exaust glow

[fast90mini]

We are running a 350 engine with a holley 500 two barrel, 450 lift cam, 36* of timing, after ten or so laps into the race the exaust starts glowing, we went up in jets and are running 78's now, was told it could be a vaccume leak but changed the intake and still doing the same thing, plug check looks perfect, any ideas?

[fast_crew]

High exhaust temps are caused by a few things. Retarded timing (36* should be ok if this is what it is) overly rich mixture, (your jetting is alittle rich, try around 74's) and low compression engines have higher exhaust temps due to lower effieciency and fuel burning in the exhaust. What is your compression?

[SRXSRULE]

What fuel are you running? what compression? If you have low comp and are running pump gas that can cause problems this time of year. All pump fuel are "winter" blend right now. You should run straight race gas or atleast mix it 50/50 with premium untill about may. Eric

[fast90mini]

We are running pump gas mid grade, and the compression is 150, all stock 76cc heads, 78 jets last night and it was still the same.I never heard of winter gas, do they have that in south florida?

[SRXSRULE]

I cant tell you for 100% sure about florida but more then likely they do switch the fuel over down there too. Pretty sure Ive seen it getting below freezing in florida.

The EPA defines April to June as the "transition season" for fuel production [Source: EPA]. Refineries switch over to summer-blend production in March and April [Source: EPA]. Gas stations have by June 1 to switch to selling summer-grade gas, while terminals and other facilities "upstream" from pumping stations have to switch by May 1 [Source: EPA]. Following the summer driving season, companies switch back to winter blends beginning in September, with the first winter increase in RVP allowance occurring on Sep. 15.



so it looks like your 9:1 or LESS compression. Sounds like your PLENTY rich on jetting. I would say you need to be closer to 72's and still be on the safe side. I would still not rule out a fuel Vapor Pressure issue with the pump gas. Eric

[chevy370lsx]

As mentioned the two most common reasons for the exhaust to glow is not enough timing and overly rich conditions. You'd be money ahead to go to a dyno with a wideband and get the jets set correctly. I worked in a dyno tuning shop for several years and I've had people come in with the same problem several times and just be way to rich and some make up 100+ more hp just getting the jets set correctly.

[sj valley dave]

Unless your carb is goofy, that is a BIG jet. We had a gauge legal 4412 Willy's on a 14:1, Dart headed, .600 lift 360" deal a few years ago and we ended up with a 5.5 PV and 73 jets at an adjusted altitude of 750 feet above sea level...

[fast90mini]

Thanks for the info, I am going to get out all the pump gas and run racing fuel with a smaller jet, 72-73 and see if it helps.

[bushracing67]

first: verify the balancer timing marks are accurate and the outer ring didnt slip, then verify timing is set correct and check your advance if your dizzy isnt locked down, from there if all is good... 2bbl engines have higher exhaust temps, if your compression is under 10.5:1 do not waste money on race fuel... maybe 1 gallon of race to 5 gal of pump gas... i would bet the main reason you are seeing headers glowing are because the tubes are thin, my schonefleds always had orange spots in them, sometimes even in the garage... if it bothers ya i would prolly just buy thicker headers

start with 73-74 jets and 4.5 power valve, the power valve can be the hardest part to get right with a 4412, i have used everything from a 3.0 to 6.5 in the same engine with small cam changes and cam timing changes can have a big effect on power valve

[Egoracing]

Thanks for the info, I am going to get out all the pump gas and run racing fuel with a smaller jet, 72-73 and see if it helps.

If you are not running enough compression (and 150psi is not enough) for racing fuel it will cost power and your EGTs will go up because you are not going to be burning the mix completley. The winter mix on pump fuel is the alcohol ratio on pump fuel and an additive package but that would not cause the headers to go red on correctly jetted carb, it is to keep the fuel from absorbing water from being cold then getting warm and cooling off again. If you are in south Fla there are gas stations that cater to boaters that have fuel with no alcohol added as it can cause problems with the boat engines. Their fuel is more consistant and there is no "Winter mix" for non alcohol mixed fuel.

[really?]

ive seen this alot when running to rich the fuel burns in the headers creating the glow affect and these guys are right about everything but the gas , i deal with chad mullins at mullins race engine and he said pump gas no matter the compression is a big no no, always run atleast 110 racin gas and if you can afford it check into the oxygenated gas

[sj valley dave]

Renegade makes a 98 octane and a 104 octane race gas...Chad probably doesn't like the pump gas because of the inconsistency you get...I guarantee you that you will see more HP out of lo compression deal with 98 octane than 110 octane...non oxygenated fuel...apples to apples..Seen it numerous times on a dyno..

[really?]

i am talking about 2bl motors but i agree with you valley dave , but ive seen some big gains on oxy fuel over 110regular on a dyno, but when we are on the track its all the same ,and we all feel so much better when we spend more !lol!

[fast90mini]

We have checked the compression and it is 150 psi, we also run rhoads lifters and I think it lowers the compression, what jets should I be running on pump gas, had 76 and 78's and would glow after 15 or so laps, should I try 73 or 74's? It seems like the engine is tighting up and loosing power after it starts to glow, THANKS.

[sj valley dave]

Lean it down a couple of jet sizes...Go out run some laps and do a plug check...Don't let it sit and idle or you falsify the plug readings...

[DaveBauerSS6]

Renegade makes a 98 octane and a 104 octane race gas...Chad probably doesn't like the pump gas because of the inconsistency you get...I guarantee you that you will see more HP out of lo compression deal with 98 octane than 110 octane...non oxygenated fuel...apples to apples..Seen it numerous times on a dyno..

A few years ago I ran in Tina Mcgowens 350 hobby motor ( 180 cranking compression rule, stock heads, hyd cam, on a 2 bbl) at Watkins dyno on racing gas and regular 91 and the chart lines overlayed so well you couldnt see the difference. The numbers were the same. He recommended pump gas for those engines. All my hobby and american stock motors run on pump gas, making good power and living.

[DaveBauerSS6]

We are running a 350 engine with a holley 500 two barrel, 450 lift cam, 36* of timing, after ten or so laps into the race the exaust starts glowing, we went up in jets and are running 78's now, was told it could be a vaccume leak but changed the intake and still doing the same thing, plug check looks perfect, any ideas?

What intake are you running? Normally a vac leak will sour the idle and give you a clue.
You said you went up in jets, what did you start with, and you said the plugs looked perfect??
Did they look perfect before and after the jet change?

If so I would go with Bush suggestion on timing. Verify the timing mark on balancer and pointer. Verify the total advance at rpm and try another distributor if the problem continues. The module could be miss firing and sending out unburnt fuel. Lost a motor recently due to 7 and 8 crossfiring due to the module. This was verified by the manufacturer.

I ran into this only once, but check the exhaust system for a large restriction.

[Racingtech]

Fuel burning in the exhaust can cause the exhaust to glow. How it gets there can be caused by several things, To rich , miss fireing, if you are running a HEI ign, check your coil they can overheat and burn up and the same thing can happen to the module. Causing low fireing voltage, and fuel not being burnt in the cylinder, and being pushed out into the exhaust. I have had this same problem in the past. I think looking at the fuel causing this is a long shot.