Sorry to keep you guys hanging on the engine issue, I had to get ready for the yearly Track Rental event, which is now completed. For details and photos of that event, visit this link.
https://www.njfboa.org/forums/showthread.php?t=69513
My car was not fixable before the track rental so I had to sit this one out, which is fine because I learned a good bit of stuff by spending time on the starting line and helping people in the pits.
As for the status of my situation, I might start a new thread on it, or I can continue this one, but no matter what happens, I will gladly be seeking technical advice and input from the SBC engine gurus here on this site as I tackle the project over the winter months.
After getting home from Numidia with the car, I already had a busy weekend ahead, so it sat for a day or two. I then began more diagnostics, troubleshooting and working through stuff by the process of elimination. I wish I spent less time accusing the sniper of being the problem when I should have looked deeper elsewhere. However, after a compression check, I found that cylinder #8 had zero compression! I finally found the first indicator of my problem when I removed the passenger side valve cover and noticed some specs of "trash" at the head bolt by cylinder number 8. The trash was actually the remnants of a chewed up valve seal. As I was cleaning this out I then came across a circle piece of metal that turned out to be from the inner valve spring on the intake valve of cylinder number 8. I noticed that the rocker arm for the number 8 intake vale was also sitting crooked, but still moved up and down when I cranked the engine over by hand. I removed the rocker arm and immediately the pack of valvesprings started moving around completely loose, saw that it was not held down any longer. The keepers were in place, but had sheared off the locking ridge that keeps them in place, so everything was just floating. The outer valvespring was intact, the spring dampener was intact, but the inner valve spring had turned itself into 4 separate pieces. Also, the valve stem is physically stuck in the head tight, so I knew right then and there that this repair was going to take some time and would put me out of racing action at the track rental. So in the meantime, I just let the car sit in the garage and instead I focused on everything I needed to handle related to the track rental, plus work, family life, etc.
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Essentially what appears to have happened is that I beat on the engine for too long, too many times, at too high of an rpm, and I floated valves at the top end of the track on that last pass. In the back of my mind I've always hated revving this thing out past 6200, but I did it continually. Often! All those years on the rev limiter for the last 200+ feet at the dragstrip didn't help either. Valve springs are parts that I should have known to replace every few years, but I was more on auto-pilot and thinking that then engine was bulletproof, so I never serviced the valvetrain in the past 7 years. I remember considering doing engine maintenance, but having no real deep understanding of engine dynamics, I was more worried about messing something up as a result of doing engine servicing for all these years. I've had the car for almost 27 years now, but this 406 engine has been in it for the past 7. During its time it has clocked 11,200 miles, 204 dragstrip passes, pre-race burnouts and more fun burnouts, some dyno pulls, and 47 autocross runs. Lots of fun along the way and it fulfilled all the personal goals I set it out to accomplish with it... and then some. No regrets whatsoever.
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Engine oil filter has a little bit of glitter in it:
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So, here is what I can currently assess from the situation. No matter what, the passenger side cylinder head needs to go to a machine shop. I've had a leak at the back of the block for a while that I want fixed also and in recent years I've wanted to open up the piston rings a little bit in order to possibly accommodate a bigger (200-250hp) nitrous shot. Therefore, I'm just going to take the whole engine out of the car instead of just removing the cylinder head. I know that it will need new valves, springs, and seals. If my previous springs were decent, well now is the time to upgrade; maybe something without the dampeners. The engine builder is no longer in business, and also they were real far away, so I'd like to find a shop thats local (within an hours drive from me at 07847 zip code). I'm certainly no valvetrain expert, but I feel like now is the time I need to start learning it. I'm a hands-on learner more than a bookworm, so all those decades that I spent reading the car magazines and skipping past the black-and-white articles at the back with titles like "SBC valvetrain shootout" or "rocker arm comparisons", well now its my time to start learning and understanding it. Hearing terms like "installed height" means very little to me now, but after this ordeal is finished, I hope to be well versed in at least the nomenclature of sbc valvetrain stuff.
I don't have any intentions of changing the camshaft. However, if I can swap out my current 1.5 roller rocker arms for a set of 1.6 roller arms, that would take my .400 lift cam that used to go to .600 lift and it would bring it to .640, right? Also, if I am able to ditch the smaller sized 2.055" intake valves for a set of 2.08" or 2.10" that could be beneficial.
These heads are the Dart 215 head but they were not bought as an assembled head (see part number stamped on head, it was a bare head with parts added to it). I'll attach the engine build sheet from January of 2020 below. Additionally, it is likely I'll need to buy one piston to replace the dented one on cylinder #8 but I'm hoping the other pistons are salvageable. The part number shows I can buy one and not a whole set. I used a cheap bore-scope to look into cyl #8 the other day but have yet to do a full evaluation down the other cylinders. It was also recommended to me that I do a leak-down test on all cylinders so I have that on my to-do list. Cylinder walls looked good, and remember I (foolishly) drove 120 miles from Numidia to my house with the engine wounded like this. Oil got drained last week and honestly, didn't really have any fuel smell to it and it felt still like oil should, but I was worried about washing down the cylinder with fuel. Again, I'm not an expert, but I am just going off my observations and the situation at hand.
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In the coming weeks I will get the car's hood off, exhaust removed, transmission out, sniper efi removed, front accessories removed etc. I'd like to have the engine out and on a stand by Thanksgiving with a good idea of a gameplan where I can take it for machine work and reassembly. I welcome any and all input on how to build a strong(er) valvetrain for this 406 sbc. Stronger, more durable, and maybe even a small increase in power would be nice. However, of huge importance is to not get carried away. I'm not chasing hp numbers, instead this has to stay a fully streetable car. I'm limited in the power department by other factors also like my transmission's capabilities, fuel system's capabilities, header primary size of 1.75", and other factors. It can't turn into some monster build up. I assume engine shops always have a waiting list, but if all goes well, I'd like to have the car back up and running/driving around by my birthday which is mid April.
Its been well worth it! Build it better this next time
