@slofut: I understand what you and Roger are saying about Suncoast mounts. If the Suncoast mounts will keep my engine exactly where it is, that would be fine. If it relocates my engine and transmission rearwards, that would mean exhaust work, trans mount work and driveshaft work. If that is my only option after I try the above, then I will talk to suncoast.

 

Sanchez:


Good work, you are getting there.


Pipe too small, insert too big? Take a little off each.


A bolt and washers to create a shaft for the drill press. Touch
the file to the slowest speed turning chuck.


Any cutting tools or stones for a hand drill? Hoe out the interior of
the pipe.


The GM mounts used by Sun Coast and Jaguar-specialties are indeed
great. GM engineers ain't dumb.


But, the MOPAR units selected by John are more than all right. The
MOPAR engineers are pretty smart as well.


I'vc had no issues with the latter in my car. I like the compressed flex design.


It seems that at times, mfging tolerances just stack up. I suspect that the case here.


And, as noted, there is plan b and even c.



Carl

 

Reamed the pipe a little and I can get it in about an inch. I will take them to a shop to have them pressed in all the way. I want it to be a tight fit so I won't have to peen the end as Roger did. I will then cut to size. Will post pics later.
John replied to my query. He wants $85 each plus shipping plus the cores.

 

Hello all.
I have finally completed my wiring harness and while on the gearheadefi forum,
the question regarding the grounding of the 1227747 ECM becomes vague.
Some say that the 1227747 is internally grounded and that it should not be grounded externally. It further states that the 1227747 was mounted on a plastic bracket to prevent RF interference. Others say it does not matter.
How have you lumpers installed your ECM?
I also read a GM bulletin that states that the ground wire/s on the ECM harness should be on the same plane as the engine ground and that the ECM should be floating, i.e mounted on a plastic bracket. If this is so, I will have to go to the JY or fabricate a plastic bracket to mount the ECM.
What say you?

 

I decided not to bury the finned aluminum PCM. Just too nice. I created a 'cradle" using straps of mild steel. The cradle is suspended from the wing braces. Inputs facing astern. I did not like the triangular plastic
sound chamber and dumped it. It does "whoosh" on lots of throttle. Not an issue to me.


But, now, I may need to remove it to get at the injectors. One or more might be seeping at rest.


Carl

 

Go with what GM suggest. All GM ECM must be isolated and use a single engine based ground strategy.

If the PCM circuitry is grounded to the engine, and the case is grounded to the chassis you could have a situation where for some reason the the body to engine ground strap was left off or there is some resistance in that strap. If that occurs is the new return path to ground would be through the ECM and that's very bad for clear signaling and could be catastrophic to the PCM/ECM.

 

My PCM was mounted to the passenger side fenderwell. The grounds were done per GM...wanted to mount the PCM inside but the wires were too short to put the unit under the passenger seat. I do not remember a plastic connector? Been too many years now.

 

@ responders:
Based on what I read, most all GM ECM/PCM metal cases should be isolated from the Chassis ground and the internal ground should be used via the terminals on the ECM/PCM harness to a single point on the engine because of the variations of the ground signal on different parts of the car.
Specific mention is made about ECM #1227747,1228746 and 1228747.

 

This wiring and ground information may be helpful to all doing a LT1 conversion.

 

This is what I used on my corvette. Works great, just unclip the bail and the ecm pops right out.
https://www.ebay.com/itm/LS1-Swap-PC...6G62SA&vxp=mtr

It's plastic btw...

Bill

 

One more question.
Can I use the Original Series 3 fuel pump for the GM TBI system? Or should I purchase another fuel pump that produces lower fuel pressure. I have two new fuel pumps that I purchased from Welsh Enterprises about a year ago for my other Series 3 with the Jag system. Nominal pressure on those pumps are pretty high.
If I can, would I have to install an additional in-line FPR to lower the pressure going to the Throttle body?

 

Well, my system is not TBI. But, I think Jaguar Specialties' Andrew's early conversions were TBI. The Jaguar pump did the job in each.


The FPR of the TBI should do the job, just fine.


I use the Jaguar pump on the LT1 in my car relying on the LT1's FPR.
It has done fine for years.


As I recall, Andrew spliced the harness in his first car, to mount the ECM under the passenger seat. A TBI into an SIII.


Not sure how my after market harness grounds the PCM, hmmm. But, I am fussy about grounds and mine are sound....


To the point of making a "ground bus" for all but one of the relays back to battery ground. Mounted alongside my DIY relay rack on the cowl.


As to engine mounts. My LT1 has two possible combinations up front of he block. I used the forward set. That translates to a rearward bias of the engine. The difference isn't much.


Carl













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