200ci Ford 6 Pushrod Length issues?

[Xnke]

Got a weird one for you guys.

Built a 200i6 ford for a 13's for 1300$ car, meaning the purchase of the car plus any and all mods must be less than 1300$, and you must run a 13.XX second quarter mile. Yes, the 70 Maverick went on a serious diet and we have $41.63 left to spend to stay inside the limit. If we go over limit, we get pushed into the contingency class of 12's for 1200$ more, and we'll cram as much boost as she'll hold to get there. (new budget will be 2500$ total for the 12 second class.)

Engine got cleaned up and a burnt valve replaced, valvetrain re-fitted with LS-engine springs/locks/retainers, head machined to hold the longer springs at 1.700" installed height.

Rockers are non-adjustable, valvetrain is hydraulic flat tappet.

Head was cut 30 thou, block was not cut (that we know of) Cylinder head is the "large plenum" style, with the fox mustang larger valves.

Cam is Howards Cams 280998-10 cam and lifter kit, 275/275* advertised duration, 221/221* duration at 0.050", 0.470" lift, LSA 110*, intake centerline 106*. Confirmed cam events are IVO at 31* BTDC, IVC 63* ABDC, EVO 71* BBDC, EVC 23* ATDC, and we have 55* of overlap, as installed in the engine.

Currently the engine runs on the rear three cylinders only. Ignition is via a wasted-spark setup triggered off the crankshaft and we can swap front 3/rear 3 plug wires and the setup still only runs on the rear three cylinders.

Engine has a ridiculously bad problem with intake backfires, at any timing advance setting. Was MUCH worse before we found and solved all the vacuum leaks, but still does it even after fixing vacuum leaks.

After going through the whole engine twice over, the only thing that sticks in my mind is pushrod length. If the block deck is not square (they weren't from the factory, and we didn't fix it, so it probably isn't now) could I somehow be hanging a valve open when the engine is running, but the valves close fully when the engine is not running?

Compression test on all cylinders is good, less than 5PSI difference on all 6 cylinders at 145PSI.

[mag2555]

Well it’s back firing as you know from the intake valves not seating when running.

My question to you then is do the intake valve springs have enough seat pressure to compensate for the level of boost being run at a given rpm?

A 2.00” valve with a 11/32 stem under just 15 psi of boosts will call for a extra 45 lb of seat pressure above what the Cam card may call for to deal with that level of boost.

In terms of valve adjustments those lifter plungers may only have a total max of .100” of travel, so the stock adjustment like took .050” out of that possible.100”.
Then you took out another .040” with the head mill, and on top of that you have the valve job that was likely done also eating into that .100” of travel!

This lifter setting when running could be making for your holding the valve open issue possibly,

[PRH]

I would start with verifying the valve timing events for all 6 cylinders.

If that’s correct, I’d move to checking the lifter preload for all lobes.

[Baprace]

Got a weird one for you guys.

Built a 200i6 ford for a 13's for 1300$ car, meaning the purchase of the car plus any and all mods must be less than 1300$, and you must run a 13.XX second quarter mile. Yes, the 70 Maverick went on a serious diet and we have $41.63 left to spend to stay inside the limit. If we go over limit, we get pushed into the contingency class of 12's for 1200$ more, and we'll cram as much boost as she'll hold to get there. (new budget will be 2500$ total for the 12 second class.)

Engine got cleaned up and a burnt valve replaced, valvetrain re-fitted with LS-engine springs/locks/retainers, head machined to hold the longer springs at 1.700" installed height.

Rockers are non-adjustable, valvetrain is hydraulic flat tappet.

Head was cut 30 thou, block was not cut (that we know of) Cylinder head is the "large plenum" style, with the fox mustang larger valves.

Cam is Howards Cams 280998-10 cam and lifter kit, 275/275* advertised duration, 221/221* duration at 0.050", 0.470" lift, LSA 110*, intake centerline 106*. Confirmed cam events are IVO at 31* BTDC, IVC 63* ABDC, EVO 71* BBDC, EVC 23* ATDC, and we have 55* of overlap, as installed in the engine.

Currently the engine runs on the rear three cylinders only. Ignition is via a wasted-spark setup triggered off the crankshaft and we can swap front 3/rear 3 plug wires and the setup still only runs on the rear three cylinders.

Engine has a ridiculously bad problem with intake backfires, at any timing advance setting. Was MUCH worse before we found and solved all the vacuum leaks, but still does it even after fixing vacuum leaks.

After going through the whole engine twice over, the only thing that sticks in my mind is pushrod length. If the block deck is not square (they weren't from the factory, and we didn't fix it, so it probably isn't now) could I somehow be hanging a valve open when the engine is running, but the valves close fully when the engine is not running?

Compression test on all cylinders is good, less than 5PSI difference on all 6 cylinders at 145PSI.

Why not put a set of thin washers under the rocker stands and if the engine clears up then you know what your looking for.

[mag2555]

X2 with the above!
Easy peesy and dirt cheap to your remaining funds!

I wanted to ask, what valve burned on you and if you know why?

[cjperformance]

The 1st thing to do is simply check that the rocker on each cylinder at TDC on compression stroke can be held back against the pushrod to bleed the lifter down. If you get any clearance its not pushrod length.

Were the rest of then valves and seats recut?
Are you sure you have the cylinders paired correctly on the wasted spark setup?

[cjperformance]

What induction/carb/efi etc?

[Baprace]

Any results ?

[Walter R. Malik]

"IF" the pushrods are to long, you could try shimming the pedestals the correct amount, using a shim kit for a V8.
That kit is well under your 40 dome dollars.

[Xnke]

The 1st thing to do is simply check that the rocker on each cylinder at TDC on compression stroke can be held back against the pushrod to bleed the lifter down. If you get any clearance its not pushrod length.

Were the rest of then valves and seats recut?
Are you sure you have the cylinders paired correctly on the wasted spark setup?

Yes, all valve seats were recut and all valves replaced, we upped the valve size to use the late 1979 Mustang valves. I lapped the valves in after, and all were sealing when we installed the head on the block.

The lifter bleeds off 0.050" under just the valve spring pressure alone, when trying to find valve timing events. It made it difficult to measure properly!

The cylinders are paired properly. I use this exact same setup on Nissan and 300-I6 engines, the firing orders are the same at 1-5-3-6-2-4, and cylinders are paired 1-6, 2-5, and 3-4.

The backfiring goes away over 2000RPM. It only occurs at idle and on decel, but I do agree-it's intake valves not closing that is causing the problem.

What induction/carb/efi etc?

Carb is a Motorcraft 2100 1.33" throttle plate modified to have an externally referenced power valve and sealed throttle shafts.

Turbo is a Holset WH1C, however the turbo has been removed and we have a carb adapter connecting the carb straight to the intake manifold until we get this figured out.







Once we get the engine operating properly the turbo will go back on-Even with only 3 cylinders we were able to make 5PSI of boost at 5000RPM in neutral.

The valve seats were modified to allow us to use LS beehive valve springs.



The modification wasn't quite enough, we had to use a +50 thou valve lock set to get all the way to 1.700" installed valvespring height. The valves are 5/16" diameter stems, 1.753" intake valve diameter, 1.390" exhaust valve diameter. The LS springs are topped with stock LS valve spring retainers that have had the top lip ground down 0.050" to make damn double sure we don't cock one over on a rocker arm and unseat a valve spring retainer. It was very, very close before we cut them down.

I am concerned that either the valve spring seat pressure isn't high enough (it should be, only has to be higher than the oil pressure as long as we don't float a valve) or that the pushrods are too long.

The engine cleans up above 2000-2500RPM and will rev fast to 7000RPM+ with no sights of float that I can hear on a quick rev, we haven't held it at RPM yet due to fears of pushrod length and plug reading showing the front 3 cylinders not firing 100%.

Sorry for the long delays, day jobs and life keep us from working on this car much. It's hard to stay motivated when you've missed two racing seasons in a row, and you're an hour away from the car 5 days a week.

[Xnke]

X2 with the above!
Easy peesy and dirt cheap to your remaining funds!

I wanted to ask, what valve burned on you and if you know why?

#5 Exhaust valve was burned with 1/8 of the valve head gone when we bought the car and brought it home. I drove it 12 miles home, and we did plenty of 2 gear burnouts on the way, but when we inspected the exhaust manifold for what we thought was a crack, we found a broken manifold bolt and a stripped out manifold bolt hole that had to be fixed.

We only found the burned valve when we pulled the head to fix the stripped threads and broken bolts.