1966 Cutlass convertible blown 330 project.... - ClassicOldsmobile.com

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1966 Cutlass convertible blown 330 project....

1966 Cutlass convertible blown 330 project....

Old September 30th, 2017, 01:09 PM
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1966 Cutlass convertible blown 330 project....

Looking for input on where I am going wrong as I go along.
Budget is expandable as I see fit.
Car will be rebuilt for cruising and highway travel to shows. No racing. Nothing above 5500 RPM is necessary to me.
I consider it a resto mod.

330 is at Pro Motor in Goshen , IN for the rebuild.
Plans are to rebuild using original block, heads, crank, and manifold initially.
Bore for 8.5 to 1 SBC forged pistons and rods.
Blower cam
Replace ST300 with TH350. Column shift.
Understand I need to adapt kickdown.
Has 69 O type rear with 2.56 posi. Guessing 27"- 28" tires eventually.
Holley Sniper injection with in tank pump.
Assuming it will be a dog on acceleration initially, but is of no concern right now.
Couple years down the road plan on going with a 6-71 kit from Dyers, BDS, or Hampton.
No higher than 8 psi with the Sniper on top ( after Holley comes up with a draw through adaptation)
Max 450-500 HP.

Any input appreciated.
I am not the type to look for validation my set up is the best , just to learn, check and adjust.
Thanks in advance.

Last edited by gtuturbo; September 30th, 2017 at 01:20 PM.
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Old October 2nd, 2017, 05:59 AM
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I'd put studs and straps on the main caps and then align hone. Make sure block is sonic checked as well.
Don't use the Sniper, use the Terminator EFI. Way better control for boost etc.

Last edited by cutlassefi; October 2nd, 2017 at 06:02 AM.
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Old October 2nd, 2017, 03:53 PM
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Am I on the right track with this?

According to my builder, and holding to the fact that i want to keep my 330 , i essentially have 2 options:

1. Custom forged 330 pistons and Olds forged rods - about $1500 between the two?

2. SBC forged pistons and forged rods- about $800 between the 2, PLUS machining costs to get the combo to work in a 330?

I am addressing specifically this part of the engine build currently for personal cost analysis.
What are the concerns or advantages with each?
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Old October 3rd, 2017, 08:27 PM
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Are 6" SBC and Olds rods virtually identical except for pin bore diameter???
Will aftermarket SBC rods have offset?
Compression height of 330 pistons 1.615. Calculated is 1.6375. Will 1.6 SBC pistons suffice for this or will that end up lowering compression too much?

Last edited by gtuturbo; October 5th, 2017 at 04:01 PM.
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Old October 5th, 2017, 11:30 AM
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Am I asking the wrong questions?
Should they be somewhere else
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Old October 16th, 2017, 04:48 PM
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I rebuilt my 330 three years ago and suffered the same dilemma. I buckled and went with stock reconditioned rods and Egge cast pistons. The pistons cost about $400 at the time, but that's not a good choice with your boost scenario. I hear that stock Olds rods are the weak link, but finding a custom Olds rod is going to cost a bunch. Therefore, I can see why the cost to use 330 forged parts is cost prohibitive. On the bright side, the 330 crank is forged

If I had to do it all over again, I would investigate the Chevy rod/forged piston combo. Like you're saying, it will require some machine work on the crank, but probably cheaper than the $1500 (above) and a better long term investment since chevy pistons and rods are cheap and plentiful.

Just my two cents, I'd listen to others on this board before making a final decision.
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Old October 16th, 2017, 07:39 PM
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I am using Eagle forged 6.2" LS rods and DSS 21cc dished 1.425" forged pistons, with the engine bored to 4.0".

Couple thousandths off of the block deck and .027 Cometic gaskets gives me the 8.5:1 CR I want.

Want to thank you guys for your input.
Greatly appreciated!��
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Old March 3rd, 2018, 10:28 PM
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Something to think about from another perspective.

You may not have needed anything better than stock connecting rods with some beam polishing, shot peening, and ARP rod bolts.

Your self-imposed RPM limit with a short stroke engine is why I say this.

The forged pistons will handle the possible detonation and increased strength to live through the faster acceleration rate of the piston when making more horsepower.

”typically”, you’ll never break a stock or worked over stock rod in a small block if you keep it less than 6,000 rpm, as that was a stock operating range for a hi-performance 350....

It is when you start revving an engine to higher rpm than normally accepted stock limits that rods are likely to fail. Rods typically fail on extension, during the exhaust stroke.

The other reason why rods usually fail is hydro-locking or extreme detonation; aftermarket rods will fail the same as OEM in that way.

Under compression, even cast rods are very strong, look at stock Buick rods in the turbo Grand Nationals which safely turn 5500rpm. Those stock CAST rods can take over 450-500whp as long as the rpm is kept down. Higher than stock RPM, water ingestion (blown headgaskets), and horrible detonation are the killers of all rotating components.


A good cam with a 112 or 114 LSA, ~215-220 @.050 duration, and .480-.500 lift. With as many cam failures I have witnessed, going to a hydraulic roller setup is highly recommended.

polishing the piston crowns and the chambers and edges of the chambers will keep detonation at bay with the correct timing curve and the right air-fuel ratio with your fuel injection.





Last edited by Battenheaded67; March 3rd, 2018 at 10:33 PM.
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Old March 4th, 2018, 02:55 AM
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Thanks for that input Batten!
I already went with the forged goodies and hopefully it will be more stupid proof in the long run.
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Old March 4th, 2018, 10:22 AM
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My 330 Cutlass convertible with a 2.78 rear end was abysmal. 2.56 gears will just make you want to stomp puppies. If your plan is to have 450hp in the future why not build for that now? I wouldn't go less than 3.42 to start.
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Old March 4th, 2018, 03:34 PM
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Originally Posted by TripDeuces View Post
My 330 Cutlass convertible with a 2.78 rear end was abysmal. 2.56 gears will just make you want to stomp puppies. If your plan is to have 450hp in the future why not build for that now? I wouldn't go less than 3.42 to start.
Yessir, at this point my budget is quickly catching up to my timeline and doing it all is looking more likely! I agree that with the 2.56 and lower compression initially an 80 year old lady in a 1984 K car could accelerate faster!��

Last edited by gtuturbo; March 4th, 2018 at 03:37 PM.
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Old August 7th, 2018, 01:19 PM
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Need serious help acquiring my cam....

I am looking to acquire a custom cam for my project.
Will need to be a blower spec hydraulic roller cam cut for the 45 degree bank angle.
Comp Cam experts are worried it won't work for me if they try to grind a core they have. They didn't say exactly why.
6-8 psi boost. Didn't need more than 5500 rpm tops.We had agreed on 10 inches of vacuum with an LSA of 112-113 and more exhaust duration ( exact amount not provided).
Lift not discussed and stall not discussed.
Any help is always welcome...
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Old August 7th, 2018, 04:04 PM
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It sounds like the comp cams billet cam cores donít have enough meat on them to cut them for a 45 degree bank angle. I donít know if the SADI cam cores that Mark has will have enough room to cut them on a 45 degree bank angle.

Talk to Mark @cutlassefi to get you setup with a custom hydraulic roller cam, whether it be a billet or SADI core, I bet he can fix you up one way or another.


I just received my custom ground SADI cam from Mark for a 39 degree bank angle 455.

An SADI cam core will allow you to run a bronze or melonized distributor gear. A billet cam will require a Bronze gear and it will wear, slowly, but it will wear.
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Old August 7th, 2018, 04:06 PM
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Pmíd you.
But lots of bad info here. Stock rods donít only fail under suction, they can also fail under compression/power. And polishing etc is a waste of time. Theyíre still softer than they should be.
Use a good I beam rod with the big bolts, thatíll make the biggest difference. And a 4032 forged piston is good for 4-5# of boost but most dont recommend anything more than that. If youíre approaching 10# itís best to do a 2618.
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Old September 25th, 2018, 01:02 PM
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BBO rod failure seems to be something that used to happen a lot before forged aftermarket rods became available but
the SBO always had a reputation of revving like a small block Chevy without a problem. The W-31s were taken to 6500
in lots of 1968 and 1969 magazine tests. If you keep boost pressure down and rpms at 5500 max you can get away with the stock rods
as long as you resize the bearing crush on the tight side, replace the rod bolts (a given) and oil pressure on the high side.
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Old September 26th, 2018, 02:41 AM
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The cheap way of upgrading the SBO rods was to use the 403 rods, stronger but also heavier. I can't remember any 403 rods letting go.jmo
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Old September 26th, 2018, 03:58 AM
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Theres a big difference on rotating mass too. These are weighted by me, on same scale, back to back.
Included to weight are: connection rod bearing (both halves), connection rod itself, piston pin and locks if needed, piston, and all rings. 350 engine.

My original rotating "unit" weighted 1675gr. Stock bore.

New one weighted 1317gr. SRP forged pistons and 6.200" Scat I-beams.

So 358gr less per cylinder. At total, weight-reduction is 2864gr's. Thats alot off from rotating mass. Plus parts are new.
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Old September 26th, 2018, 11:52 AM
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Throw in a 2000+ stall converter, will help a lot getting it off the line. Mine went from fun with a 2300 stall, rated at 2200 to 2500 rpm, in front of a 2004R to blah off the line with a factory 1600 stall with a TH350. While moving, it responds fine with the 2.78 gears.
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Old September 26th, 2018, 01:38 PM
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Originally Posted by olds 307 and 403 View Post
Throw in a 2000+ stall converter, will help a lot getting it off the line. Mine went from fun with a 2300 stall, rated at 2200 to 2500 rpm, in front of a 2004R to blah off the line with a factory 1600 stall with a TH350. While moving, it responds fine with the 2.78 gears.

Agreed! Too many folks build a nice setup and then cheap out on a converter. A good converter can transform a mediocre performing car and combo into an impressive and fun setup.

I have personally used PTC and I have excellent experience with them. I want to give extra Kudos to Kenny Ford at PTC. They can design a converter that may flash at 3-3,300 rpm, but it can cruise at 2,000 with virtually zero slip at low throttle, in other words, very efficient and made correct.

Also, I recommend stepping to a 10 inch converter by PTC, built to your cam, rear gear, car weight, trans gearing, and expected power and what type of power adder you are using. PTC is also great about adjusting or re-stalling their own converters and other companies converters to get them to stall like you want. Support the small companies like this who do great work and make our cars faster and add smiles!

A higher-stall, quality converter can make a huge difference on a stock engine, and it can make a world of difference on a modified engine.
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