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Thanks for all the advice! You guys are awesome, and I'm sold on the 270H comp for my application. 224/224 duration @ .050" and .470 lift with 1.5 rocker ratio. Anyone know how a 1.6 rocker ratio, bringing the lift to .500 with the same duration would affect performance? Just asking the question.
Thinking of Short headers with Flowmaster super 44's into 2.5" exhaust. Opinions on this welcome also.
My "to buy" list is growing, and it's so fun!
Regards...….
Last edited by Greaser69; Jan 12, 2020 at 10:43 AM.
I have a 383 with same heads you do here's the dyno sheetI know the date is wrong my dyno guy isn't in to time just engines.
Oh I guess if you look where it say 409 Perf The date is right. Anyway it's a hydraulic roller
Thanks for all the advice! You guys are awesome, and I'm sold on the 270H comp for my application. 224/224 duration @ .050" and .470 lift with 1.5 rocker ratio. Anyone know how a 1.6 rocker ratio, bringing the lift to .500 with the same duration would affect performance? Just asking the question.
Thinking of Short headers with Flowmaster super 44's into 2.5" exhaust. Opinions on this welcome also.
It's interesting. One of the car mags did a test of header performance vs tube size, using a 383 stroker. They used 1.5" med. Length as their " base". They allowed more torque than all the other larger full length headers. Now high rpm was a different story, but from about 4000 and under, the small tube mediums beat them all. I'll continue to read and educate myself, and I sure appreciate all the opinions and knowledge.
It's interesting. One of the car mags did a test of header performance vs tube size, using a 383 stroker. They used 1.5" med. Length as their " base". They allowed more torque than all the other larger full length headers. Now high rpm was a different story, but from about 4000 and under, the small tube mediums beat them all. I'll continue to read and educate myself, and I sure appreciate all the opinions and knowledge.
That is absolutely true that smaller primaries will help with low end torque and bigger primaries will help mid to high RPM. There is no free ride!
Reno-What roller cam specs (Duration, lift, LSA)? Compression for that motor, 10+? I am guessing with 485 Gross HP and almost 500 Gross TQ 230/235 duration. .550 lift, and 10.5 compression.....
Last edited by jb78L-82; Jan 12, 2020 at 03:12 PM.
That is absolutely true that smaller primaries will help with low end torque and bigger primaries will help mid to high RPM. There is no free ride!
Reno-What roller cam specs (Duration, lift, LSA)? Compression for that motor, 10+? I am guessing with 485 Gross HP and almost 500 Gross TQ 230/235 duration. .550 lift, and 10.5 compression.....
It is 10to1 The cam can only be bought from Skip White Performance. Idles at 500 sounds frickin awesome. Pulls like a freight train. Skip calls it the Magic Cam
It is 10to1 The cam can only be bought from Skip White Performance. Idles at 500 sounds frickin awesome. Pulls like a freight train. Skip calls it the Magic Cam
Wow..great! I was freaking close....LOL
A little low on duration at 230/235 (I thought of going 235/240 earlier), pretty close with compression @ 10 (.5 either way negligible) and a bit high on my lift at .550 (.520/.540) but close. Goes to show that you can get awful close predicting power with certain combination of parts....Thanks for sharing.
Last edited by jb78L-82; Jan 12, 2020 at 03:26 PM.
Those are fabulous numbers but you would need a retro roller cam which requires a bit of a conversion to use with a Gen 1 block versus a flat tappet cam....Roller cams in general produce quite a bit more area under the curve......
Those are fabulous numbers but you would need a retro roller cam which requires a bit of a conversion to use with a Gen 1 block versus a flat tappet cam....Roller cams in general produce quite a bit more area under the curve......
No conversion howards retro rollers and the correct push rods.
If you look in the comp cams you will find the XR288HR . Will not say it is identical but i think dam close . That is the cam i am running in my 355 cu inch build
No conversion howards retro rollers and the correct push rods.
May be I was not clear with what I stated, sorry. I have a howards retro roller in my 355, as well.
A roller cam requires a cam button of some sort, most importantly, making sure that your measure the pushrod lengths carefully for your cam and cam gear/distributor gear, fuel pump pushrod compatibility (NOT an issue with Howards rollers, though). If you know what to expect, there is a little bit more involved than a simple flat tappet cam swap.......
What amazes me is Comp Cams never listed or sold a HR/SR cam like this until I ordered a custom cam with these duration and valve event specs about 20 years ago. Comp cams ask me how I came up with retarding the cam 4 degrees compared to any of their existing XE cam line up. I told them from extensive time on engine simulation software to get the highest average power over the widest rpm. I also had seen how crane cams was using @ 4 degrees retarded on their street roller series. I found some of my old Desk top dyno 2000 runs referred to as +4 dated to about 20 years ago. Because I bought the program when it first came out. I posted a bunch of the stuff online when I build my first 383. You can see where Skip White calls it a 110+4
Mine used bigger SR lobes with over .600 lifts. I have something like .620/.644. This is a picture of it when I received it from comp cams from their custom designed billet steel cams.
May be I was not clear with what I stated, sorry. I have a howards retro roller in my 355, as well.
A roller cam requires a cam button of some sort, most importantly, making sure that your measure the pushrod lengths carefully for your cam and cam gear/distributor gear, fuel pump pushrod compatibility (NOT an issue with Howards rollers, though). If you know what to expect, there is a little bit more involved than a simple flat tappet cam swap.......
Yes you are correct there are a few little things maybe even valve springs. But still pretty straight forwardBut for drivability and the power yeah buddy it is worth it
If you go roller cam.....you will need a corresponding roller spring. At .540 lift on the exhaust.....careful consideration for retainer to guide boss has to be considered as well.
I like the 270H with the 1.6 if you are on the cheap.......you could run the Z/28 Elgin springs and it is not exotic at all.
I know the date is wrong my dyno guy isn't in to time just engines.
It's called that for a reason
But for drivability and the power yeah buddy it is worth it
