I've got a slightly ported SuperRam intake on my 383. Also using a BBK 58mm TB. Cam specs are 218*/224* @ .050, 112 LSA, .525" intake lift (1.6 RR) and .502" exhaust (1.5 RR). Heads are iron Sportsman IIs, mildly ported, 200 CFM runners, at 10.5 compression, with 2.02/1.60 valves.

I seem to be running out of "ooompf" around 5200-5300 RPM. Motor flattens out, feels like it's losing power, etc., during datalogged WOT runs in 2nd and 3rd gear.

WB shows AFR still in the low 12's while the injector duty cycle is between 80-88% on the end of these runs.

The max injector BPW from Datamaster is just barely under 10.

My MAP readings stay between 96 and 100 kPa during the entire run, so I still seem to be breathing okay if I'm reading it correctly.

What kind of results are the rest of you seeing with the SR's? When do you seem to be running out on the top end?

Also - has anyone ever checked to see if they're running the same kind of AFR's on both banks of the motor? My passenger side is noticeably richer than my driver's side.

Just looking for others experiences with these intakes.....

 

The AFR will be a little different but if it's way off, look into your timing tables.

Try leaning out the fuel to around 13:1 - 13:3 across the board.

 

You're saying AFR will vary from one side of the motor to the other because of timing?

 

Cylinder heads?

You might have insufficient spring pressure to rev more with the 1.6's. HR's and springs are a whole other issue.
I don't think you have enough cam to make power at a higher rpm anyway though.


You could have an exhaust leak on one side.
You shouldn't have a noticeable diff side to side. Especially being batch fire.

 

I suspect you're right about the revving higher, Scott.

As for the AFR differences between bamks of the motor, I'm at a loss there too. I'm on my second pair of Percy's 6layer aluminum gaskets trying to be sure I don't have an exhaust leak. I guess the next step is go to copper gaskets, replace the collector gaskets, and check for a pin hole somewhere on one of the header welds.

I'm using SLP Tri-Y headers, and frankly they have lots of visible "holes" in outside welds on joints and flanges. However, none are obvious leaks (no sound, can't feel any pulsing at them, etc.). Might be a good time to pull out the JB Weld and just plug all of them as well just to be safe. Other than that, it almost has to be something internal to the motor I would think.

Worst case I guess I can run the ECM's NB sensor on the leaner side for engine safety and just let the right side run rich. But I hate to not have it "right", ya know?

Another idea I have from a trouble shooting standpoint is to disconnect and cap the A.I.R. lines at the headers temporarily. Maybe something is still going on there even though I have it diverted and disabled temp wise in the prom. Maybe I have a bad check valve or seal in there somewhere....

 

I go with the AIR or collectors first.
Pin holes would have little black trails by now.

 

Good idea and point, Scott. Thanks!!!

 

My guess is that your cam is installed at 108 degs. The SuperRam will pull more rpm by retarding the cam to 110 degs.

John Lingenfelter(RIP) installed his 74219 cams at 110 degs. This will shift the powerband.

As far as AF ratio, you want to keep the fuel around 12.8 at peak torque and lean it to 13.0 at max hp. I would be a little concerned at running 13.3. Better to error on the rich side.

What is your total ignition timing?

www.geocities.com/dzperf

 

Comp actually recommended installing it at 108*, so that's how it was done.

I'll try your suggestion on the AFR's at peak TQ and HP. Once I get my two issues worked out (1.0 - 1.5 difference in AFR between banks of the motor, what injector constant to use, covered in two other threads).

I think I'll probably leave the cam alone at the current setting and just accept that the max RPM/shift point is gonna have to be under 5400 RPM - basically before the flattening out happens.

To answer your other question, my WOT timing is 20-22* BTDC. The Sportsman II iron heads don't seem to like or need a lot of timing with the heart shaped fast burn chambers, altho the 10.5 compression probably affects that too. The only knocks I'm recording right now are more at cruising accels and tip-in from cruise.

Appreciate your reply and any future ideas or input!

 

I know that Comp grinds cams with 4 degs advance built in. This is apparently done to compensate for chain stretch. I know it's a pita to advance the cam unless you have a 2 piece cover.

When I put my 406 together, I used a Cloyes Hex Adjust timing chain and matching cover. The cover has an access hole that you can easily remove and make quick changes to the cam phasing.

Your total timing 20-22 degrees. What is your base? If you are running 8 degs. base, total timing of 28-30 degrees is very conservative. I feel that you're leaving some significant power on the table (IMO).

I had problems with false knock and eliminated my knock sensor. I'm using DFI so wigging the computer out is not a concern.

BTW - I'm running 38 degrees total timing on my 11.0-1 406.

 

That is my total, it includes the 6* base.

What heads and intake system are you running that allows 38* timing at WOT, and what RPM? That sounds awfully high to me. 38* at cruise I can believe, but not WOT. What's your base set at? And what computer system (7730/$8D, etc.) are you using if you don't mind my asking......

 

My motor is a 400 block bored .020 with SRP flat tops, zero decked, Brodix RR200 heads with 68cc chambers. Quench is right at .040!

I use a DFI 6 for engine management. Yes, 38 degrees is very aggressive for my compression. The MiniRam intake performs best with that timing.

I really feel that you are lossing a great deal of power by running a total of 20-22 degrees timg at WOT.

A buddy of mine with the same basic set up but in a Vette ran the same timing. You can do a search on Corvette Forum for more info.

 

I'll take a try at increasing the WOT timing again now that I have the WB hooked up. Thanks for the advice and infoi!!!

 

A 383 and a 400 are different.
Bore size being the diff.
With a 218 @ .050 and 10.5 cr on iron heads. I don't think you be able to go more that 32 at WOT.
Go up 2 degrees at a time till you get knock. then pull a little.
I'd guess you'll only be able to get 28 or so since we have similar motors. But 22 is low. If you can't get more than that, you need a bigger cam. Well actually, you need a bigger one any way imop.

 

Thanks for that info, Scott! I plan to creep it up a little at a time (2* sounds good) and see where the knock starts to creep back in. I'm trying to figure out the fuel injector constant I shouldbe using first, lot of disagreement there on what the LS1 injectors should be set at.

Since I'm hitting over 80% duty cycle but the NB and WB both say I'm really rich, I suspect a higher FIC is needed. I was set at 28 at 43PSI, then I raised it to 49PSI, which calcs out to about a 30. May try that just to see the effect. Am hoping to figure out the rich right bank problem soon, don't really want to due too much WOT until that's settled for motor safety reasons....

 

Z69 - I ran the same ignition timing on the 383. I will need to find my old ET slips to get the exact performance increase when going from 34 degrees total to 38 degrees total.

 

I'm not disagreeing on what works for you.
I chassis dyno'd mine with & w/o race gas and 28 and 34 degrees total on my current solid cam.
Only 6-10 hp diff. on race gas and 34.
On my old 280 hyd cam, I ran 34 no problem. Never checked to see what more timing would do. Went to a 4 degree smaller solid cam but same IC point and had to pull 6 degrees and swap to a 160 stat from a 180. That's why I'm swapping to RR200's.
My point is that the cam can make a huge diff in timing tolerance.

 

AN UPDATE.....

I disconnected and plugged the AIR check valves last night to see if that was the cause of the right bank reading 1.5 richer AFR than the driver's side. No change. So I'll probably hook that back up tonight or tomorrow.

I also raised my injector constant this morning to 30#, which is what the equation says when using a 28# injector at 50 PSI. Having to do some re-tuning now. Made the injector constant change assuming the LS1 injectors were rated at the standard 43.5 PSI. Haven't heard back from Rich up at CruisinPerformance to see what these typically flow, so I'm made the assumption. Seems like everyone on split 50-50 on whether they flow 28# at 43PSI or 58 (or whatever). Probably have the same issue if I went to SVO's (rated at 39 or 43 PSI?).

Once I tweak the VE and accel tables a bit, I'll start raising the WOT and cruise timing per the suggestions already made here.

Thanks for the inputs!

 

vernw - Keep us posted on your findings.

 

UPDATE --- I called Rich at Crusin Performance, and he said the LS1 28# injectors are rated a 4-bar (58PSI). So I thought I had it finally resolved. Then I went to Racetronix web site, and noticed they had the 28# LS1 injectors with the same part number as mine and they said they tested them at 28# and 43 PSI. So I called them, too. They told me there are 2 different LS1 injectors, and these are the higher flowing ones and do flow 28# at 43PSI. So now I'm all confused again. Getting to be a regular state with me.....



Running rich on one side update....

As for the running richer on the passenger's side. Disconnecting and capping off the A.I.R. did NOT change anything. I also disconnected and sealed off the PCV valve for a few minutes since I didn't know what cylinder(s) it feeds into. But that didn't make any difference either. So then I swapped out the dizzy with a brand new MSD knock-off with new rotor and cap I had sitting on the shelf just in case it was something internal to it. Nope, that didn't do it either. Running out of ideas here folks. Swapped NB oxy sensors, took out the AC-Delco AFS-74 and put in a Bosch to test, and no change there either.

I've done it in the past, but I guess I'll try another plug swap. Possibly the plug wires as well. Maybe the coil, too. I've also disconnected the MSD Digital 6+ for testing in the past, but guess I could do that again as well (one thing at a time!). After that, the only thing I can think of is checking the valve lash and if that doesn't do it then I'll have to pull and re-seal the intake manifold next. I know the EGR is not causing the problem because mine is disabled and plugged with a block off plate (my heads aren't drilled for the EGR passage). I'll take pix of the individual plugs and label which cylinder they came from when I pull them in case anyone wants to see them.

Can anyone think of anything I may have over looked?

One thought rattling around in my head is this: The O2 sensors read the amount of oxygen in the exhaust, right? And then we
***ume that too much O2 means it's running lean, and too little means we're running rich. Right? Is there some other way oxygen can get into particular cylinders that I haven't thought of? Maybe an exhaust gasket leak? I would think that I'd hear that kind of a leak though. Guess I could pull the Percy's 6 layer aluminum gaskets and put in some copper gaskets to rule that one out.

Also, the fact that the NB is mounted horizontally, and the WB is mounted vertically (threads in from the top), that shouldn't make any difference could it? Sounds like I'm starting to grasp for straws here, doesn't it?

I welcome any and all ideas on this one....

 

Incomplete combustion or misfire also will show as lean.
Could very well be a high resistance plug wire. I would't think the coil due to one side being ok. Plugs and wires may change things.

 

think your cam is too small. thats a nice modded TPI or superram cam in a 350. you should go with 224/230 or the 230/236 and you'll find those higher rpms. superams are suppose to flow to 5800rpms.

 

Thanks for the suggestions. Been raining here the last few evenings, planning to pull and examine plugs tonight, will do a wire swap is anything looks "off".

Have swapped in a new MSD knock-off dizzy, and noticed one kinda strange thing while resetting the base timing, at 2 or 3 degrees advance, the WB was reading about 16AFR at idle, but as soon as I got to the normal 6*BTDC it was back down to 12.5-13.0 like "usual" (this is while idling in closed loop). Is it "normal" to see that much leaning out with less timing? Could have still been in open loop then due to the restart, but I don't think so...

 

I do not believe that the computer goes in to close loop at idle. I may be wrong on this.

The retarding of the base timing will increase combustion temperatures and promote better burn. That's why most people retard timing for emissions tests.

I looked back on my program from when I had the 383/SuperRam. My total timing was 32 degrees. The motor was sensitive to timing. This was with the LPE 74219 cam and 11-1 compression. Best ET with that combo 12.00@ 113.8

I really feel that you're leaving some serious power on the table with you present timing.

 

I think I am too. Once I get the rich passengers bank figured out I'll be raising the WOT timing and seeing how far I can go without knocking.

 

Well, I pulled the plugs this weekend, and other than #1 looking to be slightly leaner than the rest of them, all 8 look to be running rich, and not any major differences between cylinders or sides of the motor. For some reason, two different 3-wire heated O2 sensors are reading too much O2 in the exhaust and are richening up the motor.

So, where do I go from here? I would think an exhaust leak would be obvious, but I don't hear it, nor do I see any carbon tracking on the parts of the headers you can easily see.....

 

At this point, I would let it run rich at idle and work on your full throttle timing.

Are you using a wideband to measure the AF ratio?

 

Yes, I am, but it's reading that same 1-1.5 lower (richer) AFR at pretty much all RPM levels. So how do I know what to tune for at WOT? Sounds to me like I still need to resolve the NB reading rich on the driver's side. My next thoughts, unless someone has a better idea, is to change the collector gasket for that side, and if that doesn't do it, pull the header on the drivers side and look for some pin hole leak somewhere and replace the exhaust gasket.

Anyone concur or have any other ideas?

 

yeah if you have the money and time, go for the new gaskets..... then see where that gets you

 

Anyone want to see the plug pix? I can email them to you.....

 

No other ideas? I'm feeling pretty lost right now....

 

e-mail them to my work address

 

I've also got them posted here:

http://www.cardomain.com/ride/552958/4

Can still send them e-mail if you want. To "daioildale" or "igalaxy"? Not sure which one is work, but would guess the first one.....

 

my old pu truck once had a minute (one inch) hairline crack in the stock exhaust manifold. It sucked air in, causing the o2 to read lean and set a check engine light, as well as telling the computer to add more fuel. It ran real rich till I found the crack and replaced the manifold. It was a 1985 GMC.

 

Back to the original question. I have a SR on my blown 383, worked TF heads, 218/224,520/520, and I shift it at 6000. Pulls great.

 

apples and blowers-not a relavent comparison.

 

I've got the SuperRam pulled, and discovered a couple of things in the process. I RTV'ed it on last time with "sensor safe" RTV, but several of the screws were only finger tight! I don't know how that happened, but it did. In addition, I found out that one of the SR gaskets between the runners and the lower intake is a built-in vacuum leak. And it's NOT the gasket that's been mentioned in the thread where the EGR hole has to be no more than 1.75" long. The new gasket set I got from Summit has the correct opening for that port on the drivers side.

The problem is the back gasket on the passenger side. The gasket there for the curved EGR like port on the driver's side is has way too big an opening for the ports in the runners, and since the runners outside edge is not cut very large, there is only a 32nd or nor more than a 16th of an inch of gasket overlap. Either the hole in the gasket needs to be smaller, or the outside diameter of the runners themselves needs to be larger. Since I've gotten 2 new gasket sets the same way, and they match the old gaskets, I thinks its safe to assume no "correct" gaskets have ever been made. So I built up the outside edge of the runners in this area to allow more gasket mating surface. Used JB Weld stick, and it's curing right now. Will file it down and fit it in the morning.

I also noticed the new runner to plenum gaskets no longer has the little narrow strip between the ports. Now there are just two large openings in the gasket, one for the front pair of ports and one for the back pair. Guess it won't hurt anything, but kind of strange still.

What's everyone's opinion, should I use RTV on SR gaskets, or assemble them dry? Kind of torn on his subject. Just re-read the installation instructions and they say to use RTV, so I guess I will.

I've also got my "new low mileage" SVO 30# injectors back from Rich at Cruzin Performance. All cleaned and tested out within 1% of each other. So I've got KNOWN good injectors going back in, and should have plenty of fuel flow now. WIll be dropping the fuel pressure back to 43 like it should be, Will also probably replace the pass. side header exhaust gasket with the solid copper one while I've got it down. Hopefully the rich/lean banks [rpblme will be resoled after this work. I also lightly filed off a couple of high spots/lumps on the runners to make sure I have a smooth flat mating surface. Going everything I can think of to make sure everything is "right".

Any other suggestions from anyone?

 

Vern - Definately use the RTV. It's not worth taking the chance of putting it together dry. The SR is a pita to install (as you probably know).

I've always used Fel Pro header gaskets with great success. I also apply a coating of Hi-Temp RTV to both side of the gaskets. Never had a leak!

Good luck.

 

At least your finding some things that "could" have caused your issues. Sucks when there is just no reason something isn't working.
Hope that that was it.
I've always been a fan of dry sealing everything that can be, but if they're suggesting sealant than it might be best.
Jp

 

Main reason I put RTV on the runners is so they come off.
Ever tried getting 70k mi gaskets off that were installed dry?
Note: this was before those red brillo disc's became popular.
I recently (today) tried out Hylomar. My Jag mechanic buddy swears by it. Pre Ford Jaguars are known leakers.
It's similar to RTV, non hardening, and gas resistant. Didn't notice if it was O2 safe. My sensor will remain it the GM bag for a while yet.

You might try and gaskacinch the gaskets to the plenum.
And your choice of sealant on the runner sides.
The plenum is a lot easier to clean than the runners.

I'm curious as to how long your JB stuff will stick to such a small area. I'd either make a new gasket or have some
welding done to the flange. Has anyone checked with accel
on this? I know, no one has a week to devote to getting through on their tech line.

 

Ha-Ha - never thought of that "reason" for using RTV! I doubt I'll ever have to worry about 70K miles on a set of SR gaskets though!

Never tried or heard of Hylomar. May have to look into it for the next time. Let me know hw it works put please.

Naturally, I found more problems. The outside bolt holes in the plenum-to-runner gaskets are a third to half a hole diameter off. So much gasket material in those areas that the only way a vac could be created would be if the gasket buckles. I'm opening up thise holes tomorrow night to make sure it doesn't buckle and cause a problem.

I am using a sealer on both sides of all gaskets except the plenum lid. I'm using the sensor-safe black Versa-Chem stuff.

We'll see if the JB holds. My "patch" is about 2 - 2.5 inches long. Made it longer than needed for the very reason you stated. I also took a file and slightly roughed up where the JB was going. It held fine while filing on it to make the built up area flush with the runner's gasket face. Hopefully it will continue to. Planning to call Accel about that problem later this week.

I sure appreciate all the interest and suggestions on this! Hopefully yhis will end up making a real difference. With any luck I'll know Monday evening, or possibly Tuesday night.

Keep the thoughts coming, and I'll keep ya posted!

 

Before I re-installed the SuperRam, I pulled the header on the driver's side to replace the Percy's 6-layer gasket with a heavy gauge solid copper one. Low and behold, onece the header was off I noticed treh A.I.R. tubue going into cyl #7 was cracked all the way around and you could see daylight thru it. So I had the welded back up, SR back on with RTV (except for the plenum lid), new SVI 30# injectors installed, FP set back down to 42 at idle with the vac line connected (46 unconnected), injector constatnt set to 31 per the flow test results from Rich, and it looks like it has HELPED (but not solved) the rich-right/lean-left bank problem.

The LCD display on my WB was showing 13.5 - 14.5. range AFR while driving to work this morning. Couldn't do any datalogging today, my laptop dropped the serial port yesterday afternoon. Dell is replacing the mothrerboard on it for me, but not until Monday (bummer!). So the data logging and tuning is on hold for a couple more days. Feels smoother at idle, and feels stong, but no way to log it for now.

Will get back with another update then.

Have a Great Weekend, and THANKS! for all the help so far!!!

 

Did the TDC check this weekend, and need to verify I did it right. Threaded center piece into #1, rotated crank by hand until it hit the stop, marked the balancer. Rotated it back the other direction until it hit hte stop, marked the balancer. Rotated it until marks were at the bottom, and marked halfway between the two previous marks with a flexible ruler. Guess what - instead of zero it came out being at the 4* BTDC mark. So since I set my base timing at 6* BTDC, does this mean I'm really only running it at 2* BTDC?

Is it normal ot see one off like this? Of course, I used a dime store cheapy stamped indicator when we installed the engine, so I guess I shouldn't be surprised.....