Competition 370's spray pattern pic

[Jim Fulmer]

Many people have talked about the spray pattern of 370's but no one seems to come up with a pic for people to see! I just pulled the head off a 500 HP stock turbo'd truck as the head gasket finally started leaking after 1. 5 years at 38-46 psi (imagine the drive pressure) and got a real good view of the pistons, the rest of the motor looks real good as there is no scuffing of the Cyl walls and all the hone marks are like new, no ring edge either..... 210K on the clock. This is with timing at 17. 5 and plasma torch EGT's without water, and those that are worried there was no rust from the water injector either as it's been on for a year or better.



Jim



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[Sled Puller]

Having never seen a piston with a spray pattern on it, I would guess the injector had the wrong washer under it, and thats what kept the spray out of the bowl.

Shouldn't the pattern be down inside?

 

[DRAG DIESEL]

Retorical question here... . how does one keep the pattern in the bowl at say 40* BTDC of timing?

 

[Sled Puller]

Change the piston shape, or injector tip, eh? 40 Would be beyond washers.

 

[J.R. Adkins]

There are several things you can do about improper spray patterns.



1) You can bore the injector hole to get the injector pattern down further into the bowl of the piston.



2) You can change (tighten the pattern) the spray angles of the injector.



3) As Gene has pointed out you can use different thickness washers under the injector.



4) You can also use a piston that has a bowl that better suits the spray pattern.



There may be more but I cant think of any right now.



Jim are you gonna pull the oil pan and check the rod and main bearings? Nice pic BTW.



J. R.

 

[Cooker]

Nice pic. It provides some interesting info.

 

[justinp20012500]

Retorical question here... . how does one keep the pattern in the bowl at say 40* BTDC of timing?

Good point...

I just finished with my fire ring job and my pistons where very clean. No spray patterns on the top of the piston outside of the bowl, and for that matter it was very hard to tell if there was any patern inside of the piston bowl.

DD's 3 for all but 15,000 miles of the total 55,000

 

[Jim Fulmer]

The cool thing is once I get this job and the other one done I'll tear mine down and get to see were EDM's run at, I know they have allot tighter pattern.



Those 370's had . 020 washers on them, the head is going to need . 010 taken off it to make it flat prior to the O-ring. Even though the pattern is off the truck runs good and smokes very little for it's power level... ..... or it did till I played with it again prior to pulling the head.



I figure this is not bad for a cheap injector, now if he wants to spend twice as much he can fix that pattern stuff and have a much better injector.



Jim

 

[J.R. Adkins]

It only cost about $15 per injector hole to bore it. That would fix it.



J. R.

 

[KERMA]

Having never seen a piston with a spray pattern on it, I would guess the injector had the wrong washer under it, and thats what kept the spray out of the bowl.

Shouldn't the pattern be down inside?

The difference is this:



stock injectors have a 145 degree spray angle

the 370 injectors have a 155 degree spray angle

It looks like the spray pattern is not even across all 5 holes, like the injector is not aligned on the center of the bowl. IOW the spray cone might be slightly canted to one side compared to stock.



the extra 10 degrees is what you are seeing- the spray overlaps the edge of the bowl when the timing is advanced, or duration is too long.



The 3gen CR stuff is different in this way also between the 03-04 and 04. 5. The 04. 5 has a ~20 degree tighter spray angle, I would presume this is to run more advanced timing. The bigger holes also help "cylinder penetration", ie a bigger hole atomizes larger, so the droplets travel farther. At one extreme of this is some of the HUGE bored-out EDM or honed nozzles that don't atomize at all- or some of the older indirect injection diesels that rely on contact with the piston wall to ignite the stream of fuel.



I don't know if the pistons are different between early and later 3gen and that could account for some of the difference- but I'll bet it has a lot to do with PCM tuning differences that affect timing.



Ideally you would see the fuel impinging only inside the bowl. Bet this truck smoked pretty good (bad)

 

[KERMA]

Here is a picture of my wee little 1. 9 VW tdi with the head off after it dropped a valve. You can see the spray pattern inside the piston bowl. There is no overlap to the top of the piston, it is all inside the bowl.



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I'm stretching a bit here, but I think I saw a pic of a 370 marine piston once. If I recall correctly, the piston bowl is a lot wider and "flatter" than the ones in the trucks. That makes sense if you consider how that spray looks on that piston in the first picture.

 

[ProMac1K]

Thanks for thinking of us once again Jim. Thumbs up!!!

 

[Jim Fulmer]

Granted the 370's could be better but it's hard to beat the price, yea a guy could work on the head (if it was off) and make them work better but it just seems much easier to buy a different injector that started out with a new tip and adjusted the pattern for this, I don't like Marine piston cause the compression is just too low by the time you fly cut them for a real cam.



Most people don't start there(High HP)trucks at 10 degrees F without being plugged in, did that this morning!



Jim

 

[JoshPeters]

Granted the 370's could be better but it's hard to beat the price, yea a guy could work on the head (if it was off) and make them work better but it just seems much easier to buy a different injector that started out with a new tip and adjusted the pattern for this, I don't like Marine piston cause the compression is just too low by the time you fly cut them for a real cam.



Most people don't start there(High HP)trucks at 10 degrees F without being plugged in, did that this morning!



Jim

Even my piddly 325hp needed to be plugged in last night! (then again we hit -13 at my house)



Josh

 

[CNichols]

Most people don't start there(High HP)trucks at 10 degrees F without being plugged in, did that this morning!



Jim

Does this have to do with timming? Cause mine is sort of cranky now that the timming is set.

 

[ProMac1K]

Mine also starts slower with 18° of timing. It is bareable, but it started lightening quick when I got it, with just the #6 plate and boost elbow installed. I should bump my idle up a bit too. Idles slow when cold, but idles just right when warm. I'm getting an off-pedal stalling when cold, sometimes even when slightly warmed. The automatic trans makes this more drastic, as well. I've only started it twice when sat overnight in cold temps, once with it plugged in and once without being plugged in. Getting it started isn't a problem, it's the prolonged initial fire that is the problem for me. It cranks hard. Just when you think the batteries are about to go dead, it speeds up a bit and starts. Then you have to keep it running, won't idle at all right away. That's why I want to set the idle up. When cold it idles below the second mark after the 0 on the tach, in neutral. Not sure what that is. When warm it idles halfway between the 1k mark and the mark below it, in gear. That's a big change between warm and cold idle rpms, in my opinion.



I left the truck sit out last night, but plugged it in in the afternoon. I suppose it got down to the mid to upper single digits below zero last night. We'll see how it starts this morning.



I'll attach a picture of the way the truck idles before I did the pump work. Now it idles just below the 1k mark when warm and in park, but still idles low in park when it is cold.

 

[JoshPeters]

Mine Idles above 1000 when warm in park. Slightly below what your pic has when its in gear. Cold... . it's lower than that... . I have a specific ice scraper that I prop on the throttle and the armrest that I can set to "idle" at about 1750 to warm it up.



Josh

 

[CNichols]

Mine used to start just fine even if i didnt plug it in dow into the singles... Now if its in the low twentys, i still cycle the grids 3 times then attempt to start it will almost start then i cycle them once more give it a tiny bit of throttle just past where all the slack is out then may be an 1/8th inch more. it fires right away then and stumbles a bit then will smooth out... never had to do this but i had my timming set in OCT.

 

[Sled Puller]

Tmas, try this: Hold the throttle on the floor, crank it, as soon as it starts to turn over, let off the throttle.

This as been the only way mine starts with high timing(30s), I bet it helps at slightly higher than stock, also.

 

[JoshPeters]

Good point Gene... I do the same thing when it doesn't fire right away.



Josh