Welcome to V8Buick.com.
Results 1 to 14 of 14
  1. #1
    Join Date
    Nov 2010
    Location
    Rapid City, SD
    Posts
    88

    Default Can excessive lifter preload cause bad idle?

    Just looking for a little feedback: I have gotten my engine to idle pretty good with idle circuit mods per Cliff Ruggles, but I think it could be better. Initial timing is 22*, total timing is 35* all in before 3000 rpm, vacuum advance is 10*. Idles at 800 rpm in park and 600 rpm is drive with a bit of a lope, with 14" hg and 10" hg vacuum respectively @ 4000 feet above sea level. Cam is TA 212 and degreed in at 109* ICL. Is this about what kind of vacuum to expect at idle with this cam? Is my timing about in the ball park? If the initial timing is backed off, vacuum will fall off and the engine will not idle at all, in fact it will just plain die below 1000 rpm. I suspected a vacuum leak so I replaced the Edelbrock composite gasket and trimmed down steel valley pan gasket per TA instructions, with just a new steel valley pan gasket with 3 coats of copper coat (the composite gasket was sliced at the bottom from the edge of the valley pan and was actually being squeezed out the top by about 1/8"). There was no change. When I built the motor, the exhaust valves were replaced with 1.755" TA stainless steel valves, but the factory intake valves were reused. As a result, the intake valve stems are about .020" higher than the exhausts. The heads were milled to clean up (.010"? and I don't know if they have been milled previously) and the block was decked about .010". The pushrods are stock length with stock rockers. I didn't measure the exact lifter preload, but the lifter plungers were about 1/3 of the way down their travel on the exhausts, while the intakes were down about 2/3's. Not ideal, I know. I am wondering if this excessive preload could be preventing the engine from idling at it's best? Is 22* initial timing too much to run with this mild of a cam? I would like to run 10*-12* initial, or am I just worrying about nothing? Would like to know before I spring for shorter or adjustable pushrods, or do the right thing and take the motor apart and have the intake valve stems cut down .020"--would any of these improve anything? Thanks for reading this far.
    Steve, Rapid City, SD
    1969 Chevrolet C/10: 1976 455 BBB, stock block, .030" over KB 357 pistons, .000" deck height, 9.75:1 CR, stock rods w/arp bolts, stock crank .010"-.010", TA oil pump booster plate and adj. regulator, TA 212 cam, stock valve train, 1972 pocket ported Stage 1 heads, B4B intake, 800 cfm Q-Jet, ported exhaust manifolds, 2 1/2" exhaust, Flowmaster Deltaflow 50 mufflers, TH400, stock converter, 3.73 posi truck 12 bolt, 3800 lbs empty.

  2. #2
    Join Date
    Apr 2002
    Location
    Nova Scotia
    Posts
    3,405

    Default Re: Can excessive lifter preload cause bad idle?

    Quote Originally Posted by puddle View Post
    Just looking for a little feedback: I have gotten my engine to idle pretty good with idle circuit mods per Cliff Ruggles, but I think it could be better. Initial timing is 22*, total timing is 35* all in before 3000 rpm, vacuum advance is 10*. Idles at 800 rpm in park and 600 rpm is drive with a bit of a lope, with 14" hg and 10" hg vacuum respectively @ 4000 feet above sea level. Cam is TA 212 and degreed in at 109* ICL. Is this about what kind of vacuum to expect at idle with this cam? Is my timing about in the ball park? If the initial timing is backed off, vacuum will fall off and the engine will not idle at all, in fact it will just plain die below 1000 rpm. I suspected a vacuum leak so I replaced the Edelbrock composite gasket and trimmed down steel valley pan gasket per TA instructions, with just a new steel valley pan gasket with 3 coats of copper coat (the composite gasket was sliced at the bottom from the edge of the valley pan and was actually being squeezed out the top by about 1/8"). There was no change. When I built the motor, the exhaust valves were replaced with 1.755" TA stainless steel valves, but the factory intake valves were reused. As a result, the intake valve stems are about .020" higher than the exhausts. The heads were milled to clean up (.010"? and I don't know if they have been milled previously) and the block was decked about .010". The pushrods are stock length with stock rockers. I didn't measure the exact lifter preload, but the lifter plungers were about 1/3 of the way down their travel on the exhausts, while the intakes were down about 2/3's. Not ideal, I know. I am wondering if this excessive preload could be preventing the engine from idling at it's best? Is 22* initial timing too much to run with this mild of a cam? I would like to run 10*-12* initial, or am I just worrying about nothing? Would like to know before I spring for shorter or adjustable pushrods, or do the right thing and take the motor apart and have the intake valve stems cut down .020"--would any of these improve anything? Thanks for reading this far.
    Steve, in your profile listed at the bottom of your page it says you have 0 deck? Don't those pistons you used have a factory pin height? If so your deck height should be some where around .045 if you only removed .010? Does the vacuum gauge bounce at all? I have run the 212 cam in a 400 with the lifter preload set at .110 with no problems at all. If your using a 1405 lifter you can run with up to .200 lifter preload. Did Cliff build the carb? Are you saying you only have 10 inches of vacuum in drive?
    70 stage1 clone 464 iron STG1 heads, 4.11 gears 10 10.17@129.8
    72 GS LS gone BBB going back in! Went 9.93 with BBB power
    GSX clone 462 9.3:1, STG2se 3.73, 11.0s 439.39 RWHP/437.99 TQ
    Without data, you're just another guy with an opinion.
    Your lack of prior planning does not Constitute a emergency on my part!

  3. #3
    Join Date
    Apr 2002
    Location
    Nova Scotia
    Posts
    3,405

    Default Re: Can excessive lifter preload cause bad idle?

    Quote Originally Posted by GranSportSedan View Post
    Chris, is that really true?? almost 1/4 inch of preload with no issues? what keeps the lifters from pumping up and lifting valves off their seats? just trying to learn here
    I built a 400 about 5 or 6 years ago, when I checked the push rod length as I do on all builds I found that I had .115 prelaod (engine mentioned above) I went through hell to find out how come this engine had so much lifter preload. Stuck the old cam back in with a couple old lifters only to end up with the same preload and also the .115 preload was with a felpro gasket not the .020 steel shim it left the factory with so it would have left the factory with closer to .135 preload. I knew the history of this 400 and it had never been opened since it left the factory, and it still had the factory steel shims in it when I pulled it apart. This is not uncommon to see. Those lifters have .300 travel and it was the engineer at Delfi that told me that you can run them down to .200 I am not sure if you have played around with any of the older ford stuff but you use to set the preload .100 of the bottom of the lifter. If you think about setting up lifters on a SBC while its running, if you adjust the preload to fast it starts to stumble and then it levels off.

    In Steve's case, the fag that comes up for me is that if he only has 10 inches of vacuum at idle in gear is that he doesn't have enough vacuum to pull in the power piston that pulls down the primary metering rods and it must have a vacuum leak some where to be that low with that small cam. If the vacuum gauge is bouncing that would indicate bad valve seal/leakage.....
    70 stage1 clone 464 iron STG1 heads, 4.11 gears 10 10.17@129.8
    72 GS LS gone BBB going back in! Went 9.93 with BBB power
    GSX clone 462 9.3:1, STG2se 3.73, 11.0s 439.39 RWHP/437.99 TQ
    Without data, you're just another guy with an opinion.
    Your lack of prior planning does not Constitute a emergency on my part!

  4. #4
    Join Date
    Nov 2010
    Location
    Rapid City, SD
    Posts
    88

    Default Re: Can excessive lifter preload cause bad idle?

    If I remember correctly, KB 357 pistons have a compression height of 2.010" so with a stock deck height they are .010" down the hole--deck it .010" and it is zero deck. I failed to mention I am using .040" felpro head gaskets. Yes, only 10 inches vacuum at idle in drive, and the needle fluctuates rapidly about 1/2 an inch of vacuum. Needle is really quite steady at idle in park at 14". I built the carb and tuned it and calibrated the idle circuit using Cliff Ruggle's book, and it does have the stock power piston spring in it. I will check to see if it is pulled down at idle. Sounds like I need to do some more checking to rule out a vacuum leak for sure.
    Steve, Rapid City, SD
    1969 Chevrolet C/10: 1976 455 BBB, stock block, .030" over KB 357 pistons, .000" deck height, 9.75:1 CR, stock rods w/arp bolts, stock crank .010"-.010", TA oil pump booster plate and adj. regulator, TA 212 cam, stock valve train, 1972 pocket ported Stage 1 heads, B4B intake, 800 cfm Q-Jet, ported exhaust manifolds, 2 1/2" exhaust, Flowmaster Deltaflow 50 mufflers, TH400, stock converter, 3.73 posi truck 12 bolt, 3800 lbs empty.

  5. #5
    Join Date
    Apr 2002
    Location
    Nova Scotia
    Posts
    3,405

    Default Re: Can excessive lifter preload cause bad idle?

    Quote Originally Posted by puddle View Post
    If I remember correctly, KB 357 pistons have a compression height of 2.010" so with a stock deck height they are .010" down the hole--deck it .010" and it is zero deck. I failed to mention I am using .040" felpro head gaskets. Yes, only 10 inches vacuum at idle in drive, and the needle fluctuates rapidly about 1/2 an inch of vacuum. Needle is really quite steady at idle in park at 14". I built the carb and tuned it and calibrated the idle circuit using Cliff Ruggle's book, and it does have the stock power piston spring in it. I will check to see if it is pulled down at idle. Sounds like I need to do some more checking to rule out a vacuum leak for sure.
    What I find that works well for me is to get a white zap strap and sit the head of it down the vent hole with the engine turned off and push the power piston/metering rods down until they bottom out and mark the zap strap with a black felt pen flush to the vent hole. Start the engine and watch to see if the power piston is getting pulled in all the way, sometimes you can watch the zap strap going up and down as it sits on top of the power piston.
    70 stage1 clone 464 iron STG1 heads, 4.11 gears 10 10.17@129.8
    72 GS LS gone BBB going back in! Went 9.93 with BBB power
    GSX clone 462 9.3:1, STG2se 3.73, 11.0s 439.39 RWHP/437.99 TQ
    Without data, you're just another guy with an opinion.
    Your lack of prior planning does not Constitute a emergency on my part!

  6. #6
    Join Date
    Nov 2010
    Location
    Rapid City, SD
    Posts
    88

    Default Re: Can excessive lifter preload cause bad idle?

    Thanks, I will give the marked zap strap trick a try and see what my power piston is doing at idle. I do have a lighter power piston spring stashed somewhere and I could give that a try if pp is not staying seated.
    Steve, Rapid City, SD
    1969 Chevrolet C/10: 1976 455 BBB, stock block, .030" over KB 357 pistons, .000" deck height, 9.75:1 CR, stock rods w/arp bolts, stock crank .010"-.010", TA oil pump booster plate and adj. regulator, TA 212 cam, stock valve train, 1972 pocket ported Stage 1 heads, B4B intake, 800 cfm Q-Jet, ported exhaust manifolds, 2 1/2" exhaust, Flowmaster Deltaflow 50 mufflers, TH400, stock converter, 3.73 posi truck 12 bolt, 3800 lbs empty.

  7. #7
    Join Date
    Apr 2002
    Location
    Nova Scotia
    Posts
    3,405

    Default Re: Can excessive lifter preload cause bad idle?

    Quote Originally Posted by puddle View Post
    Thanks, I will give the marked zap strap trick a try and see what my power piston is doing at idle. I do have a lighter power piston spring stashed somewhere and I could give that a try if pp is not staying seated.
    I wouldn't modify anything until you find the vacuum leak, the 212 cam should not need any mods to the carb and should have way more vacuum then you have. Try pinching all the vacuum lines one at a time with a pair of needle nose pliers to block any possible leaks ie: brake booster, pcv valve, vacuum advance etc. If have seen a NIB B4B that from the factory they drilled and tapped right into the intake runner on the front pass bolt boss where the AC bracket fastens. You can try using a propane torch turned up high (do not light ) and start around the carb base, intake flange, pull out the pcv and stick it in the hole to check for a leak on the under side of the intake flange etc. At 10 inches of vacuum it won't be pulling in the power piston which will cause more problems on top of the real cause. Re-check your vacuum, the needle should not be bouncing and if it is a leak down test might be in order.......
    70 stage1 clone 464 iron STG1 heads, 4.11 gears 10 10.17@129.8
    72 GS LS gone BBB going back in! Went 9.93 with BBB power
    GSX clone 462 9.3:1, STG2se 3.73, 11.0s 439.39 RWHP/437.99 TQ
    Without data, you're just another guy with an opinion.
    Your lack of prior planning does not Constitute a emergency on my part!

  8. #8
    Join Date
    Feb 2002
    Location
    Oakland Gardens, N.Y.
    Posts
    22,087

    Default Re: Can excessive lifter preload cause bad idle?

    Quote Originally Posted by buicksstage1 View Post
    I wouldn't modify anything until you find the vacuum leak, the 212 cam should not need any mods to the carb and should have way more vacuum then you have. Try pinching all the vacuum lines one at a time with a pair of needle nose pliers to block any possible leaks ie: brake booster, pcv valve, vacuum advance etc. If have seen a NIB B4B that from the factory they drilled and tapped right into the intake runner on the front pass bolt boss where the AC bracket fastens. You can try using a propane torch turned up high (do not light ) and start around the carb base, intake flange, pull out the pcv and stick it in the hole to check for a leak on the under side of the intake flange etc. At 10 inches of vacuum it won't be pulling in the power piston which will cause more problems on top of the real cause. Re-check your vacuum, the needle should not be bouncing and if it is a leak down test might be in order.......
    Chris, he is at 4000' above sea level. I didn't think 14" sounded so bad in Park. 10" sounds low in gear though. Maybe the converter is too tight?
    Larry
    1998 "Fully Optioned" SC3800 Riviera
    70 GS 455 Stage1, TSP 470, 602 HP@ 5900, 589 TQ @ 4900
    TA Hyd Roller Cam, 230*/238*, 112, .544"/.577" lift, 4-7 swap
    MSD Digital 6+, Ignitionman Distributor w/MSD trigger
    1967 BT Switchpitch ST-400, Gear Vendors OD
    with TSP 3200/1800 converter
    AED 1000 HO Carb, 800 CFM 7042240 Quadrajet
    8.5 10 bolt, 3.73's
    Best E.T. 11.54@ 115.00. Best MPH, 11.58@ 115.89
    Larrymta@verizon.net, GSCA #291
    BPG # 1063
    N.E. GS/GN Club Assistant Director

  9. #9
    Join Date
    Apr 2002
    Location
    Nova Scotia
    Posts
    3,405

    Default Re: Can excessive lifter preload cause bad idle?

    Quote Originally Posted by LARRY70GS View Post
    Chris, he is at 4000' above sea level. I didn't think 14" sounded so bad in Park. 10" sounds low in gear though. Maybe the converter is too tight?
    Even at 4000' I would think it should be closer to 14 inches @ 700 rpm idle in gear. No over lap, Initial timing is 22*, 9.75:1, has little primary's that should provide a strong signal for idle circuit. Right now its not pulling enough vacuum to pull in the power piston (unless someone has cut the spring) or to operate the power brakes. The needle should not bounce at all.......
    70 stage1 clone 464 iron STG1 heads, 4.11 gears 10 10.17@129.8
    72 GS LS gone BBB going back in! Went 9.93 with BBB power
    GSX clone 462 9.3:1, STG2se 3.73, 11.0s 439.39 RWHP/437.99 TQ
    Without data, you're just another guy with an opinion.
    Your lack of prior planning does not Constitute a emergency on my part!

  10. #10
    Join Date
    Nov 2010
    Location
    Rapid City, SD
    Posts
    88

    Default Re: Can excessive lifter preload cause bad idle?

    The converter is on the tight side. Its a stock 13", and this motor stalls it @1600 rpm before I just can't hold it with the brake any more. No brake booster so that is not an issue. Are you guys thinking an idle speed of 600 rpm in drive is just too slow? Plan on borrowing Dad's propane torch today. I had checked over manifold and vacuum lines in past, but will double check them. Thanks.
    Steve, Rapid City, SD
    1969 Chevrolet C/10: 1976 455 BBB, stock block, .030" over KB 357 pistons, .000" deck height, 9.75:1 CR, stock rods w/arp bolts, stock crank .010"-.010", TA oil pump booster plate and adj. regulator, TA 212 cam, stock valve train, 1972 pocket ported Stage 1 heads, B4B intake, 800 cfm Q-Jet, ported exhaust manifolds, 2 1/2" exhaust, Flowmaster Deltaflow 50 mufflers, TH400, stock converter, 3.73 posi truck 12 bolt, 3800 lbs empty.

  11. #11
    Join Date
    Nov 2010
    Location
    Rapid City, SD
    Posts
    88

    Default Re: Can excessive lifter preload cause bad idle?

    Just got done checking for vacuum leaks. Ran a fully open (but not lit) propane torch along where the manifold meets the cylinder heads, and all around the base plate of the carburetor, and pulled the PCV valve and shoved some propane in there. Detected no change in rpm, vacuum, or how it ran. Pulled vacuum modulator line and plugged (only vacuum line), and again no change. PCV hose and valve are new--appear to be fine and functioning properly. Distributor vacuum advance hose is new, and so is the vacuum advance canister, and that all seems to be working great as well. All the unused vacuum ports on the carburetor are plugged. Power piston is fully seated at idle both in neutral and drive. 98% sure I do not have a vacuum leak. Maybe my vacuum gauge is inaccurate and reads low? My Grandad gave it too me and it's old as dirt. I will check the compression next, and then fabricate a rig to do a leak down test. Never done one of those before...
    Steve, Rapid City, SD
    1969 Chevrolet C/10: 1976 455 BBB, stock block, .030" over KB 357 pistons, .000" deck height, 9.75:1 CR, stock rods w/arp bolts, stock crank .010"-.010", TA oil pump booster plate and adj. regulator, TA 212 cam, stock valve train, 1972 pocket ported Stage 1 heads, B4B intake, 800 cfm Q-Jet, ported exhaust manifolds, 2 1/2" exhaust, Flowmaster Deltaflow 50 mufflers, TH400, stock converter, 3.73 posi truck 12 bolt, 3800 lbs empty.

  12. #12
    Join Date
    Feb 2002
    Location
    Oakland Gardens, N.Y.
    Posts
    22,087

    Default Re: Can excessive lifter preload cause bad idle?

    I've often noticed that vacuum gauges will read differently. I use a permanently installed Autometer gauge. I have it mounted in the engine compartment so I can see it when adjusting the carburetor.
    Larry
    1998 "Fully Optioned" SC3800 Riviera
    70 GS 455 Stage1, TSP 470, 602 HP@ 5900, 589 TQ @ 4900
    TA Hyd Roller Cam, 230*/238*, 112, .544"/.577" lift, 4-7 swap
    MSD Digital 6+, Ignitionman Distributor w/MSD trigger
    1967 BT Switchpitch ST-400, Gear Vendors OD
    with TSP 3200/1800 converter
    AED 1000 HO Carb, 800 CFM 7042240 Quadrajet
    8.5 10 bolt, 3.73's
    Best E.T. 11.54@ 115.00. Best MPH, 11.58@ 115.89
    Larrymta@verizon.net, GSCA #291
    BPG # 1063
    N.E. GS/GN Club Assistant Director

 

 

Similar Threads

  1. Thread for lifter preload
    By alrobjr in forum Small Block Tech
    Replies: 4
    Last Post: 02-06-2012, 01:40 PM
  2. Setting lifter preload
    By gsxwannab in forum Street/strip 400/430/455
    Replies: 1
    Last Post: 06-14-2011, 01:07 AM
  3. Lifter preload
    By piston1 in forum Street/strip 400/430/455
    Replies: 5
    Last Post: 07-22-2008, 11:50 AM
  4. Lifter preload adjustment.
    By Billy in forum Race 400/430/455
    Replies: 17
    Last Post: 05-03-2007, 09:04 PM
  5. lifter preload
    By Judd in forum 'Da Nailhead
    Replies: 1
    Last Post: 06-10-2005, 04:24 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Back to top