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Wolfpack Rugby

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1986 270 Crusader FWC with 1180 hrs. Leak down test, compression test indicate valve job needed. Engines burn zero oil. Looking to rebuild heads, replace riser and elbows and 2 new electronic distributors. Getting mixed opinions from friends and co workers. " Tightening the top will create a problem for the bottom" . What do you guys think.? No budget for new engines
 
Here's what I would suggest regarding your friends and co workers comments:

*..... Let's say at 1,180 hours, the valves did NOT require any attention and both engines are running just fine....... What now would they be saying about your bottom ends?

**..... How many of them are qualified to discuss this with you?

***..... If you do pull these engines down and have the cylinder heads re-worked, what is the best and/or worst case scenario?

Scenarios:
a..... re-working the heads renders a significant improvement in performance. :D
b..... the piston rings begin to show signs of leaking presure........ not necessarily a deal breaker! :(
c..... the piston rings do NOT begin to show signs of leaking cylinder pressure. :D
d.... in the event that this does not work well, the cylinder heads are ready for fresh "long blocks" in the not-so-distant future. :)
e..... you've spent X hours removing and replacing the cylinder heads and with un-satisfactory results. :(

Can you live with any of the above?



**********************************************

Before pulling these down, bring each crankshaft around to 6* BTDC C/S for #1 cylinder. ( C/S = compression stroke )

By the way..... if you do a cylinder head exchange, make dang sure that you get cylinder heads back with the same identical casting numbers ( I.E., same combustion chamber volume, etc,) and also verify that YOUR casting numbers were correct to begin with.
(1986 5.7L SBC was likely fitted with the GM full dished pistons, of which would have involved the 65cc chambers)

Also, measure the compressed thickness of the existing head gaskets, and use matching gaskets.
(keep a few pieces of the old gasket..... ask your machinist to measure it)

Use the 8 stop static procedure when you adjust the cam followers (not the 2 or 3 stop).
Begin with #1 cylinder TDC C/S, and go right down the firing order 7 more times.

New Ignition System:
I have no idea what you are doing re; new ignition systems.
Please keep in mind that the Pertronix kits do ZERO for any existing distributor shaft and/or advancing mechanism wear.

Edit:
One last suggestion...... put your timing light on each engine and see where the TA comes in at.
If the TA is within specs, and when you initially set up your NEW ignition systems, time them for the same TA.
Water Test run each engine and see if you feel an improvement.
You can then later adjust for the correct BASE and TA .



Good luck with it!



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Last edited:
One more thing...... if by "FWC" you mean that your engines are fitted with "Closed Cooling Systems", you can use high grade automotive head gaskets (more choices) and you'll save a few dollars to boot!


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Is the engine holding good oil pressure when hot? Can you still see crosshatching on the cylinder walls? If the cylinder walls are glazed you really should do a complete rebuild in my opinion.
 
Seems like an intelligent approach to me.....just make sure the new distributors are marine rated and you make their advance characteristics with what you have and you should be good for another 1000 hours....
 
See your OEM work shop manual for the correct Ignition Advance Curve.

The OEM knows which piston selection was used in their 1986 270, therefor the advance curve will be limited to what works with that design.

Avoid Ignition Induced Detonation...... Do NOT exceed the Maximum Advance at the prescribed RPM.

Your curve will look similar to these:
(Examples ONLY.... see your OEM curve!)
 

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  • Ignition advance line graph VP 5.7L .jpg
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Wolfpack Rugby said:
1986 270 Crusader FWC with 1180 hrs. Leak down test, compression test indicate valve job needed. Engines burn zero oil. Looking to rebuild heads, replace riser and elbows and 2 new electronic distributors. Getting mixed opinions from friends and co workers. " Tightening the top will create a problem for the bottom" . What do you guys think.? No budget for new engines
Click to expand...

Questions: just how were the cylinder pressures taken? did a qualified mechanic take these readings?
I
MO, a person should allow each cylinder to pass through at least 3 compression cycles. Why..... because the pressure gauge and the gauge's hose will be somewhat accumulative.

With your compression gauge installed, and with the throttle plates partially open, and with the ignition system completely disabled...... crank the engine over at least 7 revolutions per reading.

Ideally, your test per engine should offer a low reading that is no more than 10% lower than the high reading.


*********************

I realize that the OP has posted only once...... perhaps we're talking to a ghost! :D



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Gents, no ghost here. Do some traveling during the week. Testing was done by certified technician. Several outside conversations have brought up other possibilities about what I could run into with top end rebuild. Crusader with their soft cams, cylinder wall wear ect..
Visited A.C. Boat show yesterday. Spoke with Crusader about 5.7 power pack . Base carbureted block reusing bolt on components . Thinking this is the way I'm going. Question.. Can I reuse my Velvet drive transmission ?
new motor rated 300 hp ( current 270 )
Really appreciate hearing back from you guys . Hopefully some day down the road I can be of help to someone else.

Lou R.
36 Mainship D/C
 
Trans will be fine with that extra hp long as it's in good condition. Mine two lasted over 30 years without a rebuild!

Jeff
 
Lou, if you were to build your own SBC Marine Engines, or if you were to have a machine shop custom build a pair of these for you........, get as far away from the GM Full Dished pistons as you can.

Take a few minutes, and read this thread beginning at post #7 through post # 26.

I know..... you are probably wondering why GM (and many rebuilders) would continue using this piston if it is not a good choice.
Quite honestly, that would be a fair question.

In this thread, I go into detail regarding Marine Engine loads and Detonation potential, and the proper SBC build that will prevent Detonation and will allow for greater torque.

Most any good machine shop is capable of doing a Q/E build.
It will cost you zero for the asking!


Good luck.


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