1.7 Cobra rockers on stock-ish engine dyno. Good AND bad.

Here's a poor pic of the dyno. Two afters and one before.

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In David Vizard's book about 2 Billion 5.0 dyno tests or whatever, he notes that he *lost* 1hp form the 1.7 swap because of the stock springs. You now see some more information to back this up. I gained roughly 10 lbft accross the board with the rockers, and roughly 10rwhp peak. However with the stock springs you can see the valvetrain fall apart after 5600. The almost invisible "before" green line goes to 6000 without such trouble.

Other significant mods: Cobra intake (also in the before as well) and 4.10s (-10rwhp on dynojets generally, but on in both before and after)
Conclusion: 1.7 rockers are worth it (10rwhp/10rwtq) as a relatively easy swap, IF you swap the stock springs for something without 125k miles on them at the same time (about double the expense/work).

I put this up here because after searching all I found was supposition on these rocker's worth on a stockish 5.0

N8Miller said:

wait... did you add the cobra intake and the 1.7 rockers---then dyno it? if thats the case, the intake might have had something to do with it.

Off topic: why would gears cause you to lose HP? Its still putting down the same power.....

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The 1.7s were the only addition between dynos

Gears cause you to lose HP because if the ratio is lower, the engine will spin up more quickly to accelerate the dyno. The quicker inertial acceleration of the engine will then cost a larger portion of the HP, leaving slightly less to the rollers. Ive done back-back dynos before/after 4.10s and seen 11rwhp on a LS1 Camaro lost from 3.42s to 4.10s.

The 4.10s have been in the Mustang for both dynos though, and other than overall power for the setup, mean nothing for this post.

2muchtime said:

on a stock 302 your not making h.p. after 5500 so there realy is no bad
except for the springs bottoming out..
i wonder what the 1.6 wil do mabye 5 rwhp?

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Prior to the 4.10s, my shift light was calculated to be set at 5800. The Extrude Honed Cobra Intake is the reason for the 5800 and not the 5400 calculated for the completely stock longblock.

No clue about the 1.6s

ECU5.0 said:

well thats pretty good info...guess i should switch out my springs (they have 198k miles on them). nah, ill just wait till the new engine is built

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Or find a cheap dyno

I'll say that the car really does feel like it falls on its face at about 5700 rpm, so you would probably notice it if its happening to your car.