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Hello, recently my 350 was damaged so I've torn it down. Now that I have it apart, I'm thinking about changing some parts out. It's in my daily driver so getting better mpg is important. If I can get more power without hurting mpg, that'd be good too. It appears to be stock 1974 (#8 heads). Where should I start?
What car is it in? Transmission and rear gear ratio? I say a modern flat top piston or close to is necessary for your #8 heads if it needs an overbore. Any cast replacements will yield dreadfully low compression. Get a modern piston, not only does the thinner rings add hp, they also help with mpg's, less friction. Thanks CP piston is hone to size. https://www.summitracing.com/int/par...ake/oldsmobile https://www.summitracing.com/int/par...ake/oldsmobile
This one actually goes in an 80s Fleetwood (sorta close to a vista cruiser in weight and size) with a few hundred pounds of batteries and pumps in the trunk. Transmission is a th350 but might get changed out for a th2004r.
I guess it'd probably help if I gave a better outline of what I'm going for: I'm hoping for around 14 mpg or better (at least 12 mpg). Horsepower isn't as important but I'd like around 270 or better with a decent amount of torque. Since there doesn't seem to be much damage or wear to the engine, it's hard to justify spending over $800 unless it REALLY needs it (and I'd like to go less than that).
How torn down is it? The problem is, with aftermarket head gaskets, factory is .017" vs .040" for most aftermarket head gaskets, you will lower the factory 8 to 1 compression even lower. Your #8 heads have a restrictive lip under the exhaust valve and have large chambers. If you can find a set of 4 through 7A 330 or early 350 heads for a good deal, get them. With cheap Felpro head gaskets, you will be at 8.5 to 1 to 9 to 1 on a stock 1973 to 1976 short block, depending on if the heads had been milled. Then add a mild cam like a Lunati High Efficiency 207/207 .461/.461 on a 112 LSA, a nice boost over stock but very mild. Also a good time to change the timing set, probably on it's last legs.
About compression, wouldn't changing to flat pistons also raise compression? Is there any advantage to changing heads vs changing pistons to raise compression?
Once a bowl hog or grinder is used on the #8 heads exhaust bowls, they will flow the same as early 350 heads. Flat top pistonswith give close to 9 to 1 compression with #8 heads unmilled.
I get between 8-10 mpg with a pretty stout 355 running low 12's but you said pumps and batteries so I'm guessing hydraulics ??? I got a 350 olds in my 77 Pontiac Bonneville. pretty basic 350 with older 72 heads on a 73 short block , towing cam , stock short block , stock heads, th350 and 3.08 gears. She don't shred tires but she cruises real nice and has enough pep sadly mpg are about 10 lol. In my 72 cutlass that engine went 13.7's in the 1/4 mile.
Since your are trying to move such a heavy car why not try to find a good running 455 ??? it will bolt right into place. Will make more tq. to move all that weight. I love small blocks but even on my Pontiac I could use a bbo but I decided to do an LS swap and have atleast one LS swap vehicle in the fleet.
Yes 6L N/A will be a his n hers daily driver for me and my soon to be wife and it will be her bracket car. She wants to get into racing but this car will remain daily driven as it has been during the nice weather months.
My dad and I restored this car a while ago and I recently bought him out so I can do a few things to it and make it a full time daily driver. Car has been in the family 30 + years.
One place you will gain even carbed is in mpg. I bet it will be quite measurable and torque will be decent with a 6L LS. I personally wouldn't even consider a 5.3 in anything. Make a thread in the non Olds engine section when you do the swap. To the OP get your cylinders measured if you are tearing it right down. Either the DSS available in standard bore or CP pistons in a .012" oversize, they just hone to that size, are much nicer than the Speedpro pistons. Not only lighter but a much thinner and more efficient ring pack.
Last edited by olds 307 and 403; February 9th, 2018 at 05:28 AM.
Ok I have another question on compression: what is the highest compression I can have to still safely expect to run 87 octane fuel? Just looking for a ballpark number.
Are you running it on the factory computer? I ran 9 to 1 with very aggressive timing on 87 with my Olds 350. The issue I had was bucking at low speed. That was 22 initial, lighter springs and a 30 degree vacuum can off manifold vacuum. I switched to 20 degree can and the bucking went away but felt less responsive part throttle. I also ran 9.6 to 1 with a 204/214 cam, it need 91 and a very limited timing curve. I would say 9 to 1 is safe with 87 and a smaller cam, mine is 214/214 duration. You can go slightly more but I find Olds V8's are more efficient with aggressive timing curves, no doubt due to the old school combustion chambers. Is your local 87 an ethanol blend? I actually switched to non ethanol 91 in my 88 Cutlass and 1970 Oldsmobile Cutlass S. My boss, who runs the fuel department only runs premium in his vehicles. Because premium is non ethanol, with the extra mileage gained, it needs to be 13 cents a liter more or a 1/4 gallon than regular to make purchasing regular a smart buy. It is never that much more. I would like to switch our Challenger to premium. I bet we would hit 35 mpg imperial on long trips and would gain power being a 10 to 1 motor as well. But my Wife is cheap, I get that.
Last edited by olds 307 and 403; February 9th, 2018 at 05:53 AM.
It's hard to find non ethanol anything around here, Some of the pumps are even E-15. I'm guessing I can't get away with older heads AND flat pistons then?
It's hard to find non ethanol anything around here, Some of the pumps are even E-15. I'm guessing I can't get away with older heads AND flat pistons then?
February 5th, 2018, 08:59 AM
