A
Anonymous
Guest
I'm running 10" @ 900 RPM's or so....
Thanks,
Doug
Thanks,
Doug
A
Anonymous
Guest
It's a Clifford 272H. I think it has .449 lift and 272 duration IIRC with 1.5 ratio rockers. I'm running 1.6 so its more like .480 lift or somthing like that 
Later,
Doug
Later,
Doug
doug, did this condition start after your complete overhaul. your old timing chain was probably 6 degrees retarted, which would smooth the idle because the intake valve would open later. the installation of the roller timing chain & gears advanced the camshaft which would open the intake valve sooner,agravating the overlap. from you previous post you re-used the clifford 272 cam. you might want to put a degree wheel on the balancer & degree the cam since the installation of the fspp roller timing chain. are you sure you possibly made a mistake, because of the wide adjustment latitude with this adjustable setup.
make sure tdc is correct. with #1 piston at tdc is the timing mark on 0 on the dampner?
remember the larger exhaust valve will possibly roughen the idle because of more valve area exposed during the overlap period.
are both idle screws responsive to adjustment on your holley??
disconnect the vacuum booster line from you power brakes to make sure there is no vacuum leak?? good luck on your problem. william
make sure tdc is correct. with #1 piston at tdc is the timing mark on 0 on the dampner?
remember the larger exhaust valve will possibly roughen the idle because of more valve area exposed during the overlap period.
are both idle screws responsive to adjustment on your holley??
disconnect the vacuum booster line from you power brakes to make sure there is no vacuum leak?? good luck on your problem. william
Howdy Doug:
Relax Doug. 10" of vacuum with that cam is not too bad. At 110 degrees of lobe spread, you're getting quite a bit of overlap between intake opening and exhaust valves closing.
If you still have an auto trans (C4) with a vacuum modulator to help with shifting you might be experiencing some problems due to low vacuum.
The other factor is the big two barrel. Another factor might be high elevation.
If I were you I'd be trying a #5 Holley power valve.
Have you taken a drive with a vacuum guage hooked up and in the car so you can watch it? It would help you select an appropriate power valve.
Adios, David
Relax Doug. 10" of vacuum with that cam is not too bad. At 110 degrees of lobe spread, you're getting quite a bit of overlap between intake opening and exhaust valves closing.
If you still have an auto trans (C4) with a vacuum modulator to help with shifting you might be experiencing some problems due to low vacuum.
The other factor is the big two barrel. Another factor might be high elevation.
If I were you I'd be trying a #5 Holley power valve.
Have you taken a drive with a vacuum guage hooked up and in the car so you can watch it? It would help you select an appropriate power valve.
Adios, David
A
Anonymous
Guest
Slade,
No vacuum leaks (that I can find) and timing is set at 10 degrees at idle and around 38 degrees total.
William,
Just started on this overhaul. Last year it was around 14" at idle and you are right...it was running smoother last summer...now it has an agressive idle but it drops into gear just fine. Usually with a vacuum leak it will stall or run really bad when you drop it in gear.
Idle mixture screws work correctly and it has manual brakes.
I had to unhook my water injection because of the low vacuum at idle it would run all the time while it was idling. While you were driving it though (at speed) it would operate correctly.
TDC reads 0 on the balancer (shows that in one of my build up pics) but I keep thinking that maybe I screwed up the installation of the double roller timing chain & gears because there are 5-7 different keyways. I did not degree the cam....Easy to second guess myself though.....
The RPM range moved on it also. Last year it pulled good from almost idle to to 5500-5800. Now it seems to be rather slow off the line but pulls hard from 2500-6000 (highest I've ran it to so far) and shows no sign of running out of power.
It had a massive bog (which it didnt last summer) but I cured that by opening up the center squirter from .030 to .036.
Another problem is it has the tendency to run on after you shut off the ignition. I was running autolite plugs (46's IIRC) and they are a hotter plug than the Accel U grooves I usually run. It was pointed out to me that the hotter plug might be causing this so I swapped back to the Accell plugs. It still runs on but not as bad.
I am planning on filling it up with premium to see if that stops it from dieseling.
The wierdest thing of all is that last summer (10:1 compression) you could tell when the water injection would run out of water...it would start pinging like crazy, but right now with the 10.5:1 compression, it does not ping at all (water injection shut off) Even with mid eighties temperature were having up here.
It's not smoking or running hot....everything is A-OK except for what I explained here. Although, according to the plugs, it looks like I should jet it a bit richer and with the low vacuum, switch the 7.5 power valve to a 5.5 or a 4.5 if I read my Holley book right...
David,
Shifting is still allright @ full throttle in drive it shifts around 5,000 rpm's in 2nd & in 3rd (adjustable vacuum modulator). The elavation I think is right around 800 feet so I dont think that is a factor
I'll hook up my vacuum gauge this weekend and take a drive so I can post the results. I'll also order a 5 and a 6 power valve to play with.
I think it will take some tuning to get it right.....It's just a huge change from what I had before! 8) 8)
Thanks guys!
Doug
No vacuum leaks (that I can find) and timing is set at 10 degrees at idle and around 38 degrees total.
William,
Just started on this overhaul. Last year it was around 14" at idle and you are right...it was running smoother last summer...now it has an agressive idle but it drops into gear just fine. Usually with a vacuum leak it will stall or run really bad when you drop it in gear.
Idle mixture screws work correctly and it has manual brakes.
I had to unhook my water injection because of the low vacuum at idle it would run all the time while it was idling. While you were driving it though (at speed) it would operate correctly.
TDC reads 0 on the balancer (shows that in one of my build up pics) but I keep thinking that maybe I screwed up the installation of the double roller timing chain & gears because there are 5-7 different keyways. I did not degree the cam....Easy to second guess myself though.....
The RPM range moved on it also. Last year it pulled good from almost idle to to 5500-5800. Now it seems to be rather slow off the line but pulls hard from 2500-6000 (highest I've ran it to so far) and shows no sign of running out of power.
It had a massive bog (which it didnt last summer) but I cured that by opening up the center squirter from .030 to .036.
Another problem is it has the tendency to run on after you shut off the ignition. I was running autolite plugs (46's IIRC) and they are a hotter plug than the Accel U grooves I usually run. It was pointed out to me that the hotter plug might be causing this so I swapped back to the Accell plugs. It still runs on but not as bad.
I am planning on filling it up with premium to see if that stops it from dieseling.
The wierdest thing of all is that last summer (10:1 compression) you could tell when the water injection would run out of water...it would start pinging like crazy, but right now with the 10.5:1 compression, it does not ping at all (water injection shut off) Even with mid eighties temperature were having up here.
It's not smoking or running hot....everything is A-OK except for what I explained here. Although, according to the plugs, it looks like I should jet it a bit richer and with the low vacuum, switch the 7.5 power valve to a 5.5 or a 4.5 if I read my Holley book right...
David,
Shifting is still allright @ full throttle in drive it shifts around 5,000 rpm's in 2nd & in 3rd (adjustable vacuum modulator). The elavation I think is right around 800 feet so I dont think that is a factor
I'll hook up my vacuum gauge this weekend and take a drive so I can post the results. I'll also order a 5 and a 6 power valve to play with.
I think it will take some tuning to get it right.....It's just a huge change from what I had before! 8) 8)
Thanks guys!
Doug
Try advancing the timing, you may need as much as 15-20 degrees initial to get it to run right. If so, then you will need to limit the advance so as not to have too much on the upper end. Advancing the timing will speed up the idle, then you can close the throttle to bring the idle back down. This should give you better vacuum and better throttle response. Good luck.
Joe
Joe
A
Anonymous
Guest
JW,
Tried that tonite on the way home Any less than I have now and the power drops off...any more and it starts to miss slightly and idle funny, so I think I'm in the sweet spot... 
Thanks,
Doug
Tried that tonite on the way home
Any less than I have now and the power drops off...any more and it starts to miss slightly and idle funny, so I think I'm in the sweet spot... Thanks,
Doug
DOUG, THE POWER VALVE WOULD ONLY PRESENT A PROBLEM IF BECAUSE OF THE LOW VACUUM YOU WERE INTO THE MAIN METERING SYSTEM OF THE CARBURETOR VIA THE VENTURI DISCHARGE NOZZLE.
BECAUSE OF THE LOW VACUUM AT IDLE THIS COULD POSE A PROBLEM. LETS BACK UP? DID YOU HAVE THE 1.6 ROCKER ARMS ON THE PREVIOUS ENGINE?
AFTER YOU DEGREE THE CAM IN, IF IT CHECKS TO SPECS, JUST ADVANCE THE INITIAL TIMING TO SAY 14-16 DEGREES, IF THIS HELPS YOUR LOW VACUUM CONDITION, THEN YOU NEED TO PULL THE DISTRIBUTOR TO MECANICALLY LIMIT THE CENTRIFUGAL ADVANCE FROM SAY 28 DEGREES TO TO 24 DEGREES + 14 DEGREES INITIAL ADVANCE = 38 DEGREES TOTAL.
IF THIS FAILS YOU COULD GET A CAM WITH 112 LOBE CENTER WHICH WOULD LESSEN THE OVER LAP CONDITION.
IF THE CAM DEGREEING CHECKS OK THE LAST RESORT IS TO DRILL A .060 HOLE IN THE THROTTLE BLADE OF THE CARBURETOR SO THE BLADES ARE IN THE LOWER PART OF THE TRANSFLER SLOT OF THE BASE THROTTLE BODY. I DON'T THINK YOU WILL HAVE TO GO THIS FAR.
IF YOU HAVE TO LIMIT THE CENTRIFIGUL ADVANCE YOU MAY HAVE TO BRAZE OR WELD A STOP IN THE ADVANCE MECHANISM TO LIMIT THE MECHANICAL TRAVEL.
IF I CAN HELP YOU FURTHER ADVISE. WILLIAM
BECAUSE OF THE LOW VACUUM AT IDLE THIS COULD POSE A PROBLEM. LETS BACK UP? DID YOU HAVE THE 1.6 ROCKER ARMS ON THE PREVIOUS ENGINE?
AFTER YOU DEGREE THE CAM IN, IF IT CHECKS TO SPECS, JUST ADVANCE THE INITIAL TIMING TO SAY 14-16 DEGREES, IF THIS HELPS YOUR LOW VACUUM CONDITION, THEN YOU NEED TO PULL THE DISTRIBUTOR TO MECANICALLY LIMIT THE CENTRIFUGAL ADVANCE FROM SAY 28 DEGREES TO TO 24 DEGREES + 14 DEGREES INITIAL ADVANCE = 38 DEGREES TOTAL.
IF THIS FAILS YOU COULD GET A CAM WITH 112 LOBE CENTER WHICH WOULD LESSEN THE OVER LAP CONDITION.
IF THE CAM DEGREEING CHECKS OK THE LAST RESORT IS TO DRILL A .060 HOLE IN THE THROTTLE BLADE OF THE CARBURETOR SO THE BLADES ARE IN THE LOWER PART OF THE TRANSFLER SLOT OF THE BASE THROTTLE BODY. I DON'T THINK YOU WILL HAVE TO GO THIS FAR.
IF YOU HAVE TO LIMIT THE CENTRIFIGUL ADVANCE YOU MAY HAVE TO BRAZE OR WELD A STOP IN THE ADVANCE MECHANISM TO LIMIT THE MECHANICAL TRAVEL.
IF I CAN HELP YOU FURTHER ADVISE. WILLIAM
A
Anonymous
Guest
*off topic...so whats more anoying? All caps letters or my ........? frankly i find reading all caps screwy on the eyes...the dot dot dot thing isnt so bad.....lol...
Doug, what is your cranking compression?
If the cam were too far advanced, your power curve would be higher in the rev range, but at the expense of low end power.
Since you have adjustable rockers, try this as a test. set the valve lash at something like .018-.020" and observe the manifold vacuum. Maybe even take it for a test drive.
You won't be able to keep the lash there, but a short drive won't hurt. If the vacuum is way up and the low end power is back, you may need to advance the cam a couple of degrees.
If the cam were too far advanced, your power curve would be higher in the rev range, but at the expense of low end power.
Since you have adjustable rockers, try this as a test. set the valve lash at something like .018-.020" and observe the manifold vacuum. Maybe even take it for a test drive.
You won't be able to keep the lash there, but a short drive won't hurt. If the vacuum is way up and the low end power is back, you may need to advance the cam a couple of degrees.
A
Anonymous
Guest
A 236/236 at 50 cam with 110 LSA is around 10.5 vacuum at 750 rpm
66 Fastback
Famous Member
The 1.6 ratio rockers will increase the effective durations and overlap. So your 272 cam would behave as if it were bigger contributing to lower vacuum and shift the power curve up in the rpms. The lower vacuum coupled with the bigger carb is probably going to cause a low end bog or loss of low end torque and a shift in the power curve.
As mentioned by Lazy JW, your dieseling problem sounds like you have your throttle plate open too far trying to achieve a smooth idle. You want at least 24 deg of advance at idle (initial + vacuum adv). Then you can reset the throttle plate where it will eliminate the vacuum advance. If the distributor is not tied into manifold vacuum then give that a try. The higher idle advance may raise the engine vacuum sufficiently.
What is your advance at idle with the vacuum connected? I saw on your site that you have an adjustable vacuum can. Make sure that your vacuum advance is fully deployed at your now lower engine vacuum.
As mentioned by Lazy JW, your dieseling problem sounds like you have your throttle plate open too far trying to achieve a smooth idle. You want at least 24 deg of advance at idle (initial + vacuum adv). Then you can reset the throttle plate where it will eliminate the vacuum advance. If the distributor is not tied into manifold vacuum then give that a try. The higher idle advance may raise the engine vacuum sufficiently.
What is your advance at idle with the vacuum connected? I saw on your site that you have an adjustable vacuum can. Make sure that your vacuum advance is fully deployed at your now lower engine vacuum.
A
Anonymous
Guest
MustangSix":3n5a2ex3 said:
Jack,
Not sure what the cranking compression is? I dont have access to a compression gauge anymore so I cant check it right now until I get one
I'll try readjusting the rockers for a test tomorrow and see what happens!
66Fastback,
This is the same carb that I've used for the past couple of years (shoulda mentioned that!
) The throttle plate really isnt to far open it idles around 800-900 rpms and I cant run that kind of advance at idle because it start to miss and idles funny.
I have to change my site. I tried to install the adjustable vacuum cannister but it wouldnt fit
Thanks,
Doug
Mustang_Geezer":kqp7399x said:MustangSix":kqp7399x said:
Jack,
Not sure what the cranking compression is? I dont have access to a compression gauge anymore so I cant check it right now until I get one
I'll try readjusting the rockers for a test tomorrow and see what happens!
Doug, I meant to say "if the cam were too far retarded", not advanced. Retarding pushes the curve higher, advancing the cam moves the curve lower. Sorry, I was not watching what I was typing.
Let me know if opening the lash makes a difference.
PS. You need to degree the cam.
A
Anonymous
Guest
Doug,
You mentioned that you enine diesels after ignition shut down. Throttle plate setting is a large contributor to dieseling as is retarded timing which increases EGT. When you advance the timing and get a rough idle, it could be because the plate is open too far and the fuel metering is inconsistent because you are transitioning out of the carb's idle circuit. Have you checked to see that 10" of idle vacuum fully advances the vacuum cannister. If it the vacuum advance is not fully advanced at a couple of inches below 10", then the timing will be inconsistent. I was not implying that you need to set your initial timing to 24 deg. I meant that the combined total of the vacuum advance and initial advance should be about 24 deg.
Doug
You mentioned that you enine diesels after ignition shut down. Throttle plate setting is a large contributor to dieseling as is retarded timing which increases EGT. When you advance the timing and get a rough idle, it could be because the plate is open too far and the fuel metering is inconsistent because you are transitioning out of the carb's idle circuit. Have you checked to see that 10" of idle vacuum fully advances the vacuum cannister. If it the vacuum advance is not fully advanced at a couple of inches below 10", then the timing will be inconsistent. I was not implying that you need to set your initial timing to 24 deg. I meant that the combined total of the vacuum advance and initial advance should be about 24 deg.
Doug
A
Anonymous
Guest
do you have an EGR valve? is it working? try raising the idle speed to around 1000 RPM and then just playing around with that.. if u cant advance the timing any more then just tighten the idle speed screw...alot of problems i have encountered were simply fixed by raising the idle speed and playing with the air/fuel mixture screw...i cant have my idle mixture screw at the stock "bottom out then undo 2 turns" i have to go like 5 turns or it'll be a very rough idle...i tune by ear and have never been dissapointed...only thing i would use a timing gun for is to make sure the timing isnt retarded too much...but i was surprised how much difference the air/fuel mixture screw made in the way it idled...never made a difference really when it was stock but the more i mod my engine the more 'touchy' things seem...i really hope u can figgure out the problem...take care...
doug, the other members have posted some real good advice. since your combination ran good before, go back to your original main jets & accelerator discharge nozzle. i feel your camshaft timing is retarded. that will make the lower end soggy & lower the cranking compression, thats why the engine does not ping on acceration.
run a compression test & degree the camshaft. just make 1 change at a time then you can pinpoint the problem.
good luck on your witch hunt. when i install the austrailian full roller timing chain setup i will carefully check the camshaft timing. good luck william
run a compression test & degree the camshaft. just make 1 change at a time then you can pinpoint the problem.
good luck on your witch hunt. when i install the austrailian full roller timing chain setup i will carefully check the camshaft timing. good luck william
Doug, did you ever find the problem with your engine???
competion cams has a decent link for degreeing a camshaft. www.compcams.com/technical your clifford camshaft was ground by erson. you might want to call them for the degrees at the intake center line to degree it properly. other wise call mike at fspp for one of his camshafts. i just purchased a 264 cam from him @ got all the proper information from mike & george at clay smith cams. my camshaft is a H-264-12-B. this cam has a 112 lobe center for a smooth idle with a stock converter on my c-4 trans. my degrees are 109 at the intake lobe centerline for a split overlap. hope this helps on your situation. respectfully william
competion cams has a decent link for degreeing a camshaft. www.compcams.com/technical your clifford camshaft was ground by erson. you might want to call them for the degrees at the intake center line to degree it properly. other wise call mike at fspp for one of his camshafts. i just purchased a 264 cam from him @ got all the proper information from mike & george at clay smith cams. my camshaft is a H-264-12-B. this cam has a 112 lobe center for a smooth idle with a stock converter on my c-4 trans. my degrees are 109 at the intake lobe centerline for a split overlap. hope this helps on your situation. respectfully william
Similar threads
