tccombs

engine considerations.

58 posts in this topic

You guys are WAY overthinking the difference between "car" engine and "truck" engine.

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Don't forget that GM uses a specific marine camshaft for many of the offerings as an example to match to a prop demand curve.

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Update!   The boat is finished!      

we ended up   fixing some corosion on the aluminum exhast  this is very common 

Bored the engine .30 over  to fix a bit of corrosion in 2 cylidars 

new crank  (internally balanced this time) .. special part   couldn't find it. so it had to be a custom order. 

could not find the proper replacement pistons for   it either.. as they are very rare...   and now that it was bored .30 over they had to be replaced.   so the machine shop   bought  new ones and did some more work to customize those to fit and balance as well. 

 

All reassembled.. the first test run   ran horrible.. 

it turns out the distributor had some crappy plastic  part that snapped.   this caused  the timing to vary.   (  this is also the likely cause of the engine crank to stap    if it had backfired due to timing at high rpm.)

 We replaced the distributor.. 

It now runs better, than it did even new!      after being bored out.. my 383 stroker    is now closer to a 390  with all the work the mechanic thinks  its pushing about 420HP now.  

 

But for the cost,  i might as well got a brand new engine.   

 

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35 minutes ago, tccombs said:

Update!   The boat is finished!      

we ended up   fixing some corosion on the aluminum exhast  this is very common 

Bored the engine .30 over  to fix a bit of corrosion in 2 cylidars 

new crank  (internally balanced this time) .. special part   couldn't find it. so it had to be a custom order. 

could not find the proper replacement pistons for   it either.. as they are very rare...   and now that it was bored .30 over they had to be replaced.   so the machine shop   bought  new ones and did some more work to customize those to fit and balance as well. 

 

All reassembled.. the first test run   ran horrible.. 

it turns out the distributor had some crappy plastic  part that snapped.   this caused  the timing to vary.   (  this is also the likely cause of the engine crank to stap    if it had backfired due to timing at high rpm.)

 We replaced the distributor.. 

It now runs better, than it did even new!      after being bored out.. my 383 stroker    is now closer to a 390  with all the work the mechanic thinks  its pushing about 420HP now.  

 

But for the cost,  i might as well got a brand new engine.   

 

So what did it end up costing?  Just preparing myself if my 383 ever needs to become a 390.

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@tccombs:  Glad you boat is repaired and back on the water.  Did you replace the distributor with a standard or aftermarket unit, and if aftermarket did you get any info on why it would be better?  Just an FYI, the overbore I would guess is .030" over, commonly referred to as 30 over.  Pistons should be fairly common for that overbore, surprised they were hard to find.  Does it run well now and are you following a prescribed break in procedure, if not I will provide some links to review.

Some information on engine break in:

http://www.indmar.com/Libraries/Manuals/2015_GM_Based_Operators_Manual.sflb.ashx

http://paceperformance.com/p-3978-engine-start-up-procedure.html

http://www.camaros.net/forums/18-engine/36639-new-engine-break-procedure-gm-crate-motor.html

http://static.summitracing.com/global/images/instructions/atk engine break in.pdf

Basically, check all your systems, make sure everything is tight, verify ignition timing, don't run too hard for the first few hours but do vary engine speed and load, change initial mineral oil supply soon to purge out the contaminants from the build.  At that point, I would recheck everything and re-torque the cylinder heads / intake and exhaust manifold bolts and check ignition timing.

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Last engine I had bored from my machine shop they pretty much told me boring isn't going to give you any more power than you had 

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Hammerhead...  the cost was estimated to be  between 5 and 6 thousand..

  but the total  cost exceeded the estimate... and  ended up costing   $6900.00  for the full rebuild...     

two surprises  caused the extra fees..  

1.  boring it out, and hard to find pistons...

2.  replacing the distributor

 

If I had to do it over....  I would not do the rebuild...   I still worry something like this could happen again..      Instead I  would buy a new 350 crate motor   which would have cost me about the same. 

 

 

If I had to do it over again... I s

 

 

 

 

  

 

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1 hour ago, tccombs said:

Hammerhead...  the cost was estimated to be  between 5 and 6 thousand..

  but the total  cost exceeded the estimate... and  ended up costing   $6900.00  for the full rebuild...     

If thats the worst it got, thats not terrible.  I had my flex plate blow last year on the 4th and that alone was nearly $2k to get fixed.  Not to mention boat was out of the water for 3 weeks in the best months.

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