5.7L to 7.4L Swap - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ktooker · 07-09-2015, 10:55 AM

I have a 99 C1500 with the 5.7L Vortec. I am swapping to the 7.4L Vortec. The 5.7L has a spider injector with 1 plug to the intake but the 7.4L has individual injectors. Do I need the change the entire engine wiring harness or just the lead to the intake and the ECU?

clinebarger · 07-10-2015, 10:05 PM

The Harness Routing between the two are pretty far off.

A 454 harness out of a similar ('96-'00) truck would be best, Will need minor changes If your still running a 4L60E. Though I would swap in a 4L80E at the same time.

07-09-2015, 10:55 AM	#1
ktooker Registered User Join Date: Jul 2015 Location: Houston, Texas Posts: 2	5.7L to 7.4L Swap I have a 99 C1500 with the 5.7L Vortec. I am swapping to the 7.4L Vortec. The 5.7L has a spider injector with 1 plug to the intake but the 7.4L has individual injectors. Do I need the change the entire engine wiring harness or just the lead to the intake and the ECU?

07-10-2015, 10:05 PM	#2
clinebarger Senior Member Join Date: May 2009 Location: Fort Worth, TX Posts: 6,370	Re: 5.7L to 7.4L Swap The Harness Routing between the two are pretty far off. A 454 harness out of a similar ('96-'00) truck would be best, Will need minor changes If your still running a 4L60E. Though I would swap in a 4L80E at the same time.



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