New Member 1971 350 Hp question

[gbaum040]

Hi everyone ! I recently bought a 71 buick custom with original 350 engine (69k miles on it). It was previously semi-cloned to a GS. It had a oil leak around the rear main so I had the engine pulled and rebuilt. I'm getting the crank turned down & going one size bigger on the cam. It has dual exhaust with no mufflers and a four barrel quadrajet carb. The specs say it should be making 260hp factory. Does anyone have any idea roughly how many hp it would have with the bigger cam and dual exhaust?

[bob k. mando]

Does anyone have any idea roughly how many hp it would have with the bigger cam and dual exhaust?


you're going to have to give us more than just "next size up" for cam info.
and what 'kind' of hp are you asking about, anyways? flywheel? chassis dyno?






The specs say it should be making 260hp factory.

you have to remember, 1971 was still a gross hp rating. 1972 is the first year motors were rated in SAE Net, which is much closer to what we use for modern HP ratings. 1972 is almost the same engine configurations as 1971 and the change from Gross to Net dropped the WB code engine to 195hp from the 260hp that the TB 350 was rated in 1971.

since it looks like you're doing a full rebuild you want to get the 1970 SP code pistons, money permitting. the 1970 SP code engine was rated in Gross but it was still 315hp. most of that comes from the 10.25:1 compression that is due to the shallow dish pistons.

[bob k. mando]

oh, and here's the page for the oiling upgrades:
http://automachperf.com/350.html

[gbaum040]

oh, and here's the page for the oiling upgrades:
http://automachperf.com/350.html

Thanks Bob. I had NAPA rebuild the engine.The # on the side of the block was TDI39 and I think the # on the front was 1H157631.They had me to order a master engine kit for a 72 350 and said something about having to use the 72 kit because of having to turn down the crank??. They said to go 1 size bigger on the cam that came factory with the kit. They also said something about the pistons being able to use unleaded gas???. Sorry I don't understand much about engine rebuilds thats why I had Napa do the rebuild (I'm basicaly a backyard mechanic capable of general maintanance). I don't know if this info will tell you anymore or not. Thanks for any info you can give me.

[bob k. mando]

TD was the 1971 single exhaust version of the 350, factory rated at 260 Gross HP.



and said something about having to use the 72 kit because of having to turn down the crank??.

i don't know. if they turned down the crank, that should just mean that they had to use extra thick bearings to take up the extra space. maybe they mean they can't get the 1971 kit with properly sized bearings?



They also said something about the pistons being able to use unleaded gas?

that should be a reference to the static compression ratio. in the 350, this is almost exclusively a function of how deep the piston dish is. deeper dishes give lower compression ratios which work with lower octane gas.

you can get high octane unleaded, it just means you have to buy premium or mid-grade in order to prevent pinging.

100 LL AvGas ( stands for 100 octane 'low lead' Aviation Fuel ) is also an option.

the high octane options are probably beside the point now, though.



They said to go 1 size bigger on the cam that came factory with the kit.

if they turned down the main bearings on the crank, now you've got me wondering if they align honed the cam bore and used over size bearings in that. if so, that's not a reference to a variance in the cam lift profile at all.

[gbaum040]

Thanks Bob

[gbaum040]

TD was the 1971 single exhaust version of the 350, factory rated at 260 Gross HP.



and said something about having to use the 72 kit because of having to turn down the crank??.

i don't know. if they turned down the crank, that should just mean that they had to use extra thick bearings to take up the extra space. maybe they mean they can't get the 1971 kit with properly sized bearings?



They also said something about the pistons being able to use unleaded gas?

that should be a reference to the static compression ratio. in the 350, this is almost exclusively a function of how deep the piston dish is. deeper dishes give lower compression ratios which work with lower octane gas.

you can get high octane unleaded, it just means you have to buy premium or mid-grade in order to prevent pinging.

100 LL AvGas ( stands for 100 octane 'low lead' Aviation Fuel ) is also an option.

the high octane options are probably beside the point now, though.



They said to go 1 size bigger on the cam that came factory with the kit.

if they turned down the main bearings on the crank, now you've got me wondering if they align honed the cam bore and used over size bearings in that. if so, that's not a reference to a variance in the cam lift profile at all.

I got my engine back from Napa and had it put back in. When you start it the oil pressure is about 25 and after about 3-4 min. it drops to 0. Napa looked at it and double checked the gauge and cant figure out why so they ordered a high capacity oil pump.I talked to the man I bought the car from and he said the existing oil pump is about 2 years old and that the oil press. dropped off like that even after replacing the pump so he always thought the gauge was wrong. Napa checked it with 2 external gauges and got the same result. This engine just got new pistons,bearings,cam,and everything. Can you think of anything that may be causing the low oil pressure or are 71 350's known for requiring high capacity oil pumps?

[bob k. mando]

something is very wrong somewhere.

you CAN'T run an engine with 0psi oil pressure for any length of time without grenading it. it's just not physically possible. bearings and rods detiorate very quickly in an absence of lubrication.

they haven't somehow tapped the pressure relief side of the relief spring to read pressure from, have they? pressure readings should be taken from the rear of the block and you'll likely have to drill and tap into the oil passage in order to read from there.

http://www.buickperformanceclub.com/Oilmods.htm

[gbaum040]

I don't know Bob but I will ask them tomorrow. I was reading old threads about oil pressure problems and in a couple of them people said not to use Fram filters. I don't know what kind Napa used on mine but is this true about Fram and if so why? Before the rebuild the pressure at start up would be about 25-30 and after about 3-5 minutes it would drop to 0 or close to 0 at an idle and at pull(going up hill etc.) it would run 5-10.

[bob k. mando]

I don't know what kind Napa used

the "Napa Gold" filters are rebranded Wix filters and they're very good. i'm not sure what the origin for "Napa Silver" is, but it's only a price savings of a dollar or two, why would you bother with the cheaper filter?



is this true about Fram and if so why?

the main, name brand Fram stuff is extremely cheaply built. as in *CARDBOARD* end pieces for the filter media cheap. people have cut them apart and found the entire filter media crushed by the suction of the oil pump because they're so flimsy.

does this happen to everyone? no. some people never use anything but Fram and their engines go 100k miles.

is a Fram filter guaranteed blow up your engine? nope.

but we're back to the question about "Napa Silver" filters. you CAN'T save more than a couple of dollars going with a Fram / STP filter. you can lose the entire value of your engine due to loss of lubrication. what's the risk / reward split on that?



Before the rebuild the pressure at start up would be about 25-30 and after about 3-5 minutes it would drop to 0 or close to 0 at an idle and at pull(going up hill etc.) it would run 5-10.



definitely not enough pressure, although you must still have some residual oil flow. warm idle oil pressure should be over 5psi and you should gain over 5psi per 1000 rpm.


there are a couple of other tricks for this engine.

1 - ask the rebuilder if he is aware of the oil passage mods that should be done on these engines. they should be pretty much identical to any mods they would have for a Buick v6 or Rover v8 4.6L. also very similar to any mods he would do to a Buick 455 / 430 / 400. if you need help on this i can post links, however i'm leaving town tomorrow and i'll likely be gone for a week.

2 - get a 5/8" dia oil pickup from a v6 or TA Performance. that's a quick bolt on and it would only require dropping the oil pan. not as useful as it could be if you don't do any oil passage mods but far better than nothing.

3 - upsize to the largest filter that you can find that will thread on and seal up. you can often gain 2-3 pounds of pressure simply by doing this.

4 - run Shell Rotella 15w-40 diesel oil at a minimum. you can try going up to a 20w-50. diesel oils carry a lot more detergents but run just fine in street cars.

5 - you could pull the oil pump apart and check the end plate for scoring. the housing is aluminum and the gears are steel. which is not good for the housing. excessive end wear will allow the oil to back feed around the sides of the pump gears resulting in a loss of pressure.

TA offers steel end plate shims.

http://www.buickperformanceclub.com/oilpumpwear.htm