Ok I have a 89 Fomula 5.0 LO3 car but I just had a 350 built by a well known engine builder in my town and I am very happy with the engine but its not preforming the way it should. I took it to the track and made a few passes and the car will not run over 93 mph in the 1/4. Let me tell you alittle about my engine first. 350 bored .30 flat top pistons total compression is 9.76:1, 1.96, 1.50 valves in truck heads " I know these are killing me because of the raised bump in the intake port but it shouldn't be this bad" stock intake, 1/2" TBI spacer 350 injectors, ulitmate tbi mod including afpr, open air cleaner, no smog, no cat, 3" pipe going into a flowmaster, 1 1/2 tube headers, can't really tell you much about the cam besides the lift is 414 on both intake and exhaust, dur @50 110 " I think" engine is fully balaned, 160 stat. roller tip rockers 1.6. Now for the times this isn't my best run but its close, 60' 2.054--330 5.936---1/8 9.206 @ 74.59 1000' 12.05 1/4 14.46@92mph, best run was 14.30 @ 92mph, the question I have is why is my car slowing down at the last few feet of the track? I raced my buddy in a mudstain gt and I was in front of him until the 1000' mark and car went to crap, I am digging for any info that will help me out. Short of spraying it, I have played with my timing from one end to the other and same for the fuel pressure all the way from 10psi to 20 psi. Does anyone have any ideas?

Someone told me that it might be not enough fuel volume due to the fuel filter, so today we pitched the stock filter and put a canster type filter set up on it, also changed the ecm, ECM come out of a 89 Chevy Truck with a 350. I am sorry this is so long but this car is driving me insane, can anyone help?

BTW I also have a MSD 6a box and MSD module

 

What transmission are you using? It also may be affected by your rear end gears.

 

Just bt the numbers, it looks like you might be running out of breath at higher RPMs.

I've got the same questions. Manual or auto trans? Rear gears? Injector sizes? Fuel pressure setting?

 

Your car probably isn't slowing down over the last 500', but it's obvious that it isn't speeding up either.

That would be consistent with a very small cam and swirl-port heads and tiny-tube headers. The engine has good torque and acceptable mid-range but no top end whatsoever.

You ought to run the car on a chassis dyno; post the curve, it should be quite informative. But it looks to me like you have a whole bunch of parts that are all matched and set up quite carefully and accurately to run good at low speeds and have good low-RPM torque, but to produce no HP by design.

 

I am running a 700R4, and I have 3.42 gears, and when I go to the track I am running a 26" slick. Is there anything I can do to give it that last little breath? Besides changing heads and cam and spraying it? and the injectors come out of a 89 chevy p/k with a 350 same for the ecm. As far as the fuel pressure goes I have tried 10psi all the way to 20psi and every setting in between.

 

Decent rear gears, fairly stock diameter tyres, injector pressure adjustable to a point that should be able to support the RPM with 62# injectors. Older stock 350 truck injectors are 62#/hr and should be more than engough for a 305. nwere TBI injectors may be only 55#. The problem is that you also need to flow the appropriate amount of air along with that fuel. there's the rub.

 

You can check yout injectors' flows by noting the color on the top "cone" of each one and comparing that to this table:

http://www.diy-efi.org/gmecm/compone...injectors.html

 

so heres what I am thinking about doing, Gonna get a edlebrock intake from summit and I have a 454 TBI, if I put this on my engine would it wake it up?

 

Doubt that will change much about any of these things....

The engine's ability to do useful work comes from burning fuel. Without fuel, no work gets done. To burn fuel you need air. A certain amount of energy comes from each fuel molecule; the more you manage to burn in each cylinder's firing event, the more force it exerts. There's a direct measurement of this force: it's called "torque". An engine's peak torque will occur at the RPM at which it most completely fills the cylinders. For a given CID of naturally aspirated engine, the peak torque will always be about the same, within a very narrow band, as any other engine of the same CID and similar design. The 2 engines might be set up to produce this torque at completely different RPMs; but it will be about the same. You won't see any variation greater than 20% or so, since 100% cylinder fill corresponds to completely filling it with air/fuel, up to atmospheric pressure; and engines usually achieve aywhere from 85% to 95% of theoretically perfect fill at the optimum operating RPM.

Power, measured in "horsepower", is the time rate of doing work. It is usually calculated from the torque at a given RPM; it's equal to torque times RPM times 2 times pi, divided by 33,000. Since work comes from burning fuel, then it follows that horsepower is proportional to the number of fuel molecules burned per unit time.

It takes air to burn fuel; the 2 ingredients must exist in a well-known proportion. So, in order to produce high horsepower (many fuel molecules per unit time), you must also supply many air molecules per unit time. There are many ways you can measure an amount of air; cubic feet is a convenient one. Time can be measured in many units; for engine purposes, the minute is also convenient. Air molecules per unit time could therefore be expressed as cubic feet per minute. Therefore, your engine's horsepower is directly proportional to its ability to flow air molecules - not to any other thing. It is not proportional to cam duration, nor money spent, nor chrome on parts, nor the willpower of the owner; it is proportional to FLOW.

Imagine your motor as a string of pieces of garden hose. Imagine that you walk out to your yard and hook them to your faucet. Imagine that you have 25' of ½" hose (we'll call this the "TB") followed by 25' more of ½" hose (let's call this one the "intake") followed by 50' of 3/8" hose (let this one be the intake port in the head) followed by 10' of ¾" hose (the intake valve) followed by 25' of ¾" hose (the exhaust valve) and at the end of it all, 40' of ¼" hose (your exhaust). Imagine that we turn on the faucet and fill a bucket and measure how long it takes to do that. (In cubic feet per minute, or gallons per hour, or whatever other units of flow you find convenient )

Now, imagine you start changing hose pieces. Let's imagine that you take that first 25' piece of ½" hose, and replace it with 1" hose. Clearly a major removal of restriction at that point. But what did it do to the system as a whole? Let's measure how long it took to fill the bucket. How much did it change?

None at all, of course. Your engine is the same way: if the restriction lies elsewhere, then changing the quickest, easiest to get to, shiniest, most buzzwword-laden part, will accomplish absolutely nothing whatsoever; except for its effect on the car's weight (the driver's wallet will be lighter).

Now imagine that you also change the second piece of ½" hose, that we called the intake. You're ready to get radical now, so you put in a piece of 2" hose. Now measure how long it takes to fill the bucket. What happened to the time it took?

Get the point?

Want to go faster? Then identify the thing that's acting as your limit, and fix it. Don't just indiscriminately start changing the easy-to-swap parts on top of the motor, because that's not what's making it slow.

In your case, start with the headers; then get some real heads; then put in a better cam.

 

well spoken, and i just want to add that the bigger you go on heads cam exhaust intake carb the worse your fuel economy will get and the worse your low speed drivability will be.

since you are moving everything up, everything at the bottom suffers. if you daily drive that thing then perhaps what you need is some high end cylinder pressure boost (like N20) i know you prefered to not use it, but it cetainly wouldnt hurt to have a small 100 shot to help fill those cylinders when they start to choke up top.

 

That was very well put...........but do you think I will gain anything from the intake?

 

I don't think so. It's not your restriction. It might even hurt, by diluting the effects of what makes the engine do what it does best now.

 

Yeah, but what happens if you use a funnel?

Again, RB has exhibited his knowledge and understanding, and related it in clear terms. That's a very thorough explanation and analogy.

You've got a lot more patience than I. I know you must've covered this 50 times before. Rather than thrashing the expired equine, I'd be more inclined to shoot it in the head by pointing out the SEARCH feature. Tax time always gives me a short fuse...