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Topic: 88 sport rebuild , need advice (Read 30971 times) previous topic - next topic

88 sport rebuild , need advice

Reply #240 –
Quote from: TOM Renzo;420831
Clearly @130 something is wrong! But how many times did you crank the engine to do the test?? Normally a compression test is useless as a LEAK DOWN is what should be dun. As far as a wider seat that means nothing as many cars use a combination 44-45* valve cut. So without a leak down that cylinder can not be determined to have an issue as with a valve or ring issue. You need leak down numbers not compression numbers.

Normally i use 30* valve jobs years ago as that flows better than 45* at the lower RPM BAND. But with 3 angle valve jobs and 5 angle valve jobs 30* cuts are not normally used. Also having a wider seat on the intake is MOOT. The Exhaust needs a wider seat to dissipate the heat of the exhaust valve to the head for cooling the hot exhaust valve. This is a simple explanation. Valve cutting is a science in it's entirety. Also did the machinist vacuum test the valve JOB???


Note to confirm a tight valve on position 5 loosen the rocker and then take a compression reading. If it corrects the issue the valve is to TIGHT!!




, i didnt think of that.. should have seen if we could finagle the valve cover off the drivers side to shuck back the rockers a bit and check that.
thanks,, and noted next time mason comes home.
i did tell him to get a leak down test, my home made one is down.

in normally crank till the needle stops jerking,, and tops out just so you know.
i also do a compression test with no spark plugs in so it doesnt wear down the battery as quickly along with unplugging the TFI & coil input
This way the injectors wont dump fuel,, good idea eh?

88 sport rebuild , need advice

Reply #241 –
I had a local guy do a valve job on my Edelbrock heads a few years back because the guy I always used before that was over 8 hours away after I moved to Texas.  After putting the heads back on I checked the compression and was having all kinds of erratic numbers.  Called my buddy back home and on his advice sucked it up and bought a MAC leak down tester and found the problem...5 bent valves.  Shipped the heads to my buddy back home and a couple of weeks later all the problems were gone.  Lesson learned, not all machinists are created equal and some just outright suck.

Good luck with the compression issues but I think Tom is on to something with the rocker arm possibly being too tight.  Hopefully the machinist did not overlook something with the valves but after all the BS you two have gone through with this build it would not surprise me one bit.  I hope I am wrong and the rocker is just a bit on the tight side.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

88 sport rebuild , need advice

Reply #242 –
Do you have a vacuum gauge handy? If so you can hook it up to the engine and check for a leaking/sticking valve. See here: http://www.secondchancegarage.com/public/186.cfm

As reference the engine in my Thunderbird pulls down 17" of vacuum at idle, the stock HO in my Mark VII pulls down 18". The engine in your son's car should pull down between 17-18 or so, being that it has a stock HO cam.

BTW I see you got rid of the Ford blue paint on the Explorer intake I sold you. Looks good.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

88 sport rebuild , need advice

Reply #243 –
Yeah he painted it but it does look really good

The car isn't here but when it gets back with my boy I will do the test

88 sport rebuild , need advice

Reply #244 –
, son called and about croaked.

oil presure shot up to near 90%  and the temp went up as well.  first thought was instrument panel conflict but he said no, the engine was struggling.

he had to run it like that for about a minute before he could pull over. he stopped and restatted and problem solved.

sketchy spooky !

the machinest said the mains were very tight, just a little under .001.
thats why we are running 5w30 now,, maybe he can go thinner for a while.

runs fine thought!  lol

what a pita

88 sport rebuild , need advice

Reply #245 –
Jay i did not want to worry you but those clearances are in spec but to tight for me. Normally i run .002 on the mains and rods. If you run those tight clearances the oil can not take the heat away from the journals. You need a certain amount of bleed off to remove the heat. Just saying!!

Try 0W20
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

88 sport rebuild , need advice

Reply #246 –
Agreed. clearances are on par with modern OEM stuff, seals and gaskets are new, galleys are clean, pump is new; no reason NOT to run a 0w20 synthetic.  Or even a 5w20 semi synthetic (like Motorcraft).  I'd stay clear of conventional, but I'd put you in the 5w20 range (0w20 if it were me).

88 sport rebuild , need advice

Reply #247 –
I would have that engine regone through by a reputable engine builder and give the guy who did the work the tab.  I would not feel comfortable with it, all the trouble you have been having.

I was always told for break in oil and first oil change to use dino oil and not synthetic to help rings set properly.  Any theory behind that?

88 sport rebuild , need advice

Reply #248 –
Quote from: jcassity;420966
, son called and about croaked.

oil presure shot up to near 90%  and the temp went up as well.  first thought was instrument panel conflict but he said no, the engine was struggling.

he had to run it like that for about a minute before he could pull over. he stopped and restatted and problem solved.


sketchy spooky !

the machinest said the mains were very tight, just a little under .001.
thats why we are running 5w30 now,, maybe he can go thinner for a while.

runs fine thought!  lol

what a pita


My gauges would do that and then drop back down on their own.  I put aftermarket in to keep a better eye, along with stock gauges. Is your TFI breaking down causing it to start struggling after driving?

88 sport rebuild , need advice

Reply #249 –
Quote from: beast50;421007
I was always told for break in oil and first oil change to use dino oil and not synthetic to help rings set properly.  Any theory behind that?

That's BS.  You working on out of date information.

88 sport rebuild , need advice

Reply #250 –
updates on compression numbers
i was able to get some readings yesterday along with fuel presure which was fine.
seems things are changing to a little better, still has less than 500miles on it thus far.
im glad to see cylinder 5 doing better, but there still is a fairly wide spread on the numbers.,, cylinder 5 techincally still shows trouble state but lets give it a few more miles.

1 - 160
2- 160
3 - 170
4 - 160
5 - 150
6 - 165
7 - 168
8 - 170

88 sport rebuild , need advice

Reply #251 –
Cyl 5 is coming around a bit but still LOW. It shows improvement as all the cylinders do with a new engine. That is normal. The engine is broken in by now with 500 on it so those numbers wont change to much from now on. Unless the valves were not ground properly. Time will tell. Once again a leak down is always better just saying. Other than that how does the engine run. You said it still has some issues. Thanks

1= 150
2=160
3=160
4=150
5=130 >> retest when hot = 118
6=150
7=150
8=150

1 - 160
2- 160
3 - 170
4 - 160
5 - 150
6 - 165
7 - 168
8 - 170

As expected the numbers do not pan out. One was higher before the 500 Miles and now some are higher. That is why a compression test is useless and not good to evaluate an engine. The numbers show that no question bout that. I never use a compression test for comparison or evaluation. It is to unstable a test and i have found it un-reliable
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

88 sport rebuild , need advice

Reply #252 –
Have you stuck a vacuum gauge on it to see if it has a sticky valve or sealing issue?
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

88 sport rebuild , need advice

Reply #253 –
A brand new engine or better said a rebuilt one with a sticky valve??? Not happening. As a guide fit to tight would show up almost immediately. I am assuming the machinist installed guides. Most times 99% of older heads need guides and inserts are the fix. Normally i do not use inserts or knurling. Inserts are good but normally on cast head i use OS valves and go from there. But a hung up valve i do not think so. If one or many of his guides needed inserts that means most likely the stems were questionable anyway. So new valves would have to be installed. If new valves had to be installed a set of OS ones would be the logical FIX. If a guide was to loose it would only get worse and that is easily identified. Using a Vacuum gauge is ok i guess but a little antiquated at best.  But do it and see what happens. Better test the leak down that is the true test of a good sealing cylinder!!

Note normally a machinist will fit the guides LOOSE is my experience. It depends on the machines they have and how accurate they are. Being on the loose side is insurance for them so a guide seizure does not happen. Personally the engine in question is broken in and the numbers are the numbers. I do not think they will change much other than carbon build ETC. Also app 75% of valve heat is transferred from the seat and the other 25% is from the guide. So guides are very important. There fit is very critical at best. Also modern stem seals can be to tight and not allow sufficient amounts of oil to reach the stems. A lot of machinists can get hung up ion valve seals that are to efficient for a performance engine. One has to remember the guides need oil and some must pass by the seals. To much and the engine will smoke to little and the guides will seize  up. Once again a subject that is complicated  and is sometimes taken for granted. The build sheet should show the stem clearances and type of seals used. And also the type of guide used. There are several types of guides and all are not equal. Guide clearance is very evident when a PORSCHE engine is started or for that matter any high performance car you talk about. When started cold they smoke. Every performance vehicle like Porsche will smoke on start up from stem seal oil seeping in to the cylinders. To much and the cats will clog. To little and they may seize up. It is a delicate balance. Personally i never reuse a valve i always replace them. Reason being they will always have to much wear on them and that can play havoc on a new valve guide insert . Thanks
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

88 sport rebuild , need advice

Reply #254 –
A vacuum gauge will tell him if he's got a valve hanging open or not sealing. It's possible either the rockers on #5 are miss-adjusted or the valve is not sealing right. That would show up on a vacuum gauge as a vibration of the needle. My guess though is possibly a not so good ring seal on #5. I doubt that the engine has a head gasket issue as there would be other signs of that.

A leak down test would be better but if he doesn't have the equipment a vacuum gauge will work in a pinch.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.