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#241
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I don't believe there's anyone out there who hasn't seen a difference in some vehicle when one method is chosen over another, so how do you explain that happening? That's why you try it both ways. Every package is different and no one method is going to be the best in all situations. I used to tune emissions era engines for friends to make them more drivable and help their mileage, and all of those stock engines worked better when using manifold. I was not saying that Jake should have used fmv, I was only asking if he had tried it after advancing them cam.
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Rich The real democratic American idea is, not that every man shall be on a level with every other man, but that every man shall have liberty to be what God made him, without hindrance. Henry Ward Beecher "The problem with socialism is that you eventually run out of other people's money." Margaret Thatcher |
#242
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well that's just splitting hairs. whats 1 mile minus 1 inch? the answer is 1 mile (significant digits). on an analog gauge that only reads inches of hg, what's 21 inches minus the tiny restriction caused by the throttle plates? the answer is 21 in/hg. the vac can cannot tell the difference and will act the same is my point.
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John J. |
#243
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Rich The real democratic American idea is, not that every man shall be on a level with every other man, but that every man shall have liberty to be what God made him, without hindrance. Henry Ward Beecher "The problem with socialism is that you eventually run out of other people's money." Margaret Thatcher |
#244
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as i mentioned earlier, many things could be wrong: a restriction in the line or carb that is slowing flow, a slow moving vac advance mechanism (could be dirty or sticky) or a bad vac can. a properly working vac advance system should see no difference in response time; it's almost instant.
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John J. |
#245
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Rich The real democratic American idea is, not that every man shall be on a level with every other man, but that every man shall have liberty to be what God made him, without hindrance. Henry Ward Beecher "The problem with socialism is that you eventually run out of other people's money." Margaret Thatcher |
#246
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bottom line: if your vac can doesn't move right away, something is wrong and running fmv to try to cover it up is silly, imho.
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John J. |
#247
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My experience with FMV vs. ported has been that USUALLY I've been working with an HEI that came from a smogger car.
Those things have too much mechanical advance built into the curve. Somewhere between 20-24* usually. That was so they could use ported vacuum, have slow timing 0-8* initial, and still have 30-34'ish at WOT. The slow timing at idle was purely to clean up HC emissions at idle, and it does work for this. However it KILLS throttle response. So the ported would bring on some timing when the throttle was cracked open to get some acceleration. You can use FMV to get more instant throttle response in this scenario. Lighter mech advance springs as well. The REAL fix is usually to limit the mechanical advance so you have 20*+ at idle, and ~36* total or whatever the engine likes. The you use vacuum advance purely for part throttle cruise to improve mileage and driveability. Somebody did this distributor correctly. It is also a points type dizzy converted to electronic, so it may not have had that much mechanical built into it. I've used FMV in many cases and USUALLY it does work better. On this car, it brought in too much timing at idle before we retimed the cam, however after we got the cam in correctly it seemed less sensitive to timing over 20* at idle.
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www.jakesperformance.com Racing Automatics and LSx Engine components |
#248
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With my old HEI dist, changing from manifold to ported vac made absolutely no difference anywhere....even at idle. Put I knew it was problematic. So I bought a new dist (HEI...thanks PDude!) and the ported vs man vac makes a big difference. On the new dist, I put a hose to the vac can and sucked on it and I could hear it pull and snap back without a whole lot of effort. That is the extent of my testing. I guess what i am saying is that I am making 14 hg of vac, on a brand new dist and can, and I do see a slight hesitation, with ported advance, before the advance comes in (but I dont know that it is vac advace...could be mechanical is coming in??). With manifold vac, it is very smooth and no noticeable transition. Is there a problem here??? Doesnt seem to be...but i couldnt say for sure. By the way I am making 16* at idle with 36* in by 3000 rpm |
#249
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John J. |
#250
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"There could be a problem...It would make a difference if"... There's nothing concrete here, it's all speculation. Jake's right on the money. As I said, before, fmv is a band-aid, just the same as throwing more fuel in at idle.
A quick story. A buddy of mine had a '69 Le Mans, 250" Chevy six/powerglide. I recurved the distributor, changed it from ported to manifold and played with the carb a little. He was tickled with it, the power improved and he picked up over 2 mpg. The really impressive thing was the time he nailed it from an idle and almost ran over another friend. The tires broke loose and the car leapt off the line! He hadn't expected that and just missed his friend. He ran in the house, all excited, to call me and tell me about it. There were 3 vehicles I played with that didn't pick up mileage, although they did run better. One was a 400 Chrysler, one a 360 Ford pickup (although a 351 pickup did improve) and one a 400 Ford wagon.
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Rich The real democratic American idea is, not that every man shall be on a level with every other man, but that every man shall have liberty to be what God made him, without hindrance. Henry Ward Beecher "The problem with socialism is that you eventually run out of other people's money." Margaret Thatcher |
#251
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The car is really running well how it is.... but I just want to do it to see how it affects things. |
#252
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Well Jake, how does it run now? Any improvement with degreeing the cam?
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Kenny Cincinnati, Oh 1971 Ventura II 400 .060 Eagle Rods |
#253
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#254
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Update!
Monday I had Jake install the long branch manifolds wifey got me for christmas and today a new 2 1/2 exhaust with dynamax super turbos was installed (thanks you Tom Hand for your research!) She is really pulling harder, we are headed in the right direction
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67 Firebird Convertible - SOLD 80 Firebird Formula Turbo |
#255
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How is the direction now??? Updates??
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1967 Pontiac Tempest 2dr HRDTP Coupe 468 C.I. 500 HP 5 speed = FUN!!! 1990 Chevy Suburban R2500 Daily Driver 1986 Volvo DL245 Wagon.. Project car!!! The Burb Files |
#256
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I don't think Tony gets on everyday.
I know we installed a helper fuel pump awhile back. He felt that since the mods the car runs better but seemed to fall off in the upper rpms before the 2-3 shift. Sounded like a classic case of fuel starvation. I haven't gotten any feedback on whether that improved it or not.
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www.jakesperformance.com Racing Automatics and LSx Engine components |
#257
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Hey all!
Jake the helper pump did solve the problem. Car is still a little soft off the line, which I think is converter related. After that it pulls real hard, last time out at WOT right before the 1-2 shift the tires broke loose and that got my attention I think there still more potential to be had and I think the performer manifold may be choking things a bit. I bartered for a factory 68 intake that I may send to SD for the CNC Cliff's port special. But there hasn't been much talk/reviews of it on the forum, so I'm not sure. Other than that and the converter, I'm hesitant to make any other major changes as I don't want to mess things up, the car is an awesome cruiser and a blast to drive on the backroads with the top down.
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67 Firebird Convertible - SOLD 80 Firebird Formula Turbo |
#258
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"Combo
72 400 block w/428 rotating assembly from PPR D-port 96 heads rebuilt and ported by butler comp cams hyd roller XE276HR (yes the same cam that has been the subject of much discussion here) - 276 I - 282 E 224 I - 230 E .502 I - .510 E q-jet - rebuilt by Cliff performer intake" We back to back tested the prototype ported iron intake on a 428 engine. We used a 1967 428 block, stock Arma Steel crank, Oliver rods and Ross pistons. The engine was topped with unported KRE aluminum "D" port heads with 74cc chambers. We used a custom ground HR cam from Comp Cams, 236/242/110. Aside from a tad more compression and a bit more camshaft, the combo's aren't that far off each other. Our KRE heads were stock, not ported. We did clean up the runners a bit and the seats down into the bowls, and port match them exactly to a stock Felpro blue intake gasket. We tested three intakes back to back with the following results: Ported HO aluminum intake (reproduction), 487HP Stock Edelbrock RPM (port matched), 491HP Ported factory iron intake, 497HP I ran that same intake to mid-11's in my old 455 engine. My new engine is using a 1971 HO intake ported to the same specifications, as the iron intake didn't have quite enough material for a good port match to the larger runners in the new 290cfm KRE heads from SD Performance. I only dyno tested a Performer intake once, and it was down some on power for the combination of parts. I attempted to street/strip test the same Performer intake, but my engine ran poorly with it in place, and we decided not to continue the testing.......Cliff
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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), |
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