Engine Carnage

[bobcowan]

It's a Dart block, prepped cost is about $2,500-3,000. I'll talk to the machine shop and see what needs to be done, and what it costs. Might be cheaper to buy a new one from Mike Forte. Might not be. We'll see.

I was decelerating when it happend; 4th gear and closed throttle. Hadn't quit got on the brakes yet, and hadn't downshifted yet.

Lash caps sound interesting. I thought the were simply to support the valve tip, or correct geometry issues by making the valve stem a tad longer. I didn't know they pushed down on the locks. If that's the case, whay are they not used very much? They're pretty cheap.

I looked at the tips of the remaining valves under a magnifier, and they look fine.

[YerDugliness]

Originally Posted by vector1

lash caps? please do tell.

Originally Posted by 67FEfastback

x3 on lash caps

I had a dropped valve, years ago. After looking at the valve tips after disassembly, 90% of them were shearing little slivers of metal. This was a function of the valve lift and spring stiffness.

I'm with Vector1 on this one....please, somebody shed a little light on "lash caps".

I realize roller rockers were suppose to reduce the "shearing" effect of a rocker arm slamming down on the top of a valve stem, don't think I ever heard of lash caps.

I envision a device very much like a spring cup that the valve spring sits in on the surface of the head, except on top of the valve/spring assembly. Some sort of variation in thickness could be used to adjust the "lash"....but, perhaps the primary purpose would be to give the tip of the valve stem some protection from the impact of the rocker arm as the valve is actuated.

How far off am I ?????

Dugly

[Outwest34au]

Lash caps are also used/ called rotators or slow rotators. The valve is normally pressed down in this case just off the centre line and the cap acts as a thrust washer allowing the valve to rotate a small bit on each open/ close cycle. This is to dissipate heat evenly around the valve seat and wear evenly too. Some bigger engines have actual thrust bearings with balls.

[Rick Parker]

There hasn't been much discussion about lash caps over the years on this forum. I have always used lash caps in my 289. Originally I believe it was because it helped prevent the ends of the stems from becoming worn from the roller tips. They fit on the end of the valve stem, the rocker arm roller tip contacts the lash cap. There is a minute hole in the cap to allow oil in & out from between it and the valve stem end. I am using Ferrera valves throughout. I recall that I had to have all the ends of the lash caps that fits over the stem surface ground to reduce their length a few thousandths, so they would not contact the valve locks or keepers, so far no problems.

[RICK LAKE]

bobcowan Bob letting the motor over rev on a down shift is like banging one on a rev limiter. You may want to work on rolling on and off the throttle to stop this kind of major rpm change. Keeper broke off in the retainer and cause the damage you see. As far as the motor, unless it is cracked, it can be rebuild with a .015-.30" over bore of the cylinder. Need to have the machinist do a sonic test to see how thick the walls are. Might be easier to have a sleeve installed in the bore and keep this block for a spare or street motor. IMO racing days are over for any block with this kind of damage. I would replace, get a junk yard block or buy new and repair this one.
Are the retainers steel Bob?? Jerry has the correct ideas on lash caps, He did leave out the load of the rocker pushing down on the valve being spread out.
What valves where in the heads? Ferra's? If good top of the line parts are used, valve caps shouldn't be needed. You want to lighten the valve train , not add more weight. The other question is what oil system are you using? What pressures are you running at? It is possible that there is not enough oil getting to the top of the motor and overheating the parts. The parts are not blue in color BUT too hot for normal driving. You may want to replave the retainers and locks with stronger retainers ( lighter if possible too ) and new locks. The head can be welded and repaired. This is the fun of racing. Rick L.

[Jerry Clayton]

Bob

I know you said that you had that engine for 4 years--since then Dart has there SHP line of blocks that are much more reasonable priced and they are about 30 lbs lighter--If you want a price on one PM me for My son Corey's number and I'll teel him you'll be calling.

[Paul F]

It looks like there needs to be some expert to step up and clarify the use of lash caps.

Jerry says they press down on the keepers. Rick says they don't. It seems like both make sense.

Rick says the little hole is for oil. Comp Cams says its to provide suction relieve when removing them. It seems like both make sense.

Comp Cams doesn't say anything about if they push on the keepers or not, but does seem to indicate it is just to help save the valve stem from wear.

If they are not pressing down on the keepers, then what good are they? It's just another piece of metal that is getting pounded by the rockers that could break. Is it stronger? Won't it fatigue just like the valve stem?

Comp Cams;
Because today’s racing engines run at higher and higher rpm levels and the cam profiles are extremely harsh, the tip of the valve stem is subjected to a tremendous amount of pounding. These engines always run just on the brink of valve float—one of the most severe conditions that can exist. The best solution to this problem is the COMP Cams® Lash Cap. These lash caps are precision machined and ground perfectly flat to maintain accuracy of valve train adjustment.They fit the valve stems well and can be removed with relative ease because of a tiny hole to relieve the suction created when removing the lash cap. The Chrysler “Hemi” engine has benefitted greatly from this design. A special version is available to accommodate the very short tip on these valves. For the ultimate in strength and reliability, you will not find a better part than the COMP Cams® Lash Cap. A must for titanium valves.

[Jerry Clayton]

Expert????? do you want referances??? or can't you guys really see that the use of fitted lash caps that fit the tip of the valve/retainer/keepers will take the valve spring pressure load off the valve stem???if the lash cap doesn't push on the keepers, you are transmitting all the forces of the valve spring compression pressure waves to the groove of the valve/keeper and you will shear them creating havoc---also , on a road race car---more engine damage comes from downshifting than anything else than a poorly designed oil system---one of the main things I enjoyed about karting with my boys was no lub system, no valve train

[bobcowan]

Alhtough I race it, my engine is relativly mild for a race engine, but kinda radical for a street engine. I use a Comp Cams hydraulic roller cam, with a lot of lift and duration.

The lifters are stock Ford rollers, modified by keith craft. It's the same lifter they use in their engines. They're supposed to be good for about 6,500 rpm's - give or take. I set my shift light at about 6,200, and it rarely comes on. I have so much torque that I can shift early and keep the rpm's down, and yet still make good lap times.

The oiling system is pretty good. Ford motor sports SV/SP oil pump. Quality roadsters pan with full baffles. 2 qt accusump. I have a warning light for the oil pressure. If it ever drops below 25psi, the light comes on. That's a rare occurance. The engine oil pump feeds the engine only. the cooler has it's own external pump. I use only Royal Purple oil. I think the only way to make the oil system better is to go with a dry sump, and I certainly don't have the budget for that.

The heads are from Dart, and uses their valves. They're probably 4 years old. The springs, retainers, and locks are from Comp Cams; they're only 2 years old. The tips of the valves look just fine, even the broken ones.

Over the years I have concentrated on smooth shifting. This much power in a light wieght car, you have to shift smoothly, or you're in the dirt. I know, I'v been there. Slow is smooth, smooth is fast. I may be racing, but I try not to beat up the equipment too much. I don't have a NASCAR budget.

I don't have the budget for a new block. I'll have this one bored or sleeved, and press on. That's why I spent the bux on a Dart to begin with.

I tore down the engine yesterday. I'll take some pictures today and post what I found.

[Jerry Clayton]

Bob

I would suggest that if you still have the spec sheets for your pistons that you get the bore cleaned up and miked and get a single piston for that bore--you are lucky that you you have the individual throttle bore injectors so that you didn't have damage spread to other cylinders thru the intake--besides the oil system cleaning don't forget the exhaust.

And get some properly fitting lash caps so you don't do this again.

[Wbulk]

Back in the late 60s and 70S I used to rebuild a lot of FEs and SBF engines, and every once in awhile you would run across one that had lash caps. In school we were taught they were to reduce valve stem wear from the rocker arm. The metal for the lash caps was harder than the valve stem. Metallurgy has come a long way since then, so has the quality of oil. In those days if an engine made it to 100,000 miles that was really good.

I forgot about lash caps until I bought a 1971 302 last year that had never been torn down. Still had original bearings, bore, rope rear seal and the heads did not have hardened seats. The valves were original FoMoCo. It had lash caps on all the exhaust values. The valve stem tip was machined smaller so that when the cap was on, it was the same diameter as the rest of the valve stem. The lash cap only pushed on the top of the valve stem.

[Jerry Clayton]

Wbulk

I don't remember ever seeing a lash cap as you described those---however, there are valves that have hardened tips where the manufacturer put a golf tee shaped hard metal in the end of a titanium or ss valve--was your deal maybe something similar to that and with 100k that they had just come loose???

[Wbulk]

This is what they look like.

[Jerry Clayton]

I'd have to say that that is just a case of hardened tips coming loose after many years and miles.

I'm going to try to post some pics if I can , please be patience with the elderly!!

[Jerry Clayton]

Pics were too blurry for the detail I wanted, will have my son help me tomorrow---

[vector1]

jerry

could you expound on setting up the lash caps for the purpose you describe? i had thought they were for setting lash, this is new to me. not that i'm anybody, just curious.

[Jerry Clayton]

The most you should have to do is take a little bit of material off the tip of the valve stem so that the lash cah then sets in the recess of the keepers on the tip of the valve.

The lash caps that you speak of are for setting lash on overhead camshaft engines where the cam runs directly over the valve.

I also have some early lash caps that were split---they were a combined keeper/lashcap and worked pretty well but someone then did the recessed ones after the super locks came out which made enough room for the top hat style, but now you had 3 pieces in stead of 2 and worst --one of them is loose

[vector1]

so the end of the valve stem is not touching the lash cap, which takes all the force from the rocker and puts it into the keeper.

then when you set it up this way, you have to measure the pushrods with the caps installed.

seems like cheap insurance.

[CobraEd]

Bear with me on this, but if you push down on the keepers, wouldn't that be in the direction of sliding them open and off !!! ???

If there is any valve float loosening the tension on the keepers at high rpm, pushing down on them would pop them right off. As such, I tend to think that the lash caps fit on and push on only the tips of the valve stem, but I don't know this for a fact.

.

[vector1]

i had another thought also, he's running hyd roller with what 135 on the seat and 325 open? and pulled the end of the valve off? i could come up with some other scenarios, if that's what the assumption is.