4.6L Stroker, Help me build it please!

[XJoshua]

My cloyes dual roller timming gears are adjustable. But doesnt the renix and for that fact all 4.0 FI engines retard or advance the timming themselves. So wouldnt that make adjusting the cam gears useless?

 

[JJacobs]

A couple things. First, the computer controls ignition timing, which is when the spark fires relative to piston position in the cylinder. The adjustable cam gears control when the valves move relative to piston position. Advancing the cam will give more torque, retarding will give more higher end HP at the expense of torque.

Also, I wouldn't worry one bit about running the engine over 3000 rpm during the break-in period, or exceeding 50 mph, or any of that other mumbo-jumbo. If it's gonna blow you might as well find out sooner than later, and running the engine hard will absolutely not hurt it one bit if it's built right. In fact you run the risk of the rings not seating if you baby it too much. About the only break-in procedure worth mentioning is to not stay at any one rpm for very long, i.e. vary your cruise speed on the highway a little, or shift in and out of overdrive. Drive it like you want to or risk a soft engine.

Be realistic with your expectations. A 17% displacement increase (4.0-4.7) is not likely to give a 56% power increase (177-277hp), even counting the cylinder head work.

 

[XJoshua]

So then with the blow up factor i should be fine running stock stamped steel rocker arms for a couple months?

 

[Frank Z]

So then with the blow up factor i should be fine running stock stamped steel rocker arms for a couple months?

Got em in mine and they are staying put.

 

[XJoshua]

Well today I started installing the rotating assembly. So far the most fun Ive had my whole summer vacation.

Just to get these did yu do it right questions out of the way.

Yes I installed the rings correctly.

Yes I used installation lube on all bearing.

No I didnt break and rings.

Yes the oil rings are properly seated.


Also when I was getting a ring compressor I forgot to get a ring expander so I used the jeeper inside me to fab up my own tool with a drill and a pair of pliers. Worked great but would have worked quicker if i had a drill press.

Now Im at a slow down since I cant get the connecting rod caps off. So Im going to walmart for a drain decloger that inflates to pop the cap and also pick up some masking tape so I can start painting the head, block, intake and oil pan.

Ill try and picture up soon, but im currently embarrased to go outside since my nose got sunburned and is peeling hardcore. Also if youre woundering why I have to go out to use the net thats because my phone can upload pics and the pc doesnt have net so I have to use the library.

 

[1bolt]

If you're leaving that compression ratio and quench alone you should prepare yourself for lots of ping, unless I'm reading what you posted wrong. You might even have issues with 91 octane.

I was too lazy to re-read the whole thread to see if you CC'ed your combustion chambers when you did the head, but your piston dish is insufficient to lower your CR into pump gas territory...

I'm sure you're fired up to move on with your build but you would be well advised to get your quench into spec and get your chosen piston dished more, before you put it all together only to have unmanageably high CR.

 

[XJoshua]

The machine shop warned me not to have the pistons cc'd since i had the entire rotating assembly balanced and that it might add roughness to my ride. I asked for the combustion chamber to be cc'd and he claimed he ran 87oct in his 10:1 chevelle. So I just asked for him to cc the head to where my combustion ratio was 9.4:1 and he said he'd do it for free since he didnt see that on my spec sheet and I had already paid. I had gotten it back in one days time so thats why I started the build yeasterday.

Ohh and the paint job looks awesome so far. Flat black for the block and oil pan. Cast alunimum for the head and i still need to clean up the valve cover but itll be wrinkle black with the platues polished.

All that i need now are small parts for the timming cover and misc bolts. Also I need to grind the head a bit because the arp head studs bolts dont tighten down. They are to close to the wall for the ones under the valve cover.

 

[Israel]

I asked for the combustion chamber to be cc'd and he claimed he ran 87oct in his 10:1 chevelle.

Maybe with a super lopy cam, but you're sure as hell not going to pull it off with your stroker. Not even with 91 octane!

 

[MudDawg]

"87 octane in a 10 to 1 Chevelle"......ummm....this ain't a smallblock....the small block is more likely to have good quench height without having to surface the block, and the heads are much more quench friendly than a 4.0.....especially early small chamber heads....if you built a short rod stroker with 4.0 pistons, the quench will be awful large even if the stock deck height on the block is even close to spec...and most blocks deck out quite a bit higher than spec....you only have one small area of the head surface to use for quench, the rest is open chamber...so you need to make as much good of it as you can...

As for the stock rockers....I ran a set of stockers for quite some time on my 2.5 Mod1 and they worked ok at RPM you can only dream of with a 4.0....eventually they did wear out....but you can break anything with judicious application of abuse...

The 2.5 in the Heep is high compression (around 11:1) and needs 100 octane to run with full ignition advance under a load....and when I uncork the blue Genie, it gets fed 116......no it's not a DD....it will "run" on 87 octane with the timing pulled way back...but that makes it really weak in the knees...

But then again dynamic and calculated CR can be miles apart depending on the cam and set up...for example on my dragbike...the calculated CR is 15.8 ..the leakdown rate is less than 4% hot.....depending on the cam timing, the cranking pressure can be as high as 255 psi and as low as 125 psi....same cams....different timing setups....in a street 4.0 with a typical cam, the VE is very good at low RPM....this drives the cylinder pressure into detonation range under a low rpm high load situation.

 

[Flash]

You might want to do some re thinking on the compression ratio...........while its still a lot easer, to change now, then after you are fed up with pinging and the ultra light foot that you have to keep using to keep it alive.
I haven't ran your number, but if every one else is right, and i thing they are..........You are going to have to add or mix racing fuel at 7-8 dollars a gallon to keep it from pinging.

I now you are excited to get it together(so would I ! ) but don't be blinded by the fact that others have built stroker, much like your, and trying to help you from makeing.......... something you will not like.

10:00:1 even in Colorado is not going to fly with a 4.0L whether its stroked or not.

Stop, do some more research before you continue.............

Flash.

 

[1bolt]

if your guy CC'ed the combustion chambers out it will be fairly easy to tell, you said you were getting a beaker anyway... If he CC'ed enough for 9.5:1 or lower you might be okay with 91 and that bad quench...

 

[Flash]

XJoshua: In order to get an accurate CR, i need to now the total cc of the piston at TDC in the bore,(this will include the cc of the dished piston) or the piston distance down the bore,(.020,.030 ETC) at TDC and the exact CC of the piston dish.

Either way i can get a much more accurate CR

Right now with all the figures you gave above, and me guessing that the piston is setting at .030" down at TDC. your compression ratio is 10.30:1:scared:

Make sure you have all you figures corrected, double checked and i will try it again.

I thing your first step is to go with the stock (thicker) head gasket then the .043/.045 head gasket.

Just changing the head gasket to the stock. 051" head gasket changed the compression from 10.30:1 to 10.17:1

As far as the machine shop worrying about the balance job. as long as all the piston are dish so that they weigh the same,..................I don't thing the out of balance would be seen, at least in the max rpm of the rev limiter!

Maybe if we turned are eng at 65 to 7000 rpm.

all you would need to do is to increase the dish depth by 4 to 6 cc to accomplices you goal.

Flash

 

[XJoshua]

Well the block is done. The machinist made a good point about not messing with the balanced rotating assembly. So Ill do everything I can to the head. The comb chamber is pretty well enlarged to allow the larger valves to open without rubbing against the dome. All Ive done to that is paint it and there is s still head work to be done so thats my next thing to get started on. Tomorrow Ill put pics up and pick up another copy of the calculator to help me get it done. All I can really do to fix stuff is change the chamber volume which I did and also change the headgasket but I dont want to go way to larger and end up with a BHG after 80k miles.

Some of these mistakes are mine because I was using the calculator wrong but mistakes are expected the first time. Also Im not the only one excitied about it my Jeep gets hot and bother everyday I read the specs to it. Pushed 210* today and has been around 170* lately. But thats because I refuse to replace the fail safe thermo.

 

[Flash]

Well the block is done. The machinist made a good point about not messing with the balanced rotating assembly. So Ill do everything I can to the head. The comb chamber is pretty well enlarged to allow the larger valves to open without rubbing against the dome. All Ive done to that is paint it and there is s still head work to be done so thats my next thing to get started on. Tomorrow Ill put pics up and pick up another copy of the calculator to help me get it done. All I can really do to fix stuff is change the chamber volume which I did and also change the headgasket but I dont want to go way to larger and end up with a BHG after 80k miles.

Some of these mistakes are mine because I was using the calculator wrong but mistakes are expected the first time. Also Im not the only one excitied about it my Jeep gets hot and bother everyday I read the specs to it. Pushed 210* today and has been around 170* lately. But thats because I refuse to replace the fail safe thermo.

like i said before, if you can enlarge the cc 4-6 CC, whether it be piston dish or head volume you will be happier in the end
the would mean a head volume around 62+CC is there enough head material to do that.............I don't know, have heard of polishing the head to get rid of the casting bumps(to help on detonation or pinging) don't know of any one trying to increase the CC of the head chamber that much.

Undo the thermostat housing and you can at least get a good idea how much there is between the combustion chamber and the water jacket....................

Flash.

 

[XJoshua]

Well Ive been procratinating and still havent gotten a gradulated cylinder to measure yet but just to mess with what Im showing I need how would this work out.

Comb Chamber Vol of 60cc
And removing some of the bumps in the pistons to 13cc
With all the old specs gets me a comp ratio of 9.6:1 using the current headgasket. My quench will be .021 below stock. Now I really need schooled on quench is that the difference between the new and old TDC? Or how far the piston sits below the deck?

But whats a accepatble amount of quench for high altitude no more or less then .020 .015 .010?

Also Ive desided to slow down but Im done doing work to the block so my problem need to be fixed with head and headgasket as listed before. Ill sand off some of the circles on the piston dishes to try and get 13cc out of them. As for the head once I measure the cc's I guess ill polish them to get every little cc I can out it.

Some other tech questions:
How far can timming be retarded or advanced before it can cause problems or consider improper use of a stroker?

Valve timming. Im all about getting torque out of it but is any damage cause by retarding I think it is, for torque? Do ignition and valve timming have any relationship to each other. Such as change one the other needs adapted? Reason Im asking is because once the timming chain cover goes on I dont want it removed for atleast 5years.

 

[Flash]

Well Ive been procratinating and still havent gotten a gradulated cylinder to measure yet but just to mess with what Im showing I need how would this work out.
Go to a veterinarian hospital and ask then for a 60 cc syringe ( Shot for a horses......large animals) there like $2

Comb Chamber Vol of 60cc
And removing some of the bumps in the pistons to 13cc
With all the old specs gets me a comp ratio of 9.6:1 using the current headgasket. My quench will be .021 below stock. Now I really need schooled on quench is that the difference between the new and old TDC? Or how far the piston sits below the deck?

Does that mean that you are .021" below the deck at TDC? or are you saying it is .021" below stock..... .042". This is vary important and need to be measured exact, before a accurate number can be figured

But whats a accepatble amount of quench for high altitude no more or less then .020 .015 .010?

Basically, Quench is the distance the piston is form the head( piston below deck at TDC + head gasket thickness)
Piston below deck (.030)
Head gasket ------- (.045)
-------------
______________=.075" Quench
less Quench, is better, but raises compression, and if your Quench is to tight, you could slam the piston into the head at top RPM. (there would have to be a lot of block decking to ever worry about that. on a stroker or stock 4.0L)


Also Ive desided to slow down but Im done doing work to the block so my problem need to be fixed with head and headgasket as listed before. Ill sand off some of the circles on the piston dishes to try and get 13cc out of them. As for the head once I measure the cc's I guess ill polish them to get every little cc I can out it.

Some other tech questions:
How far can timming be retarded or advanced before it can cause problems or consider improper use of a stroker?

Timing in non adj. time is set by the crank sensor and it is not adj.

Valve timming. Im all about getting torque out of it but is any damage cause by retarding I think it is, for torque? Do ignition and valve timming have any relationship to each other. Such as change one the other needs adapted? Reason Im asking is because once the timming chain cover goes on I dont want it removed for atleast 5years.

Advancing the cam from it -0- seating will raise torque at a lower rpm while lowering top HP. Retarding the cam from -0- will raise the top rpm HP but low end torque will suffer.
If you have bought a cam that you realize now, is to big or small this will help but will not fix it.
I would run it straight up!(-0-)


Flash.

EDIT
Here is a article that explains it much better then I

http://www.rbracing-rsr.com/squishcalc1.html

 

[MudDawg]

Minimum quench is .040 to .045 depending on if the piston's material and piston/cylinder clearance. Basically "0.00" deck height with the head gasket making the quench clearance.

Cam timing: The more advanced the timing, the higher the cylinder pressure at low rpm (more likely to detonate), but more torque....Retarded timing lowers the low rpm cylinder pressure (reduces the likelyhood of detonation) but moves the power higher in the rpm range.

To understand the relationship between cam timing and Compression Ratio...basically put a stock cam in a motor with stock pistons will have say... 8:1 compression and yield 175 psi cylinder pressure at cranking speed...remember the 175psi. Now we pull the stock cam out and install one with more duration and overlap with the intention of moving the power up the rpm band....in doing so because of blowdown and reversion due to the longer duration and overlap, the cranking pressure is lowered in this example to 125 psi....the result is less torque at low rpm...that is why cammed motors are soft of the bottom...one way to recover some of the lost torque down low is to up the theoretical compression ration by installing pistons with less bowl (in the case of a 4.0)...this will bring the cylinder pressure at cranking speed back to pre-hotrod cam level....fixes it right?? not exactly...the reduced combustion chamber volume cuts into fluid volume compared to the stock set up....we end up with a bit less fuel/air mixture...since the motor is powered by the amount of heat produced by combustion, the reduced volume of the charge means less volume to expand...peak cylinder pressure may match the previous number....but as the crank rotates and the swept volume increases, the cylinder pressure drops of rapidly...since cylinder pressure acting on the piston/rod apply pressure to the crank, generating rotational torque the lower the pressure, the less the torque.

This seemed to start out as a simple explaination....it could take pages...

 

[JJacobs]

It's not timming it's timing- one M.

Have you played with the burette lately? I only ask because your cc expectations aren't gonna happen the way you want. You know a typical Chevy flat top piston with the half-moon valve reliefs cut into them? Those reliefs are 2-3 cc apiece. So sanding your piston tops isn't gonna get you 13cc, no way no how.

Have you figured out quench yet? Let's try this explanation- drop a book on a table and note how the air that was underneath goes shooting out at high speed in all directions. In an engine, of course, physical contact isn't made but the parts come quite close together. The quench band in the 4.0 is the flat wedge at the top of the piston along one side. It aligns with the flat deck of the cylinder head off to the side of the valves. If the parts don't get close enough, you don't get the air blasting out from between into the chamber and swirling the air/fuel mixture resulting in uneven burns and detonation.

 

[Flash]

JJacobs,
.... XJoshua first piston spec. was 12.2 CC. It could be possible to to get 0.80 of one CC doing that. See post 380.

XJoshua, i when and re did the compression spec that you gave on post 380, and came up with a SCR of 10.2:1(assuming ) the piston is below the block .030 (a TDC) and with the piston dish cc at 13 CC and the combustion chamber at 60 cc (from the 56 CC) lowered the SCR was lowered to 9.7:1..........could be low enough for your altitude, but this is still a guess, need real world CC specs to now for sure, if you replaced the .043 with the .051 the compression dropped to 9.54:1

Flash.

 

[JJacobs]

Oops, I was going with this post. Guess that wasn't the whole story. Post 380 hasn't happened yet, in this thread anyway.

Also Ive desided to slow down but Im done doing work to the block so my problem need to be fixed with head and headgasket as listed before. Ill sand off some of the circles on the piston dishes to try and get 13cc out of them. As for the head once I measure the cc's I guess ill polish them to get every little cc I can out it.