they say it cant be done....

Topic: they say it cant be done.... (Read 4319 times) previous topic - next topic

they say it cant be done....

September 19, 2009, 12:16:17 AM

putting a cam in a speed density car without idle surge and poor driveability.

i just put a b303 in my car with a HO computer and it idles perfect. i guess this is just another thing that makes my car a freak.

http://www.youtube.com/watch?v=UJS_X3r0eWU

they say it cant be done....

Reply #1 – September 19, 2009, 12:17:47 AM

and yes i know my car needs to be washed

they say it cant be done....

Reply #2 – September 19, 2009, 01:08:57 PM

Sounds good. I didn't see any benefit from the mass air swap so I doubt you're missing much there. All my sensors were working correctly to begin with though.

I've only washed my car like 3 times over the last 3 years as it looks better hiding some flaws in the paint. I didn't wash it any of those - it's always shops.

they say it cant be done....

Reply #3 – September 19, 2009, 04:41:09 PM

I had a low miles 85 LTD LX 5.0 HO with CFI, the body rotted in half. I took that block/heads/cam and swapped it under my speed density system in my old 87 XR-7. Ran fine. I don't know what cam was in that LTD-LX from the factory. At the time I didn't know anything other than "it fits, so it's gotta work!", heh. It ran way better than the stock block (stock block had 167k miles on it, and 2psi oil pressure though...)

they say it cant be done....

Reply #4 – September 19, 2009, 07:15:30 PM

Let us know how it runs on the road in comparison to what it was before.

they say it cant be done....

Reply #5 – September 19, 2009, 10:57:46 PM

Quote from: Dougy_Fresh;291741

putting a cam in a speed density car without idle surge and poor driveability.

i just put a b303 in my car with a HO computer and it idles perfect. i guess this is just another thing that makes my car a freak.

http://www.youtube.com/watch?v=UJS_X3r0eWU

I've definitely had a py idle ever since going to aftermarket cam+19# injectors+AFPR+65mm TB. I've learned to keep one foot on the brake one one on the gas when I'm stopped and the engine is still cold to stay above idle. I tried asking my mechanic to switch it to mass-air and he couldn't figure out how to make it work.

they say it cant be done....

Reply #6 – September 19, 2009, 11:08:34 PM

look up mass air conversions for fox body mustangs and its exactly the same. are you also running a HO computer? if not the injectors are probably screwing you all up. that and your firing order is probably way off sync with your injectors.

it runs great down the road by the way. i'm going to putting flowmasters on it soon with either 2.5" pipes with no crossover or a 2.5" h-pipe, not sure yet. also putting on a ported out factory intake as soon as i finish it and redoing my CAI because it's pretty ghetto and probably hurting flow some. i'm debating on putting 3.45's in it or just going ahead and stepping up to 4.10's because i know i'm going to end up doing it anyways.

they say it cant be done....

Reply #7 – September 19, 2009, 11:13:16 PM

Nope, I'm running the stock '87 SO computer. I don't know what cam is in it...maybe an 86 HO cam? The car runs fine above idle, it just idles py. When I get a chance I want to check my plugs again. They're only about a year old, but the idle was super-smooth for a few months after I put them in.

they say it cant be done....

Reply #8 – September 19, 2009, 11:14:08 PM

firing order still stock or did you/your mechanic change it to the HO firing order?

they say it cant be done....

Reply #9 – September 19, 2009, 11:27:10 PM

I'd have to check (it's at the shop so I can't check now). I thought there are aftermarket 5.0 cams that keep the stock firing order. Isn't the 86 HO cam the same firing order?

they say it cant be done....

Reply #10 – September 19, 2009, 11:30:37 PM

as far as i know all 5.0 HO's use the 351w firing order. they do make cams that keep the stock firing order but they are pricey and there arent many grinds available i dont think.

if the one you have is for an HO though you definately need an HO computer and HO firing order for it to run right. i have basically the same setup as you (unless you have a monsterous cam) and mine runs perfect.

they say it cant be done....

Reply #11 – September 20, 2009, 01:21:53 AM

Something just dawned on me about the SD and lopey cam topic. I read this post earlier, and didn't give it much more thought, other than being jealous of a 5.0 in a Bird. I was reading something else about SD systems over on SBFTech, and it twigged this message in my head.

Most of the surging erratic idle problem with SD's and aggressive cams are due to intake vacuum pulses driving the MAP bonkers. I've read about that THOUSANDS of times, just looking for one differing opinion from someone with SD experience. That said, in most applications where it's a big issue, the MAP is connected by rigid plastic tube directly to the intake, with very little rubber hose, and the lack of one other little component that I noticed on our Fox body cars. The 6 feet of rubber tubing between the intake and the MAP on our cars will absorb a lot of the pulsations caused by radical cams. But, if you look under the washer reservoir, there's a nifty little vacuum reservoir teed into the line going to the MAP. I haven't checked the EVTM yet, but as I recall, that one has no check valve either. That little reservoir will act as a fairly decent filter (called an accumulator in the pneumatics circles) to smooth intake vacuum ripple caused by aggressive cams, to some extent anyway. I've never seen that reservoir in the MAP circuit on anything except our Fox body cars, but I can't say I've really looked for it either. I just know that the MAP on my 5.0 truck is about 18 inches away from the intake and is piped with very rigid plastic tubing with a much larger diameter ID. NO FILTERING at all. Of further note, there is NO DIFFERENCE in the MAP for a 3.8 and a 5.0. They ARE interchangeable. I've done it.

I don't know how aggressive a B303 is as opposed to the RV cam everyone recommends for the SD system in 5.0 equipped trucks. On the other hand, I have to wonder about the ill effects of that "filter" being there, and how much lag it's going to cause in the MAP signal, and if that indeed would ever be noticeable or critical. Then again, I have to wonder if this isn't why our 3.8L is such a gutless wonder when smaller displacement engines now turn out more than double the horsepower and torque.

I run a pretty wicked cam in my VW, and based on experience, it ain't just electronic systems that have big issues with big cams. I have a Weber progressive 2bbl on the bug, that runs like poopy on the cam I have now. This one is only slightly more aggressive than the one I had before, but I must have crossed a line on the Weber with it. The carb's going for rejetting soon.

My point here, is that there certainly appears to be a solution for SD systems to tolerate a decent cam and the loping idle that comes with it. The OP may have just enlightened us.

I may have just come up with another experiment to try on a stock setup to see how it affects a 5.0 by adding that accumulator.

they say it cant be done....

Reply #12 – September 20, 2009, 02:14:58 AM

Interesting...sort of like adding a capacitor to smooth out signal noise :hick:

they say it cant be done....

Reply #13 – September 20, 2009, 09:52:07 AM

my MAP line comes straight off the intake and goes to the sensor, about 9 inches of reinforced rubber fuel hose. i have no vacuum lines except the FPR, MAP, and brake booster. the tree has been eliminated.

my brother has been thinking about adding an extra vacuum canister to see if it would smooth out the idle a bit on his F303 equipped 88 mustang. i personally fully intend to upgrade to MAF when a 90mm MAF housing and the other parts i need make themselves known at a super cheap price that i simply cannot turn down. i know that 90mm is to big for my current setup, but i do not want to have to buy parts twice. this car MAY end up turbocharged, and if not it will be putting out about 400hp at the crank N/A in about 6 months, so i will need the larger MAF housing at that point either way.

they say it cant be done....

Reply #14 – September 20, 2009, 04:18:37 PM

If you add a vacuum container, it would probably have a negative effect on throttle response.