Big Cam with Speed Density?

[White86FiveOh]

Hey folks!
I'm new on here but not to stangs, I wanna know a few things about this one I just picked up, its an 86 GT 5.0L automatic... I'm gonna be installin 4.10 gears but I remember I hread once that speed density doesn't work well with big cams? Funny because I had an 88LX 5.0 with a B-cam and a 5 speed and it worked beautiful, sounded awesome!! Whats the biggest bumstick I can slide into that engine without running into too many problems? I don't want to dig into it and find that I have to order a mass-air kit, Ijust want to do it all in one day and not worry about all that other BS that goes along with electrical conversions! Also, Its an AOD with a 2500 B&M Converter and B&M kit, Only mods are an Accel coil, wires, cap + rotor, and a circa 1990 flowmaster cat-back

Thanks a ton Ladies and Gents!

Mark

86 GT 5.0L AOD, Old Rusty Flowmasters

 

[_jb_]

The 88 might have had a Mass Air Convertion. I believe that you can only go with mild cams for the Speed Density

 

[White86FiveOh]

my 88 was speed density....
I wouldn't mind putting a B-cam in this car too, however I don't know if there were any variations from year to year in engine/computer/injection, I know in 86 the heads were cheap-ass swirl port heads, and I have a set of wildly ported (Billy Howard at Howard Race engines, Barrie, Ontario) E7 cylinder heads that I'm gonna bolt on at the time I do the camshaft, and probably buy an intake too...

Thanks again
Mark

86 GT 5.0L AOD, Old Rusty Flowmasters

 

[ECU5.0]

with those heads and a cam youll probably run into problems with the speed density. it wouldnt cost too much to conver to mass air. a lot of people on here have done it for around 100 bucks i think

 

[Michael Yount]

Even with the mass air conversion the 'big' cam is a bad idea on an otherwise stock motor. It will kill bottom end, and the stock valve springs will likely float before you can rev high enough to make any more power than stock. Cam should be done last AFTER heads, intake, exhaust. Many folks out there run VERY respectably with speed density, stock cam and the other aftermarket goodies mentioned above.

 

[z9_87]

yeah i did my speed to mass air conversion for $100. Just do that and get it over with, then go wild.

 

[maverick0716]

"Big cam" and flat top pistons with no valve reliefs usually isn't a good combination.

 

[White86FiveOh]

Where did you gusy find all the pieces for the mass-air conversion for less than $100, I looked high and low, for about 3 months before I put the cam in my 88, and I couldn't find anything for less than $500 around here!!!
Aside from the speed density problems, even though its not a big cam will a B-cam fit into the 86 engine with the flat tops with no reliefs, and the E7 heads?? I also just scored some BBK Long Tubes and a matching BBK H-pipe for cheap, they're going on when I do it all so the car will be outta comission for a few days!! I want to gather as much info before I dive into it so that I don't run into much problems with it! Its already a pretty quick driver, but it doesn't even compare to what my 88 LX did...
If all else fails, I can always put the cam in it (assuming it clears the pistons) heads, and such and if it doesn't work out well buy the pieces for the mass-air conversion...

Thanks Again Guys!

Mark

86 GT 5.0L AOD, Old Rusty Flowmasters

 

[Michael Yount]

Mark - I don't think the B will clear without relieving the pistons. I just measured a friends 86 w/flat tops, ported E7's and a TFS stage II - which has similar duration to the B. It wasn't even close to clearing. In fact, it wouldn't even turn over without them hitting - let alone having sufficient clearance. The intake valve was .08" too deep (would've hit the piston); the exhaust cleared - but not by enough. It had about .06" on the exhaust - need .100" mininum. You'll need to measure to be sure, but I don't think you're anywhere close. In any event, I don't think the B works that well with the stock heads anyway. It's designed to work with better flowing aftermarket intake/exhaust/heads.

Oh, and I can almost guarantee you that the speed density system isn't going to like the B at all. The speed density system monitors engine vacuum; anything that changes the vacuum significantly at idle really gives it fits. And the B will definitely change the vacuum at idle.

 

[White86FiveOh]

Time to bring the degreeing set home!

How does mass-air work, if someone has the time to reply?

Thanks

Mark

86 GT 5.0L AOD, Old Rusty Flowmasters

 

[Michael Yount]

Speed density uses rpm, throttle position, manifold pressure and temps to calculate, approximately, how much air and therefore oxygen is entering the engine. Based on those calcs, it determines how much fuel to add. Mass air uses the maf to actually measure the mass of air entering the engine. The primary difference is that when you mod speed density, and your changes alter the amount of air entering the engine far from what the computer's calcs/tables were based on, it injects a non-optimized amount of fuel. With mass air, since it's actually measuring how much air is entering, when you make mods that affect air flow, it's measuring that change, and the computer can compensate. There are limits of course, but it has more flexibility to adapt to changes than the speed density system does. The change was made to allow tougher emissions and fuel mileage targets to be achieved.

 

[5.0Droptop]

The crower 15511 cam is an awesome SD cam but you will still need to measure VTP