1776 Head Replacement

Photos of bad head. I'm guessing whoever ported and polished the head took out too much material behind the valve seat.

Those heads are pretty messed up!

 @Eric (McGruff) said-"I'm guessing whoever ported and polished the head took out too much material behind the valve seat."

Or the press fit was wrong. How high does the engine rev with power? I'm guessing that with the added effective duration the 1.25's provide it must peak up around 6,000 rpm?

 If you want a big kick in power- up the compression to 8 3/4 - 9:1. You'll have to run premium, but it's a toy, right? And you'll be amazed at the difference in throttle response! If you're insistent on running regular you can still raise the compression 1/2-3/4 of a point safely. Again, you'll find an improvement in throttle response and should feel an increase in low end and lower mid range torque, which will translate into slightly better mileage (if you can keep your foot out of it).

Hope this helps. Al

I take it you're going for the Panchitos with the cnc'd combustion chambers?

ALB posted:

If you're insistent on running regular you can still raise the compression 1/2-3/4 of a point safely. Again, you'll find an improvement in throttle response and should feel an increase in low end and lower mid range torque, which will translate into slightly better mileage (if you can keep your foot out of it).

I take it you're going for the Panchitos with the cnc'd combustion chambers?

Originally, yes. But after reading your advice, I'm considering switching to the 54cc chambers. Losing 7cc pushes static CR to 7.87:1. If it knocks on regular, I can always buy mid-grade. and a little extra mileage never hurt anyone. Who am I kidding? I've never been able to keep my foot out of it!

Eric...this is super cool. Those are nice heads. I bought a set when they first came out -- they cool really well and are perfect for the street. 

@Pat Downs -- any thoughts on Eric's plan for his motor?

Anand

Super low compression is a dinosaur thing. Those Panchitos not only flow better, but will mix the fuel and air better. You'll have so much speed on the intake that the swirl will be better too. I'd up the compression to 9:1 minimum. FYI, I run 9.8:1 on 93 Octane Ultra(with 10% ethanol) in Headflow Masters 44 x 37 heads in a Raby 2165cc.

Gene Berg has been gone a while, and the low compression motors of old should go away these days. Alcohol in the fuel actually deters knock/detonation. All you have to do is pull back the timing a couple degrees at a time until the knock goes away. Try 32, then 30, then 28. I seriously doubt a high compression 1776 with Panchitos is going to knock. But talk to Pat Downs, he knows what to do.

Oh, and REALLY good choice on the heads, they are exactly what they are cracked-up to be.

Good choice on the heads.

    My recommendation;  Use the swivel ball adjuster instead of the elephant foot when using a 1.25 rocket. The reason being, you will run out of travel on the elephant foot and damage it with the increased valve lift.

   Second, I also recommend running a little more compression. The combustion chamber of the panchito is well designed and the head runs cool. You should be able to run 9-1 compression with mid grade fuel, Although I recommend premium on any engine I build.

   If you wanted to take it a step further, get the chambers CNC machined to 61cc and then fly cut to 9-1. You will see even more power due to the unshrouding effect of the intake valve. When I designed the panchito chamber, I had to make it fit a standard 85.5mm bore. Unshrouding it increases intake flow 7-8 cfm, about 7 horsepower.

BAM! Thanks Pat, and thanks for all the good stuff you do in this industry!

Pat Downs posted:

Good choice on the heads.

    My recommendation;  Use the swivel ball adjuster instead of the elephant foot when using a 1.25 rocket. The reason being, you will run out of travel on the elephant foot and damage it with the increased valve lift.

   Second, I also recommend running a little more compression. The combustion chamber of the panchito is well designed and the head runs cool. You should be able to run 9-1 compression with mid grade fuel, Although I recommend premium on any engine I build.

   If you wanted to take it a step further, get the chambers CNC machined to 61cc and then fly cut to 9-1. You will see even more power due to the unshrouding effect of the intake valve. When I designed the panchito chamber, I had to make it fit a standard 85.5mm bore. Unshrouding it increases intake flow 7-8 cfm, about 7 horsepower.

Pat,

Thanks for the advice. I recalculated the static CR. My engine has an 0.65" deck height, so if I start with the 61cc chambers, flycutting to 45cc yields an 8.98:1 CR. Adding the price for the shop work brings the cost to around $1225 plus shipping. Not that I'm complaining, good components are worth the price.

The mor I think about it, my engine was built by someone unknown to me and  I have no idea what issues are hiding in the bottom end. Rather than throw $1200+ into a questionable build, it makes more sense to put that money towards a new one with a known pedigree. Surprisingly, my better half concurs. So I'll be starting a new thread about a new engine as soon as I wrap my head around my goals for the build and the other changes involved, like a bigger exhaust and carburetors, or possibly fuel injection.  

Outstanding!

Great info. Good luck on the new engine

Good move on the new power plant.  It is amazing how one thing leads to another.  A top end issue soon tuns into a bottom end inspection which may as well be. Full rebuild whic turns not machine work and case welding and then you say, “screw it, may a wel order one new!”  

I can vouch for the quality, advice, communication and delivery of CB Performance.  Good luck with your project!

I would look at getting a 2110cc it is CB bullet proof size and you won’t be looking for more down the road

then the tranny might need new gearing  

then your done ... just saying 

McGruff posted:

Pat Downs posted:

Good choice on the heads.

    My recommendation;  Use the swivel ball adjuster instead of the elephant foot when using a 1.25 rocket. The reason being, you will run out of travel on the elephant foot and damage it with the increased valve lift.

   Second, I also recommend running a little more compression. The combustion chamber of the panchito is well designed and the head runs cool. You should be able to run 9-1 compression with mid grade fuel, Although I recommend premium on any engine I build.

   If you wanted to take it a step further, get the chambers CNC machined to 61cc and then fly cut to 9-1. You will see even more power due to the unshrouding effect of the intake valve. When I designed the panchito chamber, I had to make it fit a standard 85.5mm bore. Unshrouding it increases intake flow 7-8 cfm, about 7 horsepower.

Pat,

Thanks for the advice. I recalculated the static CR. My engine has an 0.65" deck height, so if I start with the 61cc chambers, flycutting to 45cc yields an 8.98:1 CR. Adding the price for the shop work brings the cost to around $1225 plus shipping. Not that I'm complaining, good components are worth the price.

The mor I think about it, my engine was built by someone unknown to me and  I have no idea what issues are hiding in the bottom end. Rather than throw $1200+ into a questionable build, it makes more sense to put that money towards a new one with a known pedigree. Surprisingly, my better half concurs. So I'll be starting a new thread about a new engine as soon as I wrap my head around my goals for the build and the other changes involved, like a bigger exhaust and carburetors, or possibly fuel injection.  

PM Pat Downs and have him build you a new motor. You won't regret it.