500 efi vs 525 lower intake differences?
 

yes they are interchangeable,

Two different engine applications, closed cooled vs non, coil on plug vs distributor......the 500 runs a t-stat housing where the 525 has a heat exchanger and the t-stat has a block off plate, but when you take everything off the lowers are the same.

They are interchangeable One has a brass crossover and one dont. I have a 525 lower for sale for $250 shipped

Outlaw - you inbox is full

Going to check out what my buddies mechanic has laying around first. Supposed to have a 500 EFI lower with a rail. Bought a couple 500 efi's that had freeze damage. One of the lowers, a t-stat housing and the two blocks were scrap. Not sure what happened to the other rail, but that is the hardest thing for me to find right now. He's out hunting, so may not know anything until later in the week. Regards,

Eric

huge differences between these 2. A bit of other info is The PCM 555 vs MEFI 3. For one there is power reduction mode in the 555 also the fuel delivery and ignition is by totally different. For one the 555 is sequential fire vs outdated batch fire. and the 555 uses a cam and crank sensor no distributor vs a distributor mefi 3 for a jist of info.

Both use 1988 fuel injector design. Way behind in that area.

sequential injection becomes batch fire at higher rpms,,only advantage ,if any is at low rpm . basically sequential was developed for emission standards.

For high rpms and race engines batch fire if the pulse widths are large then the starting point and ending point of each event gets closer and closer so basically you are correct about batch fire. But for 6500 rpms and down along with marine apps as it seems for the power boater and average boater most of the logged time on their engines is idle times. Batch fire does not provide better idle quality / and fueling vs seq fire. But there is more -- Old vs current thoughts for a jist

With batch fire the timing of the actual injection event on any given injector is NOT precisely aligned to each individual intake valve opening event. With that said there is no need to have precise camshaft to the crankshaft signal detection. Batch fire lacks fuel control of rapid / throttling compared to sequential firing. You are leaving power on the table with batch firing. Batch fire is the simplest form and easiest to build including software and internal components of the ecm and is the a lot easier to tune compared to sequential fire.

in shorts terms Seq. firing breaks down the timing of the fuel / injection to a cyc to cyc chain of events. The ecm provides a given order to fire the injectors per the firing order. Much better fuel control and events cyc to cyc.. This has a lot better fuel control for rich / lean conditions when set up correctly by experience tuners. Seq. fire in laymans terms can be set up for better cyc to cyc fuel and ignition control by far over batch fire.

I would call any top tuners and ask them what they recommend, Very few are using batch fire and a distributor period these days... OEM Marine fuel injection set ups were always at least 10 years behind the times compared to the auto side set ups.

Anyways 1100 / 1350 / 1550 / 1650 Merc racing engines has to meet ZERO emissions especially the race 1650 engine - what injection do you think they are using - it is not batch fire.

so I'll talk to myself in the mirror.:D
I use sequential on everything I build lately,I also use cylinder trim,fuel and spark.but still at the end of the day,,batch fire isn't all that bad.For the record,I have John Meany's very first dfi fuel injection computer,friend got #3 way back in 86.

Did that early stuff look like THIS? A guy dragged this stuff recently in and wanted me to install it on a blown street car, I told him to throw it in the trash!https://cimg8.ibsrv.net/gimg/www.off...c4ddd7ec43.jpg
https://cimg1.ibsrv.net/gimg/www.off...78630388cf.jpg
https://cimg3.ibsrv.net/gimg/www.off...426746db6e.jpg
https://cimg6.ibsrv.net/gimg/www.off...ecd717da69.jpg

not really,that box may be trying to drive low impedance injectors.efi box looked like a mid 80's gm ecu.made 700hp on a single turbo on a 350 in a z28.I made 450 out of a 2.8l v-6.my ecu went back for an upgrade,,idle spark stabilization, was suppose to keep it quiet.worked pretty good on the healthy cam in the v-6.
btw,about 10yrs ago I asked meany to give me an ecu w/ 8 afr sensor capability.I wanted to treat an engine as 8 individual engines.Its starting to happen now.:D

marine power at one time owned Hirel / cuttler efi for marine apps. The holley bought it all out in 1997 or close to that year. Basically that's how Holley got started with MPI efi was buying all the Hirel / Cuttler efi stuff.

In the early 90 s Holley did have a TBI set up for marine apps only.

I am not sure if this is the same Marine power shown in the pics above.

We use to install that Hirel / Cuttler efi set up back in the 90 s.

Just saying as we do not know each other here - so asking did or do you work for a EFI company that makes or sold efi components ?

I have bought that adaption for using 8 - 0 2 s and using it with stand alone ecm - That has been around for about 4 or 5 years now just saying.

The reason I ask IS if you google john meaney, big stuff, digital efi, etc, a few old links show 4352 fenton road which is in front of the house that the address that THIS Ecm I pictured has on it , somehow related, Smitty
Were you able to tune that efi back then?

A friend of mine was running this exact setup on a bbc/671 street car running on old Fast ecu. I was tuning it for him. Was very limited in features and could not hold a tune well. I'll see if I can find some pictures of it.

My brother had the Holley TBI setup on his Chevelle back in the early 90s. It did not work well and was removed. It sat on the shelf for many years.

yes,it was way better than burning chips 200 times a week.

I had tbi on my 93 gmc BB p.u.,,always had a weird idle,,tried every thing,,then one day I put a carb on it.ran beautifully.

I found some pictures from a magazine article they did on his car a few years ago. If my memory is correct he was running a FAST Classic ECU and 16 36lb injectors. I always doubted that the fuel lines could supply enough fuel to thre injectors. That's probably why the tune never held. https://cimg5.ibsrv.net/gimg/www.off...8bc66fe949.jpg
https://cimg2.ibsrv.net/gimg/www.off...0def6e2db8.jpg