Having little to no knowledge with alcohol we decided to spend a few hours on a chassis dyno to see how close we were on our initial tuneup. It was money well spent and we learned a bunch and more importantly the truck seems to like the changes. We used Nickersons in Bristol PA and I highly recommend them !!!

First thing we found was the high side fuel pressure was to high. My gauge read 9 psi but it was actually over 12. We backed that down to 8 psi and made a few pulls. Turns out we were quite fat with an afr reading of 11.4/4.9 so a few pulls and jet changes later we got that up to about 12.1/5.3 ish. I've been running the timing at 34 degrees so we tried 36 and it picked up 12 hp and sounded crisper, tried 38 and it lost power. With timing and jetting we picked up 25hp and at least now I know where we are at afr wise and adjust if needed. It's obviously still on the fat side but we've only raced in miserable 90+ weather I figure I'll wait and see how it runs when the weather cools off.

An interesting note is we are running a flat hood with about 1.5" clearance and we lost 11 hp with the hood shut Thought that was interesting ...........

So we went into this looking for some data and ended up cleaning things up and making 25 more hp. Interestingly enough the truck actually responded and ran 10.02 @ 136 when a week previous ran 10.12 @ 134. Weather was nearly identical.

The truck ended up making 603 hp at the wheels, not bad for such a simple combo.

No sound

Sounds like $ well spent and I wish I had 1.5" clearance from the underside of my hood to the carb. My bowl vents are cut down and right under the hood.



Still runs 153mph

This message has been edited. Last edited by: 1320racer,

Thanks for sharing the info, Bob. Especially of interest to me was the effect of limited hood to carb clearance, the mock-up of my 68 Camaro is putting things close to where you are at.
I figured 1.5" would not hurt airflow to the carb that much.

Bob, did you try going any leaner than 5.3? Still seems pretty fat to me but not all sensors read the same. Especially if they haven't been calibrated in a while. The shape of the afr over a run can have a large effect on et also.

Are you the hand signal guy there?

Curtis

Was the 25 hp improvement with the hood open or shut?

Dean is the hand signal guy I believe.
Chassis dyno’s always worked well for me as a start.

1.5" spacing seems sufficient. I would bet that most of the gain was from air temp with hood opening being cooler vs closed trapped engine heat being pulled in.

Many argue that under the hood temps make for more consistent result - on the track that is where 25-30HP doesn't make a hill of beans difference.

I would also say that much of what you did could have been done on the track with just watching MPH gains/losses. Especially when you can make back to back (temps all the same) passes with little effect to from weather influencing the changes.

I have tuned timing that way and just like you saw the HP gains you will see the MPH change.

The hood experiment might get a little dicey however! LOL.

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Bob, did you try going any leaner than 5.3? Still seems pretty fat to me but not all sensors read the same. Especially if they haven't been calibrated in a while. The shape of the afr over a run can have a large effect on et also.

Are you the hand signal guy there?

I figured we'd stop there and see what direction it went on the track. It was pretty linear on leaning it out, I figure another change or two will get me where we need to be. I was really looking for a baseline comparing the numbers to our LM2 readings, they were pretty close.
That was Dean Nickerson with hand signals.

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Was the 25 hp improvement with the hood open or shut?

We did all the testing with the hood open, never got an initial baseline with the hood closed.
After gaining the 25, we simply closed the hood and lost 11.
I have a cowl hood already painted, so that should be an interesting real world test.

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I would also say that much of what you did could have been done on the track with just watching MPH gains/losses. Especially when you can make back to back (temps all the same) passes with little effect to from weather influencing the changes.

I have tuned timing that way and just like you saw the HP gains you will see the MPH change.

Who's got time for that

In and out in 3 hrs and learned a bunch about this combo.
I don't think I would have ever caught the high fuel pressure on my own as my new gauge read 8.5-9 psi, why wouldn't I believe it. And we also learned the truck stops making power at 6700 ish, I would have assumed 7000 ish

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Originally posted by HS professor:

quote:

Was the 25 hp improvement with the hood open or shut?

We did all the testing with the hood open, never got an initial baseline with the hood closed.
After gaining the 25, we simply closed the hood and lost 11.
I have a cowl hood already painted, so that should be an interesting real world test.

Agreed, the cowl hood should be an interesting comparison to the closed hood. My bet is that you’ll be needing a NHRA Chassis cert tag and 3.2A/5 jacket / pants when finished even in the worst of weather racing.

I say it made the 25hp going down the track hood closed, the same as it made the 25hp hood open dyno fan blowing, on the stationary chassis dyno.

The 25hp is on the slip, it had to objectively speaking, if the conditions at the track were "nearly identical".

The racepak will confirm exactly how much more hp it made on the track. Post images of the two graphs, different days.

A couple of things to note. On my 454 SBC it likes 28* to 30* timing verified with a bunch of dyno pulls and track time. I usually run it at 28 just to be easier on everything. You should try dropping it below the 34* you tried, you may like the results.
That is interesting about losing 11 Hp with the hood. I would make a few test runs at the track with out the hood and with the hood to see if it makes any difference there.

For jetting if it is a carb jet it for peak performance on the dyno then you check the AFR. Does not matter what scale you used but that number is what you want on the track. You really should not have to change jetting much with the carb as once they are set up right they are semi self adjusting to different air density. The more air and denser that air is the more fuel it draws with it. Assuming you do not have another issue like float level or fuel supply.
One other note if you are running too much timing you can run it a little fatter but you do not gain anything. So you may be able to gain a little more by pulling some timing out and leaning it down some. Just be careful and in small steps.

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I have a cowl hood already painted, so that should be an interesting real world test.

Cowl hoods are tremendously popular. But I've always wondered why one would turn their back on the ram air/cool air effect offered by a hood scoop?

quote:

Originally posted by HS professor:
An interesting note is we are running a flat hood with about 1.5" clearance and we lost 11 hp with the hood shut. We did all the testing with the hood open, never got an initial baseline with the hood closed.
After gaining the 25, we simply closed the hood and lost 11.
I have a cowl hood already painted, so that should be an interesting real world test.

Based on the results of others that have done the same over the years, I don't believe you see anything on the time slip.

quote:

A couple of things to note. On my 454 SBC it likes 28* to 30* timing verified with a bunch of dyno pulls and track time. I usually run it at 28 just to be easier on everything. You should try dropping it below the 34* you tried, you may like the results.
That is interesting about losing 11 Hp with the hood. I would make a few test runs at the track with out the hood and with the hood to see if it makes any difference there.

For jetting if it is a carb jet it for peak performance on the dyno then you check the AFR. Does not matter what scale you used but that number is what you want on the track. You really should not have to change jetting much with the carb as once they are set up right they are semi self adjusting to different air density. The more air and denser that air is the more fuel it draws with it. Assuming you do not have another issue like float level or fuel supply.
One other note if you are running too much timing you can run it a little fatter but you do not gain anything. So you may be able to gain a little more by pulling some timing out and leaning it down some. Just be careful and in small steps.

Thanks for the info Curly !! As mentioned, I'm new to alcohol and was kinda relying on Dean to point me in the right direction. He's probably dynoed hundreds of similar combo's and honestly I was a bit surprised we went with more timing but as soon as the wheels started spinning it did sound crisper. In hindsight we should have tried 32 to see what direction it went. We also went with a colder plug a week prior to the dyno. We had started the year with -8's and went to -9's. First to second run of the day was moving around a bit then it would settle in, plugs seemed to cure that.

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Based on the results of others that have done the same over the years, I don't believe you see anything on the time slip.

Maybe not, but there is a certain amount of satisfaction to be had from knowing you have empirical data and your tune near on-the-money.

Bob already has the finished cowl hood so it's an easy swap and either way his S10 looks badazz but for those thinking that a cowl hood is worth something on the time slip over a flat hood, it has not been for several friends and competitors, some of which Bob knows. It's their results that have supported my decision over the years to stay with the stock flat hood on my former Chevelle as well on my Firebird, besides fast cars with flat hoods are all the more impressive.

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Originally posted by Canted Valve:

quote:

Based on the results of others that have done the same over the years, I don't believe you see anything on the time slip.

Maybe not, but there is a certain amount of satisfaction to be had from knowing you have empirical data and your tune near on-the-money.

It don't work like that with methanol.

You know they're giving it way too much fuel because it needs way too much lead.