Slow Blowthru engine build.

WarWagon

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Mar 10, 2007
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Rough year for the Buick, Engine is not fully torn down yet I'll do that tonight. Lost stock #2 connecting rod and perhaps cracked my last 109 block. I'm not certain exactly what failed (stock rod bolts) or the rod itself but it looks like the rod bolts broke threw the rod cap off then the crankshaft took out the rest of the rod while it was hanging. Also found the wrist pin was coming out and riding the cylinder wall on the same #2.
I'll know more tonight but I'm already prepping my last stock bottom end v6 that will accept the roller cam and top end from this engine.
 

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ek02

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Jan 31, 2008
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Time for a set of H beam rods maybe? I hope the block is repairable. You may be able to bore it or sleeve it.
 

WarWagon

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I've never put real money into a single one of these bottom ends and everything has used parts.
 
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ek02

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Jan 31, 2008
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The score in the cylinder looks pretty deep, but it's hard to tell from a photo. If it's standard bore, it may clean up at .030-.040. Worst case, a sleeve, or maybe it would be the cheapest way. You could get by with a new piston, rings, and rod and reuse the rest with a sleeve. Darton makes them for the 3.8. The problem is finding a good machinist to do it. You said you have another block so the hurt one would make a good spare if you can fix it. Good luck with it.
 

WarWagon

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Mar 10, 2007
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This block was already .030 over bore. Both of my 109 blocks have the #2 bore messed up now. I'll probably get rid of this block I don't like the o ring grooves in the deck. Future plan is to use my standard bore 140 block and take it to .030 over then use the rest of these piston/rods in that with a different stock crank I have. Right now everything in the top end and valve train is going in my oldest block that I last ran in 2008 that is standard bore and stock botton end.
 

ek02

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Jan 31, 2008
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Where those stock rod bolts? Did the rod fail and shear the bolts, or did the bolts fail and break the rod? Hard to determine the cause.
 

WarWagon

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Mar 10, 2007
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Where those stock rod bolts? Did the rod fail and shear the bolts, or did the bolts fail and break the rod? Hard to determine the cause.
Stock rod bolts were used. I believe that the bolts failed on that one and ejected the rod cap then the crankshaft took the rod out while it was hanging. Something was going on with that piston/pin/rod since the pin had slid out, I put that piston on the rod with the same wrist pin that had always been married to it. Was driving towards a stop sign at 10mph when this happened, a knock started and within three seconds it let go. I drove it two miles home then.
 

ek02

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Jan 31, 2008
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Sounds like that's what happened, but the pin coming out is unusual on a pressed pin. Good thing you were going slow.
 

WarWagon

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Mar 10, 2007
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Lost several posts in this thread after the site update.
Currently my blowthru Buick is running with the oldest engine I own. A '79 Riviera turbo shortblock, it is well used with the lowest compression. I pulled the front cam bearing out and cut an oil groove in the block like a 109 has then modified a later(109)cam bearing to fit this block. Swapped out the one bad stock piston that was killed during heavy N2O use with another stocker from my 140 block. The heads and valve train is all the parts from my last 109 build. This engine runs pretty good, it has lousy hot idle oil pressure but rises fast and has 40+ psi oil once revs are 3k. Valve train is louder than past 109's with the too short push rods. This engine is temporary until I can build a .030 over 140 block or build my 4.1 up.
 
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WarWagon

Caustic Cacophony
Mar 10, 2007
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Fairmont WV
I recently got a dial back timing light that I needed to get my high compression SBC ignition timing right, I decided to try it on the Blowthru Buick. I remember purposely setting the ignition timing low this time to help it live longer because this engine is stock short block. I got 18.25* might as well round it up to 18.5* for my base timing. Mallory 865 Ignition was pulling .3* per psi of boost, so total timing is 9.5* for WOT on 30psi of boost.
I used to run 22.5-23* base ignition timing on the 109 blocks and end up at 18* total on boost.
 

WarWagon

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Mar 10, 2007
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This is the distributor maintenance I must do every month I run the Buick frequently. The ignition has a good deal of energy for what it is and I always have to scrape off this ionized oxide layer that causes misfires and erratic ignition events. I reset the ignition timing to 24* base and have the ignition set to pull .2* per psi of boost currently, this sets final timing to 19* when boost is on.
 

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