Tq engine

JakeMoore · 10/15/12, 3:14 PM

Struggling with some issues on a 836 honda. Stock carbs with 4.5 lbs of fuel pressure. Idles great nice and strong. Runs up to about half throttle then lays on its face. Fuel pressure is constant. Dropping the fuel pressure to 3 makes it worse. Car also idles high after coming off racetrack for a few moments. engine ran great on a smaller track 2 weeks ago with 3 lbs of fuel pressure. The 1/4 mile track is where we are having this problem at least this week.

To me this is a dead give away of not enough fuel. However my experience has all been with aftermarket flat slide carbs or fuel injection all on newer engines so I'm lost with this old motor on old stock carbs. Am i correct with wanting to go with a bigger main jet? or do i need to just sink it in a lake?

TQ29m · 10/15/12, 5:42 PM

3 lbs of fuel pressure should be more than enough for an 836 Honda, provided a lot of other things are correct, you could have an ignition/coils dying, ck them, should be 3ohms, the floats are very critical, as well as levels, when you pull a bowl off, the fuel should be within 3/16 of an inch of the top, and your fuel pump may be going South, if your're running a regulator, get yourself, or make, a bypass, thats the prefered way to regulate fuel, set it by pill or whatever, to about .75 gpm, and that should be close, main feed orfices, .077, .095 should fill the bill, also ck the battery, under load, anything below 11v is not enough. Another thing, don't let that engine idle below about 3k, that's what kills cam chains, and wrecks the chain tensioner, the valve events on an aftermarket cam are so severe, it just wrecks the valve train, an even higher idle is prefered, but sometimes not practical! Bob

thebus79h · 10/17/12, 1:30 PM

Bob, the car has a bypass system for the fuel. Battery is new, all the wiring is new, and the battery reads good. The biggest issue is inconsistency. We changed nothing but fuel pressure, and this happens. So we go back to the same fuel pressure we were running before, and it won't run virtually at all.

I know you have a different engine now, but do you remember what you guys ran for the main jet on the stock carbs?

TQ29m · 10/17/12, 2:23 PM

Billy, yes, I am running a different engine now, and FI, Hilborn, which I also ran a Hilborn on my Honda, finally! The Honda carbs are very critical to any changes, the floats, for instance, if you can find a set of early brass floats, get them, that's a step in the right direction, the later "foam" floats, do the same thing they did in your Chevie's, and most other cars, they turn into sponges, so there is no setting them, and them staying that way. The carbs run great, when they are right, and I didn't have that much trouble with them, that's why I waited so long to go to FI, but that eliminated one problem, almost completly. The Honda carbs have to be run on the very edge of overflowing, or dunking the floats, that's where the brass ones shine, they don't turn into sponges. Try this, take all your floats out, and put them all in one pan of alchohol, and you'll see the difference. I know a lot of the guys, take their floats out and let them dry all week, or between races, to try and get some consistency, but I still wouldn't overlook the fuel pump, what one are you using? I know some guys are still using the little FACET, pecker pumps we called them, and they seem to be happy, and if that's still too much fuel, you can put a bypass on them also, and, some guys run an adjustable from the cockpit bypass, or learn to change the flow, just by changing the fuel shutoff, I've seen guys on a yellow, reaching for the shutoff, some have a valve they can reach on the outside of the car, and they'll be twisting on it, trying to keep the engine from loading up, but if you'll ck everything closely, something should show up, I put a fuel pressure gage in my dash, 0-5 psi, high dollar gage, worked good, but didn't measure the fuel very good at such low pressures, sometimes when it was singing the best, it'd be setting on zero, next time on 3. I took it out, and put in a voltmeter, now that is handy, when something acts up, a quick look at it, will eliminate one thing right now. Good luck! Bob

speidel21 · 10/17/12, 7:20 PM

take bob's advice, hes only been doing this 250 years

10/15/12, 5:42 PM	#2 Re: Tq engine
TQ29m Senior Member Join Date: Aug 2008 Posts: 6,232	3 lbs of fuel pressure should be more than enough for an 836 Honda, provided a lot of other things are correct, you could have an ignition/coils dying, ck them, should be 3ohms, the floats are very critical, as well as levels, when you pull a bowl off, the fuel should be within 3/16 of an inch of the top, and your fuel pump may be going South, if your're running a regulator, get yourself, or make, a bypass, thats the prefered way to regulate fuel, set it by pill or whatever, to about .75 gpm, and that should be close, main feed orfices, .077, .095 should fill the bill, also ck the battery, under load, anything below 11v is not enough. Another thing, don't let that engine idle below about 3k, that's what kills cam chains, and wrecks the chain tensioner, the valve events on an aftermarket cam are so severe, it just wrecks the valve train, an even higher idle is prefered, but sometimes not practical! Bob __________________ "Being old, isn't half as much fun, as getting there"! Ole Robert I! _________________________________________________ Last edited by TQ29m; 10/15/12 at 6:03 PM.

10/17/12, 2:23 PM	#4 Re: Tq engine
TQ29m Senior Member Join Date: Aug 2008 Posts: 6,232	Billy, yes, I am running a different engine now, and FI, Hilborn, which I also ran a Hilborn on my Honda, finally! The Honda carbs are very critical to any changes, the floats, for instance, if you can find a set of early brass floats, get them, that's a step in the right direction, the later "foam" floats, do the same thing they did in your Chevie's, and most other cars, they turn into sponges, so there is no setting them, and them staying that way. The carbs run great, when they are right, and I didn't have that much trouble with them, that's why I waited so long to go to FI, but that eliminated one problem, almost completly. The Honda carbs have to be run on the very edge of overflowing, or dunking the floats, that's where the brass ones shine, they don't turn into sponges. Try this, take all your floats out, and put them all in one pan of alchohol, and you'll see the difference. I know a lot of the guys, take their floats out and let them dry all week, or between races, to try and get some consistency, but I still wouldn't overlook the fuel pump, what one are you using? I know some guys are still using the little FACET, pecker pumps we called them, and they seem to be happy, and if that's still too much fuel, you can put a bypass on them also, and, some guys run an adjustable from the cockpit bypass, or learn to change the flow, just by changing the fuel shutoff, I've seen guys on a yellow, reaching for the shutoff, some have a valve they can reach on the outside of the car, and they'll be twisting on it, trying to keep the engine from loading up, but if you'll ck everything closely, something should show up, I put a fuel pressure gage in my dash, 0-5 psi, high dollar gage, worked good, but didn't measure the fuel very good at such low pressures, sometimes when it was singing the best, it'd be setting on zero, next time on 3. I took it out, and put in a voltmeter, now that is handy, when something acts up, a quick look at it, will eliminate one thing right now. Good luck! Bob __________________ "Being old, isn't half as much fun, as getting there"! Ole Robert I!

10/15/12, 3:14 PM	#1 Tq engine
JakeMoore Member Join Date: Nov 2008 Posts: 36	Struggling with some issues on a 836 honda. Stock carbs with 4.5 lbs of fuel pressure. Idles great nice and strong. Runs up to about half throttle then lays on its face. Fuel pressure is constant. Dropping the fuel pressure to 3 makes it worse. Car also idles high after coming off racetrack for a few moments. engine ran great on a smaller track 2 weeks ago with 3 lbs of fuel pressure. The 1/4 mile track is where we are having this problem at least this week. To me this is a dead give away of not enough fuel. However my experience has all been with aftermarket flat slide carbs or fuel injection all on newer engines so I'm lost with this old motor on old stock carbs. Am i correct with wanting to go with a bigger main jet? or do i need to just sink it in a lake?

10/17/12, 1:30 PM	#3 Re: Tq engine
thebus79h Senior Member Join Date: Jul 2007 Posts: 446	Bob, the car has a bypass system for the fuel. Battery is new, all the wiring is new, and the battery reads good. The biggest issue is inconsistency. We changed nothing but fuel pressure, and this happens. So we go back to the same fuel pressure we were running before, and it won't run virtually at all. I know you have a different engine now, but do you remember what you guys ran for the main jet on the stock carbs?

10/17/12, 7:20 PM	#5 Re: Tq engine
speidel21 Senior Member Join Date: Sep 2007 Posts: 389	take bob's advice, hes only been doing this 250 years