1993 C1500 project: 4.3L to 7.4L swap > 454SS clone

[DirtyLarry]

So I got a new project lined up. My father in-law has a really clean ’93 2wd Sportside with a 4.3L 5-speed that just needs more power. He has always wanted a 454SS truck and I happen to have a Gen V 7.4L with 5,000 miles on it lying around (not a reman but a brand new crate 7.4L). It is not a roller engine but I did add Vortec heads. The plan is to drop the 7.4L in and buy a new 7.4L throttle body so we can keep TBI. The 7.4L is set up with L29 accessory brackets which is nice so I don’t have to use another POS R4 A/C compressor.

I spoke to Howell Engine Development and they can reprogram the current 4.3L PROM to a 7.4L w/manual trans calibrations as well as add a hot tune and turn off EGR and still use the 4.3L engine harness. I also realize the NV3500 trans is light duty and the 8.5” rear axle will be taxed but my FIL is 70 years old with a light foot so I am not too worried about those components. That said, a big block with a NV3500 in a light little truck should be fun to drive when it is done!

I have never done any major modifications to any of the GMT400 trucks so I have a few questions for you all.

1) What a needs to be done to the engine mounts to go from a V6 to a V8? It looks like just remove the V6 bracket and move the mount to where the V6 bracket bolts to the frame. It is really that easy??

2) Has anybody here done a 7.4L swap into a 1500 series chassis? I spoke with the folks at JBA headers and they have Shorty headers especially for a 454SS truck because a 2500 series truck with a 7.4L is different somehow. The JBA tech guy said the 2500 series headers hit the engine mounts on a 454SS trucks. That has me curious what is unique to the 454SS engine mounting. For those that have installed a big block in a GMT400 ½ ton chassis what mount saddles and engine mounts did you use?

3) I plan to use stock exhaust manifolds instead of headers (brand new manifolds can be purchased from Napa for under $100 a piece). I hate headers but I am open to trying a set of shorty headers if we must. Does anybody know where a stock 7.4L exhaust Y-pipe can be purchased? I checked everywhere and it seems Walker and the typical exhaust suppliers are not building service replacement Y-pipes. Of course, an exhaust shop can build one but I would like to have an OEM type Y-pipe. If I go the route of JBA shorty headers they do offer a Y-pipe but that is pricy. FIL is not too concern about the cost of the swap but I have to use some discretion here

My in-laws spend half their year in CO and half in FL so I have to have this thing ready to fly by May when they come back. The plan is to start stock piling parts now and do the install sometime in January or February. That should give me plenty of time to work out any bugs before May. When he gets back from FL the truck is going in for paint (going with a sport truck look... painted bumper covers, mirrors, 454SS grill, and new 18" Coys or American Racing Torque Thrust wheels).

The project. Just did installed rear drop shackles on it the other day. Looks so much better sitting level!




The 7.4L. Using this intake but adding an OEM ’88-’91 7.4L TBI adapter that was used on the old Mark BBC to convert them to TBI.


When this engine was in my ’78 K10


Same engine but with a Marine L29 SFI intake. I could never get the MEFI-4 ECM calibrated correctly so I yanked it out and dropped an 8.1L in its place. Problem solved! The Marine L29 intake has been since been sold and this engine has been hanging on an engine stand in the corner of the garage for the past few years just waiting to be swapped into something. I only ran this engine for about 5,000 miles before swapping in the 8.1L


Should be a fun project. I can't wait to get started on it!

[Pop's C-10]

454 5 speed SS clone step side...sound like a cool build.

[jb1016]

Very exciting project...you'll want to hook up with member "TonawandaKid" because I think he's done the 4.3 to 7.4 swap in a 92.

And I've been waiting for a long time to see somebody put 18" coys on one of these trucks...I think they'd look great, even better than 20s!

[Orangette]

you will need whole new engine mounts, engine and frame side, i believe SBC ones are the same as BBC.

4.3L's use a different mounting system (clam on frame, rubber on motor)

[70BLAZERX2]

I had a 90 454SS here with a blown 350 someone put in it...had 2 thrown rods..700R4 ..I bought it..pulled the 350 700r out...put a 454 th400 back in out of a 90 ton.. I then kept the 454SS 14bolt 5lug rear,put a 10 bolt rear in it...off to the auction it went and i trippled my money in the rust bucket..

It was just to make money on..but i cant keep them all...you know..

The stock 350 motor mounts on those are the same as 454 mounts..will bolt right up

you will have to lose the stock V6 motor stands..and bolt the mounts to the frame..

But its not to bad to do...headers are pricey..yes but stock 454 truck manifolds work good too...

Up grade your trans for sure..while your in there..

[70BLAZERX2]

I have a set of new "454 SS" bedside decals and the "CHEVROLET " for the tailgate..$60 shipped correct for a 1990 454SS

[DirtyLarry]

Thanks for the input everybody. I am headed to the junk yard next week to grab the V8 pieces. I’ll take pics of the V6 and V8 mounting for reference in case anybody wants to see that for their projects. I have already started ordering parts for the swap although I probably won’t start on it until late January or February.

70blazerx2,

Thanks for the offer on the decals but we’ll pass. The tailgate decal would be nice but since this truck is a sportside the decal will be too big to fit the tailgate. I would be interested in a set of “clean” 454SS wheels if anybody has any lying around.

[70BLAZERX2]

I have this ,perfect for a 454SS clone...and will bolt right in...

http://67-72chevytrucks.com/vboard/s...d.php?t=498908

[sean1969c10]

I'm looking forward to this build. I looked at your trans swap build thread on your 78. I was really impressed, you do very nice work.

[cjracing15]

Oh my! Very interested in this one Larry. Subscribed!

[DirtyLarry]

The first of many parts for this project arrived today. A nice UPS guy dropped off the OEM GM ’87-’91 big block adapter to mount a TBI unit on a Qjet intake. Yoohoo!



The 454 still in the bag where it has been in for the past few years since the K10 8.1L swap

[DirtyLarry]

Here is a funny photo. This poor little 454 sitting in the back ground on a BFG tire as it was getting replace by an 8.1L back in 2008 (WOW! has it been that long already??). It’s been hanging on an engine stand since then. Hope the valve steam seals haven’t dried up! Glad to finally put it back to use. Nobody puts baby in the corner!

[Zoomad75]

Should be a fun build! I'm here to help too...Just as long as I get to row the gears once or twice when it's done! I might have a source on the chrome 454SS wheels too. A friend of mine from high school that hangs out with my Dad is in the middle of a 454SS build. I remember Dad saying he had 2 sets of 5 wheels. I'll ask when I'm up there tomorrow.

I think the 18" coy's would be a sweet choice too. Dad got a set of 15 inchers for his Roadmaster wagon and they are very nice wheels for the money. 18's would still allow for a little more rubber than 20's would too.

I like the idea of something that GM should have built too. A 5 speed sportside 454ss is something that SHOULD have been built. Knowing your keen eye for making things look stock but aren't will be pretty cool to see.

[BigBlocksRule]

I have a 454TBI, PM me and maybe we can work out a deal.
Are you going to stick with 5-speed or convert it to 4L80E?
My guess is you've already figured out you're going to need a new rearend? A 10-bolt with a gov-bomb ain't gonna last long behind a big block.

[DirtyLarry]

Originally Posted by BigBlocksRule

I have a 454TBI, PM me and maybe we can work out a deal.
Are you going to stick with 5-speed or convert it to 4L80E?
My guess is you've already figured out you're going to need a new rearend? A 10-bolt with a gov-bomb ain't gonna last long behind a big block.

I already have a reman 7.4L TBI unit sourced. Thanks though. Yes, I am sticking with the NV3500 5 speed and the open 10 bolt rear end with 3:08 gears (No gov-bomb). My FIL is not a lead foot nor does he ever pull anything with the truck so I am not worried about those pieces right now. If a 5 lug 9.5” rear axle pops up I’ll grab it but I am not going on a treasure hunt to find one.

[70BLAZERX2]

Originally Posted by DirtyLarry

I already have a reman 7.4L TBI unit sourced. Thanks though. Yes, I am sticking with the NV3500 5 speed and the open 10 bolt rear end with 3:08 gears (No gov-bomb). My FIL is not a lead foot nor does he ever pull anything with the truck so I am not worried about those pieces right now. If a 5 lug 9.5” rear axle pops up I’ll grab it but I am not going on a treasure hunt to find one.

I have a 3.73 posi 14bolt 9.5 rear out of a 90 454SS .... $600...I was going to use it in my 94 shortbed 4.3,was going to V8 it for a tow rig,but got a 99 tahoe now for tow rig..so i wont be using it..

I wont have it long once someone see's it..,Hard to find..limited produced..I have it on CL and soon it will go on ebay...


Get a posi unit out of a 91-96 caprice or roadmaster...90% of wagons had posi...the spid lable in inside the tailgate on the right side. G80 is posi..

They are the old clutch type and will bolt right in. You need 2 wheels pulling that BB

[DirtyLarry]

Originally Posted by 70BLAZERX2

I have a 3.73 posi 14bolt 9.5 rear out of a 90 454SS .... $600...I was going to use it in my 94 shortbed 4.3,was going to V8 it for a tow rig,but got a 99 tahoe now for tow rig..so i wont be using it..

I wont have it long once someone see's it..,Hard to find..limited produced..I have it on CL and soon it will go on ebay...


Get a posi unit out of a 91-96 caprice or roadmaster...90% of wagons had posi...the spid lable in inside the tailgate on the right side. G80 is posi..

They are the old clutch type and will bolt right in. You need 2 wheels pulling that BB

Again, thanks but no thanks. I am not concerned about the little 8.5 10 bolt axle with him driving it, especially as light as the truck is and the fact it never tows anything. If I come across a 5 lug 9.5” axle for a lot less than $600 and not 1,500 miles away I’ll think about it. The 5 lug 9.5" axles also came in many ½ ton 2wd long bed extended cab trucks of that era. So they are not just limited to 454SS trucks. That said, they are not that rare around here but certainly not as easy to find as a 14 bolt full floater.

[BigBlocksRule]

Originally Posted by DirtyLarry

The 5 lug 9.5" axles also came in many ½ ton 2wd long bed extended cab trucks of that era. So they are not just limited to 454SS trucks.

Sorry, DirtyLarry, but that's wrong. The ONLY vehicle that got 14-bolt semi-floating 5-lug axles was the 454SS. Half tons got 10 bolters, the heavy half and 3/4 tons got 14-bolt differentials but they were all either 6 or 8 lugs. That's what makes 'em worth his asking price. I've seen good ones with everything intact and in good shape go for a grand.
Head to the 454SS site with TBI questions, those guys have pretty much got it figured out and they're a helpful bunch.

70Blazer, are you sure about the clutch posi's in Roadmasters and Caprices? I need a posi for my '97 Tahoe that now has a one tire fryer, I don't really want a locker and won't waste my time installing a gov-bomb in this 10-bolt rearend.

[Zoomad75]

Ok Larry, I'm up here at my Mom and Dad's place and I remembered a poster that might be some inspiration to the project. I remember going to the Denver Auto show back in 10th grade (dating my self here) and seeing the 454SS there. They had a really cool brochure for the full line of 1990 Chevy trucks that folded out into large poster of the 454SS. It just so happens I found it in the basement (along with many other cool Chevy posters I had forgot I had!) and thought that it might go along with what you are doing. I'll bring it over sometime this week. Here's a sneek peek from a crappy cell phone pic:

[DirtyLarry]

Originally Posted by Zoomad75

Ok Larry, I'm up here at my Mom and Dad's place and I remembered a poster that might be some inspiration to the project. I remember going to the Denver Auto show back in 10th grade (dating my self here) and seeing the 454SS there. They had a really cool brochure for the full line of 1990 Chevy trucks that folded out into large poster of the 454SS. It just so happens I found it in the basement (along with many other cool Chevy posters I had forgot I had!) and thought that it might go along with what you are doing. I'll bring it over sometime this week. Here's a sneek peek from a crappy cell phone pic:

Oooo, that is cool! Don’t forget to ask your dad about a set of wheels too. Have a Merry Christmas dude!

[Zoomad75]

Originally Posted by DirtyLarry

Oooo, that is cool! Don’t forget to ask your dad about a set of wheels too. Have a Merry Christmas dude!

I did talk to my Dad about the wheels, he did confirm that he's got a second set of SS wheels. He did say he might be putting them on another truck he has. This guy has many projects too! I'll have Dad ask him if he's willing to part with them.

Merry Christmas too! Tell your Mom too. Oh and share some of the toffee with her as well!! Hogging it to yourself is bad karma!

[DirtyLarry]

What toffee? You didn't leave any toffee here

[Zoomad75]

Since it's not a true 454ss for 600 bucks you could build 9" ford axle and have 2-3 times the beef of a 8.5 or 9.5 corporate axle.

That being said, between the light weight lack of traction the 8.5 can survive. Guys building V8 S10's go hunting for the 8.5 because it was the biggest factory axle put in them. Yes the S10 is lighter, but some of these guys are running full tilt gen 3 6.0L's without a problem.

Hell, 93-02 F-bodies with LT1 and LS1's ran the cheesy 7.5" 10 bolt and they survived in stock form. The problem came in when guys added sticky drag radials or slicks and other traction devices to hook them up. I can say this, stock 454ss's didn't hook up that well out of the box and neither will this one. I did a lot of drag racing back in high school and had a couple of spoiled buddy's that their parents bought them 454ss's. Neither one hooked up well out of the hole. They both struggled to break into the 15 second zone at Bandimere speedway's 5800 feet altitude.

Axle survival matters just as much with how you drive it in addition too the type of axle it is.

[BigBlocksRule]

Wow, sounds like you've had more than your share of problems with the 9.5" semi-floater. I've had 3 trucks with 'em that I worked hard and have never experienced any of the situations you described. Maybe the drivers were revving 'em up before dropping 'em in gear or dropping the clutch???

And ZooMad, you ain't going to get any Ford 9" built that's 2 - 3 times the strength of a 9.5" semi floater for anywhere near $600. Biggest you can slip in with stock parts is 31 spline, the Chevy semi-floater has 33 splines and similar bearing support to the 9". Once you go aftermarket, the sky is the limit, just like the pricing. I've seen dozens of 9" rearends puke the pinion out the front, it takes a nodular center section and Daytona pinion support to help cure this problem, should take 750hp or so with that and aftermarket axles. Again, I've NEVER seen a 9.5" puke the pinion out the front or otherwise blown up from too much power. I know a couple of guys with 454SS trucks with turbos putting out close to 1000rwhp, all they've done is upgraded the carrier to a good posi/locker.
The 8.5" is another animal, I wouldn't run one in anything with power, period.

DirtyLarry, I'm not trying to talk you into running a 9.5" rearend...it's your money and in the end, you need to be comfortable with how you spend it.

[Jharris29]

Truck looks great!! Hey was wondering what kind of motor mounts did you buy and where did you get them? Im currently finishing my 454 i have for my 94 single cab shortbed gmc k1500 4x4 with a 4.3L 4l60e transmission. also did you have to change the computer and harness? im getting close to dropping it in, i just want to make sure i have everything thats needed.