Mindgame

I hate to say the same thing over and over but I agree with Jordon.
I think alot of people give up power by assuming that the LTx intake is so good that it can't use any improvement. I have never seen an intake that couldn't.... even on a mild engine it's worth power if done right. A stroker has big airflow demand and with a cam like you're running (not too aggressive IMO), I'd want a ~220 cc port. That's just what the strokers seem to perform best on.
Not saying that the smaller ports don't perform well, they just set the engine up to make less hp but similar torque at a bit less rpm. If this were a tugboat race, that's the way I'd go. But you can't go wrong having those intake passages opened up to allow that engine to breath. I bet if you could throw a Super Victor Jr intake on that thing as it sits, you'd find another 15-20 hp. It's there.... you just need a bigger straw.

-Mindgame

Denny McLain

Normally I’m in awe of the amount of knowledge on this advanced list and pretty much read it to get further educated. In this case, I have to disagree with what’s been posted as I have a fair amount of time observing dyno tuning and goes against the grain of what I’ve seen.

The problem here is more than likely one of two things: Something is wrong mechanically/electrically or the tune is off.

The reason I say this is due to how uneven the dyno graph is on the top end. Has nothing to do with where it peaks, everything to do with how smooth it is and the shape of the curve. I’ve seen the same uneven flat curve from mild detonation, too much timing, pulling out timing, lean/rich etc. to weak springs, ignition problems and even ring flutter. Hell, even bad gas or wrong plug gap will show up as an uneven curve.

The very first thing I would do is put fresh plugs gapped @ .042 in it and take it to shop with extensive tuning experience whom also logs each dyno run. It could very well just be the tune or by scanning it, the computer tells you it’s doing something silly. If nothing shows up, then it’s the old tried and true process of checking each electrical component, check the springs, look for oil in the intake (valve flutter) etc.

These kind of problems are super frustrating and sometimes require a lot of trial and error to correct. A restriction does not explain the unevenness of the curve nor the shape to me.

JordonMusser

ring flutter is pretty rare unless somebody is doing something "unique" with the rings.

If the springs were it, you would probably see a continual drop off.

Speedworks I would assume can handle checking for knock retard, timing issues etc.

a motor that a friend build had problems making power.. 396, all the good stuff, 395rwhp. turns out the compression was about 1.5 points too low, and the intake gaskets weren't lined up properly. Fixing these two things(new pistons and properly installing the intake) we found 50rwhp.


There is something happening at 5600 or so that is causing a restriction. whether it be port volume, or something far more complicated..

Denny McLain

I vote for: A lot more complicated then.

Again, I'm looking at both the shape of the curve and how uneven it is on top. A restiction would still have a smooth shape. Just not have the top end it should.

Denny McLain

I'm in 100% agreement that ring flutter is rare.

However, I just pulled a dyno sheet from SpeedWorks of my 398 which did have ring flutter, the shape of the curve and smoothness on top end is indentical.

I'd not rule it out because it's rare. It takes but a second to check for oil in the intake.

Dave69Z

I don't remember what rings the engine builder used in the motor. They were nothing out of the ordinary, although they did open up the ring gap a bit for nitrous use. I am in the process of installing a direct port nitrous system.

The pistons are JE Nitrous Pistons with a small dome, the chambers in the heads are 62cc, the pistons are .010 in the hole and standard Felpro 1074 headgasket were used. The compression is supposed to be 11.44 if I calculated it correctly.

I have some AC Delco plugs in it gapped at .45. I recently purchased some NGK plugs I am going to replace them with.
I will pull the air intake and take a peak into the manifold and see it I can see oil in the intake.

I figure the two other things I can do are check the valve lash and run a compression test on the motor.

If I do switch to a single plane manifold in the future, what do you think of this new Edelbrock manifold. It the Victor EFI P/N 29785. Here is a link to a pic of it:
Victor EFI Manifold

It is based on the Victor E. The description for the Victor E reads as follows: "Ideal for high-rpm drag race applications (4500-8500 rpm), the Victor-E has a larger and deeper plenum than the #350-2975. It provides maximum power in the higher rpm range for engines with standard port location iron and aluminum heads. Plenty of material at the manifold port exit allows port matching to the small port heads used in NHRA Super Stock classes. 1'' or 2'' spacers can be used for performance tuning. The large plenum and runner volume of this manifold is ideal for alcohol-fueled applications."

The Victor EFI is approximately $310 from Summit.

Thanks for the continued input.

Dave

INTMD8

A restriction would not cause the horsepower to drop, and then recover. It would just flatline.

My vote is knock retard, or too lean, or both.

FWIW, every stroker LT1 I have tuned likes between 12.0-1 and 12.5-1 air fuel, and 31-32 degrees timing from 4,400 on up.

Were any pulls made with a fatter air fuel? Any idea what your total timing is?

Even if you get the graph smoothed out, my guess is you would find 10rwhp or less. I think it's making good power for what you have, and like others have said, more extensive porting on the intake (and heads) would be very beneficial.

Mindgame

Ring flutter is an easy see when you can monitor crankcase vacuum. It'll fall off with detonation (usually around peak torque) and it'll fall off with inertial flutter at high rpms.
Then again, most of my experience is in dealing with engine dynos rather than chassis.

And yes, power does drop with restriction. You can cam the engine to spin whatever rpm you want but if the cylinder head and intake aren't there.... it aint gonna make it. Plain and simple.

WRT to the intake,
Looks good to me and I'm glad Edelbrock is stepping up to the plate. At $310 it's a steal, especially if you've ever spent the dough to have one converted for EFI. Of course this won't be a simple swap, so plan carefully.

-Mindgame

Denny McLain

Dave

First my condolences to you for having this problem. I had a very similar problem and know your frustration. Guess that’s why I’m dwelling on your information looking for something to do my best to help also hoping my input will light a fire under someone else with ideas.

Again, I have dyno sheets from the same shop that look almost identical to yours. My problem was fourfold: The 227 AFR heads did not flow as per the porter provided flow sheets, ring flutter, cats broken/blow into the mufflers and the wrong temp sensor showing zero degrees creating a rich condition preventing proper fuel/air tuning was it. It only took a few thousand $ to find the problems. Ring flutter was 80%.

Your flow sheets do not jive to me. Unless I’m reading your flow sheets wrong, (perhaps someone can correct me) they flowed five cylinders and your flow drastically varies per cylinder. Yes, #5 flows pretty spectacular flowing 294/231 @ only .400 lift but #4 only flowed 157/125 at the same lift. Unless I’m out in left field, something isn’t right with your flow sheets. Another red flag, is that it honestly takes a pretty good set of heads (as in sh*t kicking set of heads) to flow close to 300cfm on intake and 230 on exhaust at only .400 lift. Much more than a light port job.

If you ever pull the heads, I’d have them independently checked to see what someone who does not have a financial interest says. Have to agree that there may not be much more than 10-15 hp in the combo unless your tune is off……….. as in way, way off or something else is wrong.

Also, I spoke to Wes (dark hair, owns a supercharged black Mustang) last night whom does some of the tuning at SpeedWorks. If he didn’t do the original tuning, let me know and I’ll forward his number so you guys can talk. Wes is a good guy and will help all he can.

Do check for oil in your intake as it is a symptom of ring flutter and though rare, two things pop out…………. It happened to me and our dyno sheets do look very similar.

Hope it’s something else. If you find the problem, please let all of us know.

JordonMusser

he stated that those arent different cylinders, but rather the progression of no porting to the final job.

come on guys, pay attention