What causes low vacuum at idle & other tuning issues??

[Anonymous]

William,

I tore the front cover off the engine Tuesday night to inspect it....The timing chain & gears are set where they are supposed to be. I cant afford to buy a degree wheel at this time to degree it.

It should be fine being its the same cam I've ran for the past couple of years in the same block The bottom end is the same as I was running before, just freshened up.

I thought I might have inadvertantly advanced or retarded the cam by mistake when I installed it but thats not the case.

Somthing is screwed up though....Before when you pull the main vacuum line going to the pcv valve off it would instantly kill the motor....now it just speeds up the rpms when you pull it off....

It's running really rich at idle due to the low vacuum which is opening up the power valve IMO. Adjusting the distributor has no affect on it either.

Right now I'm going to rip off the adapter plates and reinstall them with gaskets and permatex sealer, like I did before. I tried a different way of sealing them the last time.....I'm starting to think I have a major vacuum leak that is causin the low vacuum which is in turn causing it to run rich.

Thanks for the concern!!

Later,

Doug

 

[wsa111]

Doug, if you pull the pcv hose off & the engine speeds up, sounds like you have blown power valve in your carburetor. it looks like the carb you have is relitively new, replace the power valve right now
if the carb is over 7 years old they have no backfire protection. if you have a holley carburetor older than 7 years old holley sells a back-fire check valve kit which can be installed int the throttle base plate. all you need is a drill press to ensure a true 90 degree counter bore for the check valve insert..
when you pull the metering plate off of the main body & the vacuum side of the power valve is saturated with wet fuel you know you have the problem solved. hope this is your problem. later william

 

[Anonymous]

William,

Carb is 2 years old but the power valve is just one out of a old kit I had laying around.....

I'll order a new holley one and replace it when I reseal my adapter plates!

Thanks,

Doug

 

[Anonymous]

Part of the problem is fixed....

Blown power valve and a vacuum leak under the front lower adapter plate where it meets the intake manifold!

When you pull off the pcv valve line it stalls the engine now and you dont have the overpowering rich smell at idle. I'll drive it tomorrow to see how it runs and throw a vacuum gauge on it to see what it running at.

Plus install some new accell plugs...old ones are trashed. No more dieseling either.

Thanks for all the help!

Later,

Doug

 

[Anonymous]

I`m Glad you`r gettin it running good how much more power do you think you`r making now with the rebuild ? How about some pics with the engin in the car ?

 

[Anonymous]

I have the pics but I have to reload the digital camera disc into my computor to get it working again....Maybe I'll have a chance to do it this weekend

As far as the power goes...It's making quite a bit

Later,

Doug

 

[wsa111]

Doug, i'm glad the power valve was part of your problem. Did you ever go back to your original jet & accerator discharge nozzle sizes??
What is the accell spark plug number you are running? T accell is made by denso, has the u-groove electrode. I have been using autolite ap46 which is a single platinium plug with good results but would like to try the denso or accell plug. glad to be of help. william

 

[AzCoupe]

Doug, you still need to degree the cam just to be certain it is right. Even tho the dots line up, it can still be one or two degrees off. Sounds to me like the cam is a bit retarded, rather than the mechanic.

Sorry , couldn't help that one.

I've been thinking about this and it seems like a lot of our members are not degreeing their cams, for two reason. Either they aren't sure how, or they don't have the equipment. So I think I am going to invest in a couple of degree kits, as well as a couple of the Clay Smith videos on cam timing.

If you want to borrow them, just let me know and I send them to you. All I ask is that you pay the shipping, which shouldn't be much. I think this would be a nice benefit to offer to the guys that buy FSPP cams. Even though you didn't buy your cam from me, we both know how many FSPP parts you have. Just my way of saying thanks.

 

[wsa111]

Mike, that would be a great help to many of your customers. i purchased a 264 cam with the 112 lobe center. i called george at clay smith & found the degree's to be at 109 at the intake lobe center for split overlap.
It would be a great addition to clay smiths timing card to just include this information for all the cams you sell. this intake lobe center is the most accurate way to degree a cam in.
Keep up the good work, cause the other cam company's just throw you to the wolves. the exception is comp cams which supplies the the intake lobe center for degreeing their cams on the timing card. thanks again for your pioneering work for us six cylinder owners. later william

 

[Anonymous]

William,

Yep, I reinstalled all the original carb stuff except I replaced the stock 7.5 power valve with a 4.5 power valve. I ordered another one (6.5) that I'm going to install tomorrow...Seems to be leaning out on the top end.

I'm going to play with the power valves for right now, then start playing with the timing and jetting again.

I'll get the accell spark plug number for you tomorrow PM

Sounds to me like the cam is a bit retarded, rather than the mechanic.

Sorry , couldn't help that one.

Mike,

I tend to think it's the mechanic thats retarded!

I'm in the middle of a house residing/remodeling project, but as soon as I get done with it I'll borrow one of the movies from ya and degree it when I can get some extra money around


Thanks,

Doug

 

[Anonymous]

Doug;
...back to the comment that '..advancing it more makes it miss...'..
Do you have the T-shaped rotor end in your dizzy? Reason I ask: the ones from the DII systems allow a wider range of adjustment only if you get the ones with the T-shaped end: a straight, narrow end is stock in early DII dizzys. Example: the "straight" one that came in my Fairmont only allowed for 50% spark contact on the towers when set to 10 degrees BTDC, but 100% contact at 6 degrees. At 12 degrees or more, it ran poorly because there was so little spark contact 'time'. I switched to the T-shaped type and I can dial in from 0 degrees to 22 degrees BTDC now with at least the 50% contact at the extremes that Ford considered normal (10 degrees BTDC is the underhood decal setting - that only gave 50% burn pattern on the towers).

 

[Anonymous]

I`m Glad you`r gettin it running good how much more power do you think you`r making now with the rebuild ? How about some pics with the engin in the car ?

heres a pic of the engine in the car and running,

Mark,

I checked and it has a "T" shaped end on the rotor. Actually its a NOS rotor & cap I got off ebay

Actually, its running pretty good now. I swapped the 4.5 power valve to a 6.5 power valve because you could feel it surging under load at part throttle.

Its still a tad soft coming off the line....I might get a new 350 cfm carb to throw on it just to see how it runs compared to the 500 cfm carb

Later,

Doug

 

[wsa111]

Doug, if the engine runs as good as it looks you have a real winner.viagra comes in second the way your engine looks. the power valve you chose should be very close to what you need.
If you try the 350 cfm carb try it as it comes out of the box then put in 59 jets with a .028 discharge nozzle, just for a comparision. As i said before holley does make a bowl with removeable plugs in the lower part of the bowl for instant jet changes with their special jet screwdriver.
Anybody who has a holley 2300 should get the holley parts book just to see the fantastic selection of accessories. plus don't be afraid to pump 7 pounds of fuel pressure to the carb. this is not a weber.
with this engine i don't think you would see a lean-out condition at top end due to inadequate fuel delivery like my 415 small block chev el camino.
Just remember if you keep having to richen up for top end performance it could be a fuel delivery problem-don't want to get off subject. 10-4 william