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2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Originally Posted by ryank9398
483chp@ 5900, 461ctq@ 4800
Smooth sailing all afternoon at the dyno....I thought it would have traded a few hp in favor of a couple more ft pounds, but I think this shows the sporty characteristic of the miniram. My little 268XFI I think would just flatline after 5800 with these heads but we saw some loss of valve control or possible ignition breakup in the 6300-6500 range.
Did you expect more TQ because of the cam? Did you use stock AFR195 springs or do the upgrade...with a steep-ramped XFI cam? FWIW...valve control will get worse over time (as springs get weaker). If not upgraded...you may need new ones in 2-3 years? OTOH...Loss of valve control in the 6300-6500 pretty typical with your build. Only mentioned springs due to SOME feedback with shorter duration XFI cams.
I'm impressed with how close Will guessed. Interesting that he was off 1k rpms on peak point. Wonder if that was a mistake or in conjunction with the cam size? 4800rpm seems about right for peak with that cam and 195's.
Sounds like a great build...and street car. You will have FUN!
Thx for posting...it provides some thought/feedback for my conversion to shorter-runnered intake (HSR) vs mega-ported SLP on there now. FYI...Would like to hear about parts used for short-block.
Last edited by GREGGPENN; 05-19-2018 at 05:51 PM.
Reason: short-block build query
Did you expect more TQ because of the cam? Did you use stock AFR195 springs or do the upgrade...with a steep-ramped XFI cam? FWIW...valve control will get worse over time (as springs get weaker). If not upgraded...you may need new ones in 2-3 years? OTOH...Loss of valve control in the 6300-6500 pretty typical with your build. Only mentioned springs due to SOME feedback with shorter duration XFI cams.
I'm impressed with how close Will guessed. Interesting that he was off 1k rpms on peak point. Wonder if that was a mistake or in conjunction with the cam size? 4800rpm seems about right for peak with that cam and 195's.
Sounds like a great build...and street car. You will have FUN!
Thx for posting...it provides some thought/feedback for my conversion to shorter-runnered intake (HSR) vs mega-ported SLP on there now. FYI...Would like to hear about parts used for short-block.
Eagle balanced rotating kit, steel crank, forged 6.0 rod, mahle forged flat top. Pretty standard block prep, just skim off the deck and +.030 holes. Used stock balancer knowing that we would never see over 6500. Melling high volume was producing 60-80psi with conventional break-in oil.
Yes I thought that cylinder-filling from the short duration cam would make this a square motor, but I guess high runner frequency wins especially when the valve is closed. Desktop dyno predicted peak tq and hp about 200rpm lower than actual when characterized as a "tunnel ram" intake.
The AFR street eliminators are straight from the box with PAC 1.290" OD Hydraulic Roller Dual Valve Spring, 140 lbs on seat, .600" maximum lift, Max RPM 6300-6500. Steel manley retainers, 3/8" screw in studs. I took the guide plates out and ran it with 1.6 aluminrum self-aligning rockers that I previously had.
The other component we wondered about was the DUI single output coil. Anyone spinning these small cap rotors out past 6000 and see some ignition breakup? Gapped to about .035. No doubt could be better with multi spark ignition.
Yes, i'll do some work on the closed loop tune in the car and probably put it on rollers at some point. I'll have to be proficient with tuning by that time because my local chassis dyno probably doesn't have an old school chip burner!
We started some pulls at 2700 and it was making 420ish ft-lbs there too. There was one or two pulls up thru 6500.
6400 383tq 466hp
6500 368tq 456hp
Thanks for the graph. Looks great. 425 tq at 3k...that things going to get going quick.
Originally Posted by STL94LT1
Do you also plan on doing a chassis dyno? Would be very interesting to see the percentage difference.
Keep in mind, it would be going from a "gross" rating to rear wheel; the diff is going to be pretty big. Bigger than the factory net ratings-to-wheel difference than we're used to seeing.
Similar motor....but making a bit more power and TQ than a 383 Lingenfelter built for me 30 years ago. Car was an '88 C4 convertible...strong 700R4....3000 RPM stall...3:23 gears. My motor was pretty square at 460 HP/450 TQ. Car ran mid to lower 12's and had a stupid top end...170+ !! It was a totally "Bad ***" street sweeper at the time...especially considering it had great "Cruising Manners" !!
we saw some loss of valve control or possible ignition breakup in the 6300-6500 range.
In an episode of Engine Masters (it's on YouTube) I think it was the roller rocker episode, they pointed out that 3/8 rocker studs can flex at high rpm and kill power, where 7/16 studs don't. Something to consider if you want to really wind it up.
Update: trapped 87mph in the 1/8 mile the first time out at 9.0s. 2.3s 60ft. This was at the Black Hills Corvette Classic track day. All the cars that I saw had street tires and there was no track prep. For reference, the stock LS1s were doing 9.5 and new C7s with launch control were just under 8.5 at 95-100mph on this day at this track. Not meant to be a strip car, but I bet with some slicks we could be deep in the 13s at 105? In drive, the car shifts to second too soon, and its hard to manually execute the 1-2 shift without going in to drive. I think a B&M Quicksilver ratchet is warranted.
Also did the autocross event and finished 12th out of about 50. I was really happy with that but has less to do with engine performance. You can imagine a lot of the drivers were not really getting after it.
In an episode of Engine Masters (it's on YouTube) I think it was the roller rocker episode, they pointed out that 3/8 rocker studs can flex at high rpm and kill power, where 7/16 studs don't. Something to consider if you want to really wind it up.
Good point, unless you run a 1.6 or have lots of lift/spring stick with a stock style (long slot) rocker arm long as you can.
No reason to run a 368 cam up to 6k or more they are done way before that esp on a 383. Good street combo though
Update: trapped 87mph in the 1/8 mile the first time out at 9.0s. 2.3s 60ft. This was at the Black Hills Corvette Classic track day. All the cars that I saw had street tires and there was no track prep. For reference, the stock LS1s were doing 9.5 and new C7s with launch control were just under 8.5 at 95-100mph on this day at this track. Not meant to be a strip car, but I bet with some slicks we could be deep in the 13s at 105? In drive, the car shifts to second too soon, and its hard to manually execute the 1-2 shift without going in to drive. I think a B&M Quicksilver ratchet is warranted.
Also did the autocross event and finished 12th out of about 50. I was really happy with that but has less to do with engine performance. You can imagine a lot of the drivers were not really getting after it.
I would suspect with drag radials you would run low 12's at 112 mph on a good hook.
05-19-2018, 06:55 AM
