[DeTomaso] FW: Webers -update

[Thomas Borcich]

Jack that's an amazing story. Never would have thought about that one. That might have been the problem on the McLaren because there was  a single throttle cable that came from the drivers pedal, (right hand drive) along side the driver, through the firewall, then made a gradual curve up over the headers which heated the hell out of the linkage hot enough melt the plastic coating if it wasn't rapped with a heat shield material...that heat could have transmitted through to the closest center links on two of the carbs on the driver side and missed the others because they were farther away and the heat disapated never reaching the other linkages. Now that I think about it there was a throttle cable linkage mounting bracket that bolted to the top and bottom of two of the carbs which was right next to and over the headers, that surely transmitted heat into the throttle body probably expanding it also. The headers on the McLaren came up (not down) off the head similar to 180's, curved backward then hit the collector.

I would guess that a 4V head with the exhaust crossover could also heat the manifold enough to make a difference if the linkage bolted in anywhere close to the crossover.

Regards,



Tom 

From: jderyke at aol.com
Date: Tue, 22 Dec 2009 15:19:51 -0500
Subject: Re: [DeTomaso] Webers -update
To: tborcich at msn.com; detomaso at realbig.com

In a message dated 12/22/09 8:28:37 AM, tborcich at msn.com writes:



.....The biggest hassle was setting the linkage set at idle so they were all pulling evenly. Don't know why, but they would change often and were a moving target it seemed every other time I drove the car....



It may have been engine-temp related. Unless the linkage from the throttle pedal goes to the center of the engine with two tie-links- one going to each head, the idle will change as the engine gets hot and expands, pulling on a single steel tie-link. This was found on one Cleveland with IR-EFI; aluminum heads expanded, changing the length of his single tie-bar link and moving the idle up by as much as 500 rpms. He had to fabricate a thick steel strap running from one head to the other to get a stable idle. FWIW- J DeRyke