My very first engine build, but........

[Poboy kartman]

WHOOPS!!!!!........HOLD ON.....Let me double check the valve lash...MY BAD...... I just realized you had a hemi....

My information was based on non-hemis.....

I'll come back with an edit to clarify.......but.....

Unless you are absolutely sure you were on the compression stroke...that's the most important thing in setting the lash.....

I pull the spark plug and reinstall with only a thread or two and the wire disconnected.....and slowly pull on the starter until I hear it hissing.....then remove the plug and drop a short screwdriver in the hole and turn it over untill the screwdriver just stops rising out of the hole.......

EDIT: I can't find a whole lot on the hemi valve lash.....but BMI sells a MOD2 cam for $49....and they recommend.003 and .003 for it.....

Oh...and when you get to TDC....watch the valves close...and make sure that all the pressure is off the valves...you may want or need to go slightly past TDC....and turn two revolutions after adjusting and check from TDC to a quarter turn past.....just to make sure that the gaps don't grow..(meaning. you weren't completely loose and on the base circle) ......

 

[Xtreme Yard Karts]

I beg to differ......TDC is 0° ...anything firing BEFORE TDC.....is advanced timing.....after.....retarded timing.......

So a stock flywheel fires 24° Before Top Dead Center......firing another 8° BTDC adds another 8° of advance......= 32°BTDC.......

It's pretty easy to understand when you consider PRE-ignition....or "pinging"....that happens in engines with too much advance in the timing....the piston is still heading up on the compression stroke towards TDC when the charge fires......causing a slamming effect on the piston.....RETARDING the timing.....allows the piston to get closer to TDC....eliminating the problem......

My math is not the only thing that's right.......

EDIT: Kart Simpson......this same phenomena makes advanced timed engines harder to crank.....but...the charge has to be firing for it to come into play.....but why so many aftermarket ignition systems have "Start Retard" to keep from burning up starters......FWIW......My stock Tecumseh almost broke my arm.....because the cam and crank were misaligned.......

He's ^^^ right. Timing advance is commonly referred to as "lead" (pronounced LEED not LED) in the automotive racing world because it refers to the amount of degrees that the plug has to fire before TDC. Inefficient combustion chamber designs require more lead than efficient ones do. Modern high swirl chambers with adequate quench pads can run much less timing than heads such as the old Chrysler Hemi's or Pontiacs. It is not uncommon to have run 40 degrees or more in those engines in race applications.

 

[OzFab]

I beg to differ......TDC is 0° ...anything firing BEFORE TDC.....is advanced timing.....after.....retarded timing.......

So a stock flywheel fires 24° Before Top Dead Center......firing another 8° BTDC adds another 8° of advance......= 32°BTDC.......

It's pretty easy to understand when you consider PRE-ignition....or "pinging"....that happens in engines with too much advance in the timing....the piston is still heading up on the compression stroke towards TDC when the charge fires......causing a slamming effect on the piston.....RETARDING the timing.....allows the piston to get closer to TDC....eliminating the problem......

My math is not the only thing that's right.......

EDIT: Kart Simpson......this same phenomena makes advanced timed engines harder to crank.....but...the charge has to be firing for it to come into play.....but why so many aftermarket ignition systems have "Start Retard" to keep from burning up starters......FWIW......My stock Tecumseh almost broke my arm.....because the cam and crank were misaligned.......

He's ^^^ right. Timing advance is commonly referred to as "lead" (pronounced LEED not LED) in the automotive racing world because it refers to the amount of degrees that the plug has to fire before TDC. Inefficient combustion chamber designs require more lead than efficient ones do. Modern high swirl chambers with adequate quench pads can run much less timing than heads such as the old Chrysler Hemi's or Pontiacs. It is not uncommon to have run 40 degrees or more in those engines in race applications.

After further research, I stand corrected... which means my thinking has been backwards for 25 years Which leads me to wonder what else am I misinterpreting?

 

[deano10972]

As to my expectations, I can't get it started. It is a Harbor Freight Predator w/ Hemi head 6.5hp. Here is a list of mods.

Removed governor
Removed low oil sensor
Billet conrod
Billet flywheel w/ 32* advanced timing
18# valve springs
0.35 main jet
.022 pilot jet
GX-140 emulsion tube
Autolite AR3910X spark plug
High flow air intake
High flow exhaust
walbro fuel pump

I have stock cam
I have stock crank shaft


It seems to be getting fuel into the cylinder and I have good spark right at the plug spark but it doesn't even attempt to fire. Thinking maybe a timing issue? I dunno. What's really weird to me is that when I give it a little throttle as I try to start it, I can hardly pull the rope. If I don't give throttle, I can pull it normally. Why is that?

I have almost the same set up on my Hemi, when you installed the valve springs, did you check for coil bind? The 18# springs seem to have that issue in a hemi unless you cut the spring pockets. Since you didn't mention doing that, I figured I'd ask. You need .080-.100" clearance between the coils at max lift. I had to go with 26lb springs and I also tried the Autolite plug but it fouled out after about 10 min. Of running and then stopped firing( think it was just burning too hot). Don't think this has anything to do with cranking, because mine still fired up, but ran like crap till I put the stock plug back in and changed the springs..

 

[Kart Simpson]

I installed the 16# springs without any midification to them. I also put the stock flywheel back in and set the coil gap to .010 and it still wont fire. Pulled the plug and confirmed a good spark and it appeared to be wet with fuel. I am certain that the cam is lined up with the crank correctly. I don't know what to do now.
I need all you guys to take a road trip to New Hampshire......

 

[Kart Simpson]

I have almost the same set up on my Hemi, when you installed the valve springs, did you check for coil bind? The 18# springs seem to have that issue in a hemi unless you cut the spring pockets. Since you didn't mention doing that, I figured I'd ask. You need .080-.100" clearance between the coils at max lift. I had to go with 26lb springs and I also tried the Autolite plug but it fouled out after about 10 min. Of running and then stopped firing( think it was just burning too hot). Don't think this has anything to do with cranking, because mine still fired up, but ran like crap till I put the stock plug back in and changed the springs..

Did you have to modify anything with the 26# springs?
Will 26# springs be ok with the billet conrod? (26# sounds tough)

 

[Kart Simpson]

So now I am thinking of getting 26# springs and possibly a Mod 2 cam. I am going to call ARC today and see what they recommend for a cam with the corresponding billet flywheel I got per zbucks advice. Still disappointed with it not firing up when I put the stock flywheel back into it. I am sure it is just adjustments needed but like I mentioned in the opening of this thread "my very first engine build". So this is all a learning process for me and I am hoping to have better results soon. I appreciate all the help and advice you all have given me so far, but we are not done yet......

 

[deano10972]

Did you have to modify anything with the 26# springs?
Will 26# springs be ok with the billet conrod? (26# sounds tough)

Yeah the 26# are tough but I had coil bind with the 18lb springs that I ordered from ARC. And I didn't have to modify anything with the 26#. I seen where NR Racing sells 18# springs specially for the Hemi Head


"Racing Valve Spring, 18lb closed pressure. Fits new style Predator (Hemi Head) engines.

Works with Cl1, Mod 2, and 230 series Cams."

I might go back to these..

 

[Kart Simpson]

Yeah the 26# are tough but I had coil bind with the 18lb springs that I ordered from ARC. And I didn't have to modify anything with the 26#. I seen where NR Racing sells 18# springs specially for the Hemi Head


"Racing Valve Spring, 18lb closed pressure. Fits new style Predator (Hemi Head) engines.

Works with Cl1, Mod 2, and 230 series Cams."

I might go back to these..

What was the indicator of thecoil bind? Just wouldn't start? Noise?
So you recommend these 18# Hemi springd over the 26# springs?

Also, ehat do uou have for a cam?

 

[Kart Simpson]

To all in this thread, with the help from you all, I finally got my engine running. Now needs some tweaks but that was expected.

 

[justinlogue5_0]

So what did it turn out to be?

 

[Kart Simpson]

When I first set my valve lash, I did it incorrectly. It is very important that it is done on the compression stroke and when I first adjusted mine, I just made sure that it was at TDC not knowing what stroke I was on.

 

[2SlickNick]

Great! I thought that was it too.

 

[justinlogue5_0]

Yep that would def do it. Glad you got it figured out.