Cam on OBD1.5? and other questions

[19Cutlass94]

I know by putting a large enough cam on OBD1.5 ( since you cant tune for it ) its going to be running a little rich. But how much of a cam is really 'too far'? What kind of lift/duration would you guys say would be good? I was looking at the milzy stage 1 and I believe it was like 207/207. Its going to be run with 1.6:1 rockers. I know I could prolly get away with a little more than that, but whats your opinion?

Also, when swapping 3500 heads onto a 3400, can I keep the stock 3400 pushrods or will I need to get a custom set?


--Jay

[bszopi]

Here is the specs on the regrind I had in my old 3100:

Duration : 214º intake / 214º exhaust (@ 0.050" lift)
Advertised : 274º intake / 274º exhaust (@ 0.001" lift)
Lift @lobe: 0.302"
with 1.6 stamped rockers : 0.483"

Once it was warmed up, it was fine. But when it was cold, you had to help it keep the idle high or it would die. What I used to recommend to people who couldn't tune is 206º intake / 210º exhaust (@ 0.050" lift) and a lobe lift around 0.295"

The MMS specs are as follows:

MMS stage 1 NA

.305/.308 lobe lift (.488/.493 valvelift)
209.4/213.1 duration
110 LSA, 108.1 IC

MMS stage 2 NA

347/.349 lobe lift (.556/.559 valvelift)
222.1/225.7 duration
110 LSA, 106 IC

[geoffinbc]

The MMS Stage 1 cam will work ok. You wont notice any big problems. There was a guy on s-series.org who was able to get his OBD I.5 ECM tuned on his 1995 CPI 4.3L. You may want to check over there and do some searching.

[3100 MPFI]

If it makes you feel any better, I am going to try an OVER .500 lift cam on an OBD2 computer and see what happens.

[PCGUY112887]

If it makes you feel any better, I am going to try an OVER .500 lift cam on an OBD2 computer and see what happens.

So? The popular "street grind" from here has a lift of 533

[19Cutlass94]

Thanks guys!

This cam is gonna go into a motor that Im gonna start to build up. Nothing huge, but its gonna take a while just cause of the cost... You know one of those build as you get money kinda deals...



Ill deff have to check that out and see if I can find out how he tuned it... if I could do that it would just mean bigger and better things!


Deff lemme know how that cam works out for ya! I LOVE the sound of big cams and that should not only sound badass but should get the ass dyno one hell of a ride. Especially with the motor youll put it in!

[Superdave]

If it makes you feel any better, I am going to try an OVER .500 lift cam on an OBD2 computer and see what happens.

I'm running a .549 /293 duration on OBD1..

it's all in the tuning...




BTW, to the OP, i don't think rich would be the problem, it may run lean...

[3100 MPFI]

I could not get my engine tuned after I dropped the compression back to stock, so I am converting the car to OBD2. Seems like it can adapt better to changes without programming (to an extent).

I am going to tune it later on, but for now, I just need it to run.

I don't care if I have any open loop issues, as long as it is fine in closed loop.

[RedBird]

If it makes you feel any better, I am going to try an OVER .500 lift cam on an OBD2 computer and see what happens.

.506/.506 lift and 224*/220* duration @ .050 on OBD1

[3100 MPFI]

I am not sure what my grind is. I just remember that it is over .500 and that it has a long duration.

At the time I got it done, no one else had ever attempted to do a grind that extreme, and ben had a hell of a time tuning it. It ran fine with the high compression, but I am now back to stock compression, and can't get the car to Ben to be tuned.

I am just doing the OBD2 swap to get the car running. I will get an hptuner later and make it better but for now, I just need to be able to drive the car.

[bszopi]

OBD1 you can tune so its not a big deal. OBD2 you can tune, so its not a big deal. He's got the OBD1.5, so tuning is basically impossible. There is a place that used to do it (www.fastchip.com), but it was $300 for a basic tune. I had it done after I installed my regrind and I was not impressed at all. The place is in Tulsa, and that is where I did my cam install, so I just went back and had him put it back to normal and got my money back.

[19Cutlass94]

yeah thats the problem and the only thing preventing me from going to a bigger cam. I really dont wanna do an OBDII swap right now at this point in time.

After I get the engine in the car and broken in, Im gonna bring it to the dyno and see what itll do and Ill also talk to the guy there and see what he can do.



But I do have a couple questions about the swap Im gonna do:

When swapping 3500heads on a 3400, you use the 3400 pushrods correct? and should I be using the 3400 fuelrail and injectors, or swap in the 3100 fuelrail and injectors?

[3100 MPFI]

3100 and 3400 fuel rail is the same. Only difference is with the lines, and that has to do more with the CAR and not the engine.

As for the injectors, if it is a 3400, you probably want to stick with 3400. Don't know how it will react with the 3500 heads, I don't know. Right now I am more interested in getting the car to run than figureing out how I want to have it set up. I will deal with the setup after I get it running.

[IsaacHayes]

use 3100 injectors and FPR. 3400 injectors and FPR are different flow rates and the PCM isn't coded for them so it will run pig rich at idle and cruise.

[3100 MPFI]

makes sense. I was thinking 3400 swap with 3400 PCM.