Head Temp / idle surge in gear

I have been struggling with idle surge in gear, and getting any kind of head temperature above 120.

Even going as lean as .8 GPM at 1900-2100 idle speed i can suck down a full fuel cell of 8 gallons in about 5 -6 minutes and about the warmest i can get the head temp is 118 degrees. This also milks the oil pretty quick as well.

I have new racepack head temp sensors and they are mounted in the threaded holes dead center between 3/5 & 4/6 below the exhaust ports on an AJPE BBC billet head.

Working with Mike at Rage fuel systems he had me raise my idle check from 9 to 12 lbs and lower my port check from 16 down to 10 lbs. Although i question going that low on the port check being afraid it would flow at idle, he says its under vacuums at idle and it should not open and he wants it to open quicker when we launch the car.

I will say after i made those changes it did help my in gear surge, didnt go away but probably decressed by 1/2 ,

With the increase in fuel pressure at idle with the higher idle poppet pressure, what would be the lowest GPM flow / leak down you can go to help build some head tempature and not be too lean?

Not sure how accurate the flow meter is at below 1 GPM at idle speed so im kind of going back and forth now between GPM and % leakage at around 74%.

 

what sort of ignition and how much timing. Assuming you have a blower what size and overdrive?

 

Fuel tech FT spark ignition 30 degrees of timing, 1471 XR1 HH at 20% OD.
Last season it made 38 lbs at the stripe at 20%.

The changes we made in the off season were a bit larger Rage fuel pump with a loop to knock out about 1gpm and a new gen 4 BOHR/Hammmer injector with the helical spray bar on top a new fresh long block.

The spray bar area was matched to our old nozzles in a BAU hat so we are putting in the same amount of fuel. Although RAGE did have us up the size of the nozzles in the back of blower a couiple sizes.

 

Coil surge is bastard. Increase the fuel flow. Mine did that as well and I idle around 17-1800 in gear. Fuel is 1.0 to 1.1. Anything less and it would surge. Also you have the coil power set at 100% at all times?

 

Yes, I have the 750MJ box and FT had me set it up at 950MJ because the box will usually out put more on a good battery. Rage fuel systems had me increase my idle check from 9 to 12 lbs and that change did help and cut the surging in 1/2.

 

Jay, can you expand on "Coil Surge"?......

Thanks

 

Thanks Mike, yes it acts way fat .
I keep chasing my tail on this thing as I keep being told it surges in gear because it’s lean but yet all signs point to being overly rich. I guess I just need to lean it out far enough that it will hesitate and go back from there.
It’s like I’m not going far enough on either side, anytime I whack the throttle it just responds with no hesitation or blubber.
I’ve purchased two brand new checks and I’ll set them as you suggested and try leaning it where I notice a hesitation and go from there.
Going leaner does help my wet and cold #2 hole but 7 and 8 get hotter than I’d like.
I guess I just need to get it to the line and do a good burnout and a 330’ pull and see if the rear cylinders cool off.

 

My leak down procedure is the same with the -10 on the backside of the BV disconnected and cap the idle check. We are just a small family run team, I tune and drive the car with help from my son. We had the doors on the car during the last couple warm ups, he didn't complain about fumes in the car. I stayed in front of the car but we were outside well ventilated with a slight breeze. Visually you can see #2 huffing fuel out though, having difficult time staying lit at idle.

 

Going back to your original post you stated that the engine would consume 8 gallons in 5 to 6 minutes. Simple maths tells me this is not .8 gallons per minute. When ever I had a surge in gear at idle it was to rich though this was only a 6 second BBC.