rmchrgr
Well-Known Member
Last Saturday my friend and I took his 438" stroker to the dyno to break it in and see what it would do. We didn't set any records but we did OK for a couple rank amateurs - best run of the day netted 442 hp @ 5,400 rpm and 472.7 lb.ft of torque @ 4,200 rpm. Nothing broke, no major leaks or noises, no wiped cam.
This is a pretty mild combination that was meant to be reliable and provide good torque. It's a 1969 .060" over 383 block with a 440 Source balanced 3.75" stroke rotating assembly and OOTB Stealth heads with approximately 9.3:1 compression. Hughes hydraulic cam 228/232 @ .050" with their standard hydraulic lifters and matching single (with dampener) valve springs. The lift is approx. .525" on the intake side. Comp cams Pro Magnum rockers, stock length 5/16" pushrods. Low-deck Performer RPM intake, standard Mopar electronic distributor. Dyno headers were rusty, swap meet junkers with 1 3/4" tubes. We will eventually be using TTi which are 1 7/8" tubes so hopefully that that won't hurt.
For fuel I believe we just used regular pump gas mixed with a little race gas, not sure what the octane level was but figure under 100. I believe the air was pretty good that day. The dyno place is about a mile from an airport, elevation is 361 ft.
We worked on the ignition timing a little bit but it seemed to like around 15-16 degrees initial best. There is an FBO advance limiter plate in the distributor which I believe is set to 16 degrees so figure it ended up at 32 degrees or so. Advancing the timing made the power drop off, we lost 7-12 hp consecutively advancing it to 18 and 20 degrees initial. At that point the dyno operator mentioned it was getting hot and suggested letting it cool off for a bit before making any more pulls. We waited for about 20 min. and tried one or two more runs at 16 initial but didn't gain or lose anything really so we called it a day.
There was one unsolved question regarding pushrod length. We are using "stock" length 5/16" 383 pushrods but they might actually be a hair too long. We had tried to set preload the night before but I had a feeling there was too much because it seemed like we were already at zero lash with the adjusters backed all the way off. I could rotate the rods between my fingers but the rocker arms were solid. When we got there I mentioned it to the operator and he agreed it was too much. We ended up backing them all off fullly to no ill affect since were able to run it up to 5,800 rpm on a few pulls.
He said we might want to double check for proper length before we put the motor in the car by installing a checking spring and grinding down a stock pushrod until we achieve some lash. When we mocked it up I only had a ball/cup length checker so we kind of rolled the dice using the stock ones and it came back to haunt us a little. Again, not a huge deal and I don't think we left much if any power on the table because of it but it may be a worthwhile exercise at least to increase valvetrain longevity.
Worst thing that occurred was taking it off the dyno the dipstick snapped at the base. It was a royal PITA to get it in the block so it was probably brittle already. When we had it tied down in the truck the tube was up against the strap putting pressure on it. Then the headers were not in the right place so we had to bend it out of the way. Kind of inevitable that it would snap.
That's all just wanted to share the results and post the sheet. No, this thing is not going to set the world on fire but it will be way more power than my friend has ever had under his right foot and should be good for block-long burnouts. I'm sure he is going to be happy with it.
- Greg
This is a pretty mild combination that was meant to be reliable and provide good torque. It's a 1969 .060" over 383 block with a 440 Source balanced 3.75" stroke rotating assembly and OOTB Stealth heads with approximately 9.3:1 compression. Hughes hydraulic cam 228/232 @ .050" with their standard hydraulic lifters and matching single (with dampener) valve springs. The lift is approx. .525" on the intake side. Comp cams Pro Magnum rockers, stock length 5/16" pushrods. Low-deck Performer RPM intake, standard Mopar electronic distributor. Dyno headers were rusty, swap meet junkers with 1 3/4" tubes. We will eventually be using TTi which are 1 7/8" tubes so hopefully that that won't hurt.
For fuel I believe we just used regular pump gas mixed with a little race gas, not sure what the octane level was but figure under 100. I believe the air was pretty good that day. The dyno place is about a mile from an airport, elevation is 361 ft.
- temperature: 42 deg f
- uncorrected barometer: 30.057 Hg
- humidity: 40 %
- vapor pressure: 0.268 Hg
- dew point: 20.626 deg f
- grains: 15.6
- air density: 103.692 %
- density altitude: -1,246.421 ft
We worked on the ignition timing a little bit but it seemed to like around 15-16 degrees initial best. There is an FBO advance limiter plate in the distributor which I believe is set to 16 degrees so figure it ended up at 32 degrees or so. Advancing the timing made the power drop off, we lost 7-12 hp consecutively advancing it to 18 and 20 degrees initial. At that point the dyno operator mentioned it was getting hot and suggested letting it cool off for a bit before making any more pulls. We waited for about 20 min. and tried one or two more runs at 16 initial but didn't gain or lose anything really so we called it a day.
There was one unsolved question regarding pushrod length. We are using "stock" length 5/16" 383 pushrods but they might actually be a hair too long. We had tried to set preload the night before but I had a feeling there was too much because it seemed like we were already at zero lash with the adjusters backed all the way off. I could rotate the rods between my fingers but the rocker arms were solid. When we got there I mentioned it to the operator and he agreed it was too much. We ended up backing them all off fullly to no ill affect since were able to run it up to 5,800 rpm on a few pulls.
He said we might want to double check for proper length before we put the motor in the car by installing a checking spring and grinding down a stock pushrod until we achieve some lash. When we mocked it up I only had a ball/cup length checker so we kind of rolled the dice using the stock ones and it came back to haunt us a little. Again, not a huge deal and I don't think we left much if any power on the table because of it but it may be a worthwhile exercise at least to increase valvetrain longevity.
Worst thing that occurred was taking it off the dyno the dipstick snapped at the base. It was a royal PITA to get it in the block so it was probably brittle already. When we had it tied down in the truck the tube was up against the strap putting pressure on it. Then the headers were not in the right place so we had to bend it out of the way. Kind of inevitable that it would snap.
That's all just wanted to share the results and post the sheet. No, this thing is not going to set the world on fire but it will be way more power than my friend has ever had under his right foot and should be good for block-long burnouts. I'm sure he is going to be happy with it.
- Greg
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