Projects My Model A Truck will soon Scream under new Power

Monday I am calling someone that I think has a flowbench to see what I can work out.....I also found plenty of plans out their to build homemade benches.......I am real close to bolting these on for a try.........I figured I would flow one that is in use now and then the new version....I had no plans originally to flow them...but the more I think about it....It would be neat to see the differance.....from a #'s stand point.....but still think the true test is @ the DragStrip on a full out pass under full load and rpm's..........Littleman

 

Patrick with Pro Systems carbs is in Michigan, you might give him a call. He specializes in custom carbs, he built my 950HP and tuned it on the bench before he shipped it to me.

http://www.prosystemsracing.com/index1.html

 

I'm anxious for an update on the motor to see if you've pinpointed the issues. I also would love to see the difference in flow on the carbs. I'd to have a set done but considering you probably have at least a 100 hours in them it may be a wee bit pricey.

 

I read back on this thread and I see the point when you said you added 1.6 rockers !! Now you do know when you installed these rockers that your valve lift also changed. It went from 550 up to 585 and from 570 up to 608 !! If you had not planned for that in the original build you will be seeing bad results. And when I measure piston to valve clearance I check in 10 degree increments on each side of TDC as with todays cam profiles the valves can sometimes be closer to the piston on either side of TDC !! And shit can the play-dough and get out the dial indicators and the degree wheel as that way you know excactly what you have >>>>.

 

Thanks for the info !......I had the 1.6 rockers on before we figured out how much we could mill the heads...and how much room we actually had to play with...and had already installed the new profile cam....Did a full mock up to figure pushrod length and such back then....I agree on the use of indicators, they do not lie !......The exhaust valve to guide clearance was .0015''..We think this was the problem..I hope it was the problem !.It has bronze guides in aluminum heads.But the more I read, that should be enough clearance....I would think anymore would pound the seats ?..I am still real sceptical that taking the .0015 exhaust valve to guide clearance to .0025'' really is the answer...I just torqued the heads back on tonight and adjusted the valve train...Littleman

 

Man it depends on what compostion of bronze guides you have as there are varius types of material they can be made of. Simply put bronze is not all the same and doesn't react the same. However I can say I don't run any of the bronze guides I use that tight >>>>.

 

I am curious......what would be rule of thumb guide clearance tolerances ? I understand that different materials will yield different expansion rates......I am just wondering if we opened them up enough........Thanks, Littleman

 

Id love to have a shop like that. beautiful! oh, nice motor too,

 

It'a alive once again.......I think our local DragStrip is actually open tomarrow........Time to stab the fun pedal and see what it will run.......Bring it home and do a leak down test on each cylinder and hope for the best.......It just might be the first time this year it does not bend any valves....I am just iching to get this thing to run consistent so I can bolt on my new Drag 94 carbs and the nitrous.........Littleman

 

You're a mad man Dave. An absolute mad man. I LOVE IT!!!

 

Give it hell Dave.

 

Well I made it to the DragStrip.....pass #1 was 11.14.....pass #2 was 11.33.....I read the ticket and said that's not good....That is what it has been running after it bends the valves after it's done playing whack-a-mole in the cylinders.......So I made a 3rd pass and it went 11.12.......I was happy with that only because it would not have run that with bent valves and had room for lot's of tuning, should be in the 10's easy...it just runs 11.30's to 11.40's bent up..........Left the track and was home by 1 pm......I decided to pull the entire engine and trans back out, so I could have the converter adjusted......I also did a cylinder leak down test before I pulled it out all the way.........

cylinder #1 was good

#8 held only 20 psi and seemed to be a bent intake valve

#4 exhaust leak...bent valve

#3 was good

#6 was ok but not good, about 11 to 14 % leak down

#5 was the same as #6, 11 to 14 % leak down

#7 same as #6 and 5, 11 to 14 % leak down

#2 exhaust leak....bent valve

I had the whole thing out in 2hrs.......but it's the 8th time this year since April 4th I have taken it out....Back to the drawing board again....Good times, Littleman

 

A few more thoughts....

Are the seats moving around in the heads? With the valves removed, run a finger from the seat down into the port and feel for sharp edges at the seat/aluminum interface. If it is sharp, the seats are moving.

Is the motor hot when you leak it down?

Lastly, you may have to just "give it what it wants". Everything appears to be correctly assembled and you're using good parts. Put more valve to piston clearance in it.

Get after it!

 

I dropped off the heads yesterday to the folks that just machined my valve seats and opened the valve guide clearances from .0015'' to .0025''...they told me today that it ate all the intake guides this time not to mention the bent exhaust valves and the end of the brand new valves are gulled up,sounds like around the keeper area ? and all this just after three passes but I will have to see for myself.....I will see them tomarrow...I am taking the short block so we can mock everything up and double check the geometry.........This is the fifth time some crazy stuff has happened in a wicked short time..........it's getting real old and exspensive this year, but am sure their is something great to learn once we figure out what's going on..........Littleman


It just might be time to finish DeathsDoorStep.....and return the Truck to the street.....

 

You've got great patience and a philosophical outlook on something that's a big pain in the ass. Hope you get it figured out soon Dave. I know you'd rather be out beating on it than tearing it apart and spending more money. Good luck-

 

How much clearance do you have between the retainer and the inside profile of the rocker when the valves closed?

 

It visually looks to be plenty and their are no witness marks on the Comp roller rockers anywhere....we are going to do a full mock up and will be revisiting everything again....Dave

 

oh man i hope you can work everything out for october and come on out to the jalopy showdown drags ! good luck rubber band sniper

 

Have you considered swapping a set of heads to isolate the issue? I would go as far as to say it is becoming a cheaper proposition than repeated repairs to these. If you want to go that route send the the specs you need and I'll loan you some(new ones).

 

I've always wondered about running those heavy roller lifters in a high RPM engine. It seems like a lot of weight/mass to ask the valvesprings to control at high rpm....this thinkin through my fingers here.
Seems like a l[heavy roller] lifter could bounce off the top of the lobe, keeping the valve open while the piston comes up to give it a nice kiss...

 

Thanks for the offer..........I just may have to look around to see what I can sell to get a different set of heads..............I am on a mission now to run a #........one way or another..I have had thoughts of reworking my stock camel hump 2.02 heads!...Thanks again, Dave

 

Rocky, this setup currently has a flat tappet solid lift cam, the cam that was swapped out over the winter was a Comp cams Big Mutha Thumper hydraulic roller.....so this just has a solid lifter right now......and I am using the Comp Cam Chrome-moly roller lifters that are fairly light............Littleman

Metalhotrodgirl, beware of the rubber band...............Dave

 

Tremendously good thread.

Following all the changes is entertaining as well as educational.

As you said, change is what hot rodding is all about....

 

Littleman,

I have read your thread and it is great and I enjoy it very much. I just want to hear that you have found the problem with your valve train. I would like to throw my 2cents worth in. I see that you have changed your lifters to solid roller but you did not say that you have increased your spring pressure? I know guys that are running up to 300 lbs with solid rollers on blown nitro. I would check this once again along with all your valve to piston clearance, also the 1.6 rockers do change the angle to the valve and you said that you changed the cam from last year. Could you have some binding in the guides? I sure hope you find the problem as I am in pain reading this thread. Stick with it, I know you will find the problem.

 

A small thought here.

Are you running single valve spings with no inner spring or damper?

Little brother ran a single on his 500 cid, 9200 rpm DRCE motor and broke a valve spring every pass.


Figuring it was harmonics that was breaking the spring he went to quality dual springs with the same # rating as the old singles and the problem went away.

 

SIDEWAYS27, Thanks....The cam is not a roller....I took out a hydraulic roller and replaced it with a solid mechanical flat tappet camshaft...It's a Comp Cam....259/266 dur. @ .050 and .550/.570 lift...then add on the 1.6 ratio rocker...Littleman

C9, I am running a double spring........Littleman

 

Money is tight for everybody but I can definitely relate to being on a mission to hitting a number. I have several sets of heads(new) and I am not running a small block right now so the offer to loan you a set is still on the table. If they resolve your issue then we'll work out the deal later (having my 6 94's checked out by someone who knows them in and out is worth more to me) and the barter system is always good.
If the specs you need don't match up to mine I can have a set shipped from French's shop with a phone call or a custom set sent from Brodix for a decent deal.
Pretty sure everybody wants to see you hit that number.

 

What the spring pressures when open? Might be worth checking as I suspect they are not high not enough.
13 or so years ago I ran a hot SB chev in a 2600lb rod and was running 11 flat at 122. I was running a comp cams solid with the first of the dart2 iron heads. lift was slightly less than yours as i was running a Magnum 294S solid lifter cam, and fitted the heads with comp cams 986 springs. Played with seat pressures and from memory was around 145lb with 310lb at .560", piston to valve clearance was around .090" Did hundreds of passes runnin at 7000 thru the traps and never broke a thing.

 

Since my engine decided for me I was not to race this weekend, so I had a good excuse and we have not figured out just yet what is going on with it..I decided to start polishing my new Drag Carbs.......It takes along while to get them to look good......I have only done two of the tops so far..which took longer than I thought it would...They still need more work, but figured I will get them all to this stage for now then start on the center sections...........I look at this way..I am sanding off material....so they should be lighter....therefore make the Truck faster..ha ha ha.......Littleman......they did not photo that well..they look scratched up in the photo but look better in person..

gudgyz.......I have about 145 lbs. of seat pressure as it sits right now......Littleman

 

everything you do looks perfect......