Ford Muscle Cars Tech Forum banner
1 - 20 of 94 Posts

·
Registered
Joined
·
2,617 Posts
Discussion Starter · #1 · (Edited)
I have a thread going in the Makin Progress section on an intake swap I've done on the 289 in my Ranger. Long story short, after the intake swap I seem to have lost about 75hp, which seems like way too much to be attributed to JUST the intake swap. So I'm looking for input from you guys on what to check, and how, to find the lost hp.

Original setup:
289 cid
Comp 282S solid lifter cam
World Products Windsor Jr 180cc iron heads, 'stage 2' ported
9.5:1 compression
1.5" long tube headers
short dual 2.5" exhaust
MSD RTR Distributor and coil, 15* initial 37* total @ 3000rpm
Weiand Xcelerator single-plane intake, 'stage 1' ported
Holley 750dp carb
5-speed T5 transmission
roughly 300hp @ 6500rpm (rear wheels)

Changes:
Weiand tunnel ram lower manifold, stock
Custom tunnel ram plenum, same volume as Weiand 2x4 plenum
4x38mm CV side-draft carburetors entering the plenum at about a 35* angle
roughly 225hp @ 6500rpm (rear wheels)

Here's a picture of the new setup so you have an idea of what it is.
http://www.fordmuscleforums.com/makin-progress/506905-motorcycle-carbs-tunnel-ram.html


It took a LONG time to get the carburetors to run right, they were very lean initially. I have an Innovate LC1 wideband O2 gauge and data logging/telemetry software on my laptop to tune it, and finally got it to where it would run at a consistent 12.5:1 at WOT, but it's still much slower than it was with the Holley/Xcelerator. The powe curve looks similar, it doesn't take a dive at higher RPM, it's just lower everywhere.

I have a vacuum gauge connected, and the highest vacuum I see at WOT redline is about 1" HG (hard to get an accurate reading with a gauge that goes to 30" HG). I think that's acceptable, maybe a little on the high side, but if it were a problem of carburetors too small or some other restriction it would take about 5" HG to account for this much of a power loss.

The one path I'm currently chasing down is uneven fuel distribution. The plenum is designed such that the air/fuel coming out of the carburetors hits the mid-line of the plenum floor, in an attempt to keep distribution between the two halves of the engine even. My wideband O2 only has one sensor in the driver's-side exhaust pipe. I'm planning to install an O2 bung in the passenger side pipe and do back-to-back runs to compare the reading between the two. The problem is, I don't think the ratio being slightly off could account for a 25% loss in power, especially if it's only half the engine that is mis-tuned. It runs smooth for the most part, but on a WOT pull through 3rd gear I may get a hiccup or two like a cylinder didn't fire. I looked at a few spark plugs and they all look evenly tan, but this was after a 10-minute drive with a couple WOT bursts, so probably not the best way to get a plug read.

Do you guys have any words of wisdom or suggestions on how I could come up with 25% less power than with the old setup?
 

·
Registered
Joined
·
691 Posts
I am far from a pro, but it would seem that with the setup in the pic, you would have a much worse fuel delivery angle on the pass side bank than the drivers side... uneven flow angle or something...

Just my uneducated thought on the subject, haha.
 

·
Premium Member
Joined
·
1,330 Posts
Make sure CVs are going open 100%. Look for air restrictions upstream of the carbs. If the O2 reading is fairly stable then fuel mixture should be pretty good.
 

·
Registered
Joined
·
5,337 Posts
If a single plane intake, it is meant for HI-RPM useage only (race). The fuel mixture will separate (gasoline falls out of air flow at street RPM's).

This intake type will work with EFI as the fuel shot is introduced at the intake valve and not be subject to turbulence.

Let me expound on this...

The engine ran fine before with the origional upper plenum and downdraft carbs?

It has to be either carb calibration and or the upper plenum design. What does it hold in vacuum @ idle? Fuel delivery pressure and volume?
 

·
Registered
Joined
·
2,617 Posts
Discussion Starter · #5 · (Edited)
If a single plane intake, it is meant for HI-RPM useage only (race). The fuel mixture will separate (gasoline falls out of air flow at street RPM's).

This intake type will work with EFI as the fuel shot is introduced at the intake valve and not be subject to turbulence.

Let me expound on this...

The engine ran fine before with the origional upper plenum and downdraft carbs?

It has to be either carb calibration and or the upper plenum design. What does it hold in vacuum @ idle? Fuel delivery pressure and volume?
This is not a daily driver, so I'm not worried much about "street RPMs" although it does run fine on the street at part throttle. The only thing is these carbs don't have an accelerator pump shot, so without the proper CV slide spring/orifice calibration, it will lean out on throttle tip-in for a second or two.

I haven't run the tunnel ram with the standard upper plenum, only the custom one. The previous intake was a Weiand Xcelerator, which is a low-rise single plane, single quad intake, and a 1" carb spacer. Used the exact same air filter setup. Here's a couple pics.




Vacuum at idle is similar to the old intake, about 7-8" HG with a 900rpm idle. The fuel system was a little on the weak side, the fuel pump (electric) was pretty worn so I put a rebuild kit in it and now it's great. The carbs aren't running out of fuel, as is evident from the good AFR reading from the WB O2 gauge.
 

·
Premium Member
Joined
·
1,479 Posts
I still have to wonder how carbs that are designed to feed a 1000cc (or whatever it was) motorcycle engine could possibly feed a small block V8. :confused: I'm sure I'll get a lesson on this but it just seems wrong to me.

I'm also thinking like FE on this. Maybe no plenum would work better on the street.

John
 

·
Registered
Joined
·
2,617 Posts
Discussion Starter · #8 · (Edited)
I designed the plenum to be a little smaller than the Weiand dual-quad plenum, figuring the plenum is shared among their other small-block tunnel rams and so probably designed for a 350cid engine, and I have a smaller 289. I also thought the smaller plenum could help with street-ability. I dunno, it's a lot of guesswork, but rule of thumb a small plenum is better for part-throttle and streetability, a larger plenum is good for WOT power, and so I don't think the large plenum would be hurting me here... if it were, then you could argue that changing to the dual-quad top and putting a pair of Holleys on it would also be down on power, and tests I've seen show that's not the case, the TR usually makes more power on an engine like this.

John: on the motorcycle one carb feeds one cylinder, where on this setup all four carb effectively feed one cylinder at a time (more like 1.5), since on a V8 one cylinder starts an intake stroke every 90 crank degrees, and the stroke only lasts about 180-220 degrees. Or a different way to look at it, on the bike each carburetor is only flowing air on the intake stroke, about 25-30% of the time, to feed a 100hp engine. On my setup, they all flow air 100% of the time, so they should be able to feet 3-4x the power.

Or you can just ignore what engine they came off of, and look at the carb itself. Each of the four carbs has a 1.5" throat, with no obstruction except the needle. The throats on a Holley 750 are only like 1.2", with the booster blocking the middle. The Holley has a shorter throat though, only about 1-2", then it opens up to the big 1.75" throttle blades, where the CV carbs are 1.5" diameter all the way through, and about 3-4" long. They end up at close to the same CFM capacity, depending on whose calculator you use.

A "no plenum" setup like you are talking about is called an individual-runner, just like on the motorcycle, one carb per cylinder. This requires larger carburetors, for the reasons above. For example when people do IR setups with Webers, the carbs are usually 44mm, which have about 35% more area than my 38mm carbs.

I guess I'm hoping it's not a fuel distribution problem, have plans to check that best I can (moving the O2 sensor to the passenger side pipe), but beyond that I'm looking for other ways I could lose that much power, other things to check. Could timing being 5-10 degrees off cause this much loss? I have a fluid damper so I don't think it's possible for the marks to slip, I'm using a new timing light but it's a much better one than my old one. I adjusted valve lash, didn't find any that were more than .001" off (some were a little tight, others were loose), is that good enough to be sure that I haven't scrubbed a lobe, or do I need to check full lift on every valve? It cranks and runs smooth, so I don't think there's a bad valve or any kind of compression loss, but should I buy a compression gauge and do a compression check anyways? It would take two dead cylinders to lose this kind of power, I think I'd notice that without the gauge...
 

·
Registered
Joined
·
10,342 Posts
I was going to toss a couple things out, but was under the impression that everything was the same except the intake setup. So, while I am surprised for example by your 37° total mechanical timing advance, I figured (right or wrong) it was at that same number 75hp ago. Are you saying other stuff may or could have changed?

David
 

·
Registered
Joined
·
2,617 Posts
Discussion Starter · #10 · (Edited)
Everything SHOULD be the same... the timing is the same that I had set before, I'm just bringing up that before I set it with my crappy old Harbor Freight timing light that since died, and this time I set it with my new quality timing light that should be trustworthy (but then again anything can be bad out of the box). Also it was years ago that I last set my timing, so I'm just throwing out the possibility that something cuold have happened like if the balancer could slip, timing marks could have moved, but again not sure if that's possible with a fluid damper.

Why are you surprised by the 37 degrees total? Does that seem like too much, or too little? It's never ping'd before (that I've noticed), I think my compression is a little low for the cam I'm running, which would make it less prone to pinging/detonation.
 

·
Registered
Joined
·
5,337 Posts
Does your mixture program show fuel ratio at all RPM's? If the enrichment system (accelerator pump(s) ) do not work properly, it may be the other carb systems will not keep up with air flow?

As to timing, at your level of expertise, I didn't want to bring IGN TIMING in but maybe check STATIC TIMING? Maybe the cam is retarded?

Look Below... ;)
 

·
Registered
Joined
·
10,342 Posts
Why are you surprised by the 37 degrees total? Does that seem like too much, or too little? It's never ping'd before (that I've noticed), I think my compression is a little low for the cam I'm running, which would make it less prone to pinging/detonation.
Too much from your listed combo, but I'm just taking a guess. Det would have nothing to do with power. You can over-advance, lose power, and never det (ping). I know that some folks say advance to det and back-off for max power, but that is totally false and is based on a specific combination and fuel that is det-limited. You may not (should not) be. If you can either time a one-gear run from X mph to Y mph, or marker to marker, or have a g-meter, you can try backing-off a couple degrees at a time until you lose power, and re-advance one step. Some systems can also read-out in rpm slew rate (time to accelerate X rpm) to tune stuff like this. You can also read your plug ground electrodes to confirm proper ignition advance, but only with a full pull and clean shutdown.

You can test your mixture distribution by reading the plugs after a good pull and shutdown, or perhaps in your driveway with an IR temp gun. Run the rpms up and hold to let header temps stabilize, and shoot the header tubes by the head looking for differences. There are always differences, and some from airflow in the compartment, but you're looking for obvious trends. While the static test does not measure the fuel ratios and changes due to WOT volume through the manifold, it can identify some basic trends - like one bank noticeably cooler than the other.

While your WBO2 may be relatively accurate, often they are not specifically accurate, meaning if it says 12.0 here and 13.0 there, they really are 1.0 apart relative to each other, but may not specifically be 12.0 and 13.0 AFR. Calibration has nothing to do with specific accuracy - only relative accuracy. Suffice it to say, you should never tune to a general AFR number. Tune for power no matter what the readout says. Once the power is found, you can then use the readout AFR to tune more areas. Even if it says 15:1 at your actual best power, that's fine, and you would then tune all WOT rpms to 15:1 on that same WBO2 controller and sensor. No, most errors are nowhere near that large, but I hope you see the concept.

You've checked for vac leaks? Is your clutch slipping under load? Are you getting boost? Oh. That's your problem. ;)

David
 

·
Registered
Joined
·
100 Posts
I ran Mikuni 38mm CV carbs on my 1166cc Suzuki dragbike then switched to 40mm Lectrons and picked up a few more MPH's. It's a PITA to drop the bowls on those CV's for a jet change, but I love the Lectrons with no jets to change. Just pop the top and adjust the needle height and your done in a minute.

It's nice to see something different !!

So how did you go from a gravity flow system to a pressure flow for those CV's, different needles and seats or floats ?

Plus I just go with Pod air filters for more air flow too.
 

·
Registered
Joined
·
2,617 Posts
Discussion Starter · #16 ·
Wow, lotsa good questions, I'll try to answer all of them, thanks for all the input. :)

A little more in-depth information on my data. As mentioned I have an LC-1 Wideband O2 sensor, it has a serial port connection which you can use the Innovate logworks program to data log. That was too limited though, an AFR reading with no other data was hard to look at after-the-fact. So I wrote software to capture the vehicle speed and RPM and AFR, using the laptop's audio-input to capture the analog rear ABS speed sensor on the left channel and the tach signal off the coil on the right channel, and Innovate's API to read the serial data from the LC-1. This gives me incredibly accurate rpm, and speed is as good as my pulses-per-mile number, which I've calibrated pretty accurately. From speed I can calculate acceleration (change in speed over change in time), from acceleration with vehicle weight I can calculate horsepower, and combine horsepower with the RPM signal to calculate torque. It works best at about 12 samples per second, with a 2-sample averaging filter on the RPM and a 4-sample averaging filter on the speed. I later added in aerodynamic drag (which I calibrate by popping into neutral at 65mph and measuring the deceleration) and correction for atmospheric conditions using the SAE formula and feeding it barometric pressure, temperature, and dewpoint. The program logs to a .csv file, which I can later open in Excel, graph and analyze the data.

I am sure it has room for error, but it is consistent. If I were seeing 5-10hp loss, I would write it off as noise, but 75hp is a definite loss. You can also see it in the rate of climb on the tach signal, ignoring all other factors it just doesn't pull as fast in 3rd gear.

So hope that answer a lot of questions, yes I can see AFR for each RPM (rather for each 1/12th of a second sample).

KULTULZ: I didn't mess with the cam at all, so it's timing is right where it used to be. The only thing that could have happened to the cam is if I somehow scrubbed a lobe or two during initial startup and tuning. I was sure to pour oil down the lifter valley before installing the intake, but I did have to crank on the engine a LOT in order to get it to initially fire (was hard to find the sweet spot for idle mix and speed to get it to fire).

PSIG: When I finally got the carbs to run at WOT, the AFR started at about 13.8:1 and 200hp. I slowly got it down to 12.5:1 after about 3 sets of changes, and each time it gained power, now up to 225hp. I've considered further enrichening, but it seemed to make best power at about 12.8:1 witht he old intake setup. Granted, a few variables could change that, and I have no problem running it richer 'till it loses power, just don't want to miss something obvious as I don't think continued jet changes will net me another 75hp if so far I've only seen 25 from a fairly major AFR change.

The IR temp gun is a good idea, would be easy to try. I may have to just pull the plugs, clean them all, then go out and do a WOT/shutdown run and check the plugs on the side of the highway. Wouldn't be the worst thing to have to do. No vac leaks, clutch engages solid (centerforce with not too many miles on it), but unfortunately no boost either. ;)

FE: Here's links to the two intakes:
old xcelerator: Holley Performance Products X-CELerator Intake Manifold 7515
new TR (minus top): Holley Performance Products Hi-Ram Intake Manifold 1988
The Xcelerator has uneven runner length (corners are long, middles are short), smaller diameter runners, and a harder angle where the port meets the head. The TR has a little larger ports (exits are about the same size, but they are tapered, the inlets are bigger), but also longer and consistent length, with a smooth transition to the head, so it should make better torque and better top-end.

RacingJake: No mods to the carb other than new O-ring seals on the fuel inlets. I have a Holley red-label electric fuel pump, and added a pressure regulator before the carbs. They seem to hold 4.5psi no problem (the max the regulator will do) but I have it dialed back to 3psi for a marin of safety. It has no fuel starvation problems, even before the fuel pump rebuild and with the regulator below 2psi.

Arnoldtx: see above on my data logging software. It's like a rolling chassis dyno. :)
 

·
Premium Member
Joined
·
34,855 Posts
I see now that you really should be getting more power and torque up higher in the rpms with this design, but I think your plenum design is a huge void that's causing the loss.

The AF may be right on your reader but I think the mixture has too much time in that large plenum.

I'm betting that if you took 1/2 the volume out of the plenum that you'd see an improvement.
 

·
Registered
Joined
·
100 Posts
You might want to try alittle test like remove the springs from the top of the slides and see how she runs ? Might be the slides on those CV carbs are not fully opening at WOT or during the next time you put it back on the dyno.

What size jets are you using now ? On my bike anything smaller than 160 Mikuni and the bike would lay over on the top end of the track.

I'm amazed that your using those carbs on an engine that's 4 times bigger. My WAG would be that the engine is not getting enough air and fuel at the same time ? But it sure does look good !!

Maybe four 42's or 45's Flatside Mikuni's with accelerator pumps would work better ?
 

·
Premium Member
Joined
·
1,330 Posts
You should be able to figure out with the data you have where the HP is dropping off. If its at higher rpm then I would suspect a lack of air flow and if thats the case then look for things that are restricting air flow. Engines are just air pumps and to get a 75 hp gain you have to do a lot of work. If engine intake manifold pressure is lower than it was during higher rpm operation that could be another indicator that there is a restriction.
 
1 - 20 of 94 Posts
Top