1st_gen_kid_19

every time i floor it for more than 3 seconds i lift off the throttle and my fb 7 makes a knocking sound i know it cant be rodknock because there arent any i just finished building this engine so i have no idea what it is please help

t_g_farrell

iTrader: (1)

Engine/tranny mounts broken? I'm guessing the engine is rocking around when you let go of the throttle.

SKYDRIFTER350

I get a bit of that... I call it 'bucking', like a horse or motorcycle...Lol.. The condition is most apparent in second or fourth gear at low REVs.. even worse when You let off gas & coast at low REVs as well. So, would You suggest I look at the tranny mounts?
The engine mounts look to have been replaced at some time & look good & solid. I have not seen the tranny mount.

Thx

t_g_farrell

iTrader: (1)

That behavior is the nature of the rotary. RacingBeat sells a bar you can bolt to the rear of the engine and the firewall to help reduce it.

Jeff20B

iTrader: (13)

I wouldn't say it's the nature of rotary at all. It is caused by soft and possibly failing motor mounts. Get competition mounts and don't forget the competition trans mount. The engine will no longer rock and roll on you and it feels like a new car. Well, better than new in some cases.

t_g_farrell

iTrader: (1)

Noted but in my experience it happens very easily at low rpms and gets compounded by your foot moving back and forth on the gas as it happens. It can be kind of comically if you exaggerate it some.

Jeff20B

iTrader: (13)

Yes, my brother's GSL-SE did precisely that. The trans mount was separated and the motor mounts were soft and probably oil-soaked. I'd try to drive it and it would accelerate, making my whole body including my foot move away from the pedal (the seat wasn't adjusted right for me). As my foot lifted off the pedal, the car would slow down, suddenly slamming me forward and my foot back on the pedal, thus accelerating the vehicle and throwing me backwards, lifting off of the pedal again and so on. This oscillation was comical to say the least.

old_skool

LongDuck

Ghetto, but something about it... Whatever works, I guess.