Question for Jay Brown - 48IDA's on 427 SO

[emorrison96]

Jay - I just picked up your book this weekend even though I already have my next project's induction system picked out.  I wanted the book for additional information on my setup as well as future projects.  Thank you for your time and effort putting it together and publishing it!

My question is regarding your IDA's on the Blue Thunder intake.  I gathered from the book and additional posts that you used 43mm venturis, 170 main jets, 155 air correctors, and F7 emulsion tubes.  Would you happen to have the specs on everything else, namely idle jet and idle jet holder size, pump jet size, and exhaust jet size?  Any comments on timing?

If I read correctly the camshaft in the 427 side oiler used for this run was a solid roller with a 110 LSA.  Were there any issues at idle?  Just asking because it seems like an aggressive profile for webers.

Basically, I want to make an exact duplicate of the engine you used for testing and since my tuning skills are limited I would like to get it as close to dialed in initially as possible and I apologize for the plethora of questions

[jayb]

Hmmm, offhand I don't know the specs on the parts you are looking for, but I still have the setup.  I will try to get a chance to take a look at it in the next few days.  One caveat on this is that I just ran the carbs with whatever idle jets and jet holders came with them.  On the dyno you are concerned with wide open throttle performance, and I'd already spent a bunch of money on the Weber setup plus the selection of main jets and air corrector jets, so I didn't want to spend any more on the other components.  I guess what I'm saying is that even if you duplicate what I have, there is no guarantee it will work in the car; idle and off-idle characteristics are best tuned in the vehicle, not on the dyno, and my setup was not tuned at all for these parameters.

As far as timing, I'm pretty sure I ran 36 total on that engine, and I don't recall having any issues at idle, but I ran the idle on that engine around 1000-1200 RPM.  Again, I wasn't paying too much attention to that, just wanted to get the HP and torque numbers.

[emorrison96]

Jay,

After doing more research it looks like the cam that was used for the 427 side oiler testing was the most aggressive solid roller that comp cams makes for the FE.  While people typically recommend a wide lobe separation angle for Webers, 110 degrees is the tightest that I have seen and many have used it with no issues.  During your dyno runs with this cam/induction setup, did you notice any popping, spitting, fuel clouds over the stacks or any other signs of reversion?  I want this to be a street vehicle so I don't want any fuel deposits on the underside of my hood or anything like that.  Any details or opinions you have would be greatly appreciated!

[jayb]

One thing about the Webers is that they really seemed to run smooth on all the engines I tested them on.  I never had popping or spitting issues.  Regarding reversion, I think you are always going to have some with an individual runner intake.  That is just how pressure wave tuning works on a short intake tract like you have with the Webers.  I remember at least once seeing the "cloud" above the carburetors (can't remember which engine that was), but it did not affect the way the engine was running during the dyno pull.  Put some air cleaners on the stacks and you shouldn't have any issues with fuel in the engine compartment.

By the way, the cam in the 427 sideoiler dyno mule is far from the most aggressive cam that Comp offers.  It is actually a pretty good street cam for a strong engine, especially in a light vehicle or with a lot of cubic inches.  But I guess I wouldn't let the induction system dictate your cam choice, especially with the Webers.  They have such a broad power range it seems to me that they would work with a wide variety of cams; the dyno mules I tested them on had anywhere from 236 to 266 degrees of duration at .050" lobe lift, and they all worked great with the Webers.

[emorrison96]

Will do on the air filters.  Thank you for all of your expertise!