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[T3] End of 1776 overheat saga and vapor lock Q. (long!)

<x-flowed>Hi All,

Some of you might remember a few weeks back I had a slew of Q's regarding the overheating condition on my new 1776. (It was overheating quickly on the freeway... up to 240 after only 5 minutes at 65 mph!). I received many great responses that enabled me to check and rule out everything but the cooler seals, at which point I let the builder know that he had to take it from there (i.e. take it back and figure out what the problem was... IMHO it's not my job to rip open an engine I paid to have built) and suggested he look at the oil cooler seals. Long story short, he picked up the engine, put it back on the dyno, and noticed that the oil pressure dropped to around 5 (!) after the engine was warm and under a load. Apparently the seals were correct, which left him essentially stumped without ripping open the case, and concluding that the problem was potentially in the new case itself (?) or the cam (?) as everything else that could possibly be checked was checked. So, frustrated and losing time/money he decided to throw that entire longblock in the corner for the time being and just start fresh. I received the second new engine (turnkey off the dyno) installed it, and after the first drive could tell that the problem with the other longblock was definitely not repeated/present in this one. Around town and quick freeway hops for the first 100 miles the temp didn't get past 200F. So, I adjusted the valves and took it out for an extended freeway drive. While I could now drive on the freeway for an unlimited time at 65-70 mph, the temp very slowly kept creeping up (as per a calibrated VDO gauge with sender at the pressure relief) until it was around 220-230F. Not terrible, but still too hot for my liking, especially since it was only 75 degrees out, and I wasn't even pushing it up a hill, or driving 80+ like we do out here. So, after going over *everything* cooling related again, and consulting with the builder, I decided to add a 72 plate EMPI cooler/fan unit with thermostatic switch to the full-flow system (shock mounted above the tranny... perfect fit!) and see what the result was. Low and behold, I've reached T3 Nirvana...after getting it up to 180F on the flats I drove 20 miles uphill (Hwy 15 up Cajon pass) at 70 mph in a headwind, and the temp didn't break 190F! The minute I started coming back down the hill, the temp went down to 180 and stuck. Once back on the flats I pushed it alternatively between 70-80 mph (still in heavy wind) and the temp went back up to around 190, but no farther. Today, it was a bit warmer out (80F outside temp), I pushed it harder, and still wasn't able to come close to busting 200F... really, I tried! ;) I figure on a hot summer day, I'll be running at around 210-220F on the freeway if I'm driving hard, which is acceptable in my book, and will allow me to watch the road instead of the gauge (always a bonus ;).

Now for the vapor lock question (I've got dual dual Solex H32/34 PDS13 with stock brazilian air cleaner setup, recently rebuilt and rebushed, balanced and running perfectly): twice now when I've had the engine at full operating temp, parked it for 15-20 min, then returned to drive it, I have only been able to drive about a block before the engine dies (clearly a fuel starvation sputter as it chokes). The first time this happened last week, I could see that no fuel was present in the in-line filter, and in pulling off the line to one of the carbs confirmed that nothing was getting through. I could turn the engine over and over, pump the gas a gazillion times, and get nothing. I tried removing and replacing the hose from each connector at the carbs and pump, and then making sure that all of the hose clamps were tight.. Still the engine wouldn't start. Then, after about 20 min, I could see some fuel returning to the in-line filter, and the engine finally started up, and ran perfectly. Assuming that this was not a problem with the fuel pump--which to my knowledge either works or doesn't-- I surmised that the fuel lines were getting too hot somewhere, and adjusted the length of all the hoses so they weren't directly touching a heat source (such as the block, or shrouds/sheet metal) and in the one spot where there is still contact (the back edge of the sheet metal covering the stock oil cooler) I put a larger diameter hose piece around the fuel line to serve as a buffer. All was well until today, when the exact same thing/condition occurred! Aside from that single spot of contact with the sheet metal covering the stock oil cooler, there is no other contact between the fuel lines and heat source(s). I turned the engine over again and again, messed with all the hoses (removed/reattached/tightened clamps) to no avail... after about 20-25 min, at which point the fuel started flowing again, and the engine ran like nothing had happened all the way home.

SO, my questions are

1) Am I correct to diagnose this as classic vapor lock? I ruled out the fuel pump because it otherwise works perfectly. Correct assumptions?

2) How could this happen again after readjusting all of the hoses in relation to heat sources?

3) Why would this happen even if the lines did touch the block/sheet metal directly? On my old motor, the hoses from the pump to the T-splitter and then to the carbs virtually laid right on the block, and I'm quite sure the in-line filter and/or hose between the pump and filter touched the sheet metal above the oil cooler directly, without the extra hose to buffer. Plus, in the last year of that motor's life, I got the engine up to 280-300F every DAY on my short commute before shutting it off, and still never had a vapor lock issue... again, with the hoses touching heat sources all over the place.

4) Does cloth braided hose stay cooler in the engine compartment than non-covered fuel line? The hoses from the pump to the T and then to the carbs are cloth braided, but the hose bringing the fuel to the pump (on both sides of the in-line filter) is the larger-diameter non-braided/covered hose. This is the one that comes closest to the heat source at the back of the cooler, and that I have buffered with the larger-diameter hose piece. Could this be a/the culprit?

5) If this is vapor lock, does anybody know any quick tricks to release the pressure/vapor and get moving again without the requisite 20-30 min wait?

Needless to say, this has temporarily suspended my T3 Nirvana... TIA for any advise!!

David Y.
68 Sqbk

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