88 sport rebuild , need advice

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88 sport rebuild , need advice

Reply #255 – September 09, 2013, 05:57:52 PM

The valves are POSITIVE STOP for adjustment. That should have been checked. But that cylinder is still low and that reflects on the MACHINIST. His machinist should have dun a vacuum test on the valve job. Or the rings in that cylinder still did not seat. What kind of rings were used???

88 sport rebuild , need advice

Reply #256 – September 09, 2013, 06:55:38 PM

Could be somthing as dumb as a weak valve spring

88 sport rebuild , need advice

Reply #257 – September 09, 2013, 08:10:50 PM

Doubt it as cranking compression is normally not effected by weak springs. Weak springs are normally a cause of lifter pump up at higher RPM. Turbo coupes are notorious for that. Once again the springs should have been replaced or at least checked.

88 sport rebuild , need advice

Reply #258 – September 09, 2013, 09:16:03 PM

ok, i reviewed the posts and ill combine my answers.
I thank you all for offering thoughts, it helps me fine tune how i go about finding out what is the deal with cyl 5 and perhaps other cylinders.

machinest did not do any assembly.
he did not do a presure test
he did not put the heads on the block to perform any leak down test.
he did insure my PTV was ok.

i assembled everything
the machinist did put in new valve springs which gave us about 105lbs seat presure.
the machinist did cut in new intake and exhaust sets .. for some odd reason,, not sure wy but he said he increased the cross sectional area of the 45deg angle to increase heat transfer.
The machinist did install new bronze guides on the intaake only i believe, but you can see them on the pictures i posted previous to this page,, way back on prob page 20(ish).

so i put everything together.

I did not know you could use a hand pump and pull a vac on a cylinder like that,,, if this is what you mean by using a vac gauge.
if you mean use the vac gauge at idle, and look for a jittery needle, then i stand corrected.

the car runs very well, has a slight miss which is *NOT* an injector or a spark plug
The miss we experience is on the passanger side and we swapped injectors and plugs which yields a miss still on the pass side.. ironically cyl 5 is a driver side so go figure.
Oddly enough the pass side is also higher compression.

again this is a minor miss that **********DOES**** come and go depending on the rpm.
the miss will go away if you simply add more gas.

I like the thougth about the guids and binding up the valve itself.
motor heats up and the guide swells a little and sorta binds up the valve...

what we are or were goign to do is dial in TDC cyl1 ,, then add air to this pot and watch the air needle drop and record the time.
we would wash rense and repeat all cylinders.

ill report back,, call me if i missed an answer i owed you but,, i certainly want to nail down this imbalance issue i see on compression.

by the way************* the motor has 563miles on it thus far.

thanks.

if someone can explain the "pull a vac" part and explain to this wv boy, id appreciate it.

88 sport rebuild , need advice

Reply #259 – September 09, 2013, 09:59:27 PM

does the spark plug look normal in #5 like the others?

88 sport rebuild , need advice

Reply #260 – September 09, 2013, 10:08:24 PM

yes it does,, i looked at that on saturday when i drove over to va to help mason do some work on it.
i do have to say it appears the cylinders are burning fairly hot,, not sure if we have hot plugs installed or not,, cant tell by the motor craft numbers,, its easy on the auto lites to tell.

im putting money on something mechanical so mason is going to schedule a leak down test with someone this thus,, i told him to get his ass on here and chime in and take over this (his) thread...! lol.

88 sport rebuild , need advice

Reply #261 – September 09, 2013, 10:55:40 PM

Here is what you need to do a good valve job. I test every head. Nothing beats this test for sealing. Normally i grind the seats @45 1/2 * and the valve @45 This makes an interference fit and seals the valves as good as it gets.

88 sport rebuild , need advice

Reply #262 – September 09, 2013, 11:01:47 PM

Pull vacuum just means to check what vacuum reading, how many inches of vacuum your engine makes at idle. With the stock HO cam and GT40 heads/intake I figure it should make a steady 17 or 18 inches of vacuum at idle. For instance the stock HO in my Mark VII makes 18 inches of vacuum at idle, my Thunderbird makes 17 inches. Both of those readings are at a 700rpm hot idle in park. You can use a vacuum gauge to see if any internal problems are present with the engine. This is a handy guide with animations to explain different readings: http://www.secondchancegarage.com/public/186.cfm

As a FYI GT40/GT40P cylinder heads use Motorcraft AGSF32C spark plugs. That's what I was running in my Thunderbird when it had GT40P heads.

88 sport rebuild , need advice

Reply #263 – September 09, 2013, 11:06:52 PM

This is what i am talking about, a vacuum testing bench like this i test every valve job i do this way my vacuum fuel pressure gauge has been in the back of my tool box for 30 YEARS. I basically never use it. Not in a very long time. If a valve job is vacuum tested that is all that is needed. A vacuum gauge has it,s uses but a new engine should not have any issues whatsoever. That is why you rebuild them !!! Below is a vacuum test bench every machinist should have!!

http://www.youtube.com/watch?v=8kKNWSjAy9I

88 sport rebuild , need advice

Reply #264 – September 09, 2013, 11:22:40 PM

You can buy the plates and use your AC vacuum pump to check valve jobs and valve leak down. Get a thick plate of glass and some thick semi firm foam to set the head on and use your spark plug air adapter to apply vacuum. If it holds you are golden. But from your post you assembled the heads RIGHT? well did you check the guide clearance? You should have as when you do a head you have to custom fit each valve to the head to get the proper clearances. This is called select fitting. Well either way the engine is dun
http://www.goodson.com/Pistol-Grip-Vacuum-Tester

88 sport rebuild , need advice

Reply #265 – September 10, 2013, 07:50:03 PM

again tom,, did not assemble the heads..... you seem to skim over posts,

88 sport rebuild , need advice

Reply #266 – September 10, 2013, 07:52:29 PM

can i pull a vac with a hand held vac gauge with a cylinder dialed to tdc both valves closed to detect a seal?

granted the end gap on the rings ould bleed the needle down but i could observe the delta between cylinders to arrive at a conclusion?

88 sport rebuild , need advice

Reply #267 – September 10, 2013, 08:51:42 PM

NOPE!! Leak down test. Sorry i thought you built the heads. My mistake.

88 sport rebuild , need advice

Reply #268 – September 23, 2013, 05:44:53 PM

Guys,
son came in for my birthday yesterday.
Today we were able to get leak down numbers.

i presurized the tester.. dialed in the adjustment to "zero" out the guage and the second guage usuall fell at 100lbs.

so upon connecting up the hose, sometimes we lost some air presure but anyway, that is the reason the psi numbers are a little different.. i think.

anyway.... in HO firing order

cyl 1 @ 86psi= 17% loss
cyl 3 @ 89psi= 18% loss
cyl 7 @ 82psi= 20% loss
cyl 2 @ 83psi= 18% loss
cyl 6 @ 84psi= 18% loss
cyl 5 @ 80psi= 42% loss (hearing air out the tail pipe
cyl 4 @ 89psi= 19% loss
cyl 8 @ 84psi= 18% loss

thoughts?

88 sport rebuild , need advice

Reply #269 – September 23, 2013, 07:22:24 PM

Mine did the same thing after a "valve job" by a reputable machine shop. I kept the leak down tester hooked up to each cylinder and used a dead blow to tap the top of the valves with. On every one of the valves that leaked doing this changed the leak down numbers. I'm not saying yours is a product of bad valves but this would help point you in the right direction.

Darren