Thread: Maybe I'm Not As Bright As I Thought

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Allright. I blew my engine up. Old engine + first build + lead foot = my bad. Destroyed the #4 valve and the piston beneath. But when I got the heads off, I saw that the #1 and #5 valves were pink-orange.

This is on a dual-quad tunnel ram. It seemed to be running fine (until it exploded) but it looks like these 2 valves were running REALLY hot. These would be the vacuum secondaries on the forward carb.

I drove it for about 4 miles after the #4 valve blew out (pictured); might this discoloration be a result of the coolant / oil / etc. being sucked into the trashed valve for 4 miles at operating temp, or are my carbs not tuned as well as I thought they were? Plugs were uniform reddish - grayish (except #4, which was bentish - shatteredish.)

"bentish - shatteredish"

It's cool. I'm new at this, and I knew this engine wasn't going to last; I just wish it'd lasted longer. The short block was really built but also really old. Figures it'd explode the day before the Mustangs NW Roundup. At least it didn't die there.

And I've already got a replacement short block (the '86 5.0L H.O. mentioned in another thread -- thanks, Denny, for your input on that) ; it's super clean, and I'm bidding on an E303 cam as I type this. Timing set, gaskets, etc. are on the way. I should have 'The Skunk' running again in 2 weeks, and this'll be the 2nd SBF I've put together in as many years of rodding. I'll be a pro in no time at this rate!

I am concerned about the pink-red discoloration. Do you think it's secondary to the far-end valve collapsing?

If i was to guess, I would have to say your burning your valves. How high of timing are you running? And tech, tell me the story again about Motor Heaven

"And tech, tell me the story again about Motor Heaven"

Well, once upon a time in a place far, far away.......

Hey, it was a far better death than most Mustang II's get.

That engine has been running super hot. Are your carbs lean? Or is there a vacuum leak?

Hey man - that'll just make you a little more careful next time right?

So how exactly did you build the motor?
What were you running other than the dual quad tunnel ram?

Dual Quad Tunnel Rammed "Are you INSANE?" T-top '78 Mustang II

Hmmm - maybe a bit of freudian slippage here.

Carry on 'hotrodder' - just a minor setback right!

Bert

The carbs were rebuilt stock a few months ago, they're 390cfm Holley 4160 vacuum-secondaries with stock jetting, running sync'd (as opposed to progressive.)

The temp gauge wasn't working but it wasn't overheating or steaming or anything. I stuck a thermometer in the radiator every trip for the first month or so that I was running the car once I put the tunnel ram on; it was running cool. Granted, I got out of this practice. (Hey, what could go wrong, right?)

By the time I got it to work (the 4 miles after it exploded), it was overheating like a mo'fo and the radiator was practically empty.

Yesterday morning when I took out the oil pressure sensor, the block peed antifreeze for about fifteen minutes. There was as much coolant in the block as there was left in the radiator.

Possible the block had cracked, and that made the engine run hot enough to self-destruct?

Denny:

Does this help?

Originally posted by SBC

So how exactly did you build the motor?
What were you running other than the dual quad tunnel ram?

The short block was built by a very old man who used to race II's. He wasn't quite sure what he had in it. He said he'd had a 331, and he thought that this was it but he wasn't sure because he'd given another engine away and wasn't sure which was which. Serious. It was free, though; he wouldn't accept any money, just "put 'er to good use." (I slipped $200 -- all I had on me -- under his cigarettes while he wasn't looking.)

He warned us that it might not have too many more miles on it but it oughta go like hell. He was true to his word.

We took the engine home and cleaned it up. It was in very good shape, or so it seemed. No major wear in the cylinders; we had a machinist friend look it over and he said it looked good. We didn't take it apart.

Those were ported '66 289 hi-po heads. The only thing was, they didn't have hardened seats. I was using lead additive, though.

First build; I'll chalk it all up to a learning curve.

Originally posted by DennyW
Staying around .500 lift, 115 pounds on seat is plenty at installed height.

The '86 H.O. I'm putting in there next weekend only has .500" of wiggle room -- flat pistons and 1.6 rockers. I'll be using a .498"/.498" cam. How would you rate the sphincter factor? Am I cutting it too close?

s long as I've got the engine torn down this far, I might as well throw down another $100 for a set of cast pistons and rings to use the cam I want.

Would new flat-top pistons with valve reliefs cut in them alleviate the clearance problem?

I've been reading numbers on this everywhere for the past two days, and I'm starting to go nuts. I've read .120, I've read .80 int / .100 exh minimum , I've read that it'll work fine, that it won't work at all, that it MIGHT work depending on whether or not the car was built on a Wednesday or a Friday -- not to mention the number of people who've told me that a dual-quad tunnel ram won't work on a SBF in the first place.

Welcome to the Internet, where everyone's an expert mechanic and runs low 10's.

But you, Denny -- I've been taking your advice for nearly a year, now. And you're still throwing out the sage answers. Thanks, man.

Hell, thanks, all of you, for your patience and encouragement. One thing I've found from poking around other hot rod boards for the last few days is that this board seems to consistently have . . . well, maybe not the "best" answers but the answers that sound the best to me. For whatever that's worth.

I've seen a SBF with dual 500CFM Holley 2bbl's adapted to a manifold like yours, worked great.