This is topic Valve ClearanceProblem, Need Experienced Help!! in forum Tech Talk at Northern California Ford Owners  .


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Posted by LAST302 (Member # 808) on :
 
I have a 95 and last year I put on TFS heads, cam, upper/lower, 1.6 rr, etc, all he bolt ons. This year I put a vortech s-trim on the car. I blew a head gasket so the heads had to come off because I did a little damage to one of the heads. The machine shop called me and said that I had 6 out of 8 bent exhaust valves. So I checked the pistons and they have ben tapping the valves. When I put this motor together TrickFlow said that I would not have a problem. Read my profile below to see the exact parts I have. What would be the cause of this piston to valve clearance problem? Trick Flow also said when I called them that I should check the cam to be sure that it is the right one. What is the largest cam that will work with stock pistons and these heads. If I have a different cam other than the stage 1 that I am supose to have,is that the problem? I have TFS Twisted Wedge heads, TFS cam(221/225@.050 .499/.50 lift), 1.6 rr, 6.700 push rod length. Any experienced advice would be much appreciated because I am at a stale mate and I have all the parts and the heads are done but I cannot put he motor back together until I find out what caused the clearance problem. [Confused] [Confused]
 
Posted by TheWrathof5.8 (Member # 436) on :
 
Wow! I would never have thought. I have seen 0.530" lift on a cam similar to yours. Is your cam retarded? This may cause this problem. Also, don't overlook spring tension either. You could have b**** slapped a few pistons this way too.

Also, this is what I do when assembling a new engine for valve clearance:

1. But a soft checker spring and install on the intake/exh valves of one cylinder.

2. Put the head on with no gasket and gently tighten 1 or 2 head bolts down.

3. Measure the clearance at different points of camshaft rotation. IE, push the valve up and down and watch the micrometer. Do this for the exhaust valve after your intake valve is starting to close. You could use clay as an alternate and add a used gasket for simulated clearance.

4. If you exceed your specs, 0.100 and 0.080 on intake, you gotta change cams or flycut those pistons.

What are the numbers on that cam? open/close points. I'm curious if its 4 degree ground advance or not.
 
Posted by shade-tree (Member # 298) on :
 
it should have worked.
my guesses include:
*rocker arms too tight causing valves to hang 'open' which then battered your pistons in spite of the fact that they would have cleared if the valves were 'closed'

*cam installed wrong

*timing chain fubared or slipped
 
Posted by 67stang (Member # 549) on :
 
I never understand posts like this... I mean, it takes 25 minutes, tops, to check piston to valve clearance. No matter how many people you call, how many guesses guys on this board make, and how many other people claim to think you can run "X" lift with "Y" heads and valves.... you still will never know for sure until you check it yourself.

Don't get this the wrong way, I am not trying to cap on you... but sooner or later, if you are serious about building/modifying engines, you must learn to do the basics.

This article may help you:
http://66.96.130.106/archives/1999/10/ptov/index.shtml
 
Posted by LAST302 (Member # 808) on :
 
67stang--Believe me, when me and my friend(currently has worked at a GM dealership for 16 yrs, his father, 32 yrs) put the motor together valve clearance is something that we went over more than once. That IS why I made this post. We had the clearance when the motor was put together but when this problem erupted, I found this out. I have had more people than not tell me that TFS wedge heads require flycut pistons. Can anyone else confirm or deny? Trick Flow says no but alot of engine builders with knowledge of 302's say yes.
 
Posted by LAST302 (Member # 808) on :
 
Cam- advertised duration:275/279

Duration @.050: 221/225

Cam lift: .312/.319

Valve lift w/ 1.6 rocker: .499/.510

Cam timing @.050: (opens intake 3.0 BTDC
closes 38.0 ABDC)
(opens exhaust 49.0 BBDC
closes 4.0 BTDC)
 
Posted by PunkINa5.SLOW (Member # 10) on :
 
Scott you can do all the piston to valve clearance checking on the planet and it isnt going to do you any good if you have a weak set of valve springs or you are adj the rockers too tight.

There was so much clearance when I checked a decked 5.0L with decked TFS heads and a 38 gasket using that same cam with 1.6s that I dont see why it didnt clear, but yes every motor is different and you should check.

I say weak valve springs.
 




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