Chris-Craft 327F low engine speed (rpm) -- CCSSC

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Date Posted: 18:17:36 02/20/05 Sun
Author: Nick Bird
Author Host/IP: Quebec-HSE-ppp3619516.sympatico.ca / 65.93.220.25
Subject: Chris-Craft 327F low engine speed (rpm)

I have a 1968 CC Futura (Plywood cruiser in the Cavalier style). Bought it when the twin 327F engine hours were low but have never been able to get high rpm (3500+)out of it. Over the years I have re-built the distributors, carburetors, added optical ignition, hydraulic trim tabs but each time only added 200 rpm. Compression is good. full 32 degree advance acheived at 3200 rpm. Vacuum falls off quickly with load. top rpm achieve is 3600 with secondary choke plates forced open (not enough vacuum to open these counter-weighted plates naturally. Propellers are 15X10 which I understand are undersized (verified by top speed being much lower than expected at 3600 rpm too). Any Ideas? Have heard it could be tired valve springs but many mechanics disagree with that theory.
Any opinions would be appreciated

Nick Bird
nick.bird@sympatico.ca

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Replies:

[> Re: Chris-Craft 327F low engine speed (rpm) -- Nick, 14:36:04 02/23/05 Wed (w040.z208037156.nyc-ny.dsl.cnc.net/208.37.156.40)

Look into your fuel system. Tank, Lines, Filters, Pump, Carbs. Check for partial or intermittent clogging in the tank, lines, filters (usually caused by rust or contaminant). Pump pressure and mechanical operation or hole in diaphram. Carbs check floats.

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[> [> Re: Chris-Craft 327F low engine speed (rpm) -- Ken J., 14:56:31 03/04/05 Fri (adsl-19-230-232.bna.bellsouth.net/68.19.230.232)

Nick - This is most likely not going to help you, however, the Chris-Craft Service manual on propellers shows a 28' Cav. Futura with twin 283's which calls for 14x10 props. The 31' Cav. Futura with twin 283's calls for 14x11 props. The smaller Futuras are shown only with a single engine. I do believe valve springs can fail. When I rebuilt my CC K-95 I found three valve spring broken off at the top. I could not find new springs that were stiff enough so I borrowed some from an old K-95 I had. That engine had five broken springs. These engines were orginally built in 1955-56. Good Luck, Best, Ken J.

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[> [> [> Re: Chris-Craft 327F low engine speed (rpm) -- Nick Bird, 21:51:21 03/04/05 Fri (Quebec-HSE-ppp3619516.sympatico.ca/65.93.220.25)

Thanks, I'm going to re-check the fuel system and also home in on the valve springs. I don't think any are broken as we'd notice that when adjusting but some may have weakened. Nick

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Re: Chris-Craft 327F low engine speed (rpm) -- WoodenBNut, 14:47:11 03/02/05 Wed (ns.courtclerk.org/216.68.49.2)

Well, yes. The valve springs might just be a factor in not being able to attain higher rpm. If the springs have never been replaced, they could definitely be on the weak side. *I really don't think the original factory springs were that good anyway. A fellow boater in the dock row that I am in had a CC 307, 327 or maybe a 350 (can't remember which). but he had a similar problem and he installed heavier valve springs and it made quite a difference in the way the engine ran. Also, there is a 'gizzmo' available that will allow you to change valve springs without removing the heads. *It keeps the valves from dropping down when you remove the keepers. Can'y remember where I saw tool advertise though. Once you got that tool - I would think you could change out the valve spings in maybe 1/2 a day. try it one one engine 1st. It can't hurt - will only help.

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[> [> Re: Chris-Craft 327F low engine speed (rpm) -- Nick Bird, 20:19:00 03/03/05 Thu (Quebec-HSE-ppp3619516.sympatico.ca/65.93.220.25)

Thanks for the input on the valve springs. The symptoms seem to point to that due to the early loss of vacuum at higher speeds. The gizmo for changing the valve springs and the valve seals is a tool made from a spark plug to supply compressed air to hold the valves up while changing. Some mechanics have these.
Nick

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