peterc005

Looking at engine options and the ZZ6 seems good:

http://www.chevrolet.com/performance...gines/zz6.html

I like the TPI setup and was thinking of getting a Vortec TPI base and using a set of 24lb Bosch 3 injectors I have sitting on the bench.

Has anyone tried a combination like this?

Damon

Guys have put the TPI on top of the old ZZ4 with pretty decent results. Given that the ZZ6 is rated around 400HP I think you're going to need a bit more than 24# injectors to feed it (even with a sharp tune).

Difference in power between the old ZZ4 and the new ZZ6 is due to better cylinder heads. All other specs are identical. Well, OK, not identical. The ZZ6 also boosts it's rated HP by using a single plane intake, which is meaningless to you since you plan to bolt a TPI intake on top of it anyway.

What if you wanted the ZZ6 but didn't want a single plane intake you are just going to have to sell on eBay anyway? And, let's say for the sake or argument, you wanted to pay a lot less for it. Then the motor you're looking for is the SP350...

http://www.chevrolet.com/performance...nes/sp350.html

It's the SAME MOTOR but since it's rated with a dual plane intake (which you also don't need) it's rating is 385HP. Who cares? You're not using the intake that either one comes with anyway!

peterc005

The difference in price between an SP350 and ZZ6 is only about $600, and the ZZ6 has forged con rods and roller rockers. They use the same Fastburn heads. Looks like GMPP don't sell the ZZ4 any more.

400hp is about 900 cfm. I guess the question is how to get TPI to flow this much.

I'm hoping 24lb injectors with a bump in pressure will go good for 400hp.

BOTTLEDZ28

iTrader: (9)

Can the ZZ6 engine be bought as just a long block?

jmd

iTrader: (4)

Yeah go to the engines on chevrolet.com ( link Damon posted, then Engines ) and look at the SP350 but see below:

The parts PDF shows 10108688 rods for both. I would triple check with GMPP before ordering. And maybe pull the pan on arrival.

I would be interested in a 4bbl efi intake on ths application rather than LTR.

Damon

$600 price difference is a lot of money for a set of aluminum roller rockers.

Aside from the intake difference (which doesn't matter if you plan to put a TPI system on top anyway) they are effectively identical engines. Same block, same crank, same rods, same pistons, same heads, same cam.

zraffz

You are aware that you can build a comparable motor for about half yhe cost, right?

thtanner

iTrader: (1)

Does that built engine come with a 36m/100k mi warranty?

Sometimes it's worth cost for piece of mind alone.

jmd

iTrader: (4)

That's a decent idea; I want the stroke of the HT383 crank too.

zraffz

I could probably build two 385hp motors for that price.

Easy enough recipe, freshen up an L31, new ls7 lifters, oil pump, mid 220/230 cam, roller lifters, springs.

peterc005

Comparing the complete Base engine with individual parts, it's cheaper to buy a ZZ6 crate engine. These are internet prices, not RRP.

ZZ6 BASE TECH SPECS Part Number: 19351532 ($5,650.00)

Engine Type: Chevy Small-Block V-8 350 Displacement (cu. in.):

Cast-iron with 4-bolt main caps Block (P/N N 10105123): ($859.97)

Forged steel Crankshaft (P/N 12556307): ($1,113.59)

Forged powdered metal Connecting Rods (P/N 10108688): ($480)

Hypereutectic aluminum Pistons (P/N 10159436): ($880)

Steel hydraulic roller Camshaft Type (P/N 10185071): ($240)

Fast Burn aluminium; 62-cc chambers Cylinder Heads (P/N 19300955): ($1,680)

Aluminium roller style Rocker Arms (P/N 19210724): ($360)

Parts total $5,613 vs $5,650 complete and assembled with warranty. The parts list does not include things like piston rings, water pump etc.

The ZZ6 looks like a well-engineered and reliable package.

Abubaca

iTrader: (3)

I completely understand wanting to use a TPI. I'm that guy too.
I also completely understand buying the quality and warranty of a GM crate engine, even if there are other cheaper options.

BUT....to pay that price....only to put a TPI on top? eeeehhhhhhh....I don't know. Assuming you go with a vortec manifold as you say, I'd probably go with an L31 replacement engine for $1900 bucks. Little bit of extra cash into those vortec heads and along with a zz4 cam (same as zz6) with the standard nodular crank in that engine, you've got a super budget, rock solid motor. Bang for the buck out the wazzoo! ....where as the TPI on the zz6 would ultimately make a "little" more power, but you're giving away a ton of potnetial power, and spending a LOT more...I mean a LOT more money!

zraffz

I am not looking to argue but the only advantage of that ZZ6 short block over an L31 (350 vortec) is the forged crank... and at that power level, it's not necessary. The L31 has the same powdered rods and the pistons look identical (perhaps the .3 compression comes from a thinner head gasket and the 62cc chambers?).

As far as the heads, you are paying $1,650 for a set of Fast Burn heads that are an aluminum version of the L31 heads with 2cc milled off... hardly an impressive head for the money. With that head budget on a L31 short block you could pick up 30+ hp easily with a set of AFR, Trick flow or dart heads.


I would venture to say the old L31 (stock long block; just a quick rebuild with 1.6 roller rockers and steel shims) with the Comp Cams XR276HR would pull on that ZZ6. I can tell you start to finish that motor had less than 3 grand into it.


So it's up to you, is the extra $4,000+ worth the warranty?

86LG4Bird

iTrader: (1)

A no-brainer to me. L31 all the way. GM cast cranks are good way beyond 400 hp; more like 600 hp.
And if you're sticking a TPI on it, 24 pph injectors will be more than enough.

anesthes

iTrader: (12)

All GM rods are forged.

-- Joe

anesthes

iTrader: (12)

I've pushed 560hp with a cast GM crank, but I've also seen them let go at 350 hp.

400hp will need 30lb injectors, unless he runs 55psi and 90% duty cycle. Which is doable, but then he's going to need a pump that can flow 40 gph at 55psi.

-- Joe

86LG4Bird

iTrader: (1)

400 hp at the crank does not need 30's. 24's can handle up to 450 at the crank.
30 pph SVO's support 600 at the crank on NA setups using stock (42-44 psi) fuel pressure.
You're probably using the "calculators" or formulas promoted by people selling fuel injectors. What I'm posting is from actual personal experience with my own and others' setups. Roadracing duty running 100+% duty cycles as calculated by the datalogging software does NOT result in injector failure. Simply does not happen
AFR on wideband dyno tuning continues to respond to fueling adjustments beyond the 100% duty cycle fictitious "wall" calculated by the logging software. When you get near the static (always open) condition of the injectors, the logging software assumptions are no longer valid.


Any GM crank that let go at 350 hp had other issues at play. Not the crank's fault.


If you call PM rods forged, then yes, all current GM rods are forged.

peterc005

I like the idea of aluminium Fastburn heads with updated valve gear on the ZZ6.

Has the casting of GM engine blocks improved in the past 30 years?

anesthes

iTrader: (12)

No, I'm using math. You burn 1/2 of a pound of fuel per horsepower.
(BSFC of .5)

Eight 24 lb injectors is 192 lbs. * 2 = 384, and that is STATIC.

Like I said, you can increase the fuel pressure and run pulsewidths in the 90s, but you need to make sure you have enough volume at the higher pressure.

No kidding. But 100% duty cycle on 24's is still under 400hp.

That is not possible. It's not a ficticious wall, it's math. On a batch fire TPI engine, you have 10 milliseconds to spray fuel at 6,000 RPM. That is 100% "Duty cycle". You can't spray fuel for 15 milliseconds if you only have 10 milliseconds, you will be into the next firing event. The duty cycle calculation is simply the percentage of time open vs time available. This is also based on the injector firing strategy (How many injections per cycle).

If you think this is some type of conspiracy with the logging software, I don't know what to tell you.

GM never made a cast connecting rod for a SBC.

-- Joe

86LG4Bird

iTrader: (1)

Joe, Have you ever tried running injectors beyond that "magical" 100% duty cycle? Hang around people who know how to go fast and you learn things
NHRA LT1 stock eliminator guys even swap back to 22's to make more power than they do with 24's.


I can do the math too. I'm well qualified. But I also don't argue reality.


Never said anything about a cast rod! but powdered metallurgy isn't a forging process.

zraffz

I still don't get the debate... that's essentially a $7,800 L31 with an aluminum vortec head and a baby cam. Unless it's got a lifetime warranty, it's hardly a deal.

86LG4Bird

iTrader: (1)

Agreed. That part makes no sense at all to me.

Abubaca

iTrader: (3)

I'll always give someone the benefit of the doubt. There's always a reason to make a given decision. HOWEVER....without knowing what those reasons are.....I have to agree with the above statement. I just don't see how to justify that massive cost difference for what will amount to little if any performance benefit.

peterc005

Although the L31 does not have 4 bolt main caps and a forged crank.

86LG4Bird

iTrader: (1)

Are you still planning on topping this engine with a TPI?
If you are, then 4-bolt caps and a forged crank are of zero value. Ie. you will not be spinning over 6500 rpm nor making over 600 hp.

Abubaca

iTrader: (3)

I haven't shopped for awhile, but a few years ago, you could get the L31 with 2 bolt or 4 bolt mains. It was about $100 extra for the four bolt. I think it USED to be for the heavy duty trucks, and GMPP was selling it as the L31R.

...but as stated, 4 bolts aren't needed, and the forged crank definitely isn't needed.

Look, we're all friends here. ...if you want the zz6, then I'm all about it. As I said, we ALL make decisions for our own reasons. I'm in the process of building my 383 right now, and I just put a MUCH better valvetrain in than I really need. I just wanted to build it right, without any bone stock, cast or stamped GM assembly line parts. BUT...I know darn well, many of those parts are more than enough for what I'm doing. But I wanted what I wanted. But that's a bit different than asking the general public if I NEED those parts. EVeryone would've said no. ......so I'm 100% behind you running the ZZ6. Awesome!!!!!!!!!! ....but if you're asking if it's the best choice, given what we know about your planned build....then no, it's probably not the best choice.

zraffz

The half ton trucks got the 2 bolt blocks and the 3/4 & 1 ton trucks got the 4 bolt blocks.

I wouldn't be worrying about a 2 or 4 bolt main or a forged crank if you are looking at a crate motor that makes 385 hp or even 450 hp for that matter.

The biggest factors that will kill a cast crank are RPMS, unbalanced rotating assembly and block flex (the entire concept behind 4 bolt mains) from tremendous amounts of cylinder pressure.

jmd

iTrader: (4)

I'd rather splayed aftermarket caps added to a 2-bolt block.

Vanilla Ice

It's absolutely possible to run in excess of 100% duty cycle. You just start digging into dwell time. Basically the injectors never close. That's why it's possible.

86LG4Bird

iTrader: (1)

^ ^
You got it
I just ended the argument because it's tough to quantify it with math. You just test things and see what ya get

peterc005

I'm starting to think the logic above makes sense and maybe the ZZ6 is over-priced.

The reason I looked at the ZZ6 is I'd been thinking about an LS3 crate engine (430hp), and getting 405 hp out of an SBC seemed an easier alternative. Problem is that that the ZZ6 and LS3 crate engines cost about the same.

anesthes

iTrader: (12)

No.

I like to use 6,000 RPM as an example because it makes the math simple.

A 4 stroke engine rotates twice per cycle. So to fire all 8 cylinders, we will have rotated twice.

1 Minute is 60,000 milliseconds.

At 6,000 RPM that's 10 milliseconds per rotation. 20 milliseconds per cycle.

On GM batch fire TPI, the injectors fire twice per cycle, which gives you a maximum window of time of 10 milliseconds per revolution.


That is 100% duty cycle.

You cannot ask the injector to be open longer than the time you have available, and expect it to provide more fuel.

-- Joe

Vanilla Ice

So what happens when every ecu cycle commands the injectors open for a set duration of time that just happens to be longer than the window available?

peterc005

On that basis, how far could you practically go with 24lb injectors, either at 43 or 50 fuel pressure?

anesthes

iTrader: (12)

The injector never closes.

For example, I can write a program that turns a light bulb on for 28 hours per day. However you only have 24 hours IN a day, so you don't get 28 hours worth of light. It simply stays on.

In the example of the vehicle, the injector is open 100% of the time delivering 100% of the fuel available. Each cycle gets the same amount of fuel.


Not to say that it's horrible, lots of guys run static and the AFR is just fine because they are providing enough fuel.

However, the statement that you can exceed 100% duty cycle and you will provide more enrichment (change in AFR) is impossible, kinda. Let me explain.

Not to get too crazy technical, but there is a point in which you will see a huge AFR spike in between 80% duty cycle and static, and that is simply because once the injectors are static you got back the lost 'dead time'. (The time it takes to OPEN and CLOSE the injectors). For example, my Siemens Deka injectors have an open time of 1.14 milliseconds, and a close time (turn off) of .85 milliseconds.

So let's say we command the injector driver to turn on for 8 milliseconds, well then almost 2 milliseconds of that time is spent opening or closing, NOT spraying. So our actual time spraying is 6 milliseconds. Now ECU's do correct for this (we program the injector latency data in), so a commanded pulse width of 8 milliseconds would add the 1.99 milliseconds of dead time in, for a total of 9.99 milliseconds.

Notice this is "Static" at 6,000 RPM.

However, if we command just a little bit more pulse width to go completly static (10+ msec commanded open) than we lose the close time, and once we hit the next engine cycle we lost the penalty of our open time. So now during that 10 millisecond window per revolution we're not opening or closing, we're stuck open and spraying for the entire 10 milliseconds not 8.

I suspect this might be why guys are seeing duty cycles exceeding 100% and a change in AFR, without understanding why this is happening. Every injector is different, some have more or less dead time.


-- Joe

anesthes

iTrader: (12)

Well that's easy. 24 * 8 = 192lbs of fuel.

If you BSFC is .5 (average naturally aspirated motor) you'll use 1/2 lb of fuel per hour. So 192 lbs = 384hp. This is STATIC, Max flow, 100%.

At 50 psi the injectors flow a little more, and it brings your max to 410 hp.

You've got to be careful with sizing injectors. For example, I had a 355 with a blower that made 565 crank horsepower.

I ran 36 lb injectors at 50psi. My BFSC was around .55 calculated, I went static around 5800 RPM but my AFR was reasonable. (car shifted around 5800 anyway).

On one cold night at the track I made a pass and it made more than 565 horsepower, or the cold air caused my BFSC to increase, but I went from a slightly lean (but reasonable) AFR that made a lot of power to detonating two cylinders and breaking the pistons.

-- Joe

Vanilla Ice

Maybe you can help me out here...
To which you say:
Then you go on to say:
I didn't make this statement. Is this why you said "no?"

How about this:
When an ECU/PCM calculates IDC by adding PW and Dwell time together, you are not static at 100%. True static is actually closer to 110% duty cycle.
This is why you'll see an enrichment beyond and in excess of 100% duty cycle, because this is the injector actually never closing. I know this is true because I disassembled a ROM that did this exact thing. I speak from personal experience and 100% knowledge of the calculation and creation of the ram variable.

Now if an ECU/PCM calculates IDC without using Dwell, you should NOT see an IDC above 100%.

In the end I'm really just wondering why you say I'm wrong when I made a comment that was so vague it's impossible to say I'm incorrect. Especially when I am correct.

anesthes

iTrader: (12)

Are you talking about a Delco ECM? If so which mask?

I don't recall any Delco ECM reporting a "duty cycle", but rather an injector pulsewidth. This number includes the dead time which is part of the calibration.

Logging software simply reports the pulsewidth, and calculates the duty cycle based on RPM. (and an assumption as to the firing strategy, which is double fire, single fire, etc based on the mask).

Looking back at your exact wording, I realize what you meant - that as you start eating up the dead time you replace it with spray time on a STATIC injector. My problem is the representation of duty cycle in the argument. You are not open for "110% of the time". You are open for 100% of the time, you are just not wasting any time opening or closing...

I guess the problem lies within what do you consider 'static'. Do you consider static an injector that is already open and not closing, or an injector that has opened, sprayed, and closed using 100% of the time available? I guess that is up to debate, and probably the source of confusing with logging software.



-- Joe

Vanilla Ice

This is exactly why there's confusion and arguments. Only full understanding of both scenarios will allow anybody to understand why it's possible to have "110%" IDC. Though "impossible" it depends on how it's calculated because it's entirely "possible."

Abubaca

iTrader: (3)

I was following this, and not having extensive knowledge, I chose not to comment. I felt I knew EXACTLY what Vanilla was getting at, and also what Anesthes was describing.....and I gotta say, now that everyone is clear...I still think the term 110% IDC is incorrect. Not arguing what is actually happening at all, and I understand exactly what you mean....just that I don't know if I would say 110% is the proper way to say it. ...however....if it's considered appropriate in the tuning world, then by all means please continue. I honestly don't know. Point is, I thought I knew what you meant, but it certainly confused me when I saw it.

...and again, I say this as a NON expert, but to keep it real with regard to the OP.....when asking about "what injector"....are we suggesting running smaller injectors wide open....all the time....at "110% duty cycle?

Vanilla Ice

Well that also assumes you are talking about real IDC as opposed to logged IDC.
Real IDC can't be over 100%.
Logged and calculated IDC can.
That's also the difference in the two types of scenario.

Vanilla Ice

Get the L31-R.

anesthes

iTrader: (12)

And that I will agree on 100%. (parden the pun).

I think the loggers are screwing people up, and without fully understanding what they are seeing they are assuming things.

I just had a CT scan this afternoon and I'm not supposed to be reading, watching tv, or using the computer for 48 hours so I better take off now before the wife catches me.. L8r guys.


-- Joe

zraffz

Any crate motor boasting 400 hp is overpriced and your factory TPI intake will choke it out... anything past the 300hp range will be ruined by an intake that runs out of steam and 4000-4500 rpms.

If you were doing something like the Holley Stealth Ram manifold, you could use something like this:
http://m.summitracing.com/parts/hpe-hp34

Although I can't comment if ATK is a reliable brand (ATK is Napa Iron I believe) or if this camshaft is ideal for a fuel injected tune port setup, this crate motor would defiantly make more power than the ZZ6 and not leave you stranded with $1,500 worth of parts that you will end up getting 35% of that back during resale.

cuisinartvette

Those heads on that engine are worlds above a production vortec head
You get what you pay for
If you started with a brand new block and nothing else bet it would cost more to build than GMs selling it for. PLus its new, not a rebuilt by some hourly something to be said for that.
Maybe overkill for the TPi but why not..new is new. Not saying GM is perfect but imo probably more reliable than most "rebuilders"

anesthes

iTrader: (12)

Lazy union auto workers vs a private shop?

I'd go with the private shop. They actually have to do a good job, to keep their job.

-- Joe

Abubaca

iTrader: (3)

The above statement and:

"GM Factory Crate motor vs. ATK Crate motor are COMPLETELY different statements!!!!!.

I would run a GM crate any day, and I don't know that you could GIVE me an ATK motor. Given the labor to physically install and potentially troubleshoot, I honestly don't know if I'd take an ATK motor if you gave it to me.

zraffz

I've never had an ATK crate motor but I've seen inside a Jasper 350 TBI... one cylinder was .030". That piston didn't even have the same deck height as the rest of the OEM pistons lmao.

Their are some shops that have a tremendous reputation but for the most part it's safe to say that GM crate motors will be held to the highest quality.

blkbrd84

Is this subject considered put to bed? I have been looking into which of GMs latest crate engines would be the best match for my 1984 T/A, and at first glance the ZZ6 sounded like the answer. The catch is, I want to get rid of the old feedback carb and all the old school emissions nonsense, and run with (perhaps) TBI system. GM sources tell me that the more radical cam on the zz6 does not allow the engine vacuum required for fuel injection, and I am told the new SP350 (357 hp) is the best bet for an injected engine. So, has anybody really tried to inject the zz6 yet??

Abubaca

iTrader: (3)

Welcome to TGO!

From what I've found, the zz6 simply uses the zz4 cam. .474"/.510" - 208*/221*. ....That's tiny compared to what guys are using for EFI. I had a zz4 cam in my 350 TPI and passed NC emissions back in the day with NO tune. It's VERY usable for EFI.

As for the zz6 engine itself, I think it's just the old Fastburn 385, which was just the step up in heads from the zz4 with the old vette/zz4/083 casting. I'm sure there may be other differences too. Single plane? I don't think GM makes a Gen1 crate engine that even comes CLOSE to being non-EFI friendly. Of course, with all hot rodding, you have to look into emissions, what's legal, and how far you're willing to push things. In NC, I haven't had to worry about it in so long, I can't speak as to what anyone else has to do to pass.

...as for the best engine for your 84....that's the million dollar question. Anything EFI will require tuning. What are your capabilities, and what is your budget? As for the engine itself and required performance...well...what do you want out of it?

...you might get more helpful responses if you started your own thread.