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See if you guess what I find wrong tomorrow


Well-known member
Dec 30, 2002
Dallas County, Texas
'75 Modified Red Ragtop: "LEFTLN"
From the following symptoms, take a guess at what I find wrong tomorrow:

It didn't take long to find the weird scary mystery noises that were getting worse and worse in the engine - so bad I had it towed home from work to not damage anything worse.

Tomorrow I tear off the intake and the head on the driver side - and, if necessary, the oil pan to get to any involved rods and pistons out.

Engine is a high end but mild SBC - 400 0.060" over (413). All forged, hyd roller. 10.6 CR. 460/500 hp/tq. Edelbrock and Comp Cams throughout. Highest level fasteners available (AARP L19) were used and everything possible is a stud. 4 bolt splayed main with billet caps. Heads extremely ported - flowing nearly 300 cfm intake and nearly 200 exhaust. One piece manleys of standard 202/160's. Custom pistons from Diamond. Ignition is MSD ProBillet with 6AL box. 750 dp Holley.

This is the albatross engine that was "professionally" machined and built and first ran at the turn of the year. Less than 5K miles, rev lmtr at 6800 and never brought to that. Has had three major breakdowns - a destroyed incorrect bronze distrib gear and two seperate head gasket failures (one from that first event), both times a few valves had to be hand lapped to reseat them due to small leaks and the blown head (don't know if the same one) was bench flow tested for leaks and such and milled 0.001-0.002 to make smooth. One of these heads blew up on a earlier motor and had a chamber welded and recreated (this was subbed out by the engine builder and was really an amazing job.) You really could not tell which was which.

I had a minimal and non-specific miss. Despite the best cooling system possible, it ran warm, but not uncontrolled. Oil pressure same as always - lower than normal due to remote oil filter and cooler -15 at fast idle, 40 at cruise, 45 max, 5-10 at 5-600rpm (no lifter noise produced). Vacuum steady and high - 16-18 normal, high at 21, low at 9-10. Both a/f gauges run super lean, but I had ascribed that to the oil and tranny leaks only recently cured - which always play havoc with them. Horrible noise that went up with RPM but not temperature, runtime or hot the engine was - something in between the deep sound of a rod knocking and that of loose lifters. No back fires or afterfires at all. Started easily. When the plugs came off, they were fine, slightly sooty but not caked with deposits - and uniform. I reset the guideplates which were making a number of the rockers be off canter quite a bit and it didn't affect anything. Oh - all the rockers rise and fall as much as each other - which is 0.560" on mine, and of course I reset all the lifters. None of the p-rods were bent or worn, nor was anything wrong with the nearly new promag roller rockers. All the valve springs look normal and even as do the ends of the valve stems and keepers. There are no marks on the stud girdles or anything else.

Well, I was going to rip off the intake to get at the lifters and then proceed to tear off the timing chain cover if I found nothing there. I decided to pull a compression test first. Had to do it cold. They all ranged 182-194 (only two over 190) - that is all, except #3, which was - ZERO. NO pressure. I thought the gauge was broken so I put my finger down there - nope, only a slight vacuum feeling as it turned over but NO air pushed out - NONE. The vacuum "pulse" was also much weaker than all those on that side.

That's the info you get - all we have so far! Take your best guess at holed piston, broken valve, broken valve seat, blown head gasket, bent rod, holed chamber. Be specific - even WHICH valve, which parts - hell, even WHERE on the piston the hole is if that's yor guess! I won't read the replies to this until tomorrow night, by which time I'll have the offending parts plucked out and will name the winner(s)!
#3 exhaust valve slightly bent and the valve and its seat burnt.
Zero compression? Holed piston, most likely right under the plug. . .

I'd say start over with a GM crate motor, but without a 400 which are prone to overheat and blow headgaskets.
Well, Craig32 & L48 are out of the running....

....unless it's microscopic..... [breathing exaggerrated sigh of relief].....

Spanishvettes & JDP6000 are still in the game - we'll have to wait until Monday or better when a shop can check the heads and valves.

No visible damage to ANYTHING! (This is not as good a sign....I would not have minded seeing something visible on the head.) All lifters seemed OK, no pushrods appeared bent or marked. No odd marks, grooves or scratches in lifter bores (or piston bores for that matter.) I only took the driver head off, but removed the whole upper valve train form both sides. Pistons (on that side) had a reasonable amount of carbon buildup, but it cleaned off quickly with carb cleaner. None of the carb cleaner leaked through the rings that I could tell on any of that side - and I put enough in #3 to cover the whole piston to about a quarter inch - it stayed there for five minutes at the same level that I could determine.

The head gasket is one of those squirelly new multipart metal cored things with no solid seperate ring, but there were no visible burnouts or flaws. (That will become a nice solid reliable copper gasket - preferrably one of the nifty new embossed and silconized things for $125 or so.) Since defined ring head gaskets were used on this engine the last time it died, I thought that was required to use them from now on, but the heads were milled 0.001-0.002" for uniformity and I could see no embossing on that head.

I checked the cam lobes - both on #3 raise and lower to the same height as the others, to within the limits I could tell with a simple depth meter/caliper: from the edge of the top of the lifter bore they range from 1.665" to 2.026" below the bore edge from top of travel to zero circle. That comes out to a 0.54" lift at the 1.5 ratio - close enough to the expected 0.560" (with a huge margin for error from the instrument and the uneven, nonmachined or controlled measuring surface.) That's enough to see I don't have a flattened lobe.

I turned the engine over by hand 3 or 4 times and everything timed and happened as expected - all pistons came up to very slightly (0.005" or less - best I can tell from hand) below deck top. I did not see much crosshatching on any of the bores and some faint vertical scratches - I would guess my idiot engine builder was having a lazy day on the final finishing stage. I would expect decent crosshatching at 50K miles with moly rings - to not see any at 5K tells me there wasn't any there to begin with. I didn't see the engine just prior to the heads going on last year. These are zero gap rings from Total Seal - I have never set or used or hand filed such rings but don't expect them to work that differently. Oh well - good pressure on the other cylinders - so what if I get a little more blow by when cold - these are forged pistons after all!

I have not pulled #3 piston yet and haven't decided whether I should or not. I really don't want to rip off the oil pan for no reason - just another thing to put back on. It didn't leak thin solvent by it's rings and there are no deep scratches in the bore, so I doubt the rings are faulty.

Tomorrow I'll pour some solvent in the upturned chamber and in the passages of #3 head and see if it leaks, then I'll remove the valves from it (if I can find one of my spring compressors.) I'll put my best steel straightedge on it to look for warps. More than that will have to wait for a machine shop to test.

After that I'll have plenty of time to stick a few needles in Ken's Voodoo doll Mr. Goodwrench CERTIFIED Voodoo Needles of course! :L
cracked cylinder. I just put this on here so I can watch the results in my email. Thanks
Testing your email link - and hope you are wrong!

Can't SEE it, but I don't know yet....valves both held a pile of carb cleaner in the ports for 5 mins with no leaks....


nah, L48, all valves were working fine before....with a little ruler they all made 1/2" + at the valve.....
Shameless trying to get to 300 posts...I am currently

unreasonably hoping this was a serious compromised head gasket.

Thinking about taking off other head, having both tested and machined for O-Rings to better use the high end copper head gaskets.

I'm still hoping to avoid crawling under the thingie, pulling the pan and start plucking pistons and cylinders, but suspect that's what I'll be doing.

If the cylinder is cracked (or severely egged) I should be able to tell if I have to do that.
Any update Wayne? Is there cruzin in your near future? Keep us up to date. . .
Much, much worse than hoped for....

Sorry it took so long to get back - computer on fritz for a while (still sortof is)...

Engine was trashed. Two spun main bearings, two rods....bores nuked

Took it to the machine shop recommended by my vette shop - which oddly turned out to be the same place that dynoed it a year ago

The last real culprit besides this bastard who wouldn't back his crappy product from Day 1 was the cam - the fuel pump lobe had rounded off so bad it was nearly flat - a good 1/4"+ of metal gone into the whole rest of the engine. Two of the wrist pin locking e-ring like things had also come off (they just don't do that - another big screw up from the builder) The cam was really alarming though - how does a fuel lobe round off in <5K miles? My machinist says he has had huge probs with Comp Cams cast iron hydraulic rollers quickly rounding lobes, but this was a first for a fuel pump one. He says the metal is simply soft. I don't know how cast iron can be all that soft, but it certainly was. A custom Crane billet number with a cast iron gear pressed on is going in there now.

The "good" news is it turned out the block was savable - scratches not so deep as a simple honing cleaned them up (it looked like the idiot who built it did not even crosshatch the bores...) All other components were also savable. So, for $2500+ in extensive machining (heads were screwed, but recoverable too) I get the bastard back to no doubt fail again. That's still the cheapest way to go - the components are all really high end and deliver 450-500hp and more torque. So far I've givne him enough to get him started - on the slow, slow do it by winter type plan....

Why oh why I EVER decided to build a decent powered small block or ever walked into Gary's Machine is just beyond me....

(The only other "good" news is with no engine in it, a torn top and slight body damage here and there, terrible paint, no p-brake, no seat belts, no horn, no PS, no A/C & worn rear tires the highly modified heap is only worth $4K or so if the financial straights chasing this engine's disastrous faults has put me in this last terrible year puts me in Chapter 7 in the next month....)

No, no cruising in foreseeable future....I only vaguely hope to have the engine back, and in the car by next year...
Geez Wayne, that's just awful. Did the guy give you any kind of warranty on his rebuild? Can you find any kind of Chevy beater down there with a running small block? I know you have a lot of time and money in the engine, but if you put another engine in it while you get the 'monster' repaired, the car won't keep you down as well. Without the engine it will just seem like a worthless pile of parts.

steel-on-steel: fuel pump PR-Cam

Steel on Steel doesn't always work out. If you have a billet steel roller cam, it probably has a steel fuel pump lobe. Your fuel pump pushrod is probably steel too.

Because of potential problems with steel-on-steel, several mfg offer steel fuel pump pushrod with either bronze-tip, ceramic-tip or roller-tip at the cam end.

The cylinder bores must be machined & honed exactly 90 degrees to crankshaft centerline... if not very, very close, the rods may tend to push the wristpins to one side ... shoving the locks out the sides of the pistons. By the same token, both big & little end of rod bores must be honed parallel to crank CL.
I built a SBC 400 CI and I have over 160K on the odometer and the only problems I had was too much toqure on the trans and on the axles... I'm running about 425 HP...
the gas milage is terrible but it runs like a scaled dog
Mike R
Sorry for the superdelayed reply....

Computer (and financial) problems went nuclear for most of the month....well, at least the computer is patched up now!

1)Yeah, the new fuel pump rod is bronze, but the old one was a lightened Moroso number that should never have harmed a cast iron (or nodular) cam lobe.

2)Good thought about the wrist pin lock dealy letting loose because of improper square of the rods on the crank - I'll ask my new machinist. He did not rebalance the assembly even though I was fairly insistant. He said the pattern of wear on the bearings did not indicate any significant imbalance - that the huge amount of worn off metal did the bearing spinning. He turned all of the bearing surfaces and they weighed the newly hung rods and slugs. He also noted I had too weak a fastener on the rod bolts - even though they had not failed (yet). They were NOT the ARP L19's used on the mains and head studs (the latter of which he dislikes for leaking problems, even though they make planting the heads super easy.) The ARP L19's don't even fit easily into SBC's, especially 400's - requiring so much block clearancing it's easy to nick a water jacket. The ARP's on there were the base level, so he changed them to the ARP2000 type.

This machinist offers a 90 day fix it free, including parts, if he builds it - including this rebuild. I will have him assemble it once I've paid for all the machining and new parts (he's in no rush - I covered the parts and most of the machining but not the assembly or redynoing.) This will wait for later October or early November.

3)Damn right - "useless worthless pile of parts" - exactly what's needed for the Chapter 7 if that is the decision I make in the next couple of weeks! :) (I got an appraisal of $3500 - YAY!) For now the engine is at the second machinist's awaiting this grim financial decision....still incomplete and only partly paid for. If I had decided to go with yet another engine I would have gone with a cheapy stroker BB as the next temporary engine, but things look good here.

4)That's excellent news on your good experience with a 400 based mill - let's hope the resurrected one performs as expected.

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