i just purchased the GM dual TB 7.4L. this will be replacing the above. i read the sticky on holley and GM. is the stock 7.4L TPS sensor correct on this 454TB or does it need to be swapped? i assume i could cross reference with my existing but thought i would ask the question. what is the favored adapter plate?. i though it was said howell make a decent unit. i see holley makes a heated(coolant) adapter that may be better since i am lacking heat at manifold. this is one reason going to a dual TB rather than my prior xram. my single plane is already shaved for clearance so will use it and expect with drop down air cleaner will be OK. also the setting on IAC needs to be reduced 50% is that correct? the connector from current TBs will need to be spliced together? parallel? i read the speed sensor area of sticky. does not the bracket from 7.4 pickup available to bolt on? also one would think a standard throttle cable would be OK. Please give me some tips on how this has worked out for you !!

 

Can I ask why you're changing over to a single dual bore tb from your current twin single bore tb setup?

Steve

 

is is somewhat of a gamble. are you familiar with xram? it is a single plane mani with a custom plenum on top. picture two pie plates in thickness and attached to mani with a bore for each TB. the design was to accomodate the crossfire in total. a bolt on program with clearance for vette hood. all linkage stock. uses stock TB's. the TB in my case 90 lbs sprays on plenum floor. from tip of inject to floor 1 1/2 to 2 inches? the atomized spray needs to make a sharp right angle to plenum of single plane and then another right/left angle into intake runner. imagine the unatoimized fuel forming a river/puddle on plenum floor. my heads have no coolant crossover and my intake has no coolant benefits that i am aware of. with cool temps not the best. if used south US, fine. now the air flow through the system is not an issue. flow #sare fantastic. however if you nail the throttle air comes rushing in. AE/TPS/MAP needs to be increased. i am at 4000 usec while stock i think is around 2000-2500(not sure). so i get a bog/stumble cool weather. moderate accell is OK. normal driving is OK. took all summer increasing the AE to diminish the bog with more pump shot. no vac leaks. now with the 454 7/.4 L dual it will provide fuel direct into the intake plenum/no convoluted passage, straight into my 2.02 valves. i can add a coolant adapter to boot. comments appreciated.

 

There are a few of guys on the boards running crossfire. One on a 400sb(Tom) one on a corvette with a blower(Joby) and the other on a 350sb(Grumpy). Grumpy lives in Ohio, he might be able to help you out with a few issues. I gave him an adapter off a 454tbi setup that bolted to a fourbarrel intake that had provisions for coolant to be plumbed through it. He made a plate for his crossfire manifold to be able to run the 454tb on top. He said it worked pretty well. If you don't know of Grumpy he most frequintly visits the diy-ecm board. He's the ecm guru and has a lot of post and about a dozen stickies.

Steve

 

i guess i gave up on my XRAM/ crossfire. maybe too soon. anyway it has some design flaws that are impossible to improve upon unless the hood is modified. i cant see a down side on the 454 TB? should be more flow efficient as a straight shot. i believe it can be bored as well to 2.13 but that may be unnecessary. plan is to swap a cam(222/234 @.05) in this spring and spin motor 5500-5800 rpms(350 cid). hopefully it can supply enough air/fuel at WOT. should be able to determine that with my WB02 and a vac gauge on windshield?