Projects My Model A Truck will soon Scream under new Power

Is it the same cylinders each time? If everything else is checking out to spec then that leaves distortion under load. I've had blocks and heads distort enough to make locating issues an ordeal.
Now if it's different cylinders consuming valvetrain each time I would be looking at the heads. I had two valves stretch a healthy amount while a third twisted just the other day. Everything on yours measured the same when clay checked?

 

Work continues on my next generation 94 carbs....eventhou I cannot stop from bending valves.....I took some old 94 carb tops and opened them up...their's not much wall thickness to begin with...but I took all I could and started to polish the bores..I still need to cut a more graceful transition angle at the top of the bore.....Littleman



Carb top ontop of the middle 94 carb body....

 

Yes it's at random, but with the heads off...you can see and study the carbon pattern on top of the pistons....you can see no carbon build up on the exhaust valves.....some are kissing not leaving marks in the piston, other's clearly left marks and bend......I took this pic the last go round a handful of weeks ago...after the Gasser Thompson meet..

 

Have you checked your valve distance to coil-bind? Have you checked deck height with a torque plate on the block? Not trying to disparage the machine shop who did some of the work. Only trying to throw out scenarios I have found.

 

Also what is your oil pressure when going through the traps/peak rpm?

 

It was zero decked...it does pop up above the deck if you rock the piston, by like .009''...say if you bring it all the way up to top dead and push on the lower half of the piston.....I do not think we have checked the valve distance travel to coil bind...The installed height and coil bind checked out for proper seat pressure.and we tested every valve...but if it coil binds that should stop it from traveling and hitting ?....I am all ears....the machine shop is stumped as well..........Littleman......oil presure is around 60+ psi at the top end..The head gaskets are .041'' compressed.

 

Have you checked the lifters? Maybe something wrong with them

I will call a friend of mine and tell him whats going on. He has built a lot of race motor's over the years. He may be able to help you out.

Ill let you know if he has any help for you.

Them carbs are lookin killer!! So how many hours do you got in them

 

Coilbind is a pushrod killer but in alot of cases the rocker will continue pushing the bound valve(if the pushrod doesn't give) and bend the stem, distort the guide, stretch rocker studs and a host of other nasties. Doesn't answer the valve collision. Is this still the Hydraulic roller you spec'd when first posting? The float is likely lifters not staying pumped at high rpm. The safe margin is 10 psi of oil for every 1k rpm of trap speed.
The block should be torque plated to check true deck height. The combo of slight variants of the block, rocking pistons and a possibly ovaled crank will do the exact result you have(valves playing whack-a-mole).

 

This is a modest solid lift cam .550-570 lift w/ .259-.266 @ .050 dur......w/ a 1.6 ratio rocker added.....It's not a killer quarter miler cam by no means but larger than the hydraulic roller I ran last year.....plus we cut the heads .030 for 13.2 to 1 compression over the winter and installed the new solid cam to go to Detroit back in March...I did notice that some of the 7/16 rocker studs threads looked chewed up this time at tear down...Dave

donut29...I am open to all ideas !...Thanks...too many hours..he he he

 

What kind of lifters do you have? Hydraulic, solid? Flat tappet, roller?

The whole .120 clearance thing bothers me..90 thou is about the bare minimum, so you should be cool. But, remember you are checking clearance with a cold engine twisting zero rpms.

My guess is at 8 grand on the track, you are either pumping the lifter where you wern't on the engine stand. Or, your cam timing is doing something diffrent at speed than when you are checking it on teh stand.

Either way, DRIVE that sucker to teh HAMB Drags this August and we'll line em up.

Intresting problem...hope you get it figured out soon.

-Abone.

 

Solid lifter.........I figured if I only had .080 I would be safe, but I have allot more....nothing is making sence as of yet.....My wife planned our Disney vacation over Hamb drags weekend...I did tell her to pick the weekend and make it happen..I never thought she would pick that weekend.I never did tell her yet..I have only been wanting to go for the last 3 or so years...and this is the last year the Truck will see Track duty.......Dave

 

My best suggestion is talking to the best oracle I know for Race motors. My uncle French has done the R&D for Brodix(and several other companies) and will hopefully be able to point you in the direction over the phone. He's a good ole guy and the one that made me want to be a machinist. Follow the link for his contact info. I'm not soliciting business for him. I have always known him to take time out of his business to help someone. I would also be willing to bet that if one of his races brings him near you he'd look at it in person.

http://www.frenchgrimes.com/

Let me know what you find out. -Chris

 

You were quicker on the reply button than me....

You say solid cam..is that a solid roller or flat tappet?? And, what is your valve lash hot?

I'm still bothered by teh .120 clearance on the stand. Where did it go? You have to think of what is going on when the engine is twisting max rpm through the traps as opposed to when it is sitting on a stand with a chunk of clay stuck to the piston.

Usually, the diffrence is in the lifter or the timing of teh cam. What are you running for a timing chain?? Advanced/retarded?

There is one more area where you can lose piston to valve clearance...If your rod bearing clearance gets too big, it will close your piston/valve gap on TDC. But you would probably see an oil pressure issue...

Lastly, there is the tolerance stacking issue....Say you have some excess rod bearing clearance AND some tight valve lash AND some cam timing issues and all of a sudden, your .120 gap turns to .060 or so and you start bending shit on the big end.....

Just a thought..

-Abone.

 

One more thing...when you say "....this is the last year the truck will see track duty.." What the hell does THAT mean????????

You aren't turning girl on us are you???

-Abone.

 

It's a flat tappet cam.......018-.020'' hot........I am going to break down the entire rotating assembly to double check everything.............Thanks everyone for your input !

rc.grimes.......I just may have to call him...thanks !...Dave

 

Ha ha ha ..........no.....The Truck weighs 2,437 lbs. with me in it.......if I build something lighter I would be faster..........Mid engine-lighter-more purpose built-faster......Littleman

The Truck's chassis really needs shored up if I keep racing it....It was really only built for street duty...and is really starting to twist with the extra power this year...that's all.....Hell I'll race you with a big wheels..I like to race..

 

Just a bit on top of what flamedabone said... .120 clearance, measured...on the #1 cyl, or on all cyls, especially the ones that show signs of interference? If you're only measuring #1 (doubtful, but...figured I'd ask) there might be enough variation between cyls to bring you closer than you think.

I'm far from an expert, but...still leaning towards the launcher theory giving you more lift. Check these out:
http://www.crateengines.com/catalog...es/CompetitionCamsLauncherSeriesCamshaft.aspx

http://www.compcams.com/Community/Articles/Details.asp?ID=702192277

Note the graph on the second URL...

 

Interesting stuff !....I never heard of these cams....but this shows that this happens whether by accident or intentionally..........I am going to look into the rev kits......I could go with a thicker head gasket or cut piston valve relief's........Littleman

 

im no expert either, but id try the rev kit

 

Just thinking...It may not be that the valve is going down too far,but the piston is comming up too much.What's your oil pressure at idle?45psi at the top end seems low to me.It should be around 80.If you're loosing it at the top end,you may be stretching the rod bolts.
Just a thought.
Shane

 

Shane....I messed that up......at the line it's around 45 psi @ running temp and 60 + psi on the top end..........We really do think I am still floating the valves.....I may go from 140ish seat pressure up to 160ish...the cam specs only wanted 130 lbs. of seat pressure...but will tear down the lower end to verify everything since the engine is out...including verifying deck height ect.......which was originally machined to zero, but with the piston rock...makes one side come up out of the hole.......Thanks, Dave

 

At Thompson this year......they finally told me to get rid of the HallCraft steel spoke wheels....since the Truck dips into the tens on occasion and they told me they were not allowed per the rules anyway's.......but allowed me to run them for the weekend.....But on Saturday I experienced the worst front end deathwobble as of yet....and while keeping the fun pedal hammered all the way thru it...I could see the front wheels trying to turn opposite direction and wanting to fold in half while I held the steering wheel straight ahead......After that pass Don and I installed a steering dampner and the front end has not done it since...But before departing for Bowling Green I robbed the Radir front wheels off of DeathsDoorStep to run them on the Truck..............I was not sure if I was going to like them, but it puts a little more rubber under the front end and they are much stronger..not to mention the front brakes bolted right on...but I think it looks much better to my surprise....The HallCrafts look killer on DDS........I figured the HallCrafts were getting a huge work out from the Truck and it was the smart decision to remove them..I cannot imagine the load they experienced while braking at the top end of the strip not to mention a few people thought they would end up hurting me at some point.....Littleman

 

The Radirs look great on the front- gives it a Stouter look upfront... crazy how much impact wheels have on the look of a car/truck...

 

Some (maybe stupid ) questions with respect to the exhaust valves hitting the pistons...

Are there aluminum rods in the motor? They'll require more clearance than steel.

Is it hurting itself on the burnout? The R's come up quicker on the burnout and the valve springs have a harder time controlling the valves.

How do the seat and open spring pressure look after a few runs?

Lastly, who's cam is in the truck? My experience with blown alky dragsters has shown me that only a couple cam makers know how to grind a cam that sets the valve back on the seat properly at high rpm. Your valves could be bouncing on the seats.

Hope that helps

 

Thanks for the info.......I hope to have everything back together maybe next weekend....I alway's watch the rr's on the burnout.....well most of the time...I roll out of the fun pedal at the top end.....It's a Comp Cam grind....The seat pressures the last go round did maintain.....The heads are going together with Ferrea valves this time around and with more exhaust guide clearance..also giving the spark plug electrode some breathing room via piston machined fire slot...we shall be makin noise pollution soon and maybe pissing off a neighbor or two...Littleman

 

My next generation 94 Drag Carbs are taking shape, I just finished cutting the upper transition at the top of the carb throat and rounded it out.....and finished polishing the thru bores that I enlarged.....next I will mask the middle and top carb body's off and soda blast the outside of them @ work...I really enjoy doing this...I almost wish I could offer this as a service..but just know their would be no takers.......Littleman

Carb tops..



Carb tops on center carb body's..


Velocity stack on polished carb...velocity stack's still need sanded and polished...they are rough incomparison to the carbs finish.....

 

Very nice work Dave.

 

man those carbs look great

 

You should try and get near a flowbench and see how much of a difference has been made. I'm curious myself, nice work.

 

I sure would like to know.

Maybe you'll find some customers with some data that backs up all the time you've put into them...it's not hard to see how much you like doing it.

BTW I like the new wheels, and I thought it was perfect at the Showdown Drags....