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Center... duh...   

Sorry, couldn't resist 

It's forecast to get into the mid-60s here next week... think I should drain my fluids and install a block heater?

 

Food for thought on ring end gaps....

I was just at SEMA 2018 talking about this exact subject with one of the reps from United Engine Machine (ICON, Kieth Black, etc).  He mentioned he used to work at Perfect Circle so I asked him what he thought about larger ring end gaps as I've always added a few thousandths to the recommended spec for safety and have never had a problem with blowby.  He said PC actually ran tests on end gaps and in a dynmaic running engine they could not measure any difference in blowby from a 0-gap ring on up past .040" gap.  Static leakdown tests will disagree, but in a running dynamic engine there was ZERO measurable blowby difference.  Honing technique (pressure, speed, final finish, etc) has a much greater affect on ring seal and blowby.  The take away for me, and he concurred, was that larger gaps have no performance drawback but will save your motor if it gets hot.  I thought it was interesting the way I was taught by the "old timer" jived with a manufacturer's test.

I've always set pistons a hair on the loose side as well.  When I say hair I mean +.0005" or so.  Same rationale, building durability and a little wiggle room into the clearances.  I probably would be more conservative on a short skirt piston but Speed Pros have a long skirt and are much more forgiving.  I wanna say we put .0055" into my buddy's 429 Ford, but his compression was up over 11:1 and he runs it HARD.

Making some huge power! And has some pvc plumbing fittings on it....im sold!

https://detroit.craigslist.org/mcb/boa/d/78-taylor-jet-boat/6655871061.html

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1400hp with a single 4bbl, mechanical fuel pump and tiny fuel lines... um, yeah... OK.

Come down here and get it lol.

LOL!  Actually, I'd have to come "up" and to the right to get it.... then figure out a way to ship it back to Honolulu!  Don't think I can paddle that far. :-D

I looked this number up in our ProSIS software and chamber sizes can vary all the way up to 122cc.  You'll need a big dome to make compression with those... not my favorite way to do it.  Closed chambers with flat tops make around 9.5:1.  IMHO if you can pick up some closed chambers for a couple hundred bucks you'll be ahead.

I should add that I'm pretty much pulling the new structure design outta my ass so if someone sees something very wrong please say something, LOL!   

Look at you! Get down with your bad self! Good job. Looking good.

Thanks, man!  I'm just stoked it's no longer coming apart and is finally going back together! 

Aaaaaand here's where ASSumption can really bite you.  I ASSumed my early 70s fiberglass boat that was molded in hippie hay day was symmetrical.  The 2 tanks were made in mirror image of each other.  The side I measured fit GREAT!!



Little did I know (should have known better) the boat is over an inch different on the Port side.  Some quick rethinking was needed!  Ended up angling the filler neck and laying the tank over to fit under the gunnels.  It'll eventually be covered by a panel but it's NOT OCD compliant!  I'll live with it, but still makes me cringe to think the tank isn't vertical like it's sister:



I'll probably put a sheet of rubber between it and the hull to prevent rubbing.

While that was going on I needed to do something positive so spent some time doing oiling mods to the Olds 455:

Used a head gasket as a template to mark where the drain back holes are located.


Might have gone a little overboard (no pun intended)



Used the oil pump as a template for the rear main cap.  Forgot to take a "before" pic but here's the "after"

I kind of wish I was able to ignore a "small" flaw in the floor, but curiosity got the best of me.  What started as a small inspection hole quickly evolved into a 2-year project










While the floor was being removed we discovered the center rib support was rotted out too.

At idle the timing was around 20 deg advanced (I don't know for sure since the indicator stops at 16).  With the timing shunt plugged into the dist the initial timing dropped to 8 degrees, unfortunately the dist was locked in place due to corrosion so I couldn't adjust the base timing up to 12 deg (1st fail).  Knowing that I couldn't adjust the base timing I decided to check the advance as i revved the engine.  Around 3k it moved up a little but probably only up to 24 deg, this was showing total advance from 20 ish at idle to 24 ish at 3k RPM. 

Disclaimer: I've only played with BBCs in cars, not boats... what I'm about to say applies to automotive but I don't see why marine would be different.  The following is based on the distributor having a mechanical advance, not electronic...


A typical GM HEI should have more like 14-18^ or so of advance from idle (I've seen it vary from model to model) .  If base is set at 20 you should see 34-38 total at 3000-3500.  Depends on weights, springs and stoppers.  If you're only seeing a 4^ advance it sounds like the mechanical advance mechanism is stuck, possibly corroded given that distributor is locked in place to the block. 

That being said, 24^ sounds awfully low to me.  Street cars with pump gas and 10:1 compression usually run in the 32-34 range as a starting point and dial it in from there.  The 1st thing I'd do is check to make sure the advance is working correctly and try adding some timing.  Go in small 2^ increments and see how that affects the top end.  Check plugs for signs of detonation between adjustments.

I've seen this type of issue in automotive a few times and this was the answer, but like I said I've not run a BBC in a boat.  Guys with more marine experience please correct me if this doesn't apply. 

Whats your plan on the head steam tubes? I found some nice adapters on eBay, and after examining the factory cooling system it looks like just plumbing them to exit somewhere on the transom is all that is needed.

I'd agree with that too... IIRC on a 4th Gen they plumb back into the radiator?  Been a while since I sold mine  

I do recall that some cars have all 4 steam holes tied together with a skinny "H" looking pipe that sits under the intake (the very early cars IIRC), while others block off the rears and only use the front steam holes.  I don't think my FAST intake cleared the "H" line running under it so I had to change over to the later style stem tubes when I ran it.