"Pinning" the secondaries open.

[robbz28]

Originally Posted by PhillipsLT5

You should be able to buy 100 unlead race gas, it will be pricey, $6 to 8 per gallon
This should help
http://www.osbornauto.com/blend.htm

The only reason I asked is because my cousin has a crop dusting service just down the road from me and he has a big ol tank of 100 LL.

[Hib Halverson]

If drag racing is your thing, disabling the port throttles might make sense.

Otherwise, on 350s and 368s, the car will probably accelerate quicker, if the port throttles are working. This is because at low rpm, with the port throttles open or removed, air velocity is very low and that decreases torque at the low end and the beginning of the mid range. Engines larger than that are, for the most part, immune from the low air port velocity problem.

As for 100LL, do not run leaded fuel if you have cats or oxygen sensors. It renders both useless in short order. Also 100LL doesn't work as well in a high-rpm LT5 as it does in a low rpm aircraft engine. Finally, it greatly decreases spark plug life.

You're much better off mixing 100 unleaded race gas with pump gas.

[Paul Workman]

Originally Posted by Hib Halverson

If drag racing is your thing, disabling the port throttles might make sense.

Otherwise, on 350s and 368s, the car will probably accelerate quicker, if the port throttles are working. This is because at low rpm, with the port throttles open or removed, air velocity is very low and that decreases torque at the low end and the beginning of the mid range. Engines larger than that are, for the most part, immune from the low air port velocity problem.

Hib...

From the perspective of one that is running sans SPTs, you'd be (pleasantly) surpised to know that ain't so!

Referring to the FSM related to conditions for the secodaries to open, accelleration so light as to keep the SPTs closed is such that velocity is more a factor of the TB plates than runner cross-sectional area. In other words, even moderate throttle demands and speeds will trip the secondaires open - making the arguement of whether to eliminate the SPTs or not becomes MOOT for practial purposes.

However, something I think we'd all be interested in is the affect running sans secondaries might have on emissions compliance. The question has been posed several times, but perhaps Sammy being the exception, to my knowledge nothing in the way of conclusive data has come to light.

From my experience in driving w/ and w/o secondaries in traffic the difference is subtle, BUT it is there. Running w/o those pesky things really makes the LT5 behave in traffic soooo much nicer...is/was my opinion. And, then there's the benefit of having the secondary port valves constantly being washed by fuel. Clean valves are always better than dirty ones from a performance perspective.


P.

[scottfab]

Originally Posted by Paul Workman

... snip...
. And, then there's the benefit of having the secondary port valves constantly being washed by fuel. Clean valves are always better than dirty ones from a performance perspective.
P.

Depending on how you drive, washing the secondary port valves is not a problem. WOT was made for that. (Wash Out Tube)
I have more trouble with the wipers hardening for lack of use. I could just rip them off and toss them but I think keeping things in good working order is best.

[Paul Workman]

Originally Posted by scottfab

Depending on how you drive, washing the secondary port valves is not a problem. WOT was made for that. (Wash Out Tube)
I have more trouble with the wipers hardening for lack of use. I could just rip them off and toss them but I think keeping things in good working order is best.

Parts that don't exist don't cost much and they NEVER fail.

I've had it both ways - have real (not hypothetical) knowledge and I'd not go back to them even if it were an option (not in my case).

I'd bet once you pulled them too, you'd need a much better reason than "working order" to go back.

And nowhere has the topic of performance @ WOT been discussed.

Well, do whatcha want. The pros for NOT having them (for me) outweighs the cons by a wide margin. But, your mileage may vary!

P.

[scottfab]

Originally Posted by Paul Workman

... snip

Well, do whatcha want. The pros for NOT having them (for me) outweighs the cons by a wide margin. But, your mileage may vary!

P.

I think that's it in a nut shell. I value being able to disable the secondaries per the original engineering design because I like the idea of removing temptation from my sons and others AND because I just don't seem to have as many issues with that system as others.
You're right about fewer failures with fewer parts. Still I choose to leave the wipers on the car even though that would be fewer parts to fail.
Each to his own and we owe it to newbies to see a clear picture of removing systems IMHO.

[Blue Flame Restorations]

Originally Posted by Paul Workman

Parts that don't exist don't cost much and they NEVER fail.

I've had it both ways - have real (not hypothetical) knowledge and I'd not go back to them even if it were an option (not in my case).

I'd bet once you pulled them too, you'd need a much better reason than "working order" to go back.

And nowhere has the topic of performance @ WOT been discussed.

Well, do whatcha want. The pros for NOT having them (for me) outweighs the cons by a wide margin. But, your mileage may vary!

P.

Having less chance for vacuum leaks is what motivated me to have Pete remove mine. Glad we removed them.

One less thing......

[mike100]

I would be curious to try a before and after emissions test.

[Fully Vetted]

Originally Posted by Blue Flame Restorations

Having less chance for vacuum leaks is what motivated me to have Pete remove mine. Glad we removed them.

One less thing......

Yep. Pete gutted mine as well.

[sammy]

i will tyr to get ahold of john and see if he has a copy of the test or can give me the new owner