4.6L Stroker, Help me build it please!

[Flash]

Sorry, post # 172, shows his spec.....I looked at his post count instead of the post #:twak:

Flash

 

[1bolt]

So hows the build coming? Did you get the CC volume and piston dish sorted out?

 

[XJoshua]

Alright Flash I finally had time to get into my garage to measure the piston distance from the deck. At TDC(or pretty damn close) the piston sits 0.0615 give or take a lilttle bit below the deck. Im just using feeler gauges since thats the most technical thing I have to measure with.

Also with the head shim according to ASC(the calculator) my compression is at 9.07:1 with a quench of 0.066 :S

Is that quench even good. Because quench is just a distance. So would it be fair to compair it to volume. Since more quench means less compression. Why would quench even matter if as I think its the same as removing cc material?

 

[1bolt]

Quench has no relation to compression what so ever. Maybe you're thinking it does because as you shave the top of the block to improve quench (make the measurement smaller) you will also coincidentally RAISE compression. As quench gets better compression does not get lower, if anything it gets higher because to improve quench in our case with home brew strokers you must do things that also tends to lower the amount of empty space for fuel and air to mix.

Quench is like taking your hands and clapping next to a candle... the less space between your hands the more forceably the air between them is pushed out. Obviously our hands can touch without consequences, but a motor needs a minimum distance so the piston doesn't slap into the head. It's better that this distance be very close so the quench effect is at it's strongest.

Compression is totally unrelated to this "quench area" and you can lower it without effecting quench at all, or raise it for that matter, by useing pistons with the same quench surface area, but deeper "dish" to lower compression.

Now all that said, your quench is not great but your compression is in the low 9's so you should be able to run 89 or 91 octane to compensate for the quench height. Good quench as many have already posted is somewhere around 040 to 045.

Is your calculator taking into account the head gasket you are using? It's thickness will have a big effect on quench, you can potentially use a slimmer gasket to improve your quench. This would raise your compression slightly (because you would also make the cumbustion chamber and piston dish closer to each other) unless you opened up the CC's or piston dish a tiny bit more.

 

[XJoshua]

The head gasket is .045". Then the head shim is .045" and I just turned the deck shave amount into a - number since Im adding block material. I dont know why the calculator needs it as a negative but thats how I munipulated the formulas.

So to tight quench causes ping. Loose quench causes less bang?

 

[streetpirate]

backwards, tight quench makes for a more efficiant burn, which creates less hot spots in the combustion chamber, which means less detonation

 

[1bolt]

as streetpirate said...

So you're shimming the head to lower compression? but it's also going to take your quench up. Honestly you might not need to do anything just leave it alone, and put it together the low 9's CR will lower the amount of ping you see and I'd be willing to bet you can run mid grade octane without ping even on hot days. My stroker has good quench and mid 9's compression (higher than yours) and I can get away with 87 octane in winter but I run 93 octane most of the time because anything less will ping under part throttle at high temps and loads.

You have lower compression which will do a lot to reduce your chances of Ping, and 060-ish quench is only 20 thousandths off.

 

[XJoshua]

You misunderstood me I run 9.07 with the shim on and 9.9ish without the shim.

 

[1bolt]

I'm pretty sure I understood you, as I said you are shiming the head to lower compression. But It's also adding .045 to your quench. The shim is making your compression lower (better) but your Quench higher (worse)

You MUST stop thinking of Quench and Compression as the same thing, or even interelated things, they are two very separate pieces of the puzzle.

One can be made worse while the other is improved, and vice versa, you want BOTH of them to be within a certain range.

It just so happens that many things you can change (gasket thickness for example) that effect compression can also effect quench. In this case it's worsening your quench and improving your compression.

Anyway I've re-read your earlier posts and there are some glaring errors here.

Math not being my strong suit I only just realized that you have .090" of gasket and shim... It's late and I'm dead tired but I can't see how you could possibly have .066 quench... delete that calculator link.

You said that your piston top sits approximately 0.0615 BELOW deck at TDC. If it was ABOVE DECK by that much you would have good quench. Quench is the amount of space between the HEAD and the PISTON TOP, not the top of the block and the piston top.

.090 and .061 makes your quench .156 or utterly horrible. If your piston tops came up dead even with the block you would get .090 quench, still terrible.

You will need to ditch the shim, and deck the block again. If your piston comes up to deck height, and you use the Mopar gasket with no shim you will have .045 quench ...

You will also have WAY higher compression as a side effect of improving quench, and you'll need to tackle that problem with larger piston dish and/or larger Combustion Chambers (CC's for short).

1) establish your quench height without thinking about compression
2) buy the silvolites with the thick tops and have them dished to lower your compression into pump gas territory.
3) if you're brave hog out your combustion chambers to lower compression even more.

The closer to 9 you get the lower octane fuel you can use
The closer to .040 quench the better.
Once again these two things are not related to each other even though one sometimes gets worse when you improve the other.

 

[XJoshua]

I was stating how far the piston sits bellow the deck for Flash. So he could do his math to get my static compression ratio I believe.

Well wouldnt a head shim and a thinner gasket be a cheaper fix? And get me to around 9.5. I would be moving my quench to a safer point to help eliminate ping but Id be forced to run Premo Gas which isnt a big deal.

 

[1bolt]

Man I don't know how to explain it better, maybe someone else can.

I made a mistake in the post when I said to just put it together, I didn't do the math. and I assumed your quench number was accurate.

It's not. If you measured the piston top at TDC in the real world and it was DOWN in the bore then that calculator you used is junk.

I have no idea how good or bad your engine would run with good compression but with quench .110" out of factory specs... The 4.0 is a "quench theory" based engine design. So I suspect you would have less than ideal combustion, lower power and fuel mileage and ping problems.

I hope you stop listening to the engine builder who suggested a head shim, I recomend you re-read all the posts in this thread, especially Flash's posts and Mud Dawgs.

Really re-read them and understand what compression is, and what quench is, and make sure you know exactly how changing one can effect the other.

For a 4.0 stroker there's really only ONE (simple and cheap) way to get good quench and keep the compression ratio down in the low 9's and that's been spelled out for you by at least three people. Good luck man, I'm not saying any of this to bust on you.

 

[XJoshua]

Well I read Flash's web link and from reading that I think after I figure actual compression and ditch the clac I can move on from there. It seems like my deck height is fairly large instead of what the page suggests of sitting at the actual deck mine is largely bellow.

Deck height + compressed head gasket thickness = quench

Tighter quench less chance of carbon build up and better air fuel mixture.

So I guess my question now is what formula can I use to determing my compression?

I know what Ive been told and thats grind away the piston dish and combstion chamber. Problem is no one will touch the pistons because they dont want to unbalance them. So I had the guy just polish the dish to get a few '0Xcc out of it. The head I can accurately attempt myself since I have a few good tools for volum. As far as getting 4 more cc safetly out of it is a long shot.

The head shim was a suggestion NAPA gave me. Funny part though my machinist said slap it together and it will run fine on midgrade with a 10.5:1. So the next motor isnt going to him.

 

[1bolt]

Deck height + compressed head gasket thickness = quench

Correct IF your piston is dead even with the deck at TDC. Sounds like you need to deck your block by 0.60 or so to achieve this, but before you do that you also need a piston that has much larger CC dish, or one that can be dished deeper. Again I think the Keith Black Silvo's that can be dished 22 cc's have already been suggested by a couple people but you are stuck on the pistons you already have... You either need to get over that chuck them out or CC the combustion chambers on the head side. Exactly how much you must hog out will be determined by your measurements AFTER you deck the block, to get your quench close to spec.

If you change your mind and buy silvo's be sure you wait to deck the block AFTER you measure how far down the new pistons tops are below deck. They aren't necessarily all the same.

Keep reading, go get four wheeler magazine for November they have an article on stroking the 4.0 with a BUNCH of info that is uncommonly detailed and well explained (for a mag)... including how to calculate your compression ratio and also a fine explanation of quench. It's all info that's available on the web (notably Dino Savva's site) but nicely organized with some diagrams and well written explanations.

 

[XJoshua]

I bought silvos in the first place. First were silvo 30 over but my block needed bore'd further so I got silvo 60 over.

 

[XJoshua]

Well five cancer sticks later. I gave McCabe Motorsports a call and he is gone til the 16th. So the 16th Ill be giving him a call and get a quote and drop it off. Get it done then buy some porable heaters for my garage and get it in.

Im going to get a quote on decking, piston cc and balancing. Ill ask for a compression of 9.3:1 so I can run 91octane. Hopefully I can still use the .045 headgasket.

So yea I guess Ill read some more articles while its gone and get my intake setup done.

 

[alex22]

I am planing on building my own 4.6 stroker so I spent the last few days reading through this thread. I have a few questions and comments to make about what I have seen.

First and foremost, your compression and quench isues. I know this sounds like a stupid question. When you pluged your engine's stats into the calculation for compression ratio are you sure you made the deck height a negative, or add the compressed volume. You would be suprised how often something as simple as that has caused a giant headache. Quench is part of what causes the rapid increace in cylinder presure at TDC. If you slow the combustion down do the milisecond, the spark plug ignights a flame colonel that travels outward. When the piston comes to TDC it squishes the fuel/air mix out and shoots it towards the colonel. That causes a much more rapid rise in cylinder presure.
Last week I disassembled a 2002 4.0 and the pistons were between .015 and .020 in the hole, giving it a quench height of .071.

Next, I saw that the issue of the cams going south in a hurry. It seems like it was droped without a definitive conclusion. Of those who had their cam go bad how many were using a roller lifter and how many were using flat tappet lifters. also were you using a synthetic oil? The reason I ask is because synthetic oil in a flat tappet engine will cause big problems. Flat tappet cams need zinc and a few other additives in the oil. The zinc was phased out of the oil back when catalytic converts became standard. The zinc, which is needed by the cam but it damages the cats. As you can see this puts jeep owners in a "damnened if you do a engine. There are a few companies producing this type of oil. Joe Gibbs and AmsOil make the oil with it mixed in. Comp cams and a few other companies make an additive you can add to conventional oil. Just my 2 cents for the day.

~Alex

 

[Frank Z]

Im going to get a quote on decking, piston cc and balancing. Ill ask for a compression of 9.3:1 so I can run 91octane. Hopefully I can still use the .045 headgasket.

So yea I guess Ill read some more articles while its gone and get my intake setup done.

FWIW, My final numbers are in Colmn III

 

[1bolt]

Next, I saw that the issue of the cams going south in a hurry. It seems like it was droped without a definitive conclusion. Of those who had their cam go bad

I'd say this has pretty much solidly been attributed to the lower ZDDP in current oils... At least that the best theory so far. It's interesting that the failures tend to happen 15 or 20k miles down the road, after the cam break in additives supplied with the cams have been changed out a time or three. Both Crane and Comp cams have been called into question, I believe most of that is simply the fact that they are two of the most popular makers.

There are no roller lifters for the 4.0, although some on the strokers yahoo group have gotten some Mopar V8 roller lifters to physically fit inside, none have been run due to the lack of a roller cam. Roller lifters will eat a normal cam.

Joe Gibbs racing makes extremely expensive oil for racing, it has little to no detergent, and is thus, a bad idea to run on a street engine.
That goes for basically all race oil's as they are formulated for engines that will be torn down regularly.

One of the additives you're thinking of is GM EOS which can be added at every change to boost levels of ZDDP. EOS is now being marketed under the AC Delco flag and is probably going to be available at parts stores instead of just GM service counters. This info is direct from the strokers list, which seems to be on the cutting edge of issues like this.

 

[streetpirate]

Just make sure to break in motors on rotella 15w-45, tons of zinc, and $9-12 a gallon jug. it might give you a little lifter noise if its real cold out until the engine warms up though.

 

[Dr. Dyno]

I am planing on building my own 4.6 stroker so I spent the last few days reading through this thread.

I saw that the issue of the cams going south in a hurry. It seems like it was dropped without a definitive conclusion. Of those who had their cam go bad how many were using a roller lifter and how many were using flat tappet lifters. also were you using a synthetic oil? The reason I ask is because synthetic oil in a flat tappet engine will cause big problems.

Yeah, I wish I knew that before my Crane 753905 cam failed last year after running it in my 4.6 stroker for 34,000 miles. That's the highest mileage to a cam failure in a stroker so far. I only had one bad cam lobe (no.6 intake) and the no.6 intake tappet was cupped, while the no.6 exhaust tappet was collapsed with no wear at all. I used Castrol GTX for the first 3000 miles before switching to Mobil 1 for the next 31,000. The engine was clean enough inside to eat dinner off it so I was very pissed at the time that the cam went south.
I swapped my old stock cam back in with new lifters, stock valve springs, and Yella Terra roller rockers. I've been very happy with this set-up and the valvetrain is still quiet (knock on wood) after almost 10,000 miles since the cam swap (approaching 44,000 miles on my stroker).