Volvo Penta AQ271C back firing 3000 rpm

Scott Danforth

Scott Danforth

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Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

Greg68S, one thing that I did not mention. My stock prestolite distributor went thru distributor caps often (one every 8 hours of use). not sure the reason, it would just corrode up. Sierra, Volvo, Mallory, brand of cap didnt matter. however if your backfiring and not getting on plane, pull the cap and clean it. I kept scotchbright and electric contact cleaner on board for that reason. if after you clean it, you instantly get full RPM under load, then the issue is corrosion in the cap.

After loosing an advance spring (and playing trial and error), and then the module started having issues, I replace the stock distributor with a Mallory unit. been working like a champ since.
 
Greg68S

Greg68S

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Re: Volvo Penta AQ271C back firing 3000 rpm

hey everyone. Im sorry i have not been updating this thread. I have found the problem. Over the winter I decided to pull my motor to see what I could see as far as internals go. Before I pulled it I ran a compression test on all cylinders. I found a positive response from all cyclinders except cyclinder 2. Where every cylinder was 165psi or better, cylinder 2 would not break 130psi. A tear down of the engine revealed and very leaky intake valve on cylinder 2 (which was most definetly causing my pop/back fire). From what I can tell it is stuck in the guides. Also I did a pressure test and the several cylinders were not up to par. Further investigation revealed some interesting results. With only 837 hrs on the engine there was significant wear. Each cylinder was over by almost .030's and each piston was under by almost .020's. Crank, Rods, Cam, are good. looks like pistons and a valve job. I hope my findings can help someone in the future.
 
Greg68S

Greg68S

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Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

ATTENTION!!!! Turns out ignotion was not even close to the problem. Check out my other thread to see what the real problem really was.[h=3]
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Volvo Penta AQ271C back firing 3000 rpm[/h]Started by Greg68S, July 28th, 2013 07:39 PM
 
Greg68S

Greg68S

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Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

This is the main thread that sums up the other two. This is the discovery of the main issue and my project as it progresses through the stages. What should I do too make this readily available to any and all especially new DIY's?
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DP290A removal of hinge Pins??????[/h]Started by Greg68S, February 25th, 2014 12:29 AM
 
Walt T

Walt T

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Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

Don't just "do pistons and valves" Replace the cam and tappets, along with cam bearings. It's silly not to. Manifolds and risers are an absolute must.
Maybe consider a Vortec upgrade, or a stroker. Good power for the money.
Do it right the first time.
 
Greg68S

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Re: Volvo Penta AQ271C back firing 3000 rpm

The cam looks to be in great shape according to my machinist. All bearings will be new. Manifolds are new. They just arrived this morning. I love it when parts start arriving. It's like Christmas.
 
Greg68S

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Re: Volvo Penta AQ271C back firing 3000 rpm

Believe me I thought about it. It was a tempting thought but I won't have this boat for long. 3 years max. I bought right at $3000 including trailer. So I have a lot of wiggle room. But I have to be smart about it. We want to upgrade. Ultimately to the 32-34' range. Did the can change help? This is where I sit. .030 will be the piston size. They will be a standard dish piston. Will the cam change increase power with out causing other issue? As it is I was running on practically 7 cylinders. Easily a 40% power loss. So I should be quite impressed with the power on the rebuild.
 
Scott Danforth

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Re: Volvo Penta AQ271C back firing 3000 rpm

yes, the cam change will wake your motor up a bit.
 
Greg68S

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Re: Volvo Penta AQ271C back firing 3000 rpm

Nice thread Scott. To rich for my blood. This time around that is. I really want more reliability than anything else with this boat. Had a few really irritating experiences this past season. Like being adrift on a regular basis. Haha.
 
Scott Danforth

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Re: Volvo Penta AQ271C back firing 3000 rpm

I understand the reliability issue

if money is tight, I would still do the following:
replace the cam and lifters like Walt mentioned (your in there currently, good thing to do)
Replace the timing chain (your in there currently, good thing to do)
replace the oil pump, pickup, and drive shaft with Melling High volume parts (your in there currently, good thing to do)
replace stock stamped rockers with summit 1.5:1 roller tip rockers (the factory stamped rockers vary between 1.4 and 1.5 on each one, being on average 1.46) http://www.summitracing.com/parts/sum-141506/overview/make/chevrolet

Here is a good article on rocker arms Rocker Arm Ratio - Super Chevy Magazine

and since you have the same distributor that I had problems with, I would replace that, or get a spare.

My old Volvo Penta specific prestolite distributor had issues nearly every time out. So I replace that with a Mallory unit.
 
Greg68S

Greg68S

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Re: Volvo Penta AQ271C back firing 3000 rpm

Is the AQ271C a gen 1, 2, or 3 engine?
 
Greg68S

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Re: Volvo Penta AQ271C back firing 3000 rpm

Ultimately I'll be happy with a stock rebuild because I've been used to running with 40% less power than I should have had. However. Reliability and efficiency are important. Will a cam upgrade and roller rockers be an ok step when I'm sticking with dish pistons? Or do I need to consider young the compression and going with a flat piston?
 
Walt T

Walt T

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Re: Volvo Penta AQ271C back firing 3000 rpm

You wont notice anymore power with just a cam change. If you want reliabilty you should replace it and tappets along with cam bearings.
 
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