Major Setback In My Build....

86lxhatch

86lxhatch

Active Member
Nov 14, 2011
113
0
26
East Tennessee
#1
So I finally made it to the point where I could mock up my heads on my motor, and begin checking my piston to valve clearances. I got a set of 1.7 Crane roller rockers off a 93 cobra(oem) and mocked up the heads, valve springs, and rockers, etc. I have heard that I must maintain at least 0.100" of clearance on my intake and exhaust valves during the engine cycle. Well, long story short, I'm running way too tight on my p-t-v clearance. I used a new head gasket, laid one of the heads on, installed light weight check springs, and finger tightened two head bolts to secure the head enough for testing. I also used the comp cams adjustable pushrod checker to find the right pushrod length. Then, I hooked up my dial indicator, and the testing went as follows:



Checked my indicator at these points in the stroke:

20 deg. before tdc and got a reading of 0.264" (okay, I'm thinkin that's good!)

15 deg. btdc- 0.202"(okay, still truckin')

10 deg. btdc- 0.151"(gettin concerned a little)

5 deg. btdc- 0.106" (uh oh...:( )

0 deg. TDC- 0.075"(oh no!)

5 deg. after tdc-0.051"

10 deg atdc- 0.042"

15 deg atdc- 0.047"

20 deg. atdc- 0.074(so then it opened up wide again after that)

So I repeated the test again, and unfortunately yielded the same results +/- 0.005"

How do I fix this???? I am running the cam advanced 2 degrees, and I think if I retard it 2 degrees, it may help some, but I am not sure if it will be enough.....I need advice!!!:bang:

Oh yeah, I am also using the sealed power/felpro gasket set #260-1169 from sumitt, but it does not specify what my head gasket thickness is...
 
#2
What cam are you running? What heads are you running? Has the block been decked, have the heads been milled? Generally its recommended .100 for the exhaust side and .080 for the intake side. Are you getting these numbers consistently from both sides? Also, you should use an old, compressed gasket when checking. I also torqued my heads down. You want to mimic what the real setup will be like. Did you used a solid lifter or modify the stock one to solid? Hydraulic lifters have to pump up during operation, so a bled down lifter will give you inaccurate readings.

You might could fudge the numbers just a bit as long as you have a well setup valve train with good springs. Valve float will hurt you if the valves are staying open when they should be closed.

Joe
 
#4
I am using gt40p heads. I am not sure if they have been shaved or not. The block has not been milled, and I am using a b303 cam. I also used a hydraulic lifter that seemed to be pumped up...i.e. the plunger was at the top right up against the c-clip at the top. I couldn't find a solid lifter to use. Where do I get one that is correct for checking?? I also used the new gasket, so my numbers should have shown more clearance, rather than less, because I didn't compress the gasket.
 
#5
Check out my write-up, I documented checking P-to-V clearance using the clay method. I prefer this method over the dial method because it gives you a better visual and a more 3D view of your P-to-V clearance. With 40Ps and a B cam, I have a hard time believing you are running out of clearance. Do the clay method, and make sure you have everything right. Converting a stock Ford lifter to solid is SUPER easy. Take one apart, and you'll see exactly how to do it. All you need to do is pull out the retaining clip, remove the guts, and reassemble it without the spring and with the plunger upside-down. Just be careful, because the clip is under pressure and WILL go flying around the garage if you don't catch it. Also be careful not to scratch or gall up the moving parts.


http://www.stangnet.com/mustang-forums/threads/checking-piston-to-valve-clearance.837135/
 
#9
It's an 86 mustang with an E5 block, which I am converting to roller using the link bar roller lifters. I am also using these pistons- http://www.summitracing.com/search/?keyword=ZL2488F30&dds=1

So I got a wild hair last night and decided to check the other side of the motor. I repeated the above procedure and got the same results. I am indeed out of room. Even if my dial indicator is off some, it wouldn't be off that much. Do you guys think retarding my cam will fix this, or how about switching to some 1.6 roller rockers?(I really don't want to do that!!) The pistons I am using do have valve reliefs, so I agree with the previous statements about how I should have plenty of room in there. I'm seeing about .515" total lift +/- .005" on the cam with the 1.7s.

Thanks for your replies guys. I really hope I can get this straightened out by this weekend, as I am trying to get ready for the efi setup and transmission/motor installation...

I'll also try the clay method today and see what it looks like...
 
#11
Those are forged stock style replacements. You should not have a problem with clearance. Like Nik said, try the clay method. I haven't read his write up on this method, and he may have covered it, but rub a light coat of oil on the piston and the valves. This will help keep the clay from sticking.

Joe
 
#12
I take it this is all on the intake valve?

I seriously doubt changing to 1.6s will do you much good. At or near TDC, the B cam is only lifting the tappet a hair over .050", which is .080" at the valve for a 1.6 rocker, and .085" for a 1.7. So you're talking about .005" difference between the two, when according to your measurements you need to make up 10x that in clearance. Granted, it looks like your worst point is around 10 ATDC, which the B cam will be further into it's lift at that point, which means there would be a proportionately larger difference between a 1.6 and a 1.7, but it still isn't anywhere close the ~.050" you need to be into a safe amount of clearance.

Try installing the cam straight up (or even retarded) and see how much that affects your numbers. Also, try converting those lifters to solid (being aftermarket link bar lifters, I don't know if the conversion process is as easy as it is for stock Ford lifters), and give the clay method a go. Also make sure you're not doing anything that would skew your measurements, like preload on the valve, etc. Make sure you're using a compressed (used) head gasket.

Have you tried measuring combustion chamber volume to see if the heads have been milled?

If all else fails, you could cut larger reliefs in the pistons.
 
#13
Nik- yes, all of the measurements were taken on the intake valve. I'm going to retard the cam back to "straight up", and re-test. I think that should help out my clearance some. Thanks for the help..I really appreciate it.

I'm gonna convert two of the lifters to solid, like you mentioned earlier...
 
#15
Joe, I've been working a lot of hours the last couple days, but I'm gonna work on it today. I called sumitt and found out that the head gasket that came with the gasket set I bought has a compressed thickness of .040". I'm gonna retard the cam and retest, and also use the clay and see what I get...I think if I can get it to around 0.070" at my closest point on the stroke, then I can probably get by with the Cometic gaskets I saw that were 0.075" thick...either way, I'll post the results good or bad...I'm glad I checked my clearance before putting this motor in!! I would've definitely regretted it....I mean instantly!!
 
#16
Okay, so I got it figured out!!!!!! I did the clay method after I retarded the cam back to "straight up" 0 deg. and got a clearance of 0.100" on top of the uncompressed head gasket. So I measured the gasket itself, and it was at 0.060" thick. The gasket has a compressed thickness of 0.040", so I will loose and additional 0.020"-----so
my measurement with the uncompressed gasket 0.100"
after I torque the head and compress it I loose - 0.020"
Which leaves me 0.080" of clearance...a little too close for my comfort, but here's a pic of the clay method in action--
SSPX0011.webp


SSPX0008.webp


So I retarded the cam again, this time -2 deg retard, and got a measurement of 0.150" on the intake side, and 0.170" on the exhaust side-and the impressions on the clay looked a lot better...it was a slight indention, rather than a full on "crush"....here's another pic of the final test...
SSPX0012.webp

So now, even if I loose the 0.020" when I compress the head gaskets, I know I'm still in great shape!!! The total valve clearance is now good, and the eyelit (valve relief circumference) check is also good to go....now to bolt on the heads!! and, of course, another pic...
SSPX0014.webp


Thanks Nik and Joe for the advice and help:nice:
 
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