Valve lash caps.

[ACPOLISH]

Hello all. Question... Are valve "lash caps" required on a 1992 2TC engine?

[Banjo]

Welcome Aboard Paul,

                                       Lash Caps are only really used of very high performance engines with roller rocker arms. They increase the area of the top of the valve stem, & prevent valve tips & rocker damage.

https://www.yellowbullet.com/threads/lash-caps-do-you-guys-use-them.35874/

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Hardened Stellite Tips are a bummer. They are just waiting to break off. When they break, they usually also take a rocker arm with them at the least, but a pushrod and possibly a lifter can follow that. Of course if you get a lifter then the cam takes a beating too. In other words Stellite tips are bad news and an accident waiting to happen.

Most all if not all Blown Fuelers and Alcohol cars and quite a number of Pro Stockers have done away with them. Reher Morrison, before they quit Pro Stock had already gone back to using lash caps because of the breakage issues of stellite. Several others have gone to the Lash Lock instead and gained reliability but an additional .100 in valve stem length. That is ok though because the Stellite Tips added another .075 to .080 in length too.

At times people use lash caps to help with rocker geometry issues, but most times it is to protect the valve tip. Problem with lash caps is if the valve lash clearance gets looser the lash caps can come off. Not good. Usually they just drop down and go nowhere but the possibility exists they can get lost in the engine. Not Good. With Titanium Valves you do need something though because those suckers aren't cheap. Lash Caps are the cheapest. Lash Locks are the best. With Stainless I let customer decide if it is worth how much to protect those high priced valves. Cheap by comparison but still high priced. I use lash locks usually on any serious engine I do. I am doing one now with stainless valves but it will get lashlocks because of the other benefits from them.

Hope this helps you some.

Cheers Banjo

Edited June 14, 2024 by Banjo

[altezzaclub]

Hey Grandpa, what's a pushrod?  ..and I thought a rocker was those old guys who get off on the Rolling Stones.

 

How high are you planning on revving your 2TC Acpolish? I don't think you'd need lash caps for the metals involved unless you're adding some flash new-tech valves, and its just another thing to jump off at 8000rpm. Wiki tells me 2Ts were made up to '85, when the 4A series engine really got going and took over from engines that only hit 7000rpm on a good day.  Does it go in that Seven?

[ACPOLISH]

Hello Gentlemen. Greetings from Canada! 

Banjo & altezzaclub: Thanks for the valuable info. The Toyota 2tc engine in question has been in, and is for, a road going "Sunday Driver" Super Seven (built by a couple of guys by the name of Fejer bros, here in Canada in the 70's & 80's (under license from Lotus) and using Toyota engines. They built and sold about 10-12 of them before they had some sort of falling out and closed up. They were building some nice "Club" racers and even built a nice Can Am racer that had some success in the wildly popular North American Can Am series in the 80's. Nothing special on this engine. Just got some work on decking the block and head. Have put in .30thou oversize pistons. Has a mild cam and some double valve springs. That's about it .The car only weighs around 800 KGS so is pretty nimble & fun like heck on the back roads and really suits an engine with around 80 to 100hp. 7,000 RPM is fine for this car and engine Not looking for huge horsepower but really want reliability with "sporty" performance. It had lash caps but I never really saw the necessity. Since there been some material removed from the head and the block, I'm wondering if using the lash caps alter things like valve duration or anything else. Having trouble finding anyone here who knows anything about working on these old reliable basically stock Toyo engines. Any comments from you guys would be welcome. Thanks again.

 

[Banjo]

Hi Paul,

             That  Super 7 is beautiful, & I'm sure is a great performer with the 2TC, because the car is so light.  You're making us very jealous ! 

Toyota red-lined the TC2 at 5500 rpm, from memory, but I'm sure the Fejer Brothers, would have modified the 2TC slightly, if they knew it would be used up to around 7000+ rpm.

As I said in my original post, the Lash Caps are installed to put a wider area, in contact with the cam tip, or the roller; in the cam tip, if one is fitted.  This is primarily done, to prevent damage, breakage or bending, of the Stellite valve stems. However, it maybe that the valves were replaced in your engine, at the time the Fejer Brothers produced these classics.

Here is a link, that You may have already read.   

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https://paradiseracing.com/products/toyota-2tc-3tc-stage-4-cylinder-head

You will notice that their alloy low weight blue rockers, have rollers, but no "Lash Caps" from what I can see.  You would assume then, that the valves were of a material, much better than the original Toyota valves.

The 2TC engine was a fairly robust engine, for it's time in history, & some incredible HP was derived from them, especially, if a blower was added.

We'd love to see a few pics, from under the hood. I imagine, the original build by the Fejer Brothers was fairly high class, & of very high standard ?

Please keep in touch !

Cheers Banjo

Edited June 15, 2024 by Banjo

[altezzaclub]

The lash cap gap will change the geometry of the rocker, you will have to check that. If you take them out you will have a gap of 10 or 20thou or more, depending on how thick they are. Screwing the rocker down to take that up will make it tilt more in one direction right through its movement, so it may jam against the pushrod end at one extreme or run the rocker end off the valve tip.

The company that set the motor up would have trimmed the valves to shorten them by the cap thickness so the rocker maintained ideal geometry (I hope!) so look at the movement carefully and leave them in if the rocker is biased one way or the other without them.

A bigger tappet gap will reduce cam duration, but we're only talking a few thou or you move off the 'soft' part of the ramp and the cam hits the whole valve train with more of a whack.

Ah Grasshopper, one day you will learn about the 4AGE motor...

Edited June 15, 2024 by altezzaclub

[Banjo]

Hi Paul,

              I've just read Altezzaclub's comments to You, & realised, that your original question was   

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Are valve "lash caps" required on a 1992 2TC engine?

It appears to me, that you are advising the the engine had lash-caps fitted, when You purchased it; but now after overhauling the engine, & decking block, & skimming head; You are now concerned as to whether the lash caps should be reinserted, as they may change the valve timing.  I would guess, it would only be an issue, if the amount decked from the block; & skimmed from the head, is enough to change the valve timing considerably.  As You've adjusted the bores slightly, to take the 30 thou O/S pistons, then that increase in swept cylinder volume, plus block decking & head skimming, would have increased the compression ratio.  Have you calculated, or measured the cylinder head volume, to work out the resultant compression ratio after these mods ?

Personally, from what you've advised, I don't think you would have changed the valve timing significantly.  You don't say, that You have  actually removed the Lash Caps, which I assume have a reasonable thickness in the top cap area.

If you are really concerned, you could always fit a timing disk; remove the spark plugs; & with a dial guage on the valve spring top retainers, take note of the opening & closing angles of all valves.

Personally, I wouldn't remove the Lash Caps. If the engine builder had originally fitted Lash Caps, I would leave them. From what I have read; when lash Caps are used, the lengths of the valve stems are shortened, to accommodate the extra thickness of the Lash Cap, so that valve timing is not significantly altered.

Your engine builder, is your best guide to obtaining the correct answer to your query, but if you would like to pop a couple of "close up", pics, of the valve coils & rockers etc., it might give us a more informed detailed look, at your concern.   Good Luck !

Cheers Banjo

 

 

[ACPOLISH]

Hi Guys: I composed a nice reply to this thread but alas, I see it was never posted. Don't know what I did but just want to say Thanks! for the great info.

Pics and further info will be forth coming, lash caps or no lash caps!

Cheers!