Big block install in a G body

Swandog66

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Jun 22, 2020
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Hi all,
So I was a member of the old forum as GMloyal and got a lot of great info from that old forum. I have had my 86 cutlass off the road since 2018 when I pulled the 403 I had swapped into it back in 2012 the 403 came out of my 79 cutlass which I swapped the 260 out of that in 2008. Sooo in 2018 after getting ten years out of that 403 that I paid $250 for and only ever put heads on one was cracked in the intake port leaking coolant. The cam went flat and I decided to contract Dick Miller to build me a 455 to replace the 403 I did that and have had the the 468 big block sitting on the floor of my garage since 2018. So I’ve only gotten as far as degreasing the engine I plan to paint that before I do anything else. I have my 11 year old son as a helper. He can’t wait to see what 500+ horsepower and 550+ TQ feels like in a G body. Oh and I’ll share some other stuff I’ve done to the car since I’ve owned it I got from the original owner who garage kept it. So when I got it it was completely unmolested. I’ve swapped in a built TH400 And a custom heavy duty driveshaft. 3” tourqe tech duel exhaust. 3:73 gears And posi in 7.5 rear Probably not gonna last long. Also kept 15” ssII wheels from 79 cutlass. Swapped over to the Rally gauge cluster. I used this cutlass as a daily driver for several years along with a 69 C20 pickup I used both to commute into NYC from the suburbs. So I will try to update this as we progress. Thanks Dan
 

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Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan
I think I remember you from the old forum. Unfortunately a lot have moved on from Olds power and now run LS😕. Glad to see you are not one. Looking foward to your progress.
 

Swandog66

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Jun 22, 2020
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I think I remember you from the old forum. Unfortunately a lot have moved on from Olds power and now run LS😕. Glad to see you are not one. Looking foward to your progress.
Thanks I think I joined the old forum in 07 and wasn’t around much towards the end only because I hadn’t been doing much work on the cutlass. Also I firmly believe in keeping my GM cars with there proper Engine families.
 

Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan
A lot of guys agree with you, I don't, I like the Olds V8 in everything 😁. People have yanked out perfectly good V8's of all makes and replace them with the sbc or ls because they are cheaper and better in their minds. I put an Olds 307 in my 78 1/2 ton, out performed two sbc 350's with 2.78 gears, even a Vin Y 5A 307 has more low end torque. I then swapped in an Olds 350 with 5A 307 heads, 8.5 to 1 compression and the 20/214 cam, even better. Then I picked up my In laws 94 Z71 and pulled the knocking swirl port sbc turd and put the same Olds 350 in it. Like I have said with the same 4L60E, 3.73 gears and taller 265/75R16 vs the 245/70R17 on 03/04 LS powered trucks, it out performed them idle to 4000 rpm, then the LS pulled away. That was with the less than ideal factory sbc tune. It was super in forgiving to any cam, I needed to crack open the throttle body and advance the base timing at least 10 degrees, factory 0 setting back fired through the throttle body. I ended up with 19 degrees as the best setting. I added 454 TBI, just killed the factory 5.3 LS in the upper rpms. The TB I got had super stiff spring pressure and the replacement TPS was flakey. With it performed as it should, the Gov lock dual wheel peel😎. I was going to get a custom tune, had custom 2.25" dual exhaust with Sanderson shorty headers. Unfortunately a shorted out block heater caused a fire and destroyed the truck. I have had Olds powered vehicles nearly continuously since our family got the Beast, our 75 Cutlass 4 door withe 350 Rocket. That car was abused to hell with a ton of miles, supposedly did 130 mph ditch driving, sold with a knocking motor and a seized on caliper. Junk dealer sold it to someone was on the road another 5 years. Our 81 Delta 88 got over 400,000 km with the Olds 307. People don't give the Olds small block the credit it deserves, I can still find good Olds 350's for cheap. This last one is 47 years old betting it is still the stock bottom end with good oil pressure. Try a sbc from the 70's, cam flattening junk in comparison. Good luck, I broke the 7.5" twice in my 88 Cutlass with a very mild 403, get the 28 spline axles and a used Torsen posi and gears from a Camaro. Good luck.
 
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Swandog66

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Jun 22, 2020
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I remember reading about the truck swap. And didn’t you also get the factory Chevy accessory serpentine set up to work on the olds Motor.
 

Olds 307 and 403

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Oct 4, 2018
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I remember reading about the truck swap. And didn’t you also get the factory Chevy accessory serpentine set up to work on the olds Motor.
Sort of, I had issues securing the passenger side. I am currently using that truck sbc setup with Extreme Supreme's adapter brackets on my 88 Cutlass, much more secure. Pacific G body also has a set. The diesel rwd V6 reverse rotation water pump is needed to complete it along with a complete truck set up, except the 302 or 351W crank pulley fits better but like a sbc crank pulley which is too big needs to be drilled to the Olds pattern.
 

Swandog66

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Jun 22, 2020
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Minor progress removed the old gas tank. And serviced the rear end while we have no tank in the way. I don’t think the posi unit has much life left it based the amount of clutch material that was in the bottom of the case. Not surprised based on the beating I put it thru over 9 years plenty of doughnuts burnouts and driving in the snow. Then I started running the new fuel line I plan on using the original as a return good thing I was able to reuse the stock clips that held that the old 3/16” line. Today’s plan is swap in new tourqe converter and service the trans. And possibly get the new gas tank in.I have to plan the fuel pump wiring. So much little stuff that adds up to a lot with adding electric fuel pump fuel,pressure regulator,Holley carb, MSD Distributor which uses separate coil. So it’s not my first engine swap and probably not my last but if your reading this and it is your first time take your time and be very patient. And plan on spending way more money than you thought.
 

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Olds 307 and 403

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What posi is it?
 

Swandog66

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Jun 22, 2020
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It is an old GM for 2 series gears. If you look you can see there is a spacer between the ring gear and the posi unit. Anyway I bought it off eBay back in 07 I think when I had my 79 cutlass had in there then saved it swapped it in this car. I have seen they sell clutch kits for the 8.5” ten bolts but never saw any for the 7.5”
 

Swandog66

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Jun 22, 2020
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Some more progress today. Got the new tank put together. With this tanks brand tank you have to cut the gauge sender to the correct height for your tank and set the fuel pump to the correct height. Then we made up the An hoses for pressure and return line. Also had to change the ends on the gauge wires. The pump still needs to be wired. And I need a longer vent hose. No 5/16” fuel to be found in my shop for the vent.
 

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Olds 307 and 403

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Oct 4, 2018
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Melville, Saskatchewan
I would go with a Trutrac, no tiny spider gears to fail. Also 28 spline Moser axles are a good idea.
 

Swandog66

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Jun 22, 2020
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More progress over the past week. Fuel system almost finished. I have to plumb from the regulator to the carb. Got the engine, headers and some of the accessory drive installed.
 

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Olds 307 and 403

Active member
Oct 4, 2018
616
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Melville, Saskatchewan
The fit looks really good on the ARH headers. What primary tube size are those?
 

Olds 307 and 403

Active member
Oct 4, 2018
616
213
43
Melville, Saskatchewan
What carb and air cleaner are you running? You will probably need a 2" drop base air cleaner.
 

Swandog66

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Jun 22, 2020
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I would go with a Trutrac, no tiny spider gears to fail. Also 28 spline Moser axles are a good idea.
Going back to your posi suggestion I had kind of figured the 7 1/2” 10 bolt wouldn’t stand up to big block tourqe So I had planned to buy a new 12 bolt from one of the companies that make them. But I’ve never upgraded a 7.5 either. So maybe it would be ok with proper upgrades.
 

Swandog66

New member
Jun 22, 2020
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What carb and air cleaner are you running? You will probably need a 2" drop base air cleaner.
So the engine was built and Dynoed and came home with a Holley 870 street avenger 4150 with vacuum secondary’s. Every carburetor car I’ve owned has been a Quadrajet so I had thought I might go back to that. I can Tune and take apart Quadrajets in my sleep. Never worked on Holleys. I might also embrace change and keep the Holley. Haven’t decided on an air cleaner yet my stock hood is full of rust holes so I thought I may go to a cowl style hood eventually. And then a taller air cleaner.
 
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