I need to find about .025 intake valve clearance on my BBC.
My machinest told me he could sink the valves into the seats by cutting the valves, or possably cutting the bottom side of the valves.
Or he can have the pistons fly cut for valve clearance.
As it is I have .066 with a .051 head gasket, I thought if I have him cut I would just go .010 more and use the .041 head gasket (I allready have).
The other option is to change cam to a smaller lift "from XE284 .574 to XE274 .552", I allready have the XE284.
Everything is new, pistons TRW2399,GMpink rods, Edelbrock heads 100cc ect......
What do the experts think is the best for the money invested way to do this?
Any advise or input would be greatly appreciated.Thanks T.C.

Is that .066 an intake figure or exhaust?

Try retarding the cam 2 deg. and see how much you pick up.

josh said what i was going to say.......i dont like messing with fly cutting and sinking valves or using head gaskets to make clearences. best bet would be to degree the cam to make sure its not screwed up from the factory and causing the close interference. play with the cam timming. this would provide the clearence your looking for.

when a camshaft is advanced, intake-valve clearence at the piston decreases and the exhaust-valve clearence increases.

the safety margin is around .100 on the intake and .125 exhaust on the clearences

for me it hard to imagine that your that close to start with. something i think isnt right. im kinda thinking that cam is WAY to far advanced. whats the clearence for the exhaust side?

i have not delt with XE profile cams....the last time i have seen anything to close was a 262/273 @ .050 cam with .561 lift with it advanced 8 degrees (on top of what was already ground into the cam). which at this point it was close enough to kiss the pistons.

Tahnks for the replys:

It is the intake side thats the problem.
I would have to recheck the exact degrees but it's around 5-15 after TDC. Looks to be on the ramp coming onto the lobe.
The exhaust has so much clearance it's not even worth measuring
I have doubble checked to make sure the cam gears are in the correct place.
Although when I bring the motor to TDC using a dial indicator the dots on the gears are slightly missaligned?
I figured this was the advance ground into the cam ?
I guess I better degree the cam to be sure it's rite.
T.C.

The cam grind will have nothing to do with how the dots align. They're supposed to line up when the piston is at TDC. If they don't, the chain and gears are assembled incorrectly. If the cam is advanced by one link of the chain compared to where it supposed to be, that would account for your situation.

Check your chain installation first. All the rest is a waste of time if the motor is actually put together wrong.

"The simplest explanation that fits all the facts is usually the right one."
— Occam, ancient Greek philosopher, from back when timing was acomplished by gears that meshed

The gears and chain are correct,I degreed the cam today and It checks out correct.
I'm not sure that even changing the cam would help as the problem is on the ramp not at total lift?
I am not sure a cam with less lift would be smaller at the point where it needs to be?
I guess I need opinions on the fix, either cut the pistons or valves.
Or take timing out of the cam?
Or put it togeather anyway?
I have a mechanic friend who said the lifter would be compressed at that point by at least .020 so it would never come into play?
Any suggestions or advise is welcome.
T.C.

TC,
You are correct, cam lift has almost nothing to do with p/v clearance.
The valves are closest on overlap with the exhaust being the most important regarding clearance as it is closing & If it floats or bounces it will get smacked.
The intake is opening & as such is under much more control but it will not collapse .020 at this point.
If you want more clearance I would either cut the pistons or retard the cam a couple of degrees & see what you have.
How far advanced is it now? Should be 4 degrees if it is in on the marks.
Absolutely do not sink the valve, it will hurt low & mid lift flow a bunch.
With all that said, I do not have a problem running the intake at .066, I have run them closer to over 7500 with a solid with no problems but you should check them all to be sure you don't have one piston higher then the one you checked.

Thanks for the reply Wolfplace:
I'm sure the cam is 4 degrees advanced thats why I thought the timing gear dots were off at TDC.
I really dont want to mess with the heads and I would rather leave the cam timing as it was ment to run.
Fly cutting the pistons will get expensive but sounds like the best way if I want more clearance.
(what do you get to fly cut?)
The motor will never see 7500 (not intenionally anyway) the cam is only good for 6500 xe284 and I will be using a MSD so the rev limit will be set.
This is going to be a street,show,ocasional strip, hot rod car.
So It wont be seeing 5000 or 6000 every day,I would just hate to miss a shift and trash the motor.
Thanks for the advice.
T.C.

I think the cost varies a bunch depending on area but for rat pistons I charge $12 ea in sets for intakes or exhausts & $20 ea in sets for both intake & exhaust

Isky rents a cool little DIY tool called a Piston Notching Tool that will cut them in the block.
I don't remember what it costs & haven't personally used one but have been told it works pretty good.
It looks like a valve with cutters on the face & goes through the valve guide & is run by a hand drill.
You might give them a call.

The isky cutter runs about $125 for the cutter and the shank. Go to their web site and you can buy direct from isky. I tried another cutter from another source at one time, and it didn't work worth a crap, but from what I here the isky works real well. The shank fits down trough the valve guide and the cutter spins onto the other end. You turn the cutter by hand, and be sure to tape up the top of the cylinder to keep aluminum from falling down into the cylinders. As wolfplace said though, as long as .066 is your tightest cylinder I would say it is ok. When the engine is loaded with your real springs (assuming you are checking this with a checker spring) you stand to gain about .010 anyways due to valve train deflection. If you don't believe this ask David Reher of Reher-Morrisons as they only check P-V with the engine fully loaded. I have one cylinder on my BBC that was a little tight like this. It checked .050 with the checkers and when the engine was fully loaded with my roller springs the clearance was .060. I cut about .018 off the face of the valve to get it to .078. This engine sees 6400 every weekend. I have heard of stock eliminator guys running intake clearances as tight as .040 in their 7500 rpm rides with no problems.

Thanks again for the replys, I will take your advise and check all the intakes.
Yes I am using the checker springs so if I gain .010 with the doubble springs that would put me at .076.
Thanks for the tip on the cutter, if I'm not happy with what I end up with I'll go that route.
T.C.

Bad news for me graemlins/angry.gif
I only got as far as the second cylinder on the left side and had NO clearance at all?
Mabe .002 if that.
I hope that tool from Isky is a good one and will cut a .040 notch? :confused:
T.C.

Before I cut those pistons,wait awhile for more people to see your thread,there has to be someone who has run that cam and heads before.The reason I say this something just doesn't seem right,I can't beleive you are that close.Imformation that I could find on those pistons say they have a dome hieght of .095 and a volume of 13.8 cc and that's a small cam to be having interferance with.My pistons have a dome hieght of .340 and 33.0 volume,cam is 255/263@50 lift .612/630 and I had plenty of room to spare,cam was degreed to 106 icl.I have not run the combo you are but I would hate for you to ruin a set of pistons only to find the problem lies somewhere else. graemlins/waving.gif

Thanks for the reply JRS70LS5:
Nothing is going to happen very quickly here as the Isky rep. told me the tool they have is only for cutting the eyebrow larger in dia., it's not for a plunge cut. Has anyone here used this tool?
How did it cut? Can I get .040 out of it?
So now I'm kinda stuck :confused:
I havent heard of anyone having a problem with this either?
It's basicly a BSE setup with alum heads, only the heads are rolled 1.5 degrees and the chambers are 100cc's ? If that makes a difference?
I think it's the duration thats causing the problem not the lift.
There is only a 5-10 degree window where there is a problem.
Beats the heck out of me? graemlins/clonk.gif graemlins/clonk.gif
I'm going to recheck the timing gears for the 10000000 time?
Thanks for any help !! graemlins/thumbsup.gif
T.C.

JRS70LS5
Dome height has nothing to do with p/v clearance, it is the valve notch depth.

TC,
Can you post exactly how you are degreeing your cam? You normally shouldn't have an intake that close & an exhaust with as much as you are stating.

I am not familiar with EDE heads. When you say they are rolled 1.5 degrees are you saying EDE angle mills the heads this much to get the small chamber?
If so 1.5 degrees is roughly .225" & if nothing is done to address the valve depth you are starting with the valves a bunch closer to the pistons.
Don't know if this is the case as like I said I don't know the head in question very well. ;)

Thanks again for the reply:
First off lets address the heads, this discription is direct from the Edelbrock cat.

Performer High-Compression 454-O
Designed for 396, 427 & 454 (7.4L) c.i.d. engines, these 100cc semi-open chamber heads feature a 1-1/2° rolled over (angle milled) design that improves intake port alignment and provides a smaller combustion chamber without shrouding the valves. The 100cc combustion chambers are coupled with the same size valves and ports as the #60459 Performer RPM heads, producing 9.2:1 compression with flat-top pistons for an outstanding high performance street head. When used on 1987-up TBI equipped 7.4L dished piston motors they produce an 8.8:1 compression ratio and made over 450 ft/lbs. torque when combined with our Multi-Point EFI System. The heads also feature an exhaust crossover passage for 50-state emission legal status. Available assembled with high quality components: one piece stainless steel, 2.19" intake and 1.88" exhaust valves: ARP 7/16" diameter rocker studs, bronze guides and ductile iron seats with 3-angle valve job. Features stock port locations, 9/16" deck thickness and heli-coils in the rocker stud and exhaust bolt holes. Mark IV rocker arms and valvetrain parts required. See chart for more specs.
Performer High-Compression 454-O
Chamber Size 100cc #60489 #60499

This may be my problem, the angle milled heads?
Although I am sure others have stated on this board they have run these heads with the 2399 pistons.

As for the degree of the cam I have a Crane cam kit I am using and going by the directions.
I have been using a dial indicator and the degree wheel to find TDC.
From there I rotate the motor .050 and record the number, then rotate untill the dial changes directions and record that number(max lift). Then rotate untill I reach .050 before closing record that number.
Mabe Im doing something wrong?
I can do it again?
I cant go any farther like it is. graemlins/clonk.gif graemlins/clonk.gif
I though about mabe the timing gear key is an offset one? But it looks to be in alignment with the ballancer key?
:confused:
T.C.

Well anyone who has built engines knows that taller pistons have deeper reliefs in them,I just can't beleive the p/v clearance is that tight with the cam your installing and the pistons your using,but I don't know anything about those heads.Hopefully someone that has used them can give you more imformation than me.

I can see the reliefs are cut deeper than the flat tops I had before.
If I didnt mention it before the problem is not at max lift it's on the intake ramp at 6 degrees ATDC.
If the timing gears are aligned at the marks at TDC, how could it be off?
Other than the cam be screwed up?
I am going to recheck everything again today?
T.C.

JRS70LS5
That's why I said the dome height has nothing to do with p/v clearance.
Your post implied that the dome had an influence on p/v clearance but I agree completly that with that cam TC should not be having a problem.

Before I cut those pistons,wait awhile for more people to see your thread,there has to be someone who has run that cam and heads before.The reason I say this something just doesn't seem right,I can't beleive you are that close.Imformation that I could find on those pistons say they have a dome hieght of .095 and a volume of 13.8 cc and that's a small cam to be having interferance with.My pistons have a dome hieght of .340 and 33.0 volume,cam is 255/263@50 lift .612/630 and I had plenty of room to spare,cam was degreed to 106 icl.I have not run the combo you are but I would hate for you to ruin a set of pistons only to find the problem lies somewhere else. =
TC
I Don't use the dial indicator to find TDC, I use a positive stop.

Put a strap across the bore & let the piston dome come up & hit it.
If it's a flat top you will need to put a bolt in the middle of the strap to stop the piston.

Record this number & turn the engine back until it hits again & record this number. Split the difference & this is TDC.
Set your pointer up so it reads zero.
Check this a few times.

It's easy to be off a few degrees using an indicator. With a positive stop it is about impossible to be off & this number is your basis for everything else you measure.

If you do use an indicator, go about .050 on either side of TDC & split the difference to find TDC

Now set the indicator up on the #1 intake lifter & be sure it is straight unless you have the cool little tool that replaces the lifter.

Turn the engine until you get the highest lobe reading, check it a few times to be sure it is the highest.

Back the engine up until you are past .050 on your dial indicator.

Rotate the engine very carefully until the indicator is exactly .050 on the dial indicator & record this number.

Keep turning until you have gone past max lift & again very carefully come to .050 on the indicator.

Record this number, add it to the other number & divide by two.

This will be your intake lobe center line which should be 106 degrees with your cam.

As for the angle milling, you will need to see call EDE & ask them if they addressed the valve to deck distance or if the valves start closer to the deck unless someone happens to know & posts the answer as I don't have a clue.

I would assume they did as you cannot just cut the head almost 1/4" off the head & expect it to work in most applications unless they recommend a particular piston with their heads that has deeper valve notches??

Let me know if I confused you more graemlins/clonk.gif

Thanks again for the replys:
This is what I did today, I followed your post as best I could and now I am confused?

I used the brass piston stop from the Crane Cam kit to find TDC (came to the same place I was using the dial indicator) but at least I know it's correct.

I then found Max lift by rotating the motor (clock wise) untill the dial indacator changed directions and got a reading of .244-.243.

Then I started over at TDC and rotated the motor (clockwise) intill I reached .050 on the dial indicator, that was 14 degrees ATDC.

I then rotated the motor past max. lift intill the dial indicator read .050 again, that was 13 degrees or 167 degrees.(same spot)
Also the dial did change directions at max. lift.

This is where I am confused because if you add the two numbers togeather and divide by 2, there is no way I can see you could get 106?
14+13 is 27
14+167 is 181 divide by 2=90.5?
I'm lost??????? :confused:
What am I doing wrong???? graemlins/clonk.gif graemlins/clonk.gif

Did you set the dial indicator to zero at max intake lobe lift?

No I didnt, I set it when I started the prosess at TDC.
Then went to .050 then to max lift then kept going past max. lift again untill I hit .050 again.
Not correct I guess? graemlins/clonk.gif
So I sould go to .050 then max lift, reset the dial indicator while at max. lift, then onto .050 again? graemlins/clonk.gif graemlins/clonk.gif graemlins/clonk.gif
T.C.

Go to max lift & set the indicator to zero then turn the engine backwards past .050.
Now turn the engine until the indicator reads .050, record the degree wheel reading, go past TDC & to .050 again & record this reading.
Add em & divide by 2 & see what you get smile.gif

It's really a hell of a lot easier to do than explain once you do it a couple of times.
Sorry for kinda glossing over a couple of steps but I do it so often it's real easy for me to understand what I meant graemlins/clonk.gif

TC,

Are you absolutely sure the valve is contacting the piston? Have you checked to see how much clearance you have between the retainer and oil seal at full lift? This might be where you have the .066 interference.

Emil Dusek:1971 SS-502

I will try it that way Wolfplace, the Crane Cam instructions didnt say to reset the dial either.
So dont worry about the missed steps.

InsuranceGuy I am sure the valve is hitting the piston.
This is how I know, I colored the valve relief with a sharpie marker.
I then put the head on the motor and with the piston at the top I removed the valve spring, then pushed the valve down untill it hit the piston.
At that point I rotated the valve so it would skuff off the ink where it touched the piston.
Each piston was skuffed at the same place on the valve relief. (upper left corner).
I will recheck the oil seal clearance though, that would be to simple?
Thanks for the replys
T.C.

TC, if you did your sharpie test without valve springs and retainers installed, it didn't really tell you that much. You know that your valve WILL hit the piston but you don't know the full travel.

Is this cam a solid or hydraulic? To check p/v
clearance you will need a solid lifter in the
lifter bore because hydraulics will bleed down,
even against the pressure of a light-weight
checking spring.

I suggest you do a full travel test of your
intake valve. First with the piston at the bottom
of the cylinder and then another with the piston
where you thought you had p/v contact.

To do these two tests, you will need to remove your rocker arm and install your checking spring.

Test #1
Bring the piston down into the cylinder and make sure the valve is FULLY closed. Center your dial
indicator on the top of the retainer and depress
the valve as far down as possible. Note indicator
reading.

Test #2
Now, bring the piston up to where you thought it
had the least p/v clearance. With the valve FULLY closed, depress the valve as far down as possible and note indicator reading.

If test #1 = #2, then you are not contacting the valve but instead probably have oil seal/retainer
clearance problems.

Test #2 gives you the max travel before you either
smack the piston or crush the oil seal. If this
test #2 figure is >= .674(.574lift + .100 safety margin)you are set to go.

I just went thru this same problem with my
383 rebuild. Luckily, I had .125 oil seal/retainer clearance. Hope this helps.

Emil Dusek:71 SS-502
93 Z-383

Thanks for the test InsuranceGuy but I have allready done this and the valve is nowhere near being fully open where I am having the problem.
The problem is just after TDC on the ramp leading up to max. lift at about 6 drgrees ATDC. The valve is just starting to open.

The test I made on the pistons using the ink told me two things.
One that the valves are all hitting the pistons at the same spot in the relief.
Two the they are not hitting the relief flat, they are hitting at an angle.
Or there would be more ink removed across the relief. This would tell me I can gain a lot of space by cutting very little.

Now as for my abillity to follow directions?
Thats a different story!
I read the directions for the Crane degree kit 100 times and Wolfplace explained it to me at least twice and I still did get it.
I finally figured out if I add the 180 to the numbers I got from the dial indicator it made a difference, now the math does work.
DUH!!!!
Anyway it still isnt rite?
This is what I have:
Set indicator to 0 at TDC, went to .050 that number is 15.
Then I rotate to Max. lift that number is.142.
I then continue to rotate to .050 again, that number was 15 also.
OK so 15x2=30 plus 180=210 divide by 2=105.
I sould be at 106, would this cause the problem I have?
T.C.

TC
Is your degree wheel marked from zero to 360 or zero to 180 & then 180 back to zero?
It sounds like you have it except your second 15 degree number would be 195 from zero as you are starting from zero & going in one direction.
So,,, 15+ 195= 210/2=105
105 is just fine & 1 degree from where Comp wants the cam.
Not a problem at all.
From what you just described about your marks on the pistons I feel the problem is you have a 1.5 degree difference between the piston notch & the valve angle which tells me EDE probably has a particular piston in mind with those heads.
I am afraid you need to cut your pistons & to have them cut at the angle of the valve in the head not at the original piston angle.

And again, you are correct. Total valve lift has almost nothing to do with p/v clearance so just measuring total valve travel tells you nothing except for retainer to seal clearance & coil bind.

Emil,
What you are doing has nothing to do with p/v clearance.
The valve is only close to the piston on overlap when the exhaust is closing & the intake is opening not at full lift.

Wolfplace,

What I was having him do is to determine if he really was hitting the piston rather then binding on the oil seals.

Emil Dusek

Thank you both for your replys?:

Wolfplace what do you think of the Isky tool for cutting valve relief's?
I know you do it the correct way with a mill or equivalant.
As I am taking such a small amount off an existing relief and the tool goes into the valve guide, it would assure correct alignment of the relief and valve.
Is this doable by a garage mechanic, or sould I take it to a machine shop?
The tool rental is 40.00 plus shipping, the machine shop price would be way over that.
I own a jewlers mill and a small lathe that I have had for years so I'm not totally new to machine work.
I realize in some cases 20-40 thou. is alot, but in this case I cant see it making a big difference?
As long as I try to keep the cut the same on all the pistons.
I would find the piston with the least amount of clearance, cut my relief to get what I need then do the rest of the pistons the same amount.
I really, feel once I start to cut I will gain space quickly due to the angle the valve is hitting the piston.
It's just going to make the relief have two different angles?
Is that a problem?
T.C.

I think in your case it should work very well because you are not hitting the whole relief.
been probably 25 or 30 years since I have even seen one but my understanding is even though they are a bit slow they work pretty well.

Try putting some clay across the valve relief in the piston & see how much cutting you will actually need to do.
It should give you a pretty good idea of the difference in angles.
Then you can tell Isky how much flat surface you are going to end up cutting & they should be able to tell you how it will work.

If you call in the afternoon after about 1:30 pacific ask for Ron Iskenderian & get the info from him. You may need to call a couple of times as he is pretty busy.
Tell him I told you to bother him :D

Thanks for the all the replys and the advise.

I will do as you suggest and call them tomorrow.
I also allready did the clay thing a coulpe of days agao.
The valve cutter is 2.250 O.D. the relief is .650 at the tallest point.
So less than 1/4 of the cutter will be contacting the piston to start.
The impression the valve left in the clay measured .010 less on the end where the valve hits.
I sould gain that .010 before I even contact the full relief, mabe more due to the angle?

Thanks again, your help is appreciated.
I'll let ya know how I make out. graemlins/thumbsup.gif
T.C.

so what was the out come???

Dunno,but it was like 7 years ago.