Maybe I'm Not As Bright As I Thought

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.)

http://memimage.cardomain.net/member...78_39_full.jpg

"bentish - shatteredish"

:LOL:

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. :eek:

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! :3dSMILE:

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:whacked::LOL::LOL:

"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? :D

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

Quote:

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

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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?

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Originally posted by SBC

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

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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.

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

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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 :confused: -- 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. :CRY:

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 :rolleyes: 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.

Get yourself a set of checking springs (available at any speed shop, Jegs or Summit), assemble an intake and an exhaust valve in the head with the weak springs and do like Denny said. Sit the head on the block without a gasket and without cinching the head bolts down. Turn the crank by hand to a position about 30-40 degrees BTDC on the exhaust stroke. Push the valves down until they contact the piston. You can measure this with a dial indicator on the valve stem or if you're careful, you can do it with a 6" caliper. Now rotate the crank 5 degrees and push and measure again. Rotate 5 more degrees, push and measure. Do this every 5 degrees until you are about 30-40 degrees on the other side of TDC. If you have 0.080" clearance on the intake and 0.100" on the exhaust all the way through this exercise, you're good to go. The closest you'll be will be before TDC when the piston is chasing the exhaust valve.

Hey, I wanted to update this.

I checked the clearances as described bove, and witht he numbers in hand, went down to Delta Camshaft. They reground the 5.0 H.O. cam to .471" lift, 219 int / 209 exh @.050, 112 deg sep.

The engine's nearly finished -- the last parts arrived yesterday -- and it should be in next weekend.

Also, as I was swapping out the Duraspark with a Pertronix, I found that my vacuum advance was broken; the actuator arm had separated from the pin. Might this have been part of the cause of the front cylinders running so lean? Needless to say, I'm getting a new distributor.

Denny, when I took my 390 apart to get the heads redone, I noticed the same type of coloration on the exhaust valves of the front 2 cylinders as WasII has on his. I also noticed that being the ol geezer I am, I hadn't seen the mismatch in port size between the Edelbrock F-380 manifold and the heads. The manifold ports are the tall ports (2.34" instead of the 1.87" that the head ports are). would this necessarily cause fuel starvation on certain cylinders? Just wondering. Gonna have to put on my old cast iron 4bl intake or buy a new alunimum one. the 3x2's will get sold.

I understand that Denny. What I can't really tell you is why I never noticed the mismatch when I put the motor together.

I guess I was just caught up in the 3X2's momentum and didn't even think to check port sizes. Dumb mistake. Should of sloped the bottom edge of the head ports to match the intake.

When I get them back from the machine shop I'll have to do that or forget using the 3X2's. Just have a lot of money wrapped up in the setup. Thanks for the input. :)

Yeah, some of us *never* make mistakes when setting up fancy carburetor rigs. :rolleyes:

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Originally posted by DennyW
:) Hey, I make mistakes too. :LOL: I wasn't impling you didn't know. Some times, I just type what I'm thinking, and it sounds, or comes out wrong. :LOL: The carbs had your mind be-dazzled. :)

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Denny, I know you weren't implying that, it just pi$$es me off that I didn't even think to stop and check it. Oh, well.

Now a question for you and Was II. I've never ported heads before. What is the best tool or bit to use in the Dremel to cut the port down at the entry a ways. Got to go down .500 of an inch. The width is okay. Thanks in advance.

Dude, have you been reading this thread? I'm not the guy to ask about the "best" way to do anything.

:LOL:

That said, I took a carbide rasp bit and put it on a Makita hand drill for the heavy cutting, then used an 80-grit and then a 120-grit stone on a Dremel for the final shaping. I used a wire wheel for the polishing. There's got to be a better way but this did it reasonably fast and pretty well.

I also stuffed paper towels soaked in WD-40 down into the ports before I cut, to catch most of the shavings, which made cleanup way easier.

Thanks, Was II. Yeah the paper towels in the ports is the only way to go there. I do that when I am even cleaning up old gaskets. Appreciate the help.

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Originally posted by Oldf100fordman
I understand that Denny. What I can't really tell you is why I never noticed the mismatch when I put the motor together.

I guess I was just caught up in the 3X2's momentum and didn't even think to check port sizes. Dumb mistake. Should of sloped the bottom edge of the head ports to match the intake.

When I get them back from the machine shop I'll have to do that or forget using the 3X2's. Just have a lot of money wrapped up in the setup. Thanks for the input. :)

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I think you're gonna be in just as bad shape if you start cutting on the heads. What you might do is mix up some JB Weld or other metal-impregnated epoxy product and build up the manifold ports to match the head ports. I've done this extensively with Briggs & Stratton Kart racing motors and never had a problem with it breaking up, cracking or otherwise causing any problem under racing conditions. It's something to think about anyway.

I agree with Tech, .5 inch is a lot of grinding, liable to hit water. With that much mismatch, there could have been vacuum leaks, too. I'd save the manifold for my next project, and put one on that matches the heads.