Truck not performing as expected. Need help! Update

I just got my truck running after a head swap and header change and made it out to Milan on Sat. Listed below is the combo with before and after times.

Old combo
88 D100
10.5:1. 493
850 demon carb
Indy dual plane
346 heads with 2.14 in. 1.81 ex., mild bowl work and gasket match
1-3/4 headers
Comp xe294 hydraulic cam
Comp 1.5 roller rockers
Performer rpm fuel pump
-8an lines from cell to pump
3/8 lines from pump to carb
Manual valve body 727
Converter flashes to about 3000 rpm
4.10 8-3/4
295/65r15 drag radials

Best time 12.10 and 110mph @ about 3800lbs.
1.68 60ft

New combo is the same but with sidewinder heads with bowl work and gasket match by Marsh Performance, 2” primary headers, 3-1/2” collectors.

Best time 11.98 and 110mph @ about 3650-3700lbs. I will be putting the truck on scales tomorrow.
1.65 60ft

I thought the weight decrease alone would have put me into the 11’s and I thought I should have gained at least a little mph. The only thing I can think of is maybe the fuel filter doesn’t flow enough to keep up.

I also have a porter .600 lift 266 @ .50 solid flat tappet can to install also but I was trying to wait to finish my Dana 60 and get a new converter.

What do you guys think? Was I crazy to expect 11.60’s out of this combo?

If you can increase the jetting, fatten it up, enough to slow the MPH down in the 1/4 mile then you have enough fuel volume for your motor
If not, then you don't
Not enough fuel volume has been a large part of a lot of drag cars and other drag race vehicles not performing as expected with other changes to the vehicle
Mine included

What was the weather previously? Its been pretty brutal here this week. 300 flash stall is pretty tight.
Doug

I never thought about it like that. I am going to change the fuel filter before I take it out again, but I will definitely give that a try. Thank you.

The previous temp was probably about 70. It was about 80 degrees last Saturday.

It seems to me that I am losing about 100hp somewhere.

You can jet it a step at a time like Cab says until it slows then obviously take it back a notch. I think your mph didn't do anything because you didn't change the cam with the heads. Basically you just made the engine more efficient but a decent cam will really wake it up. When you change the cam then the converter your expectations will probably happen. Weight and brick shape are hard to overcome. Cool though!

Pretty much agree w/ everyone else...the weather likely had a lot to do w/ it. I'd bet it'd be at least a tenth quicker in the same weather you ran the 12.10 in previously.
The new cam along w/ a looser converter will def. wake it up.

Put a fuel pressure gauge on it to make sure you have enough fuel to feed that monster.

I wouldn’t be surprised if the lifters are giving up at whatever rpm 110mph is.

I’d schedule a few pulls on a local chassis dyno.

The 60’ is soft if you’re looking to get into that mid-11 zone.

That mechanical pump setup is not going to give you a ton of volume or pressure. That said, I think your cam, converter and gear are holding you back more than anything. 3800lbs with that .520 lift cam and 4.10 gear on a 30 inch tall tire aren't going to make a ton of steam in my opinion.

It will be going on the scales at work tonight. I will update later. Hopefully I can get out to the track in a week or two to verify I am getting enough fuel. If I am, do you guys think putting the new cam in before I get the converter will hurt performance at the track?

Nothing of a technical nature to add, but damn, I love that truck. That's bad ass.

That thing is super cool.

If you decide to go the chassis dyno route, Jake's has a pretty nice one + alot of experience to go with it.

Something else to think on.
Had your old heads been cut or surfaced? You have an aluminum head that if I remember right has a big chamber. Like 84 maybe? If you have added chamber and gone to aluminum which in theory costs you a little compression, you have gone backwards in compression.

The new cam and the 3000 stall won’t play very well together.

In fact, I wouldn’t consider the current 250@.050 hyd cam and the 3000 converter to be a very good match.

I’m sure that’s a lot(most?) of why the 60’ is a bit soft.

I just got the Truck off of the scales. 3340lbs without me and 3600 at race weight. It was actually a little bit lighter than I expected. I also got everything to upgrade the fuel system from the pump to the carb. Hopefully I can do some testing and tuning here shortly. I really need to get the new converter so I can install the cam😁

A lightweight!

I think the weather had to contribute a decent amount, and will agree with the others that the converter is too tight.

I have a similar mild 493 in my Plymouth, the 9.5" converter flashes to ~4400. Even the old off the shelf 10" "3000 stall" flashed to ~4k. I normally run 3.55's and a 28" tire and weigh 3700 lb at the line.

It is pretty light for an all steel 1/2 ton truck. Lol. What is your combo and what does it run? If you don’t mind me asking.

Just a little tidbit...... and you may already be aware of this.......

But the fuel level setting on those demons isn’t like the old holleys(bottom of the hole).
I usually run those with the fuel sitting about 2/3 up the sight glass, set with the engine running.

Thank you. I will double check the float level. What heat range plugs do you guys recommend? I am currently running number 8 ngk plugs, but I know nothing about heat ranges.

10.5:1?
I’d go with 6’s.

I don’t know where you’ve been shifting, but I’d try a couple passes shifting at like 55-5600..... see what happens.
Make note of what the rpm is crossing the stripe.

I replaced the fuel filter with a high flow filter and put on a fuel pressure gauge. The fuel pressure is dropping to about 4 psi during the run. I also recorded the tach during a pass. It looks like the converter might be flashing closer to 3500-3600 and not 3000. It looks like it might be time for an electric pump.

1 3/4 headers are a little small for a 493

Mechanical pumps have their limitations for sure and a good electric pump when mounted and wired into relays can last for years............I'd go that route and keep fuel pressure 5-6 lbs according to what needle n seats you run............

I had a Carter 6903 on my 440 with stealth heads and a similar size cam, and was dropping to 3 PSI at WOT even in 1st gear. Also had crappy Hush Thrush mufflers I originally bought just to keep it quiet temporarily when the motor was fresh. I put an Aeromotive electric on and 20 inch cash Ultra Flos. The car is quieter, way more responsive, and feels like it picked up 50-100 hp.

It has 2” headers now.

I sure hope mine does the same.

You REALLY need more carb for that puppy trust me............

It is definitely on the long list of things to upgrade.

What RPM were you shifting at

Dom.. I gave my buddy your number and he will
call.. if you can see if you can help him out
on his carb.. thanks

Cool Mike,much appreciated and will hook him up...........

I was shifting at 5600-5700 trap at 57-5800. It looks like the converter is slipping about 12% also. I definitely have a lot of work to do on this thing.

12% slippage from a 3500 converter is pretty bad

That is what I was thinking. I don’t think an 11 inch converter should flash that high either. Lol.

That thing needs a nice 9.5”.

My old SB Dart would drop to ~1 psi during a run with the mech pump. installed 1/2" feed and return and an electric pump, fuel pressure was constant but the car was no faster...YMMV

Also, it needs a bigger carb! Mine would pick up ~0.2 going from 750 to 950.

Combo:
66 Belv
493; 10.25:1
-516 heads, big valves
4150 M1 w/ FITech
520/520 260/266 @ 0.050
TTI 2" headers, 3.5 x-pipe, muffs and dumps
727; 9.5" converter, flashes to ~4400
8 3/4; 3.55's
tires vary, but normally run a 28" radial

Last year I was playing with a small plate kit, so didn't have too many runs on motor, ran 11.31 @ 118 at Milan with ~1700' air last time out, and 10.83 with a 0.050 jet in the plate...

Post up next time your are heading out, I'll try to make the trek. I used to work in Ann Arbor, so it was easy to shoot down to Milan, now I work in Pontiac...

It wouldn’t surprise me if there are valvetrain stability issues setting in with the motor at 5800rpm through the traps.

Using the butt dyno to diag that situation can be tough.

If your perception is that the motor feels really strong well past 6k in 2nd gear, you might be okay........ but a few pulls on a chassis dyno could reveal something.

I have to be honest with you, I didn't read all of your specifics the first time through (on my phone). I didn't catch the fact that its a stroker, and I assumed this was a heavy 3800-4000 lb truck. MAYBE I'm missing something here, but given that its stroked and your truck is that light I would think you should be running low 11s @ 118-120 sorted out. How the heck did you get the truck that light? With that bigger cam you have I would think you had a shot at a 10.99 with the right converter once you slide that in, again unless I'm missing something. Do you know what those heads flow? I thought they were in the 260-270 neighborhood @ 600 lift?

I'd say upgrade the fuel system and go from there. My car did not show symptoms of being under fueled. In fact, I could jet it up and and peg my wideband at 10.0 at the hit, but my fuel curve was completely messed up and it would lean out at the top of every gear. Getting WOT in the 13.0 range made a big difference in the performance, but it was coming up to 14.0-14.5 at 6000 RPM. Very difficult to read the wideband too because it was bouncing alot on its way up. The car wouldn't nose over, and it revved up quick, just lacked torque. Fuel pressure would also drop much more drastically once warmed up (vapor locking).

I'm not sure what you're running for fuel, modern pump fuel is more problematic with a mechanical fuel pump too. Its designed to vaporize quickly, which is good for FI applications, but with the mechanical pumps putting it under a vacuum it vaporizes even easier, increasing the chances of vapor lock.

Basic stuff, but what is your ignition timing/curve, and have you verified that TDC on the balancer is true TDC? Did you degree the cam, and do you know what cranking compression or leakdown is? Are you SURE you're getting WOT with that trick throttle cable bracket there?

Put the solid cam in an ditch the power steering would be my first moves. probably a moroso waterpump drive and electric fan also/next. If I remember the engine compartment pic you have a pulley driven fan, waterpump, and power steering there is 2 tenths right there. I agree on the carb and converter but those are more money. Altogether though:
solid cam is probably .2
getting rid of mechanical accessories .2
1050 dominator .2 (there is et to be gained from an intake and spacer swap but I'll leave that out for this purpose)
converter maybey .3-.5
should be 11.2-11.00 (maybey 10.90's) combo based off the current 12.10 et
It should have an electric pump also. It doesn't have to be fancy either. My buddy has a bbc vette with a holley blue pump and has been going 9.70's for years with it. Not my first choice but it works.

The converter is so bad on this thing, I don’t even know if it can run faster right now. After the fuel issue is fixed, I was going to try nitrous, but that will probably make it worse.

That sounds like a good running combo. What is a 0.050 jet? About 75 hp? After my truck is sorted out, i would like to try a 150 shot. How do you like the FITech?

Should be around a ~90 HP shot. I wanted to up it to a 150-175 shot last year, but ran out of decent days.

You get what you pay for with the FITech. It evidently only flows ~850 CFM, which makes sense why it hasn't slowed the car down compared to my old 950HP PN80496 which also flows ~830...but it might pick up with more flow.

I should stop playing around and put real heads/cam on it

Be interesting to see what a set of heads....... and no other changes....... would do.

Agreed. Keeping this cam, I'd lean towards the TF240 head, but if I were to step up the cam, I might entertain the TF270 with MW ports.

You should use a seamstress tape to measure the tires actual circumference in the middle of the tread pattern and use that for your converter slippage calculations, not all tire heights are the same as advertised
I learned that lesson a long time ago when I bought a pair of drag slicks that had over three inches difference in circumference between the two tires
The stupid car started driving sideway away from the starting line at WOT It didn't do it with the other tires so I finally figured out it was in the new tires, nothing else
I've bought and used 9x30x15 inch drag slicks that varied in circumference from 92.5 inch to 96.75
Once I found out that I could get and legally use the taller tires those were the ones I bought and used from then on

I never thought about that. I will have to measure them. Thanks.

Hopefully the rain holds off today. I should be headed out to Milan tonight, to try out the new fuel pump. I don’t think it will make that big of a difference though.

To me that not to bad of a run with motor combo. The 76 D 100 truck I have that did not sale, weighs in at 3320 and so far it has run 11.30s with a 505. Since I could not sale it, it will be down the track with it and try to get close to 10s with it.

I ran the truck last night with a new dynamic 9.5 converter. It ran a best ever 11.65, pulling both front wheels, but it still only runs 110mph. I guess it’s time to put the new cam in. I was also runner up in my class, so that was cool too.

If you want to pick up MPH replace that MSD 6 with a 7. When I had similar results as you, swapped in a 7al in place of a 6al and picked up 5mph

The moroso chart shows 110 is good for an 11.90, so your ET is much better than the speed.

I’m still leaning towards valvetrain issues.

How much stall from the new converter?

I’m with you on the valve train issue.

The new converter is flashing to about 4300-4400 rpm.

How'd you make out on Saturday?
I think I saw the truck, but had to leave early

You should have said hi.
I made it to the final against a Roadrunner, where I lost by .008 seconds. Here is a video from my back bumper racing a friend in a fox body. https://youtu.be/T_JygdfX6fE

Well, let's look at the basics here.

Clutch fan or mechanical fan? Proven 30-HP loss at 5,000 RPM with a mechanical fan, near 6,000 RPM, probably quiet a bit more. If it doesn't have a fan clutch, that's the easiest power you'll make right now.

Get rid of the mechanical fuel pump, you paid -big money- to stroke the wedge to 493ci and purchase aluminum heads, a simple Walbro 255 with an Aeromotive regulator / return line will support more power than the block is capable of. That's a premium OEM pump and cost around $100. You'll never have a pressure drop and it will remove vapor lock related issues.

Mechanical water pumps don't draw that much power through parasitic drag, very slight decrease over running an expensive, failure prone electric water pump.

Sidewinder heads flow around 250 - CFM @ .500" lift (ootb, 270 - CFM with bowl work), which can support well over 500 - HP, but the MPH shows you aren't making anywhere near that. New Challenger Scat Pack weighs 4,400 lbs with driver. They run 115 MPH in the quarter with around 430 RWHP.

Your combination is mismatched, 30" drag radial, 4.10 gears, 4,000 (guess) 9.5" converter, 2" headers, 496-cubes, dual-plane intake (Indy, known for core shift), .519" flat-tappet (real lazy) camshaft, with heads that flow 270-CFM @ .500" lift (after bowl work).

This is begging for a single-plane intake (with a lot of port volume) and a SFT / Roller camshaft. You're leaving so much power on the table, this should be making enough power to be a low-11 / high-10 second D100.

Small update. I did end up swapping the rear gear to a 3.91 before the season was over. That got me an extra 2 mph, but nothing I bet. I believe Dwayne is right about the valvtrain issues. In the spring I am doing the cam swap and switching back to the 4.10 gears. I can’t wait to make a 10 second pass this year. Fingers crossed.

If valvetrain instability is suspected, it might be worthwhile contacting me to see how far off the geometry is, or if there might be other issues. From the photo of your valvetrain, it doesn't appear that anything was done to correct the rocker geometry, so that is likely a contributing factor.