Author Topic: 1.5 ration vs 1.65 rockers?  (Read 2049 times)

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Offline ski27fever

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1.5 ration vs 1.65 rockers?
« on: December 17, 2012, 07:57:52 AM »
Has anyone changed from 1.5 ratio stamped rockers to the 1.65 ratio rockers on a stock 71 455 ho engine?Ive been told this will add about 15 hp?I see ames is selling the 1.65 ratio stamped rockers and I was considering them to give me a slight bump up un hp.

Offline gilbertsta

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Re: 1.5 ration vs 1.65 rockers?
« Reply #1 on: December 17, 2012, 02:07:03 PM »
jim hands book on pontiac engines has some good info on this subject...
i dont have the book with me or i would quote it..

Offline ski27fever

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Re: 1.5 ration vs 1.65 rockers?
« Reply #2 on: December 18, 2012, 08:16:44 AM »
thanks I will try and find/buy a copy of the book.I Google it and seems to be a great choice,thanks for the tip.

Offline hada76

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Re: 1.5 ration vs 1.65 rockers?
« Reply #3 on: December 18, 2012, 12:40:59 PM »
can you just swap the rockers or are there other parts involved? (p rods, girdle, ect?)
'76 T/A 455 4sp   sold
'78 T/A Y88 auto  sold
'79 T/A WS6 4sp
'70 Z/28 4sp

jeff

Offline gilbertsta

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Re: 1.5 ration vs 1.65 rockers?
« Reply #4 on: December 18, 2012, 07:38:00 PM »
i believe there is a little grinding out in the push rod area of the heads needed also your rocker bolts will need to be pinned....

Offline Andy78TA

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Re: 1.5 ration vs 1.65 rockers?
« Reply #5 on: December 18, 2012, 07:58:33 PM »
I have the magnum "roller" comp cams rockers with 1.65 ratio on my 400. I did not need to do anything to the pushrod holes but I have a stock cam at the moment. Worked with the stock 7/16 rocker studs but there is valve lash required. When I swap my cam next week I will probably have to swap back to 1.5 rockers of which I might get the PRW brand or again the magnum "roller" brand. I think the 15-30 HP increase is extremely generous.
78 T/A pontiac 400- Custom Headers - 2.5 Pypes Violator header back system - Edlebrock Performer Intake - Edelbrock 1413 Carb - Head work - pro comp roller rocker - CVF bracket and pulley kit - Custom system - Recaro T/A interior

Offline Rocky Rotella

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Re: 1.5 ration vs 1.65 rockers?
« Reply #6 on: December 18, 2012, 09:04:54 PM »
I think you'll find similar results to what we found on a stock SD-455. You may have to check for pushrod bind, however, since the SD-455 heads are different.

http://www.highperformancepontiac.com/tech/hppp_1110_high_ratio_rocker_arms_install/viewall.html



Offline 72blackbird

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Re: 1.5 ration vs 1.65 rockers?
« Reply #7 on: December 22, 2012, 02:12:00 PM »
11 rwhp isn't bad for just a rocker swap- safe to say that's at least 15 hp at the crank. But IMO if you're looking to even get close to newly built 455 with fresh 6x's, let alone any iron heads that are ported and bumping the SCR up to 9-9.5:1, you're gonna need more than rockers to make any noticeable power improvement.

A 4-bolt 455 HO block is an excellent foundation for a high performance build- I've seen some builds where the stock round ports were ported, and along with the right roller or solid cam, power outputs in the neighborhood of 500 hp were achieved. But if you're a stock purist and porting your stock heads are not an option, get some Edelbrock aluminum heads,  a PPR TC-01 HF cam, and you'll be at 500+ hp. It also goes without saying that you should be upgrading to forged pistons and rods if you're at this power level.

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Offline oldskoolubr

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Re: 1.5 ration vs 1.65 rockers?
« Reply #8 on: December 22, 2012, 06:17:08 PM »
I think you'll find similar results to what we found on a stock SD-455. You may have to check for pushrod bind, however, since the SD-455 heads are different.

http://www.highperformancepontiac.com/tech/hppp_1110_high_ratio_rocker_arms_install/viewall.html
Nice to see you pop in now and Then Rocky!  Merry Christmas!