Ford Fiesta Valve Spring Pressure

[Rick Starkweather]

Sorry to bomb the broader list (versus just the Ford Race Cars), but I need some information...

Was checking the valve lash on my LPHP (previously IT) Fiesta over the weekend. The valve spring pressure is ridiculously low! No leaks (97-98% on all cylinders doing a leak down) but I can open the valves with my thumb! I'm new to the Fiesta (and to Limited Prep) but this does not seem kosher?

I suspect I'm looking at valve float at fairly low revs -- though in my first race in the car a couple of months ago at Road Atlanta I did not notice it.

Help?

Rick

[quadzjr]

do you have a way to check the seat and or open pressure of the spring? when you say opening them.. can you hold them open with your thumb? They have very low valve spring pressures form the factory. And as long as you are not expereinceing valve float I would run them. It is always my strategy. they lighter and smaller vavle spring components the better. the less force to open them.. the one main reason to install stiffer springs.. (illegal in IT but used often in prod motors I have built). allow you to rev your engine higher with larger cams before valve float begins.

The valve spring pressure will not influece the leak down test. There should be a minimum service pressure in your user manual. It is a good idea to maintain over that. if you have variances instead of buying new wprings provided they are not far off you can shim them.

Are you running a stock cam? You can PM me for specific questions If you would like.

[Rick Starkweather]

Steven:

The leak down wasn't to address the springs. It was to make sure I had not done any damage.

I agree with your proposed fix. Unfortunately, I don't have time to try to tackle this before the next race. So, I'll check into mimimum spring pressures and see if I can get by for one more weekend.

I'm running a Kent A3 cam. Lift is limited to LP specs, but the power curve is supposedly shifted to higher rpm. I rev'd the motor to 7200 rpm with no evidence of valve float.

Thanks for the cautious vote of confidence to go ahead and run the car (maybe with some more strict shift points).

Rick

[quadzjr]

If you are not experineceing vavle float.. Then I would say you could probably get away with it. however with weak valve spirngs, custom high lift cams, and high reving motors do not lie each other. The sacarifical part is the valve springs. IF yo udont' hear the valves and dont' feel them floating either. Then the only other way that I know of is with a high speed camera. You have one of those right? haha..

Good luck on the next race.. are you going to prodfest?

[jimbbski]

I have built a few 1.6 Kent engines for my old ITC Fiesta. A set of new stock springs will work well up to 7000 with the stock cam. I didn't rev it that high often as it didn't make power there but I never had valve float. Your cam has more duration and lift and the fact that you can push the valve open by hand says they are weak.

Do a search and you will find some info as to what spec springs you should have with that cam. Even stock "Formula Ford" springs would be better then what you have now.