Hey Tom, good to see you here. After the forum went belly up I lost interest in it and I' completely out o the loop now, I don't own a single CFI car anymore. Only CFI and X ram junk on the shelves LOL

That conspiracy theory was taken straight from the ancient Crossfire FAQ

 

Tom - what are your recommendations on picking a cam? How do you size the cam to the displacement of the engine to make it similar to the original torque curve?

 

FP check is easy; "T" into the fuel line between the engine and frame on the passengers side. Should hold set pressure at all RPM's and loads.

Is your "roughness" a misfire issue? Or a internal balance issue? If you get the engine up to the speed of the vibs and cut the ignition, do the vibs remain or instantly dissapear?

 

Man, it's great to hear from/see you too! Been a LONG time. I figured that you'd end up out of the CFI scene, just because your goals seemed to be taking you in a direction that CFI could never support. I don't have any CFI stuff anymore either, except a couple intakes ported and stock. I miss it though. I frequently day dream about buying an '84 4+3 and RE-proving to people what can be done w/one, with good documentation.

I don't really want to make a cam recommondation, 'cause it's not MY car. I got lucky when I did my combo, but I don't think that it's extremely critical what cam you use, as long as your in the ball park with duration and lobe separation. Divide your CID by your stock cam duration. Then divide that number, by 383 to give you a ball park cam size that is reletively a similar size. But based on MY experience and results, I'd guess that something in the low 220's range on a 112 split would work pretty good. You can pushing it farther than that, but the farther you push, the more you'd have to be willing to accept for idle/fuel economy/driveability issues. Know that in my 400 with the 224/234, it ran like stock...only way, WAY more so.

 

Internal balance issue?

 

it is all ball bearings these days, didnt you get the memo ?

 

When I blew up my 3.23's I replaced them with a set of 3.42's that I had left over from my 4th gen and the car actually slowed down in the 1/4...

I suspect that the reason you gained was the big cam in your 400.

 

I got tired of t-ing into the fuel line and drilled and tapped the aluminum cover for the top of the front injector pod for a shrader valve pressure fitting that I pulled off the fuel rail off of some random GM car in the JY

 

Yep, that, or a schrader installed in the tube connecting the TB's is the way to go...for tuning and repeated tests. For a one-time test for diagnosis though, the "T" in the rubber line should suffice.

Maybe. Keep in mind too, that I had a T5. So the gearing and "tq converter factor" was different. I liked the 3.23's too, don't get me wrong. They were WAY better than most of the other F-bod options.

 

Call me squeamish or whatever, but I'm a little too wimpy to cut into a fuel line and T into it.

 

 

This thread kind of steered off topic (history/restoration) two pages ago, why hasn't the thread been locked or moved to the general tech forum? Modification threads really don't belong on this sub-forum.

 

No need to cut anything, and no need to be squeamish.

*Remove the rubber fuel hose from the fuel filter.
*Insert a "T"
*Add a piece of rubber fuel hose, to another barb on the "T" and connect the opposite end to the fuel filter.
*Attache the rubber fuel hose from your fuel pressure gauge, to the third nipple on the "T"
*Commence pressure testing precedure.

We're talking a spec of 9-13 PSI here. This is no big deal. A agree w/83CrossfireTA, that if you're "tunning" and adjusting pressure all the time, his method is way easier in the long run. But for a one-time diagnostic test, HISTORY has proven that this is the fastest, easiest, cheapest way to get the data that you need. Historically.

 

History - I like that Tom!

 

I believe that spec is actually 9-12psi, and most people find that they run best at 13-15 (if your stock fuel pump can keep up).

FWIW, I actually started a fire disconnecting the line between the filter and front TB- it runs behind the alternator, and when it was loose it tagged the bat terminal on the back of the alternator, shorted and arced, and I ended up with a jet of buring gas shooting straight up... dumb (bad) luck.

FWIW2, it's not actually the correct way. The factory answer is to disconnect the line between the 2 TB's because the accumulator in the front TB can affect readings. I used to have a shrader valve t-ed in that line but after a while I got concerned about it getting tangled in the throttle linkage (either making it stick or knocking it loose eventually) which is why I plumbed it where I did, just adding a permanent test port where it was solidly mounted and generally out of the way.

 

Thanks guys. That helps me visualize both ways.

 

I read in a Camaro book that GM had a trailer full of cross ram carb intake manifolds and told the engineers to make use of them: thus that is where the entire crossram FI came from. and thats why the idea was somewhat flawed in the first place. Because really its just a modified carb setup.

I know that was mentioned, but I think it was kind of a more "make it work" concept . Either way the hoods were awesome. They should of incorporated that into the iroc somehow.

 

The base plate of the CFI is in fact based on the 1st gen Z/28 Crossram manifold. Apparently, GM still had the tooling and didn't want to spend money on an all new set up. Obviously, things work differently on a high compression, big valved, big cammed, 7200 RPM motor with dual Holley 750 cfm carbs, than they do on a 2 X 200 cfm TBI, 4500 RPM, smog legal Crossfire. For one thing, the runner size was greatly reduced to keep velocity up. Fuel distribution would have been better had they moved the rear TB forward and the front TB rearward, basically a mirror image, (that's what it's Chief Engineer said anyway), but these were it's design restrictions based on GM penny pinching.

There was a lot of potential still left in the CFI system, had development continued. But immediately after it's release, all work shifted to TPI. And if you really look at TPI, it's almost a port fuel injected version of CFI with some bugs worked out.