Accidental performance increase ??

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katsi

Accidental performance increase ??

Post by katsi »

First off, the only proof that any actual performance enhancement was achieved was via my butt meter attached to the seat. Yet, I thought it would be a good idea to get everyone's input on the subject. So here goes :mrgreen:

Reciently, I swapped out the old carb set up on my 79 with an older style intake and DFEV 32/36 Webber. As many here may well know, that involves plugging up the read valves in the head. Anyway, with the help of a few people on this site; the swap went fine and my car has been running great ever since. So, last Friday I was driving home from work when I noticed a shutter comming from somewhere. Immediatly, I shut off the radio and realized that the shutter was more of a noise comming from the engine compartment. With a few quick diagnostic throttle pumps, I simply wrote it off thinking that the spider's new exhaust pipe had sprung a leak and any worry associated with the noise emminating from the engine compartment could wait untill I got home before further investigative measures were needed. This is when I noticed that my spider had a little more pickup. Sure the noise was horrible but, she just seemed to have a little more giddy up. Now, normally I would agree that the absence of the cat and other obstructive exhaust issues would amount to the increase in HP I was experiencing but, I had already had a new pipe welded in that did away with the cat. In fact, my little car has virtally nothing more than a straight pipe leading to a simple muffler. Yet, dispite the noise, she just seemed to slip into gears a bit faster and zip down the road with a bit more enthusiam. Ten enjoyable miles later, I arrived at my driveway, shut her off and popped the hood for the initial look-see. Immediatly, I noticed that the read valve plug had come out and was lying right in the valley next to the hole in the head it was previously employed to plug. I left everything as is, went in the house, changed, opened a cold frosty one and went out to see if everything had cooled off enought to put the plug back in. Still a little warm, the valve plug went back in easy enough and I gave it just a bit more tork than the hand tight torkness I initially deemed appropriate for the task. A few moments later, I tossed the open end adjustable on the passinger's seat, leaned over and turned the key. The spider fired up and the noise, allong with the previously mentioned extra giddy-up was gone. Problem solved - or is it :shock: ?? Do the read valves ability to breath really create more HP or was I just immagining the extra zip I enjoyed on the way home? I would appreciate your thoughts on the subject. :mrgreen:

On the lighter side of things, I caught Clint Eastwood in "The Enforcer" this weekend on Encore HD and guess what I saw in the background right after the bomb scen on the police department - A brand spanking new early 70's red spider. Immediatly after that scen, a yellow X-19 can also be seen in the background and it looked dealer fresh as well. :wink:
Last edited by katsi on Mon Jan 28, 2013 5:32 pm, edited 2 times in total.
Weelan

Re: Accidental performance increase ??

Post by Weelan »

I'd guess it's making you run leaner. You can try sticking them in and leaning out a quarter turn at a time and see if it comes back.
katsi

Re: Accidental performance increase ??

Post by katsi »

Weelan wrote:I'd guess it's making you run leaner. You can try sticking them in and leaning out a quarter turn at a time and see if it comes back.
I don't quite follow allong. Can you elaborate?

The read valves are those valves that stick up between the spark plug wires and hook into the stock air cleaner. I think it's a smog thing (just guessing - I have no clue what they are for). When the read valves are off, you can see the flames running through the head on their way to the exhaust manifold. Now that I said that, I just thought about the fact that their might be less pressure to force out the exhaust when it is venting directly out the top of the head. HMM - It's a mystery to me. Maybe I should vent them. Anyone else had this problem. The gurgle is annoying when they are open though. :mrgreen:
Weelan

Re: Accidental performance increase ??

Post by Weelan »

Oh gotcha, I guessed it was something on the other side of the engine. Haha. Ya, possibly a back pressure thing? I don't know. I'm sure you don't have want to leave it out though if you can see the flames. Haha.
So Cal Mark

Re: Accidental performance increase ??

Post by So Cal Mark »

the reed valves allow air to be pumped into the exhaust port right near the edge of the exhaust valve, promoting more complete burning in the port. If you noticed a perf increase I'd say you have an exhaust restriction somewhere. Try doing some split times w and w/o the plug to see if the car is really quicker
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