Goldie will get her orginal heads reconditioned.

[mr gtx]

Hi Rip,
516 is closed chamber 73.5 cc. 1970 383 originally had open chamber 906 heads 88 cc.
I was also thinking about compression and wondering whether the transition to closed chamber would cause knock.
It's not my engine. I was talking to another guy. His 1970 383 has run fine with 516 heads for the first 5 or 6 runs with the car, but it didn't sound like he has tried wide open throttle. Also, with the smaller exhaust valves, I'm not sure whether that makes the problem worse with less cylinder evacuation at WOT.
Felpro head gasket may have added cc over the factory steel head gaskets, so that might have helped. I didn't ask what head gasket he used. Sounded like he had put the heads on without rebuilding them. Ben

never seen a 915 or 516 heads that were 73 cc unless a lot of milling. they were 79-80 cc. the 1.60 will not hurt anything other than power in the upper rpms plus the 1.6 helps your torque in the lower rpms

 

[furious70]

I agree on the cc's having measured myself.
I'd like to see dyno results showing a 1.6 valve ever helps anything.
BB heads are really sized for 361-383 engines. The max wedge head should have been standard on 440's, hp's at least.

 

[mr gtx]

I agree on the cc's having measured myself.
I'd like to see dyno results showing a 1.6 valve ever helps anything.
BB heads are really sized for 361-383 engines. The max wedge head should have been standard on 440's, hp's at least.

look at my video on this forum. how a nice build street 440 in a c-body cruiser should perform. I kept the 1.6 in the 915 heads. smaller valves are for torque that is what Buick did with the 401-425 nail head with their high torque at a low rpm. yes the smaller valve will run out of steam very easily but still good to 5200 rpms. in a heavy car with 2.94 gears the smaller valves work. read about the road test with 440 HP when they put it in the 67 GTX they talk about the small valves and heads making lots of torque at a low rpm for the street car compared to the big valve Chevy 396-427. cant compare a street driver with a max wedge race car that was fast at the track with gears and torque converters.

 

[LocuMob]

cant compare a street driver with a max wedge

You can if you're talking about flow rates.

 

[furious70]

Like I said, I've never read a single dyno pull or time slip that showed a bb head with a 1.60 valve performed better at any rpm or even 60'.
Would be interested to see it.
Your car having acceptable performance in no way means it wouldn't be faster with 906 heads on it. I'll bet a dollar it would be. And be stronger from idle.
Emulating a nail head is certainly not a goal for me.
Max wedge head on an imperial, maybe not.

 

[mr gtx]

let's back up to post 1 and post 38. post 1 is going to keep the 516 heads I would say why not for what you're doing for a nice driver. do a good valve job, check spring pressure maybe add a shim to get back some spring pressure or new springs, check for straightness and check guides. new exhaust seats maybe if they do them right but if not just add a lead additive every so often. if the exhaust valves are bad you could go with 1.74 valves if you want the cost would be the same. post 38 I say the 1.60 valve would support a 383 and even a 440 if you're not going over 5200 rpms. zymurgy can you measure how far the pistons are in the hole 2 barrels could be .070 in the hole.

 

[mr gtx]

Like I said, I've never read a single dyno pull or time slip that showed a bb head with a 1.60 valve performed better at any rpm or even 60'.
Would be interested to see it.
Your car having acceptable performance in no way means it wouldn't be faster with 906 heads on it. I'll bet a dollar it would be. And be stronger from idle.
Emulating a nail head is certainly not a goal for me.
Max wedge head on an imperial, maybe not.

there are no Dyno pulls to compare the only way to find out is for me to pull the heads off and put in 1.74 valves without doing anything else. the 906 would make it slower losing a 1/2 point compression. stronger off idle with the 1.74 valve maybe but it won't be any faster off the line The car goes sideways now with 2.94 sure grip would need some street slicks. so how much torque and horsepower will I gain with a 1.74 valve below 5200 rpms ??? did the Chrysler and Buick engineers know what they were doing with the small valves and small port heads for street performance I would say yes. did the 440 out perform the big hemi heads in the 1/4 mile with the same nice cruising 2.94 or 3.23 gears even with a 3.55 gear I say yes.

 

[furious70]

We're entering pissing match territory but plenty of real world tests show what people on this board consider 'race' parts generally help at lower rpms and more street life situations than they realize.
The compression difference depends on the specific castings. The low and mid lift flow numbers of stock for stock 906's are far better than 516's and you will feel that on the street.
Your 915's are in between them.

 

[mr gtx]

We're entering pissing match territory but plenty of real world tests show what people on this board consider 'race' parts generally help at lower rpms and more street life situations than they realize.
The compression difference depends on the specific castings. The low and mid lift flow numbers of stock for stock 906's are far better than 516's and you will feel that on the street.
Your 915's are in between them.

Sorry I am not arguing just trying to learn by going back and forth and expressing my opinion and what worked for me over the years. I already learned a lot about the site you posted up moparts.com thanks, plus everyone thinking that the 516-915 heads were 73 cc because it was passed down over the years.

 

[furious70]

Yes, I have had 1 set of 516's near that and they were heavily milled. Another set was milled some and still only 78cc
Dwayne's numbers are very valuable yes.