New build thoughts

[GoFast157]

Okay guys, give me y'all's thoughts on my current build project. I have a small yard kart and basically I am redoing everything on it. I've already ordered most of the things I will need but still considering engine options.

Engine:
Predator 212 Hemi
Governor and Oil Sensor Removed
Open Air Filter
Header with Muffler
.650 Bored carb
Black Mamba Jr Cam
26lb Valve Springs
Billet Rod
Billet Flywheel
Racing Sparkplug from Autolite
Tav30 TC (Yellow Spring) (10T)

Frame:
Sandblasted and Powder Coated Orange
Black Diamond Plate Floor
Custom Seat
Custom Rollbar
Wilwood Hydraulic Brake (2008 Hayabusa Rear Rotor)
Rack and Pinion Steering
Steering Wheel
18 in Rear Tires ( Aggressive Cleat)
15 in Front Tires ( Rounded Knobby)
Wheel Bearings (Front)
Live Axle
Axle Bearings
Sprocket (60T) and Sprocket Hub
Billet Adjustable Foot Pedals

I think that's most of it lol.

 

[ezcome-ezgo]

My thoughts are as follows in chronological order:
1) I wish I had time to work on a cool project like this,
2) Sounds like this guy has this figured out,
3) Looks like he lives in a land of dirt and gravel.

 

[landuse]

I also think you have this figured out just fine. All those mods to the engine should make it run like a beast. Let us know how the engine mod process goes as well

 

[GoFast157]

Does anyone think that this engine build will be too much for 30 series torque converter? Should I stick with stock cam and 22lb valve springs? Also, which of the ported STOCK carbs would work best with this cam? Thanks

 

[landuse]

Does anyone think that this engine build will be too much for 30 series torque converter? Should I stick with stock cam and 22lb valve springs? Also, which of the ported STOCK carbs would work best with this cam? Thanks

The 30 series is rated for 8HP, so if you are going for more than that, then yes, you need a 40 series. It can handle slightly more, but you will have premature belt wear

 

[bob58o]

Does anyone think that this engine build will be too much for 30 series torque converter? Should I stick with stock cam and 22lb valve springs? Also, which of the ported STOCK carbs would work best with this cam? Thanks

I ran the 30 series on a Hemi with a Black Mamba Jr Cam, 26lb Valve Springs, gx390 carb, Milled and Ported Head, 0.027" Head Gasket, 32 BTDC Ignition Timing, +0.020" Billet Rod, Free Flowing Intake and Exhaust,....

The 30 Series did fine for me. I upgraded the springs in the Driver Unit for 3000 RPM engagement (Blue springs, stock weight pack IIRC). I used the stock driven spring in the middle hole and I reached over 7000 RPM.

What are my options to choose from when you say ported stock carbs? Gearing so 6000 RPM is 60mph means you probably won't see much over 6000 RPM, so you probably don't need a huge carb.

 

[GoFast157]

Bob, I was looking at the .650/.675/gx390.
When you say blue spring, do you mean blue/yellow or blue/silver? What ratio would you recommend with 18 in tires? I won't have any head work but I am gonna try to get my piston to .030 head clearance.

 

[itsid]

?? blue springs are the stock ones, not? (blue springs are blued steel undipped ends)
or you talk about the ones with the light blue ends?

anyways blue springs:
3300 with aluminium weights (2200 with zinc)
3100 with zinc weights would be white springs IIRC...

light blue (aka blue/silver)...IDK 4600 with aluminium and 3700 with zinc? something ridiculous at least

'sid

 

[GoFast157]

I believe the blue spring engages at 2200 rpms. The white spring at 3100, the blue /yellow at 3300, and finally the blue/silver at 3600.

---------- Post added at 08:04 AM ---------- Previous post was at 08:00 AM ----------

IIRC Tim suggest setting the idle at 2k with this cam.

 

[GoFast157]

So took engine apart today and I am .017 in the hole with my piston at tdc. Went ahead and installed the stock length billet rod. Just wondering what y'all recommend as far as head gaskets to get closer to .030 piston to valve?? Should I go with (2) .010 head gaskets? Thanks

 

[OzFab]

Measuring only the piston drop won't give you an accurate clearance measurement, you also need to know how far the valves protrude, that involves measuring the cam lift at the valves...

I recall a case where someone installed a +0.020" conrod with no clearance issues...

Installing double head gaskets will lower your compression ratio, which hurts performance...

 

[GoFast157]

Measuring only the piston drop won't give you an accurate clearance measurement, you also need to know how far the valves protrude, that involves measuring the cam lift at the valves...

I recall a case where someone installed a +0.020" conrod with no clearance issues...

Installing double head gaskets will lower your compression ratio, which hurts performance...

Lowering compression ratio hurts performance? I thought you wanted to try to get piston flush at top deck, and leave .030 between piston and head? Then use clay to measure piston to valve clearance? By going with (2) .01 head gaskets I would bring my piston to head down from .057 to .037. Which I assume would be pretty safe for piston to valve clearance. And since I'm taking .020 away wouldn't that be the same as milling head .020? And if assuming that every .010 taken off head = .85cc shouldn't that bring my head down from 22cc to 20.3cc? IIRC an 18cc head with flat top piston at top deck should put you right at 9.8:1. Sounds to me that I should use (2) .010 head gaskets and have my head milled .045.. That would give me .037 clearance between piston and head and a 18.19cc head. Not perfect but pretty close to 9.8:1 CR. Which is alot better for performance than the 8.5:1 that I am currently at correct?

---------- Post added at 08:39 PM ---------- Previous post was at 08:31 PM ----------

OzFab I am assuming that you were thinking my stock head gasket is .010 and not .040?

---------- Post added at 09:11 PM ---------- Previous post was at 08:39 PM ----------

Would it also be safe to assume that every 4cc taken off head is equal to .5hp? So if I went from 22cc head down to 18cc I would gain 1/2 hp? So...
4cc=.5hp
.010=.85cc

Now by taking .020 away from my .040 head gasket that would be 1.7cc which =.21hp

Therefore by making piston flush with top deck and leaving .030-.037 piston to head clearance and having 22cc head milled down to 18cc (.045) that would get me a gain of .7hp?

---------- Post added at 09:29 PM ---------- Previous post was at 09:11 PM ----------

I know that's not much but similar cams to this such as NR 280-0211 call for 11 to 1 ratio minimum. Just want to make sure I am good to go

 

[bob58o]

.
When you say blue spring, do you mean blue/yellow or blue/silver? What ratio would you recommend with 18 in tires? I won't have any head work but I am gonna try to get my piston to .030 head clearance.

I was wrong. I meant White springs. - like itsid said. Comet 011190. 3100 RPM engagement with stock weight pack.
http://www.bmikarts.com/Replacement-Springs-for-20-30-Series-Driver_p_1015.html

I covered the gear ratio, right? either in another thread or in PM I believe. I like 7.2 - 7.5:1 with 18" Tires and 30 Series with 6" Driven Unit.

---------- Post added at 10:32 PM ---------- Previous post was at 10:20 PM ----------

So many threads... JK I dunno how many. lol At least two. LOL

So took engine apart today and I am .017 in the hole with my piston. Went ahead and installed the stock length billet rod. Just wondering what y'all recommend as far as head gaskets to get closer to .030 piston to valve?? Should I go with (2) .010 head gaskets? Thanks

0.017" in the hole?
Stock length rod?

I'd use a 0.010" Head Gasket.
If 0.030" is Good, 0.027" is OK too.
An old member Flying Hillbilly knows much more about engines than me, and he said 0.025" is fine.


BTW, keep up the good work. You've obviously studied up on these engines. I think the thread where I learned about 212's was like 80+ pages. I've learned much more since then. Still boat loads I don't know.

You know all the clearances you should check on the Hemi?
Cam lobes to block.
Cam lobes to crankshaft.
Piston to Head.
Valves to Piston.

I think you will be OK with the BMJr, I didn't need to grind the block or clearance the crankshaft to the cam. I believe you should be ok on P2V clearance with the stock length rod and a 0.010" gasket, BUT ALWAYS CHECK WITH CLAY OR A DIAL INDICATOR!!!

 

[GoFast157]

So got back to shop today and re-measured piston drop after installing billet rod. Stock rod had piston drop of .017. After installing new rod I have .022.. I guess I'm going to go with .010 head gasket and be at .032 p2h.

Also went ahead and milled the head .035
That should have me pretty close to 18cc
Looking for that magical 10:1 ratio lol

I received my .650 Chinese carb today. Does anyone know what jets this thing comes with?

Lastly I went ahead and ordered CM pushrods and SS valves, retainers, and lash caps.

 

[OzFab]

Lowering compression ratio hurts performance?

Well, yes, just as much as raising compression, depending on the severity...

OzFab I am assuming that you were thinking my stock head gasket is .010 and not .040?

Uh, yes I did

So, as mentioned, you quite obviously know what you're doing so, I'll just shut up now

 

[bob58o]

Also went ahead and milled the head .035
That should have me pretty close to 18cc
Looking for that magical 10:1 ratio lol

The calculator I like to use shows you are closer to 11:1 than you are to 10:1? You like 10:1 for use with pump gas? Pretty sure the Hemi is like 1cc per 0.010" Milled. Correct me if I am wrong.


70mm (2.756") Bore
55mm (2.165") Stroke
70mm (2.756") Head Gasket Bore Diameter
0.254mm (0.010") Head Gasket Thickness
18.5cc??? (~1cc per 0.010" Milled?)
0cc Piston Dome Volume (Flat-top Piston)
0.559mm (0.032") Piston Deck Clearance

10.8:1 Static Compression Ratio
http://www.csgnetwork.com/compcalc.html

 

[GoFast157]

The calculator I like to use shows you are closer to 11:1 than you are to 10:1? You like 10:1 for use with pump gas? Pretty sure the Hemi is like 1cc per 0.010" Milled. Correct me if I am wrong.


70mm (2.756") Bore
55mm (2.165") Stroke
70mm (2.756") Head Gasket Bore Diameter
0.254mm (0.010") Head Gasket Thickness
18.5cc??? (~1cc per 0.010" Milled?)
0cc Piston Dome Volume (Flat-top Piston)
0.559mm (0.032") Piston Deck Clearance

10.8:1 Static Compression Ratio
http://www.csgnetwork.com/compcalc.html

I thought I had read that it was .8-.9cc per .010 milled. In my calculation I went with .85cc per .010..

Either way I have an extra .010 head gasket on the way. And yes I'm trying to keep it on pump gas.

 

[GoFast157]

Got the motor put back together but have not fired it up yet. Been working on restoring the frame. Hopefully I will have more progress by next week. Thinking about black diamond plate floor with orange frame.

 

[bob58o]

[/COLOR]I know that's not much but similar cams to this such as NR 280-0211 call for 11 to 1 ratio minimum. Just want to make sure I am good to go

NR280-0211 calls for 11:1 CR or LOWER.
The NR280-0611 calls for 10.5 CR or HIGHER

 

[GoFast157]

Update**

Hey guys. Havent been on here in a while so figured I would share my current progress.

I am having trouble with my engine having extreme kickback. Im going to re-check the valve lash in the morning. Im probably going to have to put a 40-series TC on it. Lol, we shall see.