Im building my motor and I'm ready to slide the head on. Only problem is I'm second guessing myself as I had both the head and block redecked, and installed some S3 cams along with it. I'm wanting to know if my valves will hit my pistons as I went with big cams, reddcked the block and head, high compression pistons, and using an oem mls headgasket. Here's my specs in case any of this makes a difference:

94mm eagle crank
Manley 150mm turbo tuff rods
Manley 2.1/2.2 pistons with upgraded wrist pins
Ported head
Kiggly valvesprings
GSC S3 cams
Stock valves
Mls headgasket
Block redecked .004
Head redecked .008
MAP H11 headstuds

I'd rather not have to check for squish if I don't have to. Has anyone ran these cams with a decked head and block?

Thanks for any help

 

your pistons have those grooves so that your valves won't hit the piston. I had my head decked and was worried about this too. Make sure you turn the cams so that the valves seem to be mostly closed. I did not have my block shaved so there will be a slight difference

 

Why risk it. Check it yourself. Id be damned if i ruin a new built motor because i took someones "word" on a forum

 

Most valve reliefs leave enough room so that doesn't happen..if your local machine shop built that they should have checked clearances.

 

Removing 0.012" is significant, especially when dealing with a high lift, long duration cam with a fairly advanced (104) intake LC. You don't want to run the engine if the valve-to-piston clearances are unsafe, and machine shops shouldn't be expected to partially assemble engines to check these clearances (in case anyone wondered).

When assembling my engine, we checked the clearances, and found that my intake valves would have likely contacted the pistons. This necessitated some hand grinding and smoothing of the valve reliefs to resolve.

Ask me if I'm glad I took the time to check this before hand ... but then again, I almost always do. Better safe than sorry.

 

I'm in a similar situation. I have a head that's been surfaced 3 times (upsetting story with machine shop).

Do you use the clay method? Is there anything that needs to be taken into account (do the valves, pistons, etc change when at operating temps enough to cause issues)?

 

FWIW the FSM states that up to .008" is the maximum amount that can be removed in total between the block and the head. Now in your case you are clearly over that but there are a couple variables which make this a little tricky. Some of which may help your case but other will hurt it.

For starters you are past the manufactures suggested limit. To add to that you have large cams which Ted B pointed out. This is not ideal for clearance between the valves and the pistons.

On the defense, your upgraded pistons have larger valve reliefs built into them which will provide additional clearance. Also, I'm not sure what kind of work was done on your head but did they do a valve job? If so when they grind down the valve seat you will also gain back a little bit of clearance.

Will this be enough? I have no idea...and quite honestly I'm not sure anyone on here can give you a definitive answer, I know this isn't what you were hoping to hear but your best bet it to mock up the head and test it.

 

On any build where this much has been taken out, it better be checked. Why spend all that time and money to be "unsure" if you will bend valves?

On a side note, you can always run a thicker head gasket to make up for the material taken out but I would also do the squish method and put some clay in there and check.

 

The clay method is straightforward, reliable, and easy if the engine is on a stand. One simply rotates the piston around TDC on the intake stroke and checks the depth of the clay at the thinnest areas for both intake and exhaust valve impressions, just like using a tire tread depth gauge.

When the engine is at operating temperature, clearances change. This is why one should observe a minimum of 0.060" for the intake and 0.100" for the exhaust to account for thermal expansion. If there is an issue, one can either (a) change the cam timing and be content with that, or (b) gently massage the reliefs with a Dremel to attain the desired clearance. The latter option is always preferable. As for using a thicker head gasket, that may be an option in some cases, but one should never expand the quench area between the piston perphery and head surface to >0.060". This is important.

In my case, the reliefs in the aftermarket pistons were insufficient to account for the larger valves, advanced intake LC, 12mm lift and rapid ramp rates. It was just as well, as we used this opportunity to gently radius all sharp edges on the piston crowns, which is helpful in thwarting preignition.

 

All good info thanks for the min. Clearances to check for too on both the intake and exhaust. I'm planning on checking it tonight or tomorrow. Let's hope the pistons have enough room!

By I did also have a valve job done on the head, and re used the guides that were in the head as they were in great condition.

 

let us know how it goes!

 

Quick question, when checking squish, I'm guessing I pump the lifters up so theyre essentally "solid" or "full", correct?

 

Intake was around .130 exhaust was .100, so we are good there. The piston to head clearance is about 40 thou, what is the minimum clearance that is acceptable, anyone know?

 

Wanted to update what I found out from my machine shop, and my findings. I had .010 of squish between the piston and head, and my old oem head gasket was .030 thick, giving me a total of .040 to play with. Machine shop said this is more than enough, and if we need to in the future we can even redeck the head or block again and still be good.

So, for me my setup looks to be spot on...now to clean the clay up out of the chambers and the top of the pistons...

 

im having a similar issue i went for over sized valves and it seems that the radial clr is a bit too close too the piston, its bnot contacting but its pretty close tho