I spent the weekend putting a gm tbi for a 350 on my 84 crossfire ( I used an adapter plate bolted to the weiand x-celerator that is part of the x-ram) I have been reading lots of cfi to tbi threads trying to see if someone else has done this, because I got the car running fairly well,(seems a little rich at idle, but o2 sensor switches rich to lean like normal) and the top-end power seems about the same, but the low end just isn't there anymore, and throttle response just isn't anywhere near as good as with the x-ram. I was wondering if the upper portion of the x-ram is needed to get the off the line torque and response, and I should try another intake, or if there is something else I should try. Right now fuel pressure is at 12 psi, and I have not made it adjustable yet (stock regulator on tbi, and I am running a high pressure fuel pump). I have ran both the 350 tbi injectors and the cfi injectors, and it runs better with the tbi injectors. I thought about putting a stock tbi manifold on it just to see what it does. (I have one laying around) The reasons I am doing this are partly just to experiment, and partly because the cfi throttle bodies need rebuilt and I have tbi stuff laying around. I guess my main question is - Will I need a different intake with more volume or longer runners to get my throttle response back, or could it be the tbi that is causing the loss of throttle response? (the bores are just slightly smaller than the cfi throttle bodies)

 

I did everything to cfi.. Ported it shorted the runners boosted fuel pressure and nitrous. It has huge down low torque. If your cam and heads are still stock you miss the low end. I built a 383 with afr 195 heads and a 2802s 12 cam 490 510 lift from crane for it with lots of vacuum and it ran 13.0 quarter times. Cfi can run fast you just need to port the heck out of the intake. With nos I went 11.8. If you need help with let me know.

 

Confused.
What intake do you have the TBI on ? you say the TBI is " not as good as the X-Ram" ??????

Do you still have stock heads and cam?

 

I think the the factory cfi intake is not as bad as people think you just have to shorten the runners and in large the ports. I didn't convert to single tbi I just kept playing with duel tbi system. Many combos. Heads and cam have to go. My first combo was a small comp cam 450 lift and ported aluminum 88 vette heads that ran 13.5s. To help with the original question try increasing the fuel pressure to 13 or 14 lbs. also what chip is in the ECM ?

 

I put a truck style on my tbi in place of my cfi, I reused all the wiring. I used a sy1 intake (crossram) & a holley tbi intake (like a dual plane), I was happier with the holley intake. These modern dual plane intakes are closing the performance gap with the similar single planes.
I'd get the fuel pressure adjustable, it'll help with tuning it. Check out my engine pictures in my profile, it shows the sy1 intake.

 

Thanks for the replies, guys. After re-reading my post, I think I may not have explained properly - I do not have the stock intake, it has been replaced with an x-ram intake by the p.o., along with the cam (I just know it was changed, don't know what it is yet) and the heads are stock. The lower portion of the x-ram is a milled down weiand x-celerator, and that is what I bolted my tbi adapter and tbi to.
Here are some pics -
http://s790.photobucket.com/user/***...F0631.jpg.html
http://s790.photobucket.com/user/***...F0632.jpg.html
http://s790.photobucket.com/user/***...F0635.jpg.html
http://s790.photobucket.com/user/***...F0638.jpg.html
http://s790.photobucket.com/user/***...F0640.jpg.html
http://s790.photobucket.com/user/***...F0642.jpg.html
http://s790.photobucket.com/user/***...F0646.jpg.html
http://s790.photobucket.com/user/***...F0648.jpg.html
I made the adapter myself, and all the other parts I had laying around.
I am just wondering if I would be better off with a different intake than the weiand if I am wanting to keep the low end torque I had with the x-ram installed. I will get the tbi fuel pressure adjustable soon, and I am willing to experiment with this for a while before going back to the x-ram. I plan on going through the motor soon and putting some different heads on it, and doing a newer ecm, but wanted to start with this to see how well I could get this working before moving on.

 

another pic of intake.
http://s790.photobucket.com/user/***...F0529.jpg.html

 

I think the tbi systems work better with intakes that have smaller plenums, I think it helps by keeping up velocity in the intake. Kind of like how 2 barrel carbs make good torque on a big engines.

 

That is what I was thinking, and I have a stock tbi intake that I think I will bolt on just to see what it does for the low end. For me, upper end horsepower is not as much fun (pretty close, though) as low end torque, so I will end up doing whatever gives me the most fun. I know all of this has been done before, and even though I have a basic understanding of (some) tuning principles, I have lots of questions and not a whole lot of experience(or money, lol) , but this is part of the fun for me with this car. I can keep tinkering with it till I get it right, and I don't have to worry about having to drive it to work the next day. In the end, I may go back to the cfi, but I was thinking parts are cheaper and more readily available if I go with a tbi setup, and with an adapter plate, I can use any intake I want.

 

OK, I changed my mind, I am not going to use the tbi intake because I have the throttle body mounted backwards, and I really like how everything hooks up that way. Instead, I am going to get a used Edelbrock performer or something like it so I can use my adapter plate. I have found several so far for around 60 bucks, and I bet I can find something cheaper if I keep looking. Any suggestions on intakes to look for?

 

That's the one i'd run, the original tbi intake is marginal, even the edelbrock tbi intake isn't much of an upgrade.

 

With any luck, I'll get a chance to run around this weekend and check out some of the intakes I found on craigslist. I was also able to modify a fpr housing for my tbi to make it adjustable, so I may install that tonight.

 

Cool, I like budget builds.

 

I put on the adjustable fpr and have the fuel pressure at almost 14 psi with the stock 350 tbi injectors. With the weiand x-celerator it makes power and pulls well up to 5500 rpm, but the power doesnt really come on till about 2000 rpm. Today I hope to get to an intake I found on craigslist before it is sold, wish me luck!

 

Got an intake this morning, it's a chinese copy of an edelbrock, but it will work, and it was pretty cheap. Hope to get it swapped out today and see what difference there is.

 

Have it running with the new intake, and performance seems about the same as the x-ram, maybe a tiny bit more bottom end, maybe. It still has an off-idle bog, I guess the right size injectors and f.p. setting will take care of that? I need to write down the injector part #'s and see what I have for sure. Any suggestions for this application? Right now I have 8 degrees base timing and the fuel pressure is at almost 15 psi( the bog seemed to get smaller with higher pressure) The bog passes quickly and runs pretty well other than that with a small(not always noticeable) part throttle surge at slow cruise(20-25 mph) There is no bog if I go wot from about 1500 rpm, but shows up if I go much below that.

 

I'd stick with 350 injectors, try to find some from a cop car, they are rated a little higher.
It could bog if your running an open air filter element in the cold season, I don't know where you live. Has it cold been cold out. What temp does the engine get up to?

 

When I was running it last night it was around 40 degrees out, and running down the road the engine temp stays around 185. I am running a 2" by 12" open element filter (I modified the truck tbi air cleaner)
http://s790.photobucket.com/user/***...tml?sort=3&o=0
The bog seemed to get smaller with more fuel pressure, but seemed to get more noticeable after the engine was ran for awhile, which seems a little contradictory to me. I can kill the car if I am sitting still in drive, hold the brake and blip the throttle. ( it was at about 205 degrees when I did this)

 

The major reason the XF made the low end torque, was those small ports, which, as alluded to, kept the intake A/F mix moving fast. This was done for CAFE improvements, but really hurt high RPM performance. Changing to this or that intake would be unlikely to alter (much) that reduced charge. You are right to ask what others have found to work, but after you decide what you want the engine to do, it must be altered as a system, an air pump, with all parts complimentary to optimum airflow at your desired RPM.

 

I lowered the f.p. to 14, does not seem to run any different. I guess the bog is more of a stumble, you can feel it get rough for a second before it gets up and makes power. I guess I will keep lowering the f.p. 1/2 psi at a time and keep driving it and see what changes, then go back up the same way.