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Discussion Starter #1
Here's the parts:

SC300 NA head
Stock valves
Ported/polished/3angle valve job
.006 replane of head surface
Crower titanium retainers
Crower springs
Crower 6mm lash caps
Stock cams, reground by Crower to 276

Here's the story:

I take my head to a local head shop (no not THAT kind), they do all the work for JM Lexus and many other Toyota/Lex dealers. They do all the head work/milling/etc. He puts it together, then calls me and says "hey, they largest shim made is 3.3mm, and that is too small, you're still .108ths off of being in spec."

I call Crower, and Brian Crower tells me that I need lash caps, that will sit on top of the valve. Sounds like a plan. I get them the next day, and give them to the head guy. He says "The lash caps will interfere with the keeper, and I'll drop a valve." Crower says no, it will be fine. I have a dilemma.

The lash cap actually sits ON the keeper, it doesn't rest on the valve itself. From the way it looks to me, applying constant direct pressure to the back of the keeper would just keep it firmly in place. But I have no experience with valvetrain inside the head. Opinions? Here are pics in high res so you can see what I mean:

An entire valve assembly put together.





Closeup to see the keeper holding the valve in the retainer.





Lash cap sitting there for size/height reference.





Lash cap sitting on the keeper.





HELP please! Thanks in advance for your help!

SR
 
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Discussion Starter #2
Your head guy is right. You'll definitely drop valves with the lash caps sitting on the retainers, they should be contacting only the valve stem.... Let me ask you: You said you didn't replaced the valves right? Then your head guy replaced the valve seats? I don't get why you would get an out of spec measurement there... (the camshafts are the same ones as before the head job?)

Fer
 
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Discussion Starter #3
Oh, I see what happened. When Crower re-ground your cams, the also removed material from the base circle of your cams, and now you have more valve clearance than stock....either they fix your cams or they send you a different set of lash caps..Good luck
 
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Discussion Starter #5
Also the head guy told me it's off .108 exhaust and .102 intake. Just how out of spec is this? As stated, I know nothing of how the specs on the valves works....I just know too far down and they'll smack the cylinder. But if they're not opening by .108 less, is that such a huge difference that it'll affect performance greatly? Spinning the cam it looks like they're opening plenty. :D

And thanks for the help!

SR
 

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How much did they charge per cam? I'm interested in doing this myself, although using lash caps has always been a turn off.

Thanks
 
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If it's the space difference when the cam is NOT touching the shim, then whats the huge ordeal? Would one automatically assume that if that side of it is off, than the other side of the lobe is that far off? Sorry I'm new to any kind of custom cam stuff...lol

And it was $150 to get the pair reground. It would have been cheaper, but I'm in a hurry so I got the "hurry up" price. :)

SR
 
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Discussion Starter #9
Wouldn't the large increase in clearance (from factory spec) mainly cause tapping, from the valves slamming the seats, since the lobes let go of the valves sooner?

This was a problem w/ the built head I now have. The guy I bought it from said he had re-grinds, and it was run w/ "tapping" valves for ~400mi. He attempted to have it shimmed a couple times w/ no apparent luck.. Would this have likely damaged the valve seats (dual springs are also installed)?

Mike
 
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Discussion Starter #11
Well if my shims are too short, it wouldn't be hitting the cylinder. The problem woutl be the valve not opening enough. Is .108 really a big difference?!

SR
 

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shoot a better pic of the lash cap. Since you have an NA and it requires a distributor drive from the exhaust side you maybe able to simply run a GTE cam on the intake side. In regards to the valve cap, that is just one other item to come loose. The keepers are designed to hold the vave together via the valve spring pressure. With the cam acting on it the force would be greater during opening than it would be on the tip of the valve. At this point and time I would contact crower or ferrea and get a new set of valves that were machined to have a longer stem (at the tip area). Have your machinist throughly reassembly the head and take measurements for the valve spring installed height and lenght of the valves individually. Use these specs to order new valves to allow you to run a longer valve w/o lash caps. On motorcycles the shim is under the bucket rather than over the bucket. The valve tip is below the retainer and keepers to allow the shim to self-center itself onto the valve. It is very common for me to find a guy with a 600 cc soprt bike to grenade his engine by accidentally find the wrong gear. Once overreved the shim misplaces itself and wedges itself improperly in the retainer after extermely valve float. The valve would drop and the piston would break off the face. In a fraction of a second the engine would turn to a pile of crap.

Joe.
 

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You said Crower 276 cams? How much lift is that? According to this web site, the 276 cams will cause interference: http://www.moreboost.org/cams.htm Plus, you machined the head. Are you running a thicker hg? Even so, I think you have bigger fish to fry.

If you're building a motor just to "blow it up" as you mentioned in a previous thread either here or on CL, then you're right on plan. :rolleyes: You haven't addressed interference, piston temps on the NA shortblock, compression ratio, etc, etc. EBanks put out the big numbers because the bottom end was built. Is that your plan?

-scott
 
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motorheaddown said:
You said Crower 276 cams? How much lift is that? According to this web site, the 276 cams will cause interference: http://www.moreboost.org/cams.htm Plus, you machined the head. Are you running a thicker hg? Even so, I think you have bigger fish to fry.

If you're building a motor just to "blow it up" as you mentioned in a previous thread either here or on CL, then you're right on plan. :rolleyes: You haven't addressed interference, piston temps on the NA shortblock, compression ratio, etc, etc. EBanks put out the big numbers because the bottom end was built. Is that your plan?

-scott

This bottom end is a whole different story. I couldn't get a bottom end built up quick enough to satisfy my time requirements to have it running, hence why I picked up a new spare stock block to run now. I'll run it around 800hp or so for the next few months until I have the other engine completely rebuilt. At which time I'll keep cranking the boost and tuning until the stock block can't take it anymore. Hopefully I won't break too much other stuff in the process, and can throw in the built one, and go about my business. So I'm not building to blow it up. I'm building to test the limits of it. It blowing up is just a side-effect. ;)

Also, it doesn't say it will cause interference. It says that the engine becomes an interference engine...i.e. if the timing belt breaks and the valves are in an open position, next time the piston comes up, it's going to smack into them. At least that's how I read it. :)

I'll be running stock headgasket, as reccomended by...well...everyone here, toyomoto, sound performance, etc. It's only .006 difference so it's not enough to cause issues.

And lets not talk about Ethan until his car lasts more than 150 miles. :: ducks from Ethan :: :D (which I hear it's running quite well now!)

SR
 

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First off, yes .108 is a big deal. That won't be just a minor tapping, it will beat the buckets as well as the cams to death. Secondly to address your lash cap issues. All you have to do is grind the bottom of the lash cap where it fits over the valve just enough to get it off the keepers/retainer. Note that this will not change the actual thickness of the cap. I have run into this problem multiple times on Buick grand nationals with no problem. Just get the correct thickness lash cap and grind the bottoms down until they just don't touch the keepers/retainer and you will be good to go. Good luck, Drew
 
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Discussion Starter #16
Drew,

Thanks for the response! I was thinking of that, but what worried me is that to grind off that much of the cap, there will only be a mere 2mm or so holding it on, and with the top of the valve stem angled on the corners, I was afraid the lash cap may be able to angle over and fall off.

Is there enough *constant* pressure on the cap that theres no way it will be able to move anywhere during the stroke?

Thanks in advance!
SR
 
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Ok everyone, thanks for your responses! I decided to just not deal with Crower on this, if they messed up the cams once, who knows how good they'll be the second time. Just got off the phone with Powerhouse Racing, my HKS 272's are on the way to me now. Anyone know where I can get a distributor blockoff plate? I'm going to go with a crank trigger now.

Thanks again,
SR
 

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If you're having all this done, getting a flat piece of metal and some gasket stuff together for a block off plate shouldn't be hard at all...

Seems to me like Crower ground the cams down too far... Make them fix it. They have access to new blanks anyway. Why blow the $$ if it's not your fault?
HKS' grinds are smaller than stock base circle and they still stay in specs. Anyone with decent cam dr. software should be able to get the proper measurements for the proper grinding...
 
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theman said:
If you're having all this done, getting a flat piece of metal and some gasket stuff together for a block off plate shouldn't be hard at all...

Seems to me like Crower ground the cams down too far... Make them fix it. They have access to new blanks anyway. Why blow the $$ if it's not your fault?
HKS' grinds are smaller than stock base circle and they still stay in specs. Anyone with decent cam dr. software should be able to get the proper measurements for the proper grinding...
Well instead of making a blockoff plate, I would rather see if anyone makes one already. I have so many little things to do on this build, that the less fab work I have to do the better!

It is Crowers fault. What I'll likely do is send them back to be reground correctly, and then sell them. I don't have time to play around with shipping this here or that there, I need it to work now. Hence why I'm buying off the shelf cams instead, and before these would be reground my head will already be done. :)

SR
 

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CmputerWiz said:
... What I'll likely do is send them back to be reground correctly, and then sell them. ...
SR
SR,

If the base circle has been reduced to 276 cams, then they're toast. There's nothing Crower can do to fix them.

Second, if you're going to get a crank trigger, why not just get a TT crank trigger/oil pump assembly. Additionally, you haven't addressed the cam position. Are you planning to put cam sensors in the NA head? :wtf:

You're planning and understanding of building up a motor leaves much to be desired.

-scott

P.S. I'd like to correct a previous statement. Regrinds won't cause interference regardless of how small the base circle is. However, valve seat pressure or coil bind are issues that must be addressed, instead.
 
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