Slow89Iroc-Z

Has anyone found a way to correct the split blms for the Holley Stealth Ram and Holley 58mm TB? I know the HSR doesnt have an IAC passage to evenly distribute the IAC air. The cam's duration is 230/236.

I did the conversion to the 411 PCM and EFI Live is reporting a 12% O2 sensor difference from bank to bank. I am not sure what the is in BLMs but it seems to be significant. I have swapped the plug wires from side to side. Resealed the slip joint in then 2210 headers.

WASyL

"I know the HSR doesnt have an IAC passage to evenly distribute the IAC air."

what do you mean by that ? i have HSR with Holley 58mm TB and IAC works just fine

best regards

Slow89Iroc-Z

The later TPI and LT1 intakes have a cast in passage for the IAC air to be evenly distributed to each cylinder. The HSR does not, the IAC just dumps the air into the plenum. I never said the IAC didnt work.....do a search on "split BLMs" to find out what I am taling about. Also if you dont have an O2 sensor on each side on the engine you wont even know if there is a problem.....

Orr89RocZ

iTrader: (20)

Is this only at idle?

Those intakes are known to have a distribution problem at part throttle and idle but not sure how "off" it is. Can you check your spark plugs to verify what the cylinders are doing? Some may be rich some may be lean.

With some cam overlap you may have some false readings at idle. That cam aint huge for a 383 but can still have alittle effect at idle conditions. So dont necessarily trust the o2 readings/BLM readings. Use the spark plugs to tell the whole story.

As long as you know there are no exhaust leaks, you can start tuning from there. Can you offset the injectors bank to bank with those systems?

Slow89Iroc-Z

Seems to occur at part throttle and idle rpms.
I am not sure if there is a setting to offset the injectors.

Orr89RocZ

iTrader: (20)

yeah I just found out there isnt one in lsx software, atleast none that my buddy knows about who tunes ls based cars. Surprising because i thought sequential systems like this had offsets. Pretty sure LT1 cars did.

Try to find the leanest cylinder per bank and tune til that plug looks happy. May be forced to run rich all the time on other cylinders

gta324

Is there any good intake that dont have air distribution problems at idle/part throttle?

Orr89RocZ

iTrader: (20)

Alot of the front mounted TB type setups have issues but I'm not sure about the TPI based setups since the runners are spaced out and enter the plenum from the side instead of underneath.

A single plane intake may not have as much distribution problems since air comes in from the top to a common area, and all 8 runners feed from that. But then again, most intakes out of the box have runners that dont flow as good as some others on the same intake, so they may pass more air. Hard to say but I think a single plane is your best bet. Thats why I went with one on my turbo build. So far all the plugs look similar when I took it apart so I think at idle and part throttle its doing its job.

antman89iroc

Yeah, the HSR seems pretty bad. I don't know for sure if it's during idle, part throttle or both but I have always had richer rears than front plugs. My concern is that it's just the opposite at full throttle. I have been considering swapping intakes, ecm's or both.

Orr you swapped your car over to the 411 pcm didn't you? I'm interested in what you recommend for doing so. I have read a lot of articles on it but there doesn't seem to be a "recommended" approach.

Orr89RocZ

iTrader: (20)

If you dont like wiring and dont have a thin shell balancer like an ATI, then i would not do the 411 lol

I would go holley hp

antman89iroc

Interesting. I get what you are saying about wiring. I'm sure it is very involved grafting the two systems together. Either way it seems there will be plenty to be done. Unless you leave all the factory harnesses in tact and go aftermarket.

Have you used the Holley HP and what are the advantages/differences vs the 411?

Orr89RocZ

iTrader: (20)

Holley is abit simpler and does have some features that can be very handy for power adder cars

And you can basically buy the harnesses.

antman89iroc

I have the same intake and I haven't noticed side to side distribution issues I do have front to rear distribution issues. EBL flash doesn't have the ability to tune individual injectors so I am looking for a mechanical cure.

You mentioned HSR doesn't have idle air provisions and you're correct. I am considering adding a tube to the throttle body to route air to the rear cylinders. Another idea is to create a vacuum leak in the rear (with a needle valve or fixed orifice) and then close somewhat the throttle blades. Still the IAC will only "feed" into the front but at least there will be more air entering/available to the rear cylinders. What do you think about that idea? I already have my PCV valve feeding into the rear of the plenum but it still isn't enough air to correct the imbalance.

Orr89RocZ

iTrader: (20)

Porting intake runners may help with balance.

Ideal thing is to cut plenum so that throttle is on the side like a ford 5.0, that may help change the direction of airflow

LT1's have injector offsets for that reason

Other thing is to flow test injectors and find one thats flow slightly more and put them in the lean cylinders. Dont buy a matched set lol

antman89iroc

I have considered this (and a lot of other) idea. It would mean a lot of rework and make for a strange filter tract but hey it would be interesting to try.

With keeping the TB in the front I have considered adding a pipe, or piece of tubing to the back of the TB at the IAC passage. It could be extended all the way to the rear of the plenum with holes at the runners. Sort of like a nitrous plate. A member here did a miniram like this but he ran the tubing under the manifold in the lifter valley with outlets at each port. Mine is the same idea but done inside the plenum. If the tube was the full length of the plenum it would never go down a port to a cylinder even if it came completely loose.

It seems like this is an extreme length to go though. I think a metered leak at the rear of the plenum could accomplish 80-90% of the same affect.

I think the mechanical distribution issue should be addressed. But it still leaves a lot on the table and I think a sequential injection ecm would help a lot too. I looked at the Holley HP system and it looks very good. It's a fairly substantial investment by the time you get all the necessary harnesses not to mention optional features like fuel/oil pressure senders etc. Keeping the distributor would save some $$ but adding CnP is very interesting too. Looks like it would require a crank and cam sensor and of course the coils.

I'm kind of getting off topic here but Holley shows the Stealth ram as a step above a single plane intake- rpm wise. Seems like it would be the other way around. I am also wondering if I would still be better off keeping my EBL controls and going with a single plane manifold and using my TB with an elbow. If you were in my place (and it sounds like you basically have been in the past) what would you do? Just keep tuning what I have an see or swapping intake or ecm or both?

Orr89RocZ

iTrader: (20)

Single plane will be better for higher rpm. Similar runner lengths but they have more area in the port