1978 Oldsmobile Cutlass Supreme LQ4 + 4L80E swap - LS1TECH - Camaro and Firebird Forum Discussion

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1978 Oldsmobile Cutlass Supreme LQ4 + 4L80E swap

Old 02-22-2014, 03:21 AM
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Default 1978 Oldsmobile Cutlass Supreme 375" LQ4 swap

I got laid off from my job in November and decided I would return to school to finish my degree. I suddenly found myself with a lot of free time while I waited for school to start, and not a lot of money. I had a 1966 Thunderbird sitting in the driveway in need of serious attention, a 1963 MGB roadster in the garage waiting for a back-half and V8 swap and said V8 sitting on an engine stand in the corner. I sold the cars and my professional camera equipment and went shopping for a car that I could quickly, easily and afford-ably get my LQ4 into. The catch was that it needed to be ready for long-distance road work and have room in the back to easily put my two kiddos, a 4 year old and a new-born. I found a '78 Cutlass that ran and drove but in need of some attention. It was very clean inside and under-hood, but is a few different shades of gray and silver and red and black. Owner was in need of money for dental work. I put $1200 in his hand and drove it 90 miles home. I drove it all summer without issue, then pulled the motor and trans out and sold it for $400. So I got the car for $800. I've been a busy boy since then.

I smoothed and painted the stock LQ4 truck intake. I cut everything down with a sawzall, attacked it with a dremel, used a plastic glue made for nylon 66 plastic to glue plugs in using a black spatula as donor material, used glaze and spot putty and sanded. More glaze and spot putty and sanded. Repeat. Repeat. Rinse, prime and paint. Used a Rustoleum metalic "satin nickel" paint.


I had this bulkhead connector from US autowire sitting around and I'm using it for the guage wires, fuel pump relay and fan relay wires. Really nice piece! The stand-alone harness is from PSI Conversions.


The radiator plate is an aluminum piece that allows me to ditch the stock mechanical fan shroud and use the stock Olds radiator. I'm using a one-speed mk-VIII fan that I've used on three different cars now. Best bang for your buck ever. I had to make a delete panel for the heater/ac. It fell apart on me and the firewall was riddled with rust. It's a simple sheet cut to shape, sealed and screwed. The headers are Pacesetters for an f-body I picked up for next to nothing and cleaned and painted. Intake tubing is from intakehoses.com. Upper radiator hose is for a 2002 Silverado and a Jags That Run splice fitting is used for the steam lines.


Radiator deflector is aluminum and a really nice piece. I will probably build a box around the air filter to help keep it dry, but maybe not. I will have to see once the fiberglass bumpers show up. Hayden trans cooler.


Tubular trans cross-member and drive-shaft safety loop.


GN 8.5" posi rear with 3.42 gears. Summit diff-cover. QA1 sway-bar. New stock moog springs, Monroe Sensa-trac shocks, poly bushings on stock control arms. That's a new Dorman brand gas tank for a '86 GN with a sending unit from Racetronix with a Walbro 255 pump and AN -8 and -6 fittings.


Used pro-stick shifter I'm integrating into the center console (not shown). The tach I had from my Camaro. Steering wheel came with the car. I picked up the 3rd Gen Camaro seats for $20, shampooed them and bolted them in. The guages are custom units from Speedhut and worth every penny I spent on them!




The engine is a 2002 LQ4 with a mild Howards Cam suitable for a turbo, arp headstuds, MLS gaskets, ARP rodbolts, SLP double roller and ported oil-bump, LH8 oilpan drilled and tapped for a turbo oil-drain, stock 317 heads, truck intake. Trans is a 2004 4L80e with a Circle D 3,000 stall. Car should be fun. But I have run out of money and it might be a while before I can get a driveshaft made for it.

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Old 02-22-2014, 08:03 AM
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I really like the way that intake came out. Wish I had the patience to clean mine up like that.

I would definitely watch out for puddles with the air filter mounted there. I had mine mounted in the center under the radiator behind the deflector for a while....at least until I found a deep puddle and snapped a couple rods.
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Old 02-22-2014, 01:00 PM
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Project is coming along nicely, intake came out great.
Should be fun once you get it done!
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Old 02-22-2014, 03:39 PM
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Originally Posted by G-Body View Post
I really like the way that intake came out. Wish I had the patience to clean mine up like that.

I would definitely watch out for puddles with the air filter mounted there. I had mine mounted in the center under the radiator behind the deflector for a while....at least until I found a deep puddle and snapped a couple rods.
That is a concern that I've been thinking about. Once I get the fiberglass bumpers on, I will look at boxing it in the shield it from water from below.
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Old 04-14-2014, 09:56 PM
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And some pictures!

Nose sits a little high. I don't want to lower the car much so that I keep the ground clearance and comfy ride, so I might grab a pair of V6 springs for the front or a set of Eibachs since they don't actually lower the car much.


The bumpers are in the mail!


Side-exit exhaust actually worked out better than I thought it would as far as ground clearance goes.


Took the top off, not too bad underneath. Rear window trim is in the mail!


The other side of the roof where the lower trim was in the C-pillar is pretty rough.


Not sure I can just weld this up....but that's what bondo is for, right?


Pretty clean, eh?


The office.


GPS speedo and quad guages (volt, oil PSI, water temp, fuel).


Wide-band, check-engine light and CD player.


Small detail, the custom 442 shifter **** on my pro-stick.
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Old 04-14-2014, 09:59 PM
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Old 04-21-2014, 10:33 PM
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Got the new bumpers installed. A little bit of adjustment will be needed here and there, but they fit pretty darn good out of the box.


For reference, this is what a 1978 Cutlass typically looks like:


Much better with the integrated air-dam, I think. They're narrow and flush mount now too. I might paint the "bumper" portion a silver/gray, and the rest flat black with the rest of the car.




Makes the nose look like it's not so high anymore. But with all that weight off the nose and the small front wheels, it looks a bit high with all of that fender-gap.


Rear bumper is also now flush mount and narrowed. It was stupid-easy to install.


What the rear bumper normally looks like:




Not the cheapest thing I've put on the car, but well worth the money in my opinion.


Close-up of the nose.
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Old 04-21-2014, 11:54 PM
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cutlass will probably smoke that 86 vette!!
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Old 04-22-2014, 12:02 AM
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Originally Posted by mikesanto70 View Post
cutlass will probably smoke that 86 vette!!
Oh, without trying, it will. But, don't under-estimate that Corvette. It's got a slew of stealthy mods and it runs 13.8 at 100mph in the 1/4, yet looks like a completely stock TPI car with a cat-back exhaust. My dad gave it to me to resurrect and fix a few small issues with it, then I'm selling to to help pay rent while I go to school.
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Old 05-05-2014, 09:17 AM
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Originally Posted by 1970camaroRS View Post
I cut everything down with a sawzall, attacked it with a dremel, used a plastic glue made for nylon 66 plastic to glue plugs in using a black spatula as donor material, used glaze and spot putty and sanded.
Nice build. Do you recall what plastic glue you used for the nylon 6/6?
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Old 05-05-2014, 07:52 PM
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Originally Posted by ecir45 View Post
Nice build. Do you recall what plastic glue you used for the nylon 6/6?
Loctite 1363118, but most "plastic" specific two-part epoxys will work. The key is to scarf the area leaving a rough surface with a large surface area. My other thought was to scotch-weld using 3M 3731, but that is an expensive set-up.
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Old 05-06-2014, 07:24 AM
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Thanks, I was looking at PLEXUS MA310. Looks like the Loctite will be easier to source.
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Old 05-06-2014, 07:38 PM
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Originally Posted by ecir45 View Post
Thanks, I was looking at PLEXUS MA310. Looks like the Loctite will be easier to source.
Yes, PLEXUS was another type that came up when I was asking some material engineers I work with. But, it's a more expensive option, but isn't that hard to find: http://www.usplastic.com/catalog/item.aspx?itemid=24934. I bet it would work better than the Loctite, but I've got more than 150 miles on my setup so far without any cracks or failures. Don't think I will run it this way though when I add a pair of turbos.
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Old 05-07-2014, 12:26 PM
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Old 05-07-2014, 03:37 PM
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Looks good so far. It's pretty funny how much better the engine bay looks when compared to the rest of the car. I would suggest another flat color other than black though. A flat red would look pretty interesting
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Old 05-08-2014, 01:59 PM
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Originally Posted by BudRacing View Post
Looks good so far. It's pretty funny how much better the engine bay looks when compared to the rest of the car. I would suggest another flat color other than black though. A flat red would look pretty interesting
Too much red with the red interior. I've actually been thinking about a flat silver similar to the accent color I used on the valve covers, intake and radiator cover.
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Old 06-02-2014, 10:56 AM
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I really like that radiator cover/top support. Did you fab that yourself or buy it somewhere?

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Old 06-02-2014, 12:56 PM
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Originally Posted by -TheBandit- View Post
I really like that radiator cover/top support. Did you fab that yourself or buy it somewhere?
I picked it up from Mike's Montes. Not bad for $59.

http://www.mikesmontes.com/1978-1988...ed_p_1063.html

Took a little bit of tweaking and couple of spot welds to make it work right, but it wasn't anything terrible. I finished it with a coating of Rustoleum Satin Nickle metallic paint.
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Old 06-02-2014, 01:17 PM
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It's been a little while since an update, and I've been busy despite going to school full time and taking care of my kids. No pictures at this time, sorry.

I have pulled ALL of the trim off of the car and deleted the retaining pins for the lower trim pieces. The bodywork is completely done on the passenger side and all of the holes and rust a gone. Driver's side is stripped and I'm working on the trunk lid. Should be ready to shoot color on it this week. I picked a Charcoal Metallic paint, it's a very dark gray.

Good news/bad news situation. Bad news is that I am completely out of car money, and will be for the next few years to come, so no turbo build. Tempted to pull the ARP headstuds and sell them and install OEM bolts. Good news is that I spent the last bit of my fund on a pair of PRC stage 2.5 5.3L heads with 60cc chambers. Those heads are a hell of a deal if you get them without springs! I will just swap my dual springs over. Compression ratio should be sneaking up to 11:1 now too.

But, that left me with a major issue. I have a cam that, while great for the street and good for a turbo, it is a bit short on lift. It's a Howards Cam grind 190325-15, 226/232, .578/.587, 115. Not bad for a docile daily-driver, 3.42 gear, 4l80e, 3,000rpm stall combo, but that lift is leaving a lot on the table with the new heads.

A different off-the-shelf cam, or a used cam with a more suitable profile isn't much to pick-up, and I'm taking the heads off already, so that's half the battle done. BUT, I would have to pull the wrong clip or remove the motor from the car to swap the cams, and I'm really not very excited about that idea. I happened across a set of SLP 1.85 rockers still in box for dirt cheap. That makes the effective lift .629/.638 and make the ramp-rate more aggresive. I just got a response back from Howards and they said that the lobe-profile of my cam will work well with the 1.85 rockers and the springs I have. I'm going to have to clay the pistons and check PTV, but I'm not very worried about that.

That leaves me with my stock truck intake as a bit of a bottleneck, but I'm not about to shell out $1,400 to get an LSXrt, throttle-body and related stuff to pick-up that last 20-30 horsepower.
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Old 10-02-2014, 09:16 PM
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Long time, no update. So here ya go.

Car is painted now. Rustoleum Charcoal Metallic spray paint. Lots of runs, flaws a plenty. Don't worry about door dings.



Replaced the sealed beam headlights with Rampage buckets for H4 bulbs. I went with some nice UltraBright 4000K bulbs.





The parking lights make them look yellow, but they're very, very white.


While tuning I noticed my MAP sensor would drop to 92-94 KPA at WOT when ambient is 100 KPA. Then last week, the MAF failed. THEN the lower part of my intake tube fell off because the bracket weld failed and then I ran it over. So, I ordered up some 4" aluminum tube, 45 and 90 degree elbows to replace the 3.5" stuff I had before. I also threw the MAF in the trashcan. My old setup used a bit of a small filter, so this time I measured carefully and managed to fit a MUCH larger filter. IAT today was 66 degrees and ambient was 68, so the location works. Spare me the "you're gonna hydrolock it" comments please.





Now I'm running a open-loop SD tune and I love it. Idle and low throttle acceleration is rock solid 14.68afr, low-load cruise is 16.4afr, and WOT is 12.8 to 13...however, my injectors are over 100% duty cycle, so WOT AFR isn't consistent. MAP reads 98-100 now at WOT, so the bigger filter, 4" tube and MAF delete is working. It's a difference I can really feel!


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