GT40 vibration

[dwsa]

Hi Guys, I rebuillt my Ford GT40 engine with a complete set of iron eagle conrods that were lighter than the original conrods. Now I have vibration at idle, (in neutral) gets worse in the 1400 to 2000 RPM range, and is smooth after that. Could this be due to the lighter conrods?? I have read that the damper reduces crankshaft torsional vibration and does not do anything for an out of balance engine. Do I have out of balance with 8 new rods being lighter than original? No balancing performed during rebuild, just threw in the new rods. I have checked everything else and can't find anything wrong. Appreciate your thoughts, don't want to be chasing a red herring. Also, on checking the base timing I found the the graduated scale indicating TDC is not TDC, the TDC is the large slot cut in the damper approx 90 degrees apart. I read that Ford uses two different types, and looking at dampers on summitt website, some have two graduated scalesto accomodate this . Is anyone else aware of this, threw me for six. Thanks Greg.

[Rick]

RE: GT40 vibration

Is the engine running on a stand or in the boat. Is the tranny hooked to it. Vibration as you describe is almost always engine alignment if the engine is in the boat and hooked to the prop. The shaft and tranny need to be plus or minus 0.002. Also the boat needs to be in the water when you align it as the trailer may not support the boat the way the water does. Good Luck

[surroundsound64]

RE: GT40 vibration

I'm with Rick. Sounds like engine/transmission/driveshaft alignment.

[dwsa]

RE: GT40 vibration

I'll check the prop alignment is the water, but note my vibration is in neutral as well as in gear. Cheers Greg

[richard]

GT40 vibration

Ckeck to confirm every sparkplug fire while engine is turning ,if one not fire will entire same your case. some time the ceramic will break when tight the plug and arc will appear hence spark on outside.

[boatech]

RE: GT40 vibration

you should have sent new rods new pistons flywheel and balancer out and had it all balanced as an assembly. not saying it is your problem but it sure could be.

[dwsa]

RE: GT40 vibration

That is too specialised for Dubai workshops. Nobody here does crankshaft balancing. My best option would appear to get nearer to factory balance with stock conrods. Stock conrods are 702 gms, my new ones are 570 gms!! oops!