[DeTomaso] Muffler Opinions

[MikeLDrew at aol.com]

In a message dated 7/31/10 20 40 32, bjbstewart at yahoo.com writes:


> 
> So, I ask for your help.  What would match a high output stroked Cleveland
> engine with sound that will make the DeTomaso community proud? 
> 

Well, I'm particular to my gutted ANSA exhaust, but I realize that it is 
costing me horsepower.   Gutting them picked up 12 hp, a useful gain, but I'm 
still probably leaving a fair bit behind.   But then my engine was designed 
around a restrictive exhaust to compensate for that.

I think your problem is most likely NOT exhaust related.   Either your 
engine needs to be tweaked, or your engine builder had his 'thumb on the scale' 
when he produced the dyno numbers.   But the first option may well be the 
case.   My car has a new 408 stroker, and although it ran pretty hard, it 
wasn't perfect.   It had what felt like a lean stutter at cruise and light 
acceleration, and it had some slight detonation.

Today Stephane Bergeron attacked it with me.   First thing we did was check 
the float level, and found that the primary floats were adjusted too low 
and the secondaries too high.   Next we put a timing light on it, and found 
that the timing had moved (distributor slipped, since it's a gear drive) and 
advanced four degrees.   I was running 16 degrees initial, 32 total, which 
caused surging and bucking at low speed cruise, and detonation under hard 
acceleration.   We retarded it back to the original spec, 12 initial/28 total 
(CHI 4V heads are VERY efficient and thus don't need a lot of advance--in fact 
dyno testing proved conclusively that performance fell off with any advance 
beyind 28 degrees).

Finally, the idle mixture was a bit rich so we turned that down some.

Woo-hoo!   The changes in performance from those subtle changes were 
astounding!   Turning onto the freeway onramp, I rolled into the throttle and the 
tires just erupted in smoke!   Pulls hard all the way to the 6500 rpm 
redline, no pinging, and it's much more docile at low speeds too.

Shoveling money at an exhaust system should be your last resort.   Somebody 
told me you'd never even put a timing light on your motor, although that 
was some months ago and perhaps you've done so since then?

Mike