program I took the flat tappet Boss351 Cam and flipped the same specs to a roller cam. That alone netted a 45 Hp / 36 TQ increase. I assume it's just in the projected cam lob profiles. ?
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Thanks Rock!
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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a couple hydraulic rollers from George's cook book 69.5* IVC hyd-roller |
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72 GT Ute
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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this is Brent Lykins cam page, i'm sure he can cobble a cam for you to make it all happen. just a heads-up Brent and George didn't quite see eye to eye. give him a call & rake it over the coals, if Brent's not your cup of tea we can pull a recipe from George's web page. i know there's a hydro roller or 2 in there somewhere and get it ground by Bullet. i'll start looking if i get a chance
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72 GT Ute
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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I've been having fun with that calculator.
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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72 RS 351
Senior Member Joined: 04-September-2014 Location: Knoxville TN Status: Offline Points: 2767 |
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If you pay for a custom cam, the extra $100 gets you control over everything. You set the limits as you want them, and they should easily design a cam to meet them. If you don't want it to open the valves more than .600, you tell them that. My refresh I'm hoping to use OEM type rockers, which have a general limit of .550", if I can run them to 6000+ rpm or a little more, that's a limit I will set for the cam. Tell them what you require, it's their job to design it to work optimally within those. If you are having pre-designed cams suggested to you, then those are not going to be the best possible for your engine and vehicle.
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Don
73 Ranchero "Sport 72 front end", floor shift/console, planning EFI 7000+ rpm 351-4V &4R70W 73 Ranchero GT 351C-4V &4R70W for sale later. 92 Lincoln Mark VII SE GTC, OBDII 347/4R70W |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Now I know where the slight differences in pressure are! I've been using 300 ft. I'm at 450 but surrounding areas dip to 300. Weird going in because I just pulled the altitude out my head for consistent numbers. I've made two phone calls this week and had rambling conversations with with a guy at Howard's. That cam at 112* LSA gets me to 71 IVC. My only concern there is the .611 lift on the exhaust side without the lifter bore sleeves.
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Thanks Vince
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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72FordGTS
Admin Group GTS.org Admin Joined: 06-September-2005 Location: Ontario, Canada Status: Offline Points: 5846 |
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Ok, now I understand what you mean about Pence's preferences. But even Rock said to keep the DCR at 8 or lower too. One thing you have to remember when looking at DCRs from engines like the BOSS 351 and the other high compression engines from this era is they used higher octane fuels then that we don't have readily available today. I liked Rock' recommendation of keeping DCR at 7.7-7.8 and from his math above the 69* IVC doesn't seem to do it. I sent you a Google Drop Box download. Not sure if you got it or it worked? It might help you with the cam selection.
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Vince
1972 Ford GTS Sportsroof - Survivor, One Family car GTS.org Admin |
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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DCR's from 69* IVC Static compression ratio of 10.4:1 Your dynamic compression ratio is 8.01:1 Your dynamic cranking pressure is 163.82 PSI Static compression ratio of 10.5:1 Your dynamic compression ratio is 8.08:1 Your dynamic cranking pressure is 165.69 PSI unfortunately you don't have any elevation to speak of to help out. i've been using flat sea level. bumping you up to 1000' makes a difference but IMO you should plan for the worst Static compression ratio of 10.4:1 Effective stroke is 2.61 inches Your dynamic compression ratio is 8.01:1 Your dynamic cranking pressure is 158.48 PSI Your effective compression ratio reflecting 1000' altitude, is 7.81 :1 Static compression ratio of 10.5:1 Your dynamic compression ratio is 8.08:1 Your dynamic cranking pressure is 160.34 PSI Your effective compression ratio reflecting 1000' altitude is 7.88 :1 |
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72 GT Ute
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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What do you mean in your third point? Are you saying that George is conservative or too aggressive on the DCR because he does sports car engines? I am not really sure what you mean. My engine has mid 7s for DCR and I wouldn't want too much higher than that, especially since 91 Octane is the best I can get.
I wouldn't say he's concervative or agressive. The longer LSA's he prefers would seem to indicate his tuning preferences. Not a bad thing, a preference. Figuring that the Boss 351 was running a similar compression ratio I'm not really considering dished pistols or redoing the heads. Since the block is studded that's pulling the engine and it's taken 17 years to get this together. According to Pense the cast heads can support a dcr of 8.0 which seem to indicate cylinder pressures in 160 range. I've seen other Cleveland builds in the 180 range. Mine is right there and it would indicate to me that there are too many compromises involved in that range. I figure if Ford can offer a 10.6:1 Cleveland with a dcr in the 7.5 - 7.7 range in a production car I should be able to come up with a roller cam in the 7.5 - 8.0 range without killing it. Howard's offers an off the shelf cam with an IVC of 69 that would theoretically put the cylinder psi at 162-ish. The centerline is 106 and the exhaust lift is .611. I'm considering a design tha staggers the exhaust valve no higher than .600 and opening the lsa to 110 - 112.. I'm not sure how it works in practice but I think with a couple of tweaks I can get the PSI to 155-160 easily. The question being how does the altered cam timing effect the engine. |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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handsofstone
Senior Member Joined: 13-April-2018 Location: Northeast Status: Offline Points: 3946 |
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Chuck,
Billy Ray's Haberdashery and Tim Halstead on Facebook might have some tips as well. Billy Ray does some nice work and videos on youtube as does Tim. Not sure where Billy is located but if he is nearby it may be worth it to have him tweek the chambers to lower your compression to work with your current setup.
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72FordGTS
Admin Group GTS.org Admin Joined: 06-September-2005 Location: Ontario, Canada Status: Offline Points: 5846 |
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What do you mean in your third point? Are you saying that George is conservative or too aggressive on the DCR because he does sports car engines? I am not really sure what you mean. My engine has mid 7s for DCR and I wouldn't want too much higher than that, especially since 91 Octane is the best I can get. I agree with Rock, your DCR is too high. The way I see it is you have two viable options. First, replace the cam, which probably will move your power band, which is why I asked what gears you are running. I suggested asking George for a cam grind, but I didn't know his health was down. It's too bad because he did help me out when I was doing my build. In the end I used a custom grind designed by Tim Meyer. Second, reduce the compression, either with new pistons, or by increasing the combustion chamber size like Rock showed above. If you are pulling the intake, pulling the heads to work on the chambers might be not too bad of a job, but I can't say I'd want to go at the combustion chambers with a die grinder, I'd worry I'd mess something up. Maybe you are up for that kind of work or there is some in your area that can do it? Check you PMs, I will send you something else that might help you out.
Edited by 72FordGTS - 08-November-2022 at 9:57AM |
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Vince
1972 Ford GTS Sportsroof - Survivor, One Family car GTS.org Admin |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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The engine only has 400 miles on it and they weren't a 1/4 mile at a time. I doubt I wrecked the rod bearings and it sounds decent idling in the garage.
The cam I'll have to work on now that it's cold
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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72 RS 351
Senior Member Joined: 04-September-2014 Location: Knoxville TN Status: Offline Points: 2767 |
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The camshaft is the biggest key to cylinder pressure and all of the aspects of performance, all rpm's and driveability. The cam should be the last component chosen, designed, to mate the other hard parts together. So given the apparent issue, I think the rest of the parts are decent choices and usable as is. I think unless a full tear down and refresh etc is in order, I'd re-select the cam and do the minimum to get it back running. If it had to some apart, I'd reinspect the whole oiling system and head parts(valve seats and guides etc), plus upgrade the pistons for lighter and adjust compression if needed. I like the 10.5:1 range for performance use, with premium, with a custom cam(not off the shelf). It's better to run a point less compression if you are going to guess at a cam. A custom cam can be made to work with 11:1 and more. A proper cam designer(who knows how to make one for a Cleveland) should be able to create specs to work with the existing compression etc. But also a custom cam often needs to(or it's free power) upgrade the springs(lighter and thus quicker, more power yet and/or better lifespan). You have to be very specific with a designer to get all of the benefits of a custom cam. The 302 and 351W market is full of countless engines built with custom cams that function amazingly well, many with mismatched parts that the cam manages well.
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Don
73 Ranchero "Sport 72 front end", floor shift/console, planning EFI 7000+ rpm 351-4V &4R70W 73 Ranchero GT 351C-4V &4R70W for sale later. 92 Lincoln Mark VII SE GTC, OBDII 347/4R70W |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Been doing all the research all over again with a better understanding of tolerances and consequences.
1. Based on cylinder psi the calculator puts my compression closer to 10.4 -10.5 2. Three Howard Cams matched to 9.0, 9.5, and 10.1 wind up at just about 150 psi. 3. According to George Pence the cast heads can manage 8.0:1 dynamic compression. Alloy heads 8.4:1. I think his very informed opinions and his preference for sports car performance versus muscle cars lead to his preference for sub 8 dynamic compression ratios and higher lsa's. I don't think he's wrong. The higher pressures don't lend themselves to the durability of factory produced and warrantied drivetrains. Piston rings would last longer and high stress abuse would crack these blocks 50 years ago. 4. I'm just guessing here and I could be wrong again. With the improvement of just pulling the timing to 6 degrees I could probably run colder plugs, better than 90 octane fuel, and jet the carb richer but for what? I'm still losing 10 degrees of timing, giving up a lot of power, and still stressing the engine. 5. I haven't found the specs for the cams Pence did but I suspect they're flat tappet designed. I wish I had a Dyno program so I could play with camshaft profiles. The one Howard's cam with a 69* IVC is close but I wouldn't mind tweaking the specs on it to drop a bit of lift and maybe shift the LSA a bit to get closer to 72* IVC. I called Howard's today and my springs are good for the .611 lift too but I don't know about piston clearance or the oil band height. The guy also thought a 75* ICV was crazy. Obviously not a Cleveland guy. 😆 6. Not sure I want to do this swap myself just yet. Daily driver? Sure. Converted engine that cost more than most cars I drive not so sure. 7. Conflicting information: Read psi for street cars between 150 and 200 psi. (WTF?) Seen compression test on a Cleveland at 180 psi. Two cylinders were at 150 though..... Feel free to throw out thoughts, criticisms.... Edited by lynchster - 07-November-2022 at 5:58PM |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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i guess you could say it's posted on a bunch of were hoping George Pence would put all of it together, still no word on his health
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72 GT Ute
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handsofstone
Senior Member Joined: 13-April-2018 Location: Northeast Status: Offline Points: 3946 |
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Max, is your book available anywhere?
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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FWIW i just recently heard a theory / concept that fits, the Cleveland closed chamber is not designed to control detonation, the shape of the chamber is designed to 'connect' the intake and exhaust valve for better scavenging during the overlap period. while quench can be an effective tool for controlling detonation in an engine built specifically to run on the ragged edge, i've never seen or heard of any documentation from Ford that the engineers intended to use quench in this manner. the shape of the chamber is just that, the shape they wanted for maximum 'crosstalk' between the valves and it worked well. that's how the 351C was able to compete and beat the 7 liters on the Nascar banked ovals. taking a little bit away won't be the end of the world
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72 GT Ute
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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a couple misnomers i've caught that i feel should be addressed, overlap doesn't play a roll in reducing cylinder pressure, overlap is the opposite side of the 4 cycle chart from where the intake valve closes. overlap is the period between the closing of the exhaust valve and the opening of the intake, both valves are open at the same time. there is no cylinder pressure to speak of anywhere near the overlap period. the other you just mentioned is the lobe separation angle, that also does not play a roll in reducing cylinder pressure but it can affect overlap unless the lobe is tailored to counteract gaining or losing overlap. the only valve timing event that controls now much cylinder pressure is produced is the IVC (intake valve close) on the seat another option to reduce static CR is to 'relieve' or 'soften' the combustion chambers. if you were to remove 8 cc's of material from the chambers you'd be at 9.4:1 static and 7.75 DCR. here's a pic of an Aus 2V closed chamber head that a guy softened to fine tune his static CR. unshrouding the intake valve also improves flow
Edited by Rockatansky - 06-November-2022 at 1:39PM |
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72 GT Ute
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