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| Camshaft / Rockers Combination - 3.1 Stroker (Page 1/3) |
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82-T/A [At Work]
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OCT 05, 08:25 AM
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Guys, second tech post of the day, I'm on a roll. Disclaimer... my Fiero has been in storage for a decade, and it'll probably stay in storage for another decade. But I want to buy a bunch of parts while I can still get them and I'm on a kick right now to collect parts. Today I have a question about cam / rocker combo.
The engine is my Fiero's original 2.8 V6/60 that I had the 3.1 "Stroker Kit" from ARI Engines installed in it. When I had the engine put together by a machine shop, I had the "Fireball" cam, whatever crap that was. I "thought" I did the break-in properly... but after a few months of driving it off and on, it wiped out a cam-lobe. So... no idea. I intend to go back through the motor again, even though it has less than 2k miles on it since the rebuild. But I wanted to know if my cam and rocker selection was acceptable.
I have a Crane Cams H272 Cam and I've got the Crane 1.52:1 roller rockers installed.
I'm going to be using the factory intake and the factory throttle body. The intake has been port-matched and hogged out, and the throttle body was ported back in the day by Darrel Morse.
Again, it's a 3.1 crank and rods with a .040 overbore piston set. I remember that previously... the engine would "fall flat" around 4,500 rpms... and just didn't produce ANY power at all beyond that. It got worse as time went on to the point where it really didn't produce much power above 4,000 rpms.
I know that even as a 3.1... air is getting restricted, and I'm committed to keeping the factory intake and plenum. Question though is... will the H272 and 1.52:1 be a good combination to give me the most about of power that I'm going to be able to get out of the car?
(side note, I have 1.7lb Accel pintle-style injectors.)
Thank you!!!
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olejoedad
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OCT 05, 08:46 AM
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Have you seen the lower intake mod that removes material from the wall between the paired intake runners?
It is not visible and is claimed to raise the usable powerband.
I think lou dias posted the information.
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82-T/A [At Work]
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OCT 05, 09:34 AM
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| quote | Originally posted by olejoedad:
Have you seen the lower intake mod that removes material from the wall between the paired intake runners?
It is not visible and is claimed to raise the usable powerband.
I think lou dias posted the information. |
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No! I haven't seen that! I'll take a look!
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Raydar
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OCT 05, 09:49 PM
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When you installed the 272, did you have any head work done, to accommodate the springs? The 272 has .454/.480 lift, at the valve, using the stock ratio 1.52 rockets. Stock springs will coil bind. My aftermarket springs would coil bind.
With all of that said, it seems like a lot of Crane cams wiped lobes, back in the day.[This message has been edited by Raydar (edited 10-05-2019).]
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Notorio
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OCT 06, 12:28 AM
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82-T/A [At Work]
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OCT 06, 01:54 AM
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| quote | Originally posted by Raydar:
When you installed the 272, did you have any head work done, to accommodate the springs? The 272 has .454/.480 lift, at the valve, using the stock ratio 1.52 rockets. Stock springs will coil bind. My aftermarket springs would coil bind.
With all of that said, it seems like a lot of Crane cams wiped lobes, back in the day.
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Hey Raydar!!! Good to see you're still around!!! I haven't been in the Tech forums for a long time.
So, I've never actually installed the H272. My question on the H272 w/ 1.52:1 roller rockers was whether or not that would be a good option. The cam that was installed in my engine when it was rebuilt was actually some cam called the "Fireball" cam that ARI offered. That one got wiped out, and I don't so much care for it anyway.
My goal is to have the H272 cam installed, with the 1.52:1 rockers. But on that topic... I'm pretty sure nothing was re-used in the top-end... but I really can't be sure. It was so long ago, and I was living in an apartment and... quite frankly... shouldn't have been buying that stuff anyway. What would you recommend I buy for the top-end? (springs / clips / retainers) with my H272 Cam? The cam is oiled up, and sitting in a box in a storage unit in South Florida.
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RayOtton
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OCT 06, 09:34 AM
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FWIW, I did every single one of the airflow mods including bored out exhaust logs, "Dawg style" upper intake, bored throttle body, low restriction cat and cleaned up Y-pipe. Also put in a Hypertech chip and underdrive pulleys.
All them them made small differences according to the butt dyno.
Then I did the 1.6 rockers and the engine just "woke up".
Not so much off the line but from 3000 RPM up to 5500 RPM there is a huge difference. Before the rockers there wasn't any reason to go past 4500 RPM, after the rockers it pulls even at 6000 RPM's though generally I don't go above 5500.
I'm so happy with the results I've given up any thought of a swap.[This message has been edited by RayOtton (edited 10-06-2019).]
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La fiera
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OCT 06, 02:23 PM
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What a lot of people dont know is that when 1.6 rockers are installed the camshaft's profile changes proportionally.
In other words, your valves open earlier, stay open longer and close later in comparison to the stock rocker ratio so the cam seems "bigger".
The only concern is what Raydar mentioned about coil bind.
As far as the cam lobes being wiped out that is contributed by low quality oil with not enough zinc and phosphorous for break-in and regular service.
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Raydar
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OCT 06, 11:50 PM
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| quote | Originally posted by 82-T/A [At Work]:
Hey Raydar!!! Good to see you're still around!!! I haven't been in the Tech forums for a long time.
So, I've never actually installed the H272. My question on the H272 w/ 1.52:1 roller rockers was whether or not that would be a good option. |
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1.52 is, technically, the stock ratio. Aftermarket vendors will typically be a bit more "exacting" than the factory. (1.52 vs "sorta" 1.5.)
Yeah... The 272 is probably my favorite V6-60 cam. (I *always* prefer stock ratio rockers. They're what the cam is designed to run with.)
It's what I had in my 3.4. I used the Comp Cams roller tip rockers. Didn't see any point in springing for the full roller rockers. Seemed like a bunch of trouble and money, for very little gain.
But yeah... you'll have to have the spring pockets machined to accommodate the compressed height of the spring. Other than that, and breaking the cam in, properly, I can't really offer anything.
Good to see you man! 
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lou_dias
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OCT 07, 09:29 AM
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Keep in mind that a 3.1 with a traditionally fully ported intake should be fine for a 3.1 ... My 3.4 is 10:1 compression with a 480/480 roller cam and the dyno is lower in the video because my racing wheels weigh 52 lbs each...
When I was using 45lbs wheels my torque was up to 249 ft*lbs years before I got into serious intake mods...
 [This message has been edited by lou_dias (edited 10-07-2019).]
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