Thread: Engine startup after "rebuid" = RED hot exhaust - need advice please

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Need help!!


Facts:
SBC 355
Was running last fall, did a cam swap
new water pump
Timing at startup = 6 degrees (at 2000 rpm, with vac line hooked up)
Rams horn 2" exhaust - 2 into one exhaust
HEI has light spring kit in it
Holley 750 carb with #69 Jets (plan to switch to Qjet later this winter)

OK, so 5 minutes into my 20 minute cam breakin, the crossover pipe gets RED hot. I mean fire poker red hot. No muffler right now. It all sounded good, running it at 2000rpm and engine at 150F up until I shut it down. All cylinders are firing. 6 degrees advance (did not get the chance to up it to 10 degrees). Dual plane intake. Voodoo #2 cam (second up from the smallest voodoo made for the SBC). Aluminum Holley heads, with springs (and lifters) to match the cam per Lunati recommendation. I adjusted the lifters preload VERY carefully (3 times, only doing one valve at a time, 1/2 turn past initial contact). Good oil pressure. Coolant not circulated yet since engine not up to temp yet.

I can only think I am running rich, but there must be more. Maybe no coolant in heads caused this (BAD, right)? But without the temp up to 180, no tstat opening yet.

Ideas? I don't want to damage anything, but have 15 more minutes at 2000rpm to get the cam broken in before I move on.

You are not running rich, just the opposite, you are running to lean, have you checked the float level in the holley? There is a screw on the side of the carb that you can take out, you want to adjust the fuel level to just trickle out of that hole. If it is already there or if you get it there and it still glows red then you will want to go up in size on your jets in the carb, I would go up 2 sizes.

Pnut, A rule of thumb I use in putting in a thermostat is I drill a couple of 1/8" holes in the mounting plate so just in case it does not open I still get some water flowing. Tommy

Originally Posted by pnut

Need help!!

Facts:
SBC 355
Was running last fall, did a cam swap
new water pump
Timing at startup = 6 degrees
Rams horn 2" exhaust - 2 into one exhaust
HEI has light spring kit in it
Holley 750 carb with #69 Jets (plan to switch to Qjet later this winter)

OK, so 5 minutes into my 20 minute cam breakin, the crossover pipe gets RED hot. I mean fire poker red hot. No muffler right now. It all sounded good, running it at 2000rpm and engine at 150F up until I shut it down. All cylinders are firing. 6 degrees advance (did not get the chance to up it to 10 degrees). Dual plane intake. Voodoo #2 cam (second up from the smallest voodoo made for the SBC). Aluminum Holley heads, with springs (and lifters) to match the cam per Lunati recommendation. I adjusted the lifters preload VERY carefully (3 times, only doing one valve at a time, 1/2 turn past initial contact). Good oil pressure. Coolant not circulated yet since engine not up to temp yet.

I can only think I am running rich, but there must be more. Maybe no coolant in heads caused this (BAD, right)? But without the temp up to 180, no tstat opening yet.

Ideas? I don't want to damage anything, but have 15 more minutes at 2000rpm to get the cam broken in before I move on.

you are running lean if anything. rich cools the pipes off.

The floats look good. I have those clear sights and the level is just right. Thanks for the idea though. After it cools down (hour or so from now), I will pull the plugs and look at them to determine if I am too lean). This carb was too big for the big cam I took out (as it is set up), so it's still too much carb for this smaller cam.

Maybe I am way too retarted (timing I mean)? 6 degrees at 2000rpm with the vac line hooked up is too little. I mean, I should be running 10 degrees at idle with no vac line.

Tommy: Your right, I forgot to drill the hole (I do one 1/8") but I really don't want to drain it to do that at this point. We'll see how it goes, but I may do that later if I still have probs.

Just to be 100% sure, CCW is to advance, correct?

Originally Posted by pnut

Timing at startup = 6 degrees (at 2000 rpm, with vac line hooked up)


OK, so 5 minutes into my 20 minute cam breakin, the crossover pipe gets RED hot. I mean fire poker red hot.

You are running very retarded which will cause your exhaust to get cherry red very quickly.

At 2000 RPM your mechanical advance should have given you a figure much greater than the 6 degrees you posted.

You should have around 12 degrees BTDC at idle (600-750 RPM) with the vacuum advance hose dis-connected and plugged.

Reset the timing.

Other things to check but unlikely at this point given the info you posted. Very lean condition. Major vacuum leak which would cause a very lean condition. Are all the vacuum ports on the carb and the intake manifold hooked up or blocked off?

You don't have enough timing in and fuel is still burning out the exhaust ports. This problem is common on a new cam break in and is why most folks recommend using beater headers/manifolds you don't care about for the cam breakin. (i.e. don't throw your $400 ceramic coated Hookers on there until after break-in and things get tuned in right). You maybe too rich (or less likely too lean) but I think the timing is the biggest contributor.....

I would suggest giving it more advance and finish your break in... if the exhaust still glows don't worry about until you finish the break in. Once you get the mix and timing dialed in right it won't be a problem any more.

-Chris

^^^^ BTW: Frisco types faster than me

BINGO! I advanced the timing a bit, and it fired right up WAY quicker and smoother. I finished the breakin (20 mins 2000prm, 1 minute each 2500, 3k, 2500, 2000, 1500, 1000). Now I can focus on a new carb, finishing the exhaust, and tuning it all in.

Thanks for helping me work it through guys!

Originally Posted by pnut

BINGO! I advanced the timing a bit, and it fired right up WAY quicker and smoother. I finished the breakin (20 mins 2000prm, 1 minute each 2500, 3k, 2500, 2000, 1500, 1000). Now I can focus on a new carb, finishing the exhaust, and tuning it all in.

Thanks for helping me work it through guys!

Excellent!!!

Don't forget to change your oil and filter now. Change again at 100 miles, 500 miles, 1000 miles. After that do regular oil and filter changes at the intervals you decide upon.

ENJOY!!!