Rocker arms ratios

CORVETTE SPECIFIC - Applicable to all or most models

Moderators: DOC, MR.WOLF, australi, smackC4

User avatar
Fissan
*Senior Forum User
Posts: 442
Joined: Sat Jul 23, 2011 10:30 pm
Location: Rockingham, WA

Rocker arms ratios

Postby Fissan » Sun Jun 03, 2012 12:03 pm

Hi everybody
Has anyone had a go at changing rocker arm ratios on a stock 350 from 1.5:1 to 1.6:1 ??

User avatar
DOC
*Gold Class Member #777
Posts: 3696
Joined: Sat Jun 21, 2008 12:41 pm
Location: Rocky QLD Australia

Postby DOC » Sun Jun 03, 2012 12:20 pm

Yes. I put 1.6-1's in my engine a few years ago. Got them from Summit racing. Very inexpensive. You can spend heaps on fancy roller rockers. But truth is, on a street car, the difference in performance is so very slight, I really don't think it's a good bang for the buck.
I got the Summit brand ones that look just like the stock one's. Seems every 8 years or so, The valve seals need replacing in my car. So, while in there replacing valve seals. It's a pretty simple job to replace rockers. You have them off anyway!
It will give you just a tad more lift. Performance wise, Not huge. But also not a great cost.
I would say a little better mid range. But I have never Dyno'ed my car.

User avatar
australi
* Founding Administrator
Posts: 16513
Joined: Sun Jan 15, 2006 8:32 pm
Location: Brisbane, Queensland, AUSTRALIA
Contact:

Postby australi » Sun Jun 03, 2012 12:27 pm

Doc; when the C4's back on the road, I'll be asking (begging) you to keep your long ago quote to replace my seals; I have the whole set, plus most of the tools to do it in situ except the spring compressor. :o

...Was planning originally to DIY but couldn't be f****d.

User avatar
DOC
*Gold Class Member #777
Posts: 3696
Joined: Sat Jun 21, 2008 12:41 pm
Location: Rocky QLD Australia

Postby DOC » Sun Jun 03, 2012 12:31 pm

I have a overhead Compressor. Very simple tool, Also have the fittings to screw into the head in place of the spark plug. What I don't have, and wish I had right now, is an air compressor! Anyway, simple Job. And after all the shit I have given you over the last few years. Would be happy to come over some Sunday and help you with it.

User avatar
australi
* Founding Administrator
Posts: 16513
Joined: Sun Jan 15, 2006 8:32 pm
Location: Brisbane, Queensland, AUSTRALIA
Contact:

Postby australi » Sun Jun 03, 2012 12:38 pm

:-) :o

I have two air compressors. I also have that fitting - bought when I was going to DIY; main thing that's a pain is cranking the donk over with bugger all clearance between radiator and block; been there done that so many times I'd rather pay someone.

I have the complete brand new set of seals, but it came with two sets of exhaust ones; not sure which ones are correct for my car.

User avatar
riverracer
*Senior Forum User
Posts: 1406
Joined: Sat Sep 04, 2010 1:14 pm
Location: adelaide, south oz

Postby riverracer » Sun Jun 03, 2012 2:58 pm

in the old days, putting 1.6 on just the exhaust was a common mod to gain a better breathing engine
for memory you need to check the clearance around the push rod where they come thru the head
pressed steel roller tip will still fit under the stock tin covers
they say a gain of 15-25hp due to less friction on the valve tip

:o
Speed has never killed anyone,
Suddenly becoming stationary that's what gets you.

User avatar
DOC
*Gold Class Member #777
Posts: 3696
Joined: Sat Jun 21, 2008 12:41 pm
Location: Rocky QLD Australia

Postby DOC » Tue Jun 05, 2012 11:32 pm

Put all 16 in my 77. no issues with pushrod clearance on my block. But I did check. And yes they fit under stock covers. Which is nice as the air con compressor bracket wont fit with tall ones.

User avatar
Fissan
*Senior Forum User
Posts: 442
Joined: Sat Jul 23, 2011 10:30 pm
Location: Rockingham, WA

Postby Fissan » Wed Jun 06, 2012 8:45 am

Thanks guys I have a set of 1.6 COMP Cams High Energy Die Cast Aluminum Rocker Arms comming from summit

User avatar
DOC
*Gold Class Member #777
Posts: 3696
Joined: Sat Jun 21, 2008 12:41 pm
Location: Rocky QLD Australia

Postby DOC » Wed Jun 06, 2012 1:57 pm

Those you may need taller covers for.

User avatar
riverracer
*Senior Forum User
Posts: 1406
Joined: Sat Sep 04, 2010 1:14 pm
Location: adelaide, south oz

Postby riverracer » Wed Jun 06, 2012 4:34 pm

A) possibly screw in studs as well
Speed has never killed anyone,

Suddenly becoming stationary that's what gets you.

User avatar
Fissan
*Senior Forum User
Posts: 442
Joined: Sat Jul 23, 2011 10:30 pm
Location: Rockingham, WA

Postby Fissan » Wed Jun 06, 2012 11:00 pm

Have a look when they turn up. rocker covers not a big issue screw in studs a bit of faffing around but if I need to use screw in's I may get another set of heads and do a bit of port work to get a bit of flow happening :-) Does anyone still polish the exhaust ports?

User avatar
DOC
*Gold Class Member #777
Posts: 3696
Joined: Sat Jun 21, 2008 12:41 pm
Location: Rocky QLD Australia

Postby DOC » Thu Jun 07, 2012 12:52 am

Porting yes, Polishing is a waste of time. The shape of the port has great effect. But it been proven over and over that polishing is just for show.

User avatar
australi
* Founding Administrator
Posts: 16513
Joined: Sun Jan 15, 2006 8:32 pm
Location: Brisbane, Queensland, AUSTRALIA
Contact:

Postby australi » Thu Jun 07, 2012 10:56 am

I ported the TPI plenum of my C4, as well as siamesed the headers; made a slight difference for the better.

User avatar
Fissan
*Senior Forum User
Posts: 442
Joined: Sat Jul 23, 2011 10:30 pm
Location: Rockingham, WA

Postby Fissan » Thu Jun 07, 2012 11:00 am

I thought polishishing died out a long time ago. I think I would only match port the manafolds and clean up behind the valve seats and around the valve guides

User avatar
shipy59
Posts: 558
Joined: Tue Jan 29, 2008 11:27 pm
Location: midvale Western Australia

Postby shipy59 » Thu Jun 07, 2012 12:02 pm

thats all you need do. all i did and was easy work just be super carefull around seats if you are not reseating them! :o smooth is outdated for sure,they have prooven that a chevron patten (v shape) will help keep fuel off the walls and into the airflow. so grind pattern next best thing. match the intake for sure as they are way off. :C :)


Return to “General CORVETTE Technical and Performance”

Who is online

Users browsing this forum: No registered users and 2 guests