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C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

1.6 rockers

 
Old 05-14-2019, 01:36 AM
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racerxl83
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Default 1.6 rockers

If I go to 1.6 roller tip rockers , self aligning I presume, using the stock cam, do I need make any other changes? On my L83 it was a no brainer bolt on. Not sure about the LT1. Help me out , and thanks
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Old 05-14-2019, 08:26 AM
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LT1 will require drippers to be trimmed in stock valve covers.
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Old 05-14-2019, 10:09 AM
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ctmccloskey
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I tried a set of 1.6 Roller tip rocker arms on a 1970 LT-1 engine in my C3 Corvette and it only picked up a couple of hp.
We used a GTECH Pro for verification after modifications are made. I was expecting more but learned that they are not that helpful by themselves.
They are very easy to install and set up properly.

I hope the install goes easily for you! Good Luck with the swap.

Best Regards,
Chris
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Old 05-14-2019, 10:34 AM
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corvettenorway
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more timing and fuel .....
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Old 05-14-2019, 01:00 PM
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Dremel works great for trimming.
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Old 05-14-2019, 01:52 PM
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Engine Masters did a back to back A-B test of rocker arms a while back. Different brands, roller vs non, and 1.5 vs 1.6
It was an interesting show, but I think the bottom line was they saw a real difference in power with 1.6 and not so much anything else. This was obviously single-run tests and do not speak to longevity.

https://www.motortrendondemand.com/d...er/0_bhpycxdw/
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Old 05-14-2019, 03:55 PM
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cuisinartvette
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x2 they do something just not much, nice add on mod. If you run a cam with a steep ramp keep the 1.5
Id recommend a fresh set of springs.
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Old 05-14-2019, 05:07 PM
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The 1.5 vs 1.6 benefits will depend on cam profile and engine combination.To make it simple cam with .300 in. lift 1.5 .450" 1.6 .480" some engines will benefit from. 1.6 on exhaust only. Some on both. Strokers can require 1.6 and 1.7 due clearance concerns between rods and cam lobes. The L83 should benefit from increased lift on both.
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Old 05-15-2019, 01:10 AM
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racerxl83
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All replies appreciated thank you. The cam is the stock 94 cam. Simply changing from the stock 1.5 to 1.6 . That is what I am considering. It's an inexpensive swap from what I can see. To achieve the same lift a cam swap is much more expensive in both parts and possibly even springs. So exploring this possibility.
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Old 05-16-2019, 01:50 PM
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Depending on how many miles you have on your engine you might want to consider replacing your valve springs while you are at it. Higher mile stock springs may not have enough spring pressure to handle the additional lift that 1.6 rockers give and also check for bind. I get it that bind with a stock cam likely won't be an issue but they are so cheap that it's not worth the risk. Call up Summit and get a set of springs matched for the LT4 Hot Cam for under $100.
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Old 05-16-2019, 03:55 PM
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If you go 1.6 intake, 1.5 exhaust you will get by on stock springs. If you go full 1.6's then it's 50/50 in my experience. Some LT1's have springs that work fine, others will have one or two that bind. So if you go full 1.6 and don't want to do it twice get springs too. Personally, I like the mixed set, keeps the torque band a bit lower
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Old 05-16-2019, 04:03 PM
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Originally Posted by vetteLT193 View Post
If you go 1.6 intake, 1.5 exhaust you will get by on stock springs. If you go full 1.6's then it's 50/50 in my experience. Some LT1's have springs that work fine, others will have one or two that bind. So if you go full 1.6 and don't want to do it twice get springs too. Personally, I like the mixed set, keeps the torque band a bit lower
That's interesting, can you give a short "for dummies" explanation of how 1.6-int 1.5-exh hybrid affects torque at rpm?
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Old 05-17-2019, 03:42 PM
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vetteLT193
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Originally Posted by jayjones View Post
That's interesting, can you give a short "for dummies" explanation of how 1.6-int 1.5-exh hybrid affects torque at rpm?
This goes straight back to how cams impact performance. On a mostly stock LT1 the factory exhaust lift is pretty good, so multiplying it by 1.6 instead of 1.5 increases it beyond the level that will increase peak torque. When your exhaust lift is a bit too much you end up moving peak torque up the RPM band some at the expense of a lower peak torque. So restated: you get more torque at higher RPM's but less at peak. That might be fine if that is what you are going for, but in driving around town mode I prefer the mixed set on mostly stock LT1's because there is a bit more torque and it's available sooner in the RPM band (i.e where you drive the car the most).

I hope that makes sense. I have driven stock LT1's with just the rocker change among a few other things (open air cleaner lids, cat back exhaust, etc) and the straight full roller 1.5's lowered oil temperature but didn't seem to do much else. maybe it revved quicker. I'd guess a 5HP gain. The full 1.6's with spring change the power could be felt at only very high RPM's to me. The mixed set I could feel the difference through the meat of the power band.

I think part of the reason the full 1.6 with spring swap doesn't do it for me is the springs people pick are nuts. It's a value neutral item to go from the stock 85 lb spring and go to a much stronger spring versus a slightly stronger spring. So instead of going from 85 to 100 (like what a stock LT4 has), people tend to get 120+ lb springs. That will guarantee control over the valvetrain at the expense of power. I think most go that route because they plan on a cam, etc. Bottom line is if you are screwing with the valve train, do it all at once so everything can be properly matched so you aren't trying to gain power on rockers, then lose it with 135 lb springs.
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