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Old 04-16-2013, 12:20 PM
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will my stock connecting rods work?

hi i have a 1968 350 olds rocket engine that i plan on getting bored .30 over i believe my stock bore size is 4.057 if i go .30 over my bore size should be 4.087 right? and here's the specs on my engine

comp cams 274/286 duration .520/.523 lift cam
comp cams valve springs to match cam
comp cams hi tech racing double roller timing chain set
edelbrock performer rpm intake manifold
hei accel distributor to match cam
#5 heads shaved and ported for the second time
stock crank polished
aluminum underdrive pulleys
aluminum high volume mechanical water pump with 160 degree high flow thermostat
high volume oil pump
flowtech headers 1 3/4 primary tubes to 3 inch collectors
3 inch exhaust dumps at rear axle
tci turbo 350 street fighter trans (auto) with 2500 rpm stall converter

now my question is if i go .30 over what type of pistons should i get flat top, dished, etc?
will my stock connecting rods work ok with the engine .30 over?
and should i use a 750 cfm or 800 cfm carb?
and what would be the best place to get the pistons and connecting rods from? i checked summit racing, jegs, and a few other places and all i can find is pistons just cant find connecting rods so the help will be greatly appreciated

1968 350 olds rocket

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Old 04-16-2013, 01:10 PM
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Im pretty happy with the integrity of stock rods, but it depends what you are doing. I get them peened and secured with ARP fasteners.

Not familiar with olds rods in particular.

Do some investigation on chamber size and type. Find out the compression you need for that cam. Adjust deck/piston for a desired quench.
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Old 04-16-2013, 03:07 PM
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Flattop pistons with the 1968 #5 heads will give you 10.5:1 CR if you use a steel shim head gasket like the OEM gasket. If you use FelPro blue or similar head gaskets that have around 0.040" compressed height, you'll drop CR by around a quarter point or so. The flattops were what Olds used in the W-31 motors. You should also have the larger 2.000/1.625 valves installed in your heads, again as the factory did on the W-31s.

Yes, 0.030 over gives you a 4.087 bore, which equates to 355 cu in.

The stock rods are forged and will work fine if properly prepped. The 403 Olds rods are slightly beefier but also heavier and will require rebalancing. For performance applications many people us 6" SBC rods and have the crank turned (and sometimes offset ground for more stroke in the process...). The SBC rods let you use SBC pistons, which opens up some possibilities.
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Old 04-16-2013, 03:30 PM
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for a basic hot street enigne reconditioned stock rods will be fine, the flat top pistons are ideal but are also more expensive than some cast dished pistons. I have the cast ones in my Olds 350 and they work just fine- additionally I can run 87 octane with no problems.

The larger valves as noted will help, but you should have at least the bowls ported when that is done.

DO NOT run an accel dizzy, if you want a nice one go with the DUI unit, a BWG or Delco module on a stock unit will work just fine though. Be sure to port your oil pump and the drain backs and passages if you want a bulletproof oiling system.
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Old 04-16-2013, 05:38 PM
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Quote:
Originally Posted by oldslover View Post
hi i have a 1968 350 olds rocket engine that i plan on getting bored .30 over i believe my stock bore size is 4.057 if i go .30 over my bore size should be 4.087 right? and here's the specs on my engine.
If you bored the motor .30 over, you'd be into the water jackets. Please use the correct math.... 0.030" over.

Quote:
Originally Posted by oldslover View Post
comp cams 274/286 duration .520/.523 lift cam
comp cams valve springs to match cam
BBBBZZZZTTTT. Wrong. You've been snookered into using a radical ramp rate cam, which you do not need in a street motor. These cams have a much better chance of fraggin' themselves than a milder ramp design like a Comp Magnum design. This XE cam would work with static compression ratios of 10.00:1 to 11.00:1, but again, the chances of it fraffing are high in my opinion. Been there, done that.

Read and follow this tutorial if you expect any kind of longevity from a hydraulic, flat tappet camshaft......
http://www.crankshaftcoalition.com/w...ips_and_tricks

Quote:
Originally Posted by oldslover View Post
comp cams hi tech racing double roller timing chain set
BBBBZZZZTTTT. Wrong. You don't need a high-tech, racing, triple throwdown, ported, polished and relieved, over and under, spindle-fed, super-trick timing set. Just use a stock rebuilder unit. Been there, done that.

Quote:
Originally Posted by oldslover View Post
edelbrock performer rpm intake manifold
Good choice. Been there, done that.

Quote:
Originally Posted by oldslover View Post
hei accel distributor to match cam
BBBBZZZZZTTTTT. Wrong. A stock GM HEI will do everything you need to do. Get one from a boneyard, look online for a rebuild plan and have at it. Been there, done that.

Quote:
Originally Posted by oldslover View Post
#5 heads shaved and ported for the second time
So, do you have any idea about the size of the chambers? Ported for the second time? Do you think the walls might be gettin' a little thin and could crack? Been there, done that.

Quote:
Originally Posted by oldslover View Post
stock crank polished
OK, been there, done that.

Quote:
Originally Posted by oldslover View Post
aluminum underdrive pulleys
BBBBZZZZZTTTTT. Wrong. Use stock ratio pulleys for a street-driven car. If you were looking for that last 10 horsepower, after you had done everything else you could to make horsepower, then underdrive pulleys might be justified. You're spending money like a drunken sailor. Been there, done that.

Quote:
Originally Posted by oldslover View Post
aluminum high volume mechanical water pump
BBBBZZZZTTTT. Wrong. More money spent for no good return. Use a stock cast iron pump and paint it engine color. Been there, done that.

Quote:
Originally Posted by oldslover View Post
with 160 degree high flow thermostat.
BBBBZZZZTTTT. Wrong. Too cold. The motor needs to run hotter than that to use the fuel efficiently. Use a 195/200 degree unit that has a fail-safe feature (fails open, not closed). Been there, done that.

Quote:
Originally Posted by oldslover View Post
high volume oil pump.
BBBBZZZZTTTT. Wrong. Do not use a high volume oil pump unless you are using a larger pan and better oiling system. Been there, done that.

Quote:
Originally Posted by oldslover View Post
flowtech headers 1 3/4 primary tubes to 3 inch collectors
OK, are these long tube headers or those cheezy block hugger units?

Quote:
Originally Posted by oldslover View Post
3 inch exhaust dumps at rear axle
BBBBZZZZTTTT. Wrong. Terminating the exhaust under the car will resonate the sheet metal of the body and make you nuts pretty quickly from the droning sound. Run the pipes to the rear bumper and put some nice chrome tips on them. Been there, done that.

Quote:
Originally Posted by oldslover View Post
tci turbo 350 street fighter trans (auto) with 2500 rpm stall converter
OK, sounds reasonable. Been there, done that.

Quote:
Originally Posted by oldslover View Post
now my question is if i go .30 over what type of pistons should i get flat top, dished, etc?
Again, it's 0.030" over, not .30 over. Before you go any further, you need to make a plan. You need to know the volume of the combustion chambers, the piston deck height so you can figure the volume above the piston, what gasket you will use, what piston crown configuration and so forth. You can't just stand back and throw parts at a motor and expect to come out with a good combo. If you need help doing this stuff, just ask. First thing you need to do is find out what volume is in the heads by cc'ing them with a burette and colored alcohol. You can do this build right or you can half-*** it. Your choice.

With iron heads, I would very strongly recommend building the motor at no more than 9.5:1 static compression ratio.

Quote:
Originally Posted by oldslover View Post
will my stock connecting rods work ok with the engine .30 over?
They should work fine in a warmed-over rebuild like you are contemplating. Some fellows will add ARP aftermarket rod bolts and nuts for added insurance. And again, it's 0.030", not .30

Quote:
Originally Posted by oldslover View Post
and should i use a 750 cfm or 800 cfm carb?
If you were looking for max horsepower (which you aren't), you would use a 750 carb. For the motor you're building, a 600 or 650 will work fine.

Quote:
Originally Posted by oldslover View Post
and what would be the best place to get the pistons and connecting rods from? i checked summit racing, jegs, and a few other places and all i can find is pistons just cant find connecting rods so the help will be greatly appreciated
In my experience, the guy at the machine shop will be your best source of parts. He can buy them at wholesale and re-sell them to you at retail, making a profit for himself. This will make him happy and he will be more willing to give you a break on the machine work.

Love me or hate me, I'll always tell it like it is......

Last edited by techinspector1; 04-16-2013 at 05:46 PM.
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Old 04-16-2013, 07:05 PM
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Every author should be this lucky.

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Old 04-16-2013, 07:17 PM
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well thanks guys all the information helps out alot but as far as the distributor goes if a stock one will work fine is there any chance it'll mess up the gears on the distrubuter or mess my cam up? some people said stock hei's wont work well with .500 and up lift cams

but i think i'll do the flat top pistons and i never had a problem with the cam im using ive put them in several engines and never had a complaint but thanks for the info on that too

so other than that the compression i want to shoot for is 9.5-1 or 10.5-1 right? after the build is done it should run fine or perhaps a bit better off of 93 octane instead of regular unleaded fuel right?

the only reason why i have so many questions is cause this is my first time dealing with an engine that has a non adjusting valve train
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Old 04-16-2013, 07:23 PM
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oh and another quick question how do i tell if my engine is a w-31 one or not all i know is that the engine did come out of a 68 cutlass and was a stock 4 barrell engine but is there a code i can find that will tell me wether it is or not
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Old 04-16-2013, 07:26 PM
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In my youth I played around with Oldsmobiles. The stock rods served me fine. If you upgrade the rod bolts get the resized. Don't just pound them out and tap in new bolts. You should always check them but if the bolts are upgraded resizing is required. If you use anything than a very mild street cam consider upgrading to an adjustable valvetrain. The stock Olds pedestals are wear prone in the 1st place.
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Old 04-16-2013, 07:30 PM
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techinspector theyre full length headers for a 1980 trans am
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Old 04-16-2013, 07:40 PM
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Large/Multiple Images
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Pistons, Forged, Flat, 4.087 in. Bore, Oldsmobile, Set of 8

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Make:OLDSMOBILE
Beginning Year:1968
Ending Year:1980
Engine Type:V8
Liter:5.7
CID:350
Engine Size:5.7L/350
Engine Family:Oldsmobile V8
Rod Length:6.000 in.
Stroke:3.385 in.

these are the first pistons ive found should i use these or use

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Piston, Forged, Flat, 4.087 in. Bore, 5/64 in., 5/64 in., 3/16 in. Ring Grooves, Oldsmobile, V8, Each

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Manufacturer's Part Number:ZWL2320F30
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Summit Racing Part Number:SLP-WL2320F30

Bore (in):4.087 in.
Bore (mm):103.810mm
Piston Style:Flat top, with no valve reliefs
Piston Material:Forged aluminum
Compression Distance (in):1.612 in.
Wrist Pin Styleress-fit
Pin Diameter (in):0.981 in.
Piston Ring Thickness:5/64 in. x 5/64 in. x 3/16 in.
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Old 04-17-2013, 09:22 AM
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Lots of great info from techinspector. Listen to him. I think either piston will be fine for your application. If you have to ask, you don't have a W-31. There are no external differences between a 1968 W-31 and any other Olds 350 (except for carb and distributor numbers, which can be changed). The differences are all internal - pistons, cam profile, and valve size. You would need to disassemble the motor and measure these parts.
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Old 04-17-2013, 12:39 PM
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Quote:
Originally Posted by oldslover View Post
well thanks guys all the information helps out alot but as far as the distributor goes if a stock one will work fine is there any chance it'll mess up the gears on the distrubuter or mess my cam up? some people said stock hei's wont work well with .500 and up lift cams

but i think i'll do the flat top pistons and i never had a problem with the cam im using ive put them in several engines and never had a complaint but thanks for the info on that too

so other than that the compression i want to shoot for is 9.5-1 or 10.5-1 right? after the build is done it should run fine or perhaps a bit better off of 93 octane instead of regular unleaded fuel right?

the only reason why i have so many questions is cause this is my first time dealing with an engine that has a non adjusting valve train
You're pissing your money away on the wrong things if you still haven't upgraded the valve train. at 10.5:1 compression, it MAY run on 93 octane, or you may have to run 100 octane. It will not run on regular 87, not well at least.

Who ever told you the lift affects the distributor was selling you a big load of horse crap.

Whoever said you needed a $500 set of pistons for a mild street engine was also selling you a big load of horse crap.

Same for the timing set.

On the HV pump- they're great for street engines, not a good idea for race engines. If you'll be doing a lot of driving at 2,500 rpm or less I would run it, if it'll be over that for the most part then I would NOT run it. Regardless port the pump and the passages and the drain backs.

the 160 thermostat is too cold, but I would go with a 185, not a 200- either should be fine though.
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Old 04-17-2013, 02:59 PM
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On the HV pump- they're great for street engines, not a good idea for race engines. If you'll be doing a lot of driving at 2,500 rpm or less I would run it, if it'll be over that for the most part then I would NOT run it.
Lots of Olds engines with HV pumps are regularly raced and run at well over 2500 RPM. The whole "suck the pan dry" thing is a myth, just like the need for restrictors between the main and cam bearings. Definitely improve the oil return flow as you suggested, however.
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Old 04-17-2013, 03:17 PM
How fast is fast enough?
 
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Quote:
Originally Posted by joe_padavano View Post
Lots of Olds engines with HV pumps are regularly raced and run at well over 2500 RPM. The whole "suck the pan dry" thing is a myth, just like the need for restrictors between the main and cam bearings. Definitely improve the oil return flow as you suggested, however.
I'm aware that its a myth, at speed a HV pump won't flow a drop more than a standard pump though- once the bypass opens you're just recirculating it. Until you reach the bypass pressure though a HV pump will flow more- often that oil pressure is reached somewhere in the low 2xxx rpm range.

I'm a big believer in the HV pumps on the street as they provide additional flow at low rpm- where its often needed most. In a racing application you're just circulating extra oil through the bypass though, not really befitting anything and can cause problems. "sucking the pan dry" is not one of them.

On a race engine your oiling system will benefit the most from enlarging and smoothing the oil passages, your dynamic pressure loss will be severely cut and you will see much better flow at high rpm. Oddly enough enlarging and smoothing the passages will result in a pressure drop at your gauge too- in this case its showing that you did something right. Lowering the pressure and increasing the flow is moving in the right direction.
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