How Much Gain In The Tune Up?

I have decided just to make the 100 plus mile trip to a chassis dyno.
It has been hard t get runs at the track.I mph at 117-118 11.6 secs

To recap, my heap weighs 4000 lbs with me in it.
I have a 520 ci rb stroker, 670 net lift cam 260@50
TF heads flowing 370 @ 700, 337 intake, 2 " primary headers.

Calculators say I am making about 550 hp. Not sure if they factor in shift changes for a manual trans.

After checking the AFR, with the exhaust intact, I am at 11.6-8 range at WOT. I do run it with exhaust off though, not sure how much leaner that would make it.

After getting a good dial back timing light, I am running 42 degrees total timing all in about 3000 rpms.

Any educated guesses on how much more power I'll make by leaning it up to high 13s and limiting the advance to 36-38?

The motor “should” easily make in the 675-700hp range.
(MarkZ’s 505 with ootb TF270’s, gasket matched 337, similar sized cam as yours made a tad over 700/700 on the BES dyno).

Unfortunately, poorly set up street cars(especially those with a manual trans) rarely reward their owners with time slips representative of how much power the motor makes.

This is an example of(one of the many reasons) why I dyno anything I build.
If the motor had been dynoed, you’d know what it made, had it all tuned up, and have a reasonable idea of the potential performance in the car.

If the car was underperforming, you’d know it wasn’t the motor, so you wouldn’t waste time and energy trying to find the lost performance there.

At this point, the chassis dyno could be helpful.

FWIW, there is no such thing as a “good” dial back light, imo.

On the moroso chart 118@4000lbs shows 505hp.

With a reasonably well set up street/strip car, my experience has been that you should be able to run within 10% of the engine dyno numbers(provided they aren’t inflated).

If I assume the less than optimal manual trans set up costs you another 5%(15 total), and start at the low end of the predicted power output(670hp), you’re looking at running speeds that correspond with 570hp........ which would be 122.5mph.

However, without the dyno numbers....... we don’t know how much of that missing speed is lack of power, and how much of it is poor car set-up.

On a dyno jet with a manual trans....... you should be near 600rwhp, unless there are some serious fuel supply or exhaust system issues(or the motor is just down on power).

As an example of how good it can all work...... 69 A12 car in FAST......3900lbs, 600hp, 4 speed, g70-15 bias ply tires, ex manifolds...... 129mph in some killer air.

The MPH only at 117-118 shows that it's really down on power from it's potential with the parts you have... As mentioned above it's hard to know anything by ET, but the MPH is pretty telling.

I can tell you when my car spins, and I have to let off the throttle, then get back on the throttle, it may loose .5 sec in ET, but always comes back around on the top end within 2mph or so. Foot on the floor in high gear, there isn't much car "Setup" that can change that.

Hopefully you find something on the Dyno. I've seen so many simple things (bad timing light, throttle cable misadjsuted and carb not going WOT, etc...) The parts in the motor have good potential...

What's the gear in you ride???

Truth. Unfortunately, timing lights have become as common as carb adjusting tools in a regular mechanics box. Do a search here. There have been a number of conversations on the subject.

4.10 with 26x10.5 " bias ply
It does best to leave at about 2k rpm or I just boil them off.
I have CalTrac split leaf monos, just need the rest of the set up.

I see that now.

My buddies Snap on dial back is 4 degrees retarded from my eons old Craftsman.

Where mine shows 18 and 38 degrees, his shows 22 and 42.

For the reasons stated above worry less about what the number is and more about how it reacts when you move the timing. Just make sure you use the same timing light for verification later on.

Hopefully the dyno operator has a good light.
Will be nice to know whats going as far as peak HP and torque points.

I was just curious how much I might expect to gain by jetting and timing.

For sure, I have no idea where the torque or HP peak is. I shift at 6500, maybe need to stretch it out more.

Thanks for taking the time to explain those points.
When it was all put together, the build went from a tow truck motor to an RPM deal, because the goal was to keep it under the hood with the 337 intake.

The plan was for it to be all done by 6k. I want to go to a roller cam, and will call you for a recommendation when the time comes.

I don't power shift it, that seems like a slow shifting manual would skew the calculators from a fast shifting auto.

Optimizing the tune will help, just was wondering what guys with experience tuning would see, 50hp? 100hp?

Thanks again for your time.

Just as a comparison, my car weighs in at 3926 with me in it and a half tank of gas. 493 stroker. cam is 259/266, 623/633 lift with 1.6 rockers. 4.56 gears. Stock 18 spline tranny. My 60' are a little slow at 1.55 range, but my et's are all in the low 11's at over 123 mph. I run my car with mufflers. It has gone high 10's with open exhaust. My carb is a 1050 AN. 85/92 jets. .070/.030 bleeds. Timing is set at 37* all in at 1800 rpm. I hope this gives you a starting point. Also, my car is a street car mostly. I really don't push the rpms at the track.. I shift at 6k at trap around 6400.. No use in beating on it as I already know what she is capable of.

There are countless motors I’ve tested where I’ve forgotten I even tested them, much less the details about what was done on the dyno, but I can’t think of a single instance where I picked that kind of power by “tuning”.
Usually, when they’re down on power that much, something needs replacing.

I can think of a time or two where there was 30hp or so found in messing with the carb........but that was something that was totally out to lunch to begin with.

Unless you have something pretty far off from what the motor wants, I’d say if you picked up an honest 15hp, you’d be doing okay.

But, that’s why you test......... you might have something that’s way off.

Buy yourself a non-dial back timing light.

Years ago on a chassis dyno we picket up 60+ hp at the tires on my 470 messing with timing, jet and bleed changes.......I was way lean and needed more timing iirc and that's when I got a WB and really started studying the different circuits in a carb. Found out about changing the curve with bleeds and how Holley's tunes were quite wacky in my case so after many low 10 second passes, I got my first 9.98 pass...........Lots to learn on the dyno to at least get ya close and in some cases, bragging rights backed up with respectable et's.....

When you go to the dyno, do NOT let the dyno operator only tune with his light. Bring the light you are going to use and check your light against his.

I don't really care what numbers the timing light shows. What matters is you use the same timing light every single time. I don't care if it shows your car runs better with 60 on it.

The best situation is to buy a quality timing light and use a degreed damper. Why is your damper not degreed?

Also, you need a minimum of a 4.56 gear. Probably 4.88 because you don't have enough first gear to move that weight.

Next steps will be a roller cam and Thumper 1050!

I've slow a mid ten second car down by advancing the timing beyond 36 degrees up to 38 ( over .10)and slowed it down again by going to 40 degrees We where intentionally trying to slow the car down from mid 10.60 to run S/ST at 10.90, we ended up short shifting the 1st and 2nd gear shift points down to 5500 RPM and reduce the total timing to 30 degrees to get their We tried adjusting the throttle cable to not go to full throttle but went back to full throttle off the line and tried other things to slow it down Over revving the shift points to 7000 RPM in both gears was worth right at .10 reduction also
This was a long time ago,1984, long before throttle stops and the electronic aids available now.

Like we talked, at that weight either a skirted banjo straight 1050 Dommy for the wow factor or a BLP Billet 1.610 bore 4150 that I have on 8000 rpm puller trucks, boats, street strip and drag only cars/trucks. You need velocity to move 4000 lbs. and those Billets deliver across the board........

Wow you are way down on power for that bad boy. As said MPH will tell you what kind of power the eng is making. I agree with use one timing light and set it for best power on the dyno. Honestly if the timing light is right then 42 sounds to high as most of these engines with modern aluminum heads seem to only need between 32 to about 38. To much in high gear once rolling can actually hurt power some. Many racers would actually retard the timing some in high gear once the cars weight is moving along. As said if you can get the car on a chassis dyno and tune from there it will help a lot as you are definetly missing some power that your eng should be making. As for shift rpm ??? Maybe I am just an old fool but 99% of the time I race I never even look at the tach going down the track. I just shift by how the eng is pulling by the feel of it. When it feels like its done pulling and peeking out I shift. Then I can mess with it some from there but my car is very consistent when I just shift by how the eng sounds and feels to me. And I don't think your shift point is the problem you have. Heck it could be as much as an improperly adjusted throttle cable which I am sure you have checked ? Good luck with it but get it on a chassis dyno and if you have any friends who are very good with hotrods and engines take them with you as the more heads thinking on this can be better to help find the problem. Good luck and keep us posted. Ron

Thanks for taking time to chat.
Just as an FYI, the car weighs 3740, I weigh 260, so the race weight is 4K.
So you don't think the flow pattern hitting 6500 rpm would be better on a 4500?
I'm all ears.

Hey Ron, so this motor with the MW ports and cam keeps revving fast, It will hit the 7k chip really fast in first and second,so much you have to be on your game to grab gears.
I have been shifting it at 6500ish, just to keep the bottom end together longer.
I had a 10.3 second 63 Fury Max wedge car in the 90s that ran similar, that motor was a 13:1 426. It was faster but a lot lighter, and an automatic.
Tonight, I brought another timing light over, it matched the Snap On light. We plugged my old Craftsman in, 4 degrees lower.
I'll drop the coin on a chassis dyno, just to know where everything is at. Getting the AFR with open headers and RPMs it peaks at will be helpful. Thanks for the help!

To answer your questions on much HP can be gained on tuning I've seen 60 HP gain on a pump gas motor from the first pull to the last pull 34 puls later. That involved some cam timing, ignition timing, different range spark plug heat ranges and carb. tuning.
I've also seen only 20 HP gain from the same effort, I'm thinking the differences between those two motors was short block preparation and a good set up on the carbs to start with
No two motors prepared the same will like exactly the same thing on all the tuneable components

Anytime, and several factors come into play when I set up a carb. Power, shift points, weight, vert, gear, altitude, fuel etc ALL determine the size/design just like in cams..........As I sad, if you want a Dommy then we can add skirted banjos to get the velocity up through the boosters and it will help but the billet supoports about 850-900 so far from my dealings with different racers and you wont have to do the manifold stuff we discussed..........I'll do whatever you want either way........

You REALLY need to address the fuel supply before you hurt it..........

My pressure holds rock steady at 6.5 psi, you really think I have a supply problem? Again, I'm all ears, just trying to wrap my head around how that works? It doesn't nose over or anything.

65 it's more than just pressure. You can have pressure and no flow, or very low flow. You need volume at a reasonable pressure. IMO, the lower the pressure you can use and keep the bowls full and as much air out of the fuel as you can the better off you'll be.

I'm in the process of upgrading to bottom feed needle and seats to help eliminate aeration. Every little bit helps.

The tap for the pressure gauge is 4" from the fuel inlets, I put new .120 needles and seats in at the beginning of the summer.
I'll watch the float bowl levels on the dyno, good point though.

Dom also suggested knocking the pressure back to 6 lbs so that will happen as well.

The A/F gauge doesn’t show it leaning out at wot, right?

Negative, it stays in the mid 11s at WOT.
I dont have the AFR when running open headers though.
According to the plugs, I think it is rich everywhere.
Edit- I have 3/8" including the sender to the carb all brand new.

If you are in the mid 11s on AFR i would expect you to gain some power leaning it down into the mid to high 12s. My car likes 13:1 with 91-93 octane E10 fuel. Anything on either side of that and it loses some mph.

I’d lean it out some and see if it feels any better.

I’d shoot for mid-12’s as a starting point.

Early in the thread there was mention of an exhaust, is it for much street use at all? If it is, I'd wonder about the numbers going down the road.

If it needs work in the idle and transtion, myself I would want to start there and then move on to WOT afterwards.

I wouldn't bring it up if I hadn't made the error of too much (actually all) emphasis on wot and letting everything else fall where it may, which although it may have served me well in terms of mph I feel I would have been smarter to have worked on part throttle stuff first since that's where I really spend the majority of my time.

I had a lil talk with Thumper Dom last night, there are some things I need to check. The tip off idle really gently gets a small lean spot, then its rich. Just driving down the road, it's still pulling high 11s low 12s, It didnt do that before. I believe the T slots on the secondaries could be uncovered too far, or I just need to drop the main jets down a couple more sizes.

The end game is to get a larger carb. I had always heard the 4500s had a better fuel pattern, but, I'm thinking of leaning towards a big 4150.

With the 4 speed, you can put some rpms into it before launch, it might just be better to take the plunge and go Dominator, even though it would cost more to change over.

Hope to hit the Powerball to make things easier.

I guess for me the next logical question is...... is the car legal to run under 11.50, and does that matter where you race?

And...... has the dyno day been scheduled yet?

No it is not, it wont be hard to weld a bar onto the subframe connectors though.
On TNT nights, there is no tech at all.

A week from tomorrow for dyno day. Should give some insight.

Got the timing advance limited to 16 degrees today with 20 initial, going to drop the primary jets 2 sizes tomorrow and take it for a ride, play with the 4 corner idle a bit, see if it cleans up a little.

Anything wrong with this timing light?
https://www.summitracing.com/parts/ino-3551

Thanks for all your help.

Looks fine to me.

It just needs to not have any delay(dial back) circuitry in it that can be influenced but stray emf stuff going on under the hood.

Do you know what kind of dyno it is?

You might want to look at the Flaming River brand stand alone 2 D cell battery powered timing light
Sorry I don't have a link for you, I carry one in the race car trailer and use it at the track, I do have older Craftsman dial back in that tool box in the trailer also but I don't use it on any thing with a race type ignition in the car, I've burnt more than one of them up using them on a MSD 7 series race box

Cool, it's ordered.

No I did not ask what brand the dyno was. Our conversation was mostly about what their capabilities were with the carb.

The guy who tunes thinks he can get it dialed in pretty quickly, even so, I want larger than the 1.59 venturi 1.75 bore Demon that's on there now.

There are no Mopar shops I know of around FL, hopefully, they can catch something that will make some gains.

I only asked what it was because some brands are known for typically giving higher or lower results.
Which doesn’t really matter as long as it repeats well.

You’re only looking to make the numbers go up........ whatever they are.