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408 SBC Build part matchup

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Old 05-08-2018, 08:30 PM
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408 SBC Build part matchup

Hi Guys,

I'm in the middle of tuning/diagnosing my 24x SBC build and was wondering if someone can tell me if I would have any MAJOR problems caused by the selection of parts I'm using?

Here's the build:

400 2 bolt block
stock crank, 5.7" rods, -12cc hypertuetic pistons (sealed power) approx. 10.8:1 comp
XFI 280 Hydraulic Roller with 1.6 lifters
AFR heavily ported heads (intake around 220c) with 2.08/1.6 valves
HSR EFI Intake with 58mm TB and 28lbs injectors
EFI Connection 24x conversion kit with vortec dizzy

4L60E with corvette servo
stock convertor
2.77 9 bolt rear

Now I know the XFI cam card says you need stall convertor and gears, but they also rate those for a 350, and as I've been told the rpm range shifts anywhere from 500-1000rpm when it goes in a 400.

I'm planning on upgrading the rear end, transmission and stall later, but I'm trying to avoid chasing my tail with the tuning side of it if the problem I'm having is caused by the build itself and not by vacuum leak or otherwise.

To explain the problem, the engine doesn't want to idle even with the TB screw adjusted to 0.73v. Idle will stay between 1200-1300 but will die if it goes near 900rpm where it should be(or lower)

Lastly, when I put the car in drive or reverse and try to move, it just stalls out or hesitates severely...then stalls, there's no movement of the car.
I'd think maybe its bogging down because of the low revs, but then the reverse gear is high enough ratio that it wouldn't do it then yes?

My MAP is reading 75kpa at idle which seems rather high, and the vacuum gauge I installed is only showing 5-6"HG which seems extremely low.
There's no vacuum leaks in the brake booster, PCV valve or others, so the only place left I can think of is lifter valley/intake gasket, or a valve/s staying partially open, but i adjusted them all correctly when i put it together.

Any ways, any input is greatly appreciated.

Last edited by evilstuie; 05-08-2018 at 09:05 PM.
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Old 05-08-2018, 09:59 PM
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Re: 408 SBC Build part matchup

If there isnt a mechanical related issue then look at the tune

What timing are you commanding at idle? Does it match your timing light on the balancer?

What is your air fuel ratio? Do the plugs look right?
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Old 05-08-2018, 10:02 PM
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Re: 408 SBC Build part matchup

Plugs look fine
AFR is bouncing around between 12 and 14, timing in park is ranging from 35-39.5 through the rev range, when I put it in gear it seems to lock it in at 26 degrees and the revs drop to 450-600 before cutting out.


If you have HP tuners I can put the file up and the log.
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Old 05-08-2018, 10:19 PM
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Re: 408 SBC Build part matchup

I could try to take a look.

If timing is what you say, it should be plenty high enough. What i am curious is if commanded matches actual at the balancer with a timing light. Wondering if cam sync to crank sensor is off at all?

Air fuel should also be abit more steady, shouldnt sway much more than .25-40 or so at idle and part throttle revs
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Old 05-08-2018, 10:27 PM
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Re: 408 SBC Build part matchup

Attached.

Wideband is logged through the EGR voltage working on the formula:

(EGR volt / 0.5) +9.8

I attempted a CASE relearn, but there's no confirmation of whether it works or not, so who knows.
All the o2 readiness tests etc have been completed which iread is a pre-requisite for them to sucessfully work, but I've also got DTC 0342 & 0343 which is high and low cam sensor signal.

Voltages check out so I don't know whether it means the cam is offset or not aligned properly, or if the sensor in the vortec dizzy is damaged.

I've also read the CASE relearn only works if the cam sync is already within +/-2 degrees of alignment any way. Is that correct?
Attached Files
File Type: hpl
080518-glorious.hpl (254.5 KB, 9 views)
File Type: hpt
KITTSBCTESTFILE2.1.hpt (250.8 KB, 11 views)

Last edited by evilstuie; 05-09-2018 at 03:35 AM.
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Old 05-14-2018, 08:04 AM
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Re: 408 SBC Build part matchup

Did you get a chance to view the log?
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Old 05-14-2018, 01:19 PM
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Re: 408 SBC Build part matchup

You have a tune problem, I have almost the exact same combination but I am using the stock computer to run the car and it idles fine at 850 RPM. I suspect your timing in the tune does not match the actual timing at the crank. Your idle KPA is way to high for that combination.
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Old 05-14-2018, 01:40 PM
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Re: 408 SBC Build part matchup

I just looked at your tune, the timing seem to be way to far advanced at low RPM and your firing order is incorrect. Have you adjusted for the firing order with the wiring or is it off? Also your fuel injector size should not be the same across the entire MAP table.

Your fuel injector firing does not match your timing firing order. That may be the problem?

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Old 05-14-2018, 02:31 PM
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Re: 408 SBC Build part matchup

Hi Bjankuski, Yes I've repinned the harness for the correct firing order for coils and injectors. Also the injector A-H assignments don't correlate to 1-8 I don't tyhink, but they've been set up correctly I believe.

Are you able to PM me your tune file, I may be able to get the spark tables off that.

The fuel is set the same across I think because I'm using a AFPR with the vacuum attachment, so it adjust fuel pressure with vacuum.
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Old 05-14-2018, 04:09 PM
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Re: 408 SBC Build part matchup

Also, just for reference, what is your idle KPa sitting at?
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Old 05-14-2018, 04:13 PM
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Re: 408 SBC Build part matchup

Why is your idle stall saver 0’d out?
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Old 05-14-2018, 04:17 PM
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Re: 408 SBC Build part matchup

And my injector bank set up is different than yours and all i did was repin at the harness and started with a known 6.0 liter ls tune
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Old 05-14-2018, 04:18 PM
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Re: 408 SBC Build part matchup

Originally Posted by Orr89RocZ View Post
Why is your idle stall saver 0d out?
Ben Charles on the HP Tuners forum is doing the tune for me, so I think he's zero'd it in order to dial the idle in before putting the adders/adjusters back in, but not sure.

I pretty much just wanted to confirm that I have a vacuum leak so as not to waste his time before we get right into the tune.

All the usual suspects have been checked, so I'm 90% sure now the intake gaskets aren't sealing, either because of the intake to head angles, the bolt holes needing elongating, or something worse.
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Old 05-14-2018, 04:19 PM
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Re: 408 SBC Build part matchup

Originally Posted by Orr89RocZ View Post
And my injector bank set up is different than yours and all i did was repin at the harness and started with a known 6.0 liter ls tune
Do you have a copy of the LS tune after you made all the changes from stock but before you modified the VE/spark etc?
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Old 05-14-2018, 04:28 PM
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Re: 408 SBC Build part matchup

No lol it was a friends 6.0 turbo tune

Yours says 5.7 as base engine, was it an ls1 or the sbc 411 ecm van files ppl like to use?
I assume ls1 since you have cam sync

I also have shown cam sync volts high and low so no idea what that was
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Old 05-14-2018, 04:51 PM
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Re: 408 SBC Build part matchup

yeah LS1 from a Holden Commodore 2001 I think.
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Old 05-14-2018, 04:54 PM
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Re: 408 SBC Build part matchup

Originally Posted by Orr89RocZ View Post
No lol it was a friends 6.0 turbo tune

I also have shown cam sync volts high and low so no idea what that was
On my log or your friends?
I had a few DTCs coming up with that on mine. I wasn't sure if the vortec dizzy has crapped itself or if its something else.
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Old 05-14-2018, 06:57 PM
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Re: 408 SBC Build part matchup

No mine did same thing and no idea why. It ran fine so I ignored it
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Old 05-14-2018, 07:03 PM
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Re: 408 SBC Build part matchup

Originally Posted by Orr89RocZ View Post
No mine did same thing and no idea why. It ran fine so I ignored it
That's good to hear
Maybe it's something to do with the design of the reluctor wheel or a change they made?
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Old 05-14-2018, 07:13 PM
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Re: 408 SBC Build part matchup

I never really understood how to sync it up to the crank. I tried to follow their instructions and seemed to work but later on had inconsistent starting and backfiring while cranking. Eventually did findthe reluctor wheel keyway slot opened up on the wheel so it could have moved timing at idle.

Anyway i notice you ramp in timing off idle veryyy rapidly. Some cars might like it some might not. I tend to go more gradual. Idle timing seems ok where its at but just off idle is a fast ramp so that much fluctuation might affect the rpm control when transitioning from part throttle tps to idle control. I would maybe try relaxing that much timing ramp off idle

And enable stall saver rpm around your idle. Alot of my base idle air flow parameters are different as well. I have some throttle follower differences and various others.
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Old 05-14-2018, 10:10 PM
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Re: 408 SBC Build part matchup

Originally Posted by Orr89RocZ View Post
I never really understood how to sync it up to the crank. I tried to follow their instructions and seemed to work but later on had inconsistent starting and backfiring while cranking. Eventually did findthe reluctor wheel keyway slot opened up on the wheel so it could have moved timing at idle.
Yeah I feel like there should be an easier way to line it up. Looking at the sensor itself, shouldn't you just be able to drop it in and swing the case around until the x part of the case lines up with y part of the sensor wheel when fully seated?

Originally Posted by Orr89RocZ View Post
Anyway i notice you ramp in timing off idle veryyy rapidly. Some cars might like it some might not. I tend to go more gradual. Idle timing seems ok where its at but just off idle is a fast ramp so that much fluctuation might affect the rpm control when transitioning from part throttle tps to idle control. I would maybe try relaxing that much timing ramp off idle
I'm still getting my head around a lot of the tuning, not only is this my first obd2 tune...it's my first tune. I've paid Ben on HPT to do the tune, but I'm sort of learning myself at the same time. I still haven't been able to find a guide for tuning something from scratch though.
All the tutorials seem to be based around fine tuning, more than initial setups.
My guess is he's either used his own base tune or something similar to my setup in one way or another, and he'll get to the other table once we have it starting and running.

Originally Posted by Orr89RocZ View Post
And enable stall saver rpm around your idle. Alot of my base idle air flow parameters are different as well. I have some throttle follower differences and various others.
I'll definitely look into that, at the very least it will help keep the car running so I can finish diagnosing and checking everything out.
How does the table work exactly. Do I put what I want it to increase idle to when it reaches that rpm? e.g. in the 800rpm field, i should put my stall saver rpm to 1000, for 500, put it to 700rpm or something, or just set everything to a set rpm of 850rpm?

I'm pulling the intake this afternoon and try a few things to determine if (or more so, where) the vacuum leak is and if gaskets,elongating bolt holes, or milling will fix the issue. It's one time I really want to find a problem to explain all this trouble, as opposed to nothing.
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Old 05-15-2018, 06:49 AM
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Re: 408 SBC Build part matchup

I believe you want the stall saver lower than target idle by around 200 rpm. I’d have to double check that but i believe mine is that way
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Old 05-15-2018, 10:01 AM
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Re: 408 SBC Build part matchup

Originally Posted by evilstuie View Post
Hi Bjankuski, Yes I've repinned the harness for the correct firing order for coils and injectors. Also the injector A-H assignments don't correlate to 1-8 I don't tyhink, but they've been set up correctly I believe.

Are you able to PM me your tune file, I may be able to get the spark tables off that.

The fuel is set the same across I think because I'm using a AFPR with the vacuum attachment, so it adjust fuel pressure with vacuum.
I am using the stock computer to run this engine in my car, 1988 design so the spark table will not look like yours, but I can attach it so you see what spark I am running.

I will have to get you the idle KPA.

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Old 05-16-2018, 05:43 PM
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Re: 408 SBC Build part matchup

My idle kpa is 55 kpa at 900 rpm in neutral.
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