What would make my 454 engine race so fast that it sounds like it will throw a rod ?
We replaced a fly wheel and put a new starter with 10 teeth on my 1983 winnabago Brave class A motorhome. Went to start it up and it sounded as if it got an instant shot of speed. Like a sewing machine gone ramped… Could it be a clutch fan???
A seized fan clutch can make it sound quite loud, but does not affect engine speed.
If it is indeed revving high, the cause is almost certainly in the engine air intake system. I’d first look for an intake air duct or vacuum hose that’s not connected.
It might be as simple as a broken spring on the throttle cable/pedal. Won’t return up ? The pedal might be moving but not the cable ?
Or the butterfly valve controlling air flow into the intake may be at at fault. or a choke mechanism getting stuck , in a carburreted vehicle… an automatic perhaps ? Typically just ran off a bimetal strip mechanism…
But if you were doing work around the firewall parts, then you might have removed a vacuum hose, letting a bunch of air into the intake manifold after the buttlerfly valve… just after, and before the flow sensor ?
In a carburetted vehicle, it wouldn’t run as it won’t get extra fuel with the butterfly vavle at the regular idle position… the extra air will make it very much too lean…
but in a fuel injected engine, the injectors can supply heaps of fuel despite the butterfly valve position…
Jammed or bent throttle linkage?
Are you sure the engine is revving? I’m thinking your new starter is not disengaging and making it sound like the engine is revving.
The tooth engagement to the ring gear needs to be checked when replacing the starter and shimmed if needed. If the gear contact is too tight the starter won’t disengage when you release the key and make quite disturbing noises.
The vacuum modulator on a T400 is on the right side, under the dipstick and cooling lines. This may be a good place to check first.