Second guessing cam change
Thread Starter
Instructor
Joined: May 2007
Posts: 130
Likes: 0
From: Houston TX
Second guessing cam change
I know there have been many thrds on this subject and, having read most of them, I'm having second thoughts on my current project.
My car is an '80, stock 350, 4-spd that was ovrhauled a few years ago with balanced crank, flat top pistons but no change in heads or cam. Don't know the CR but est. 9-9.5 to 1. The A.I.R. pump has been removed and true duals with headers added.
Performance still lacking, I decided to improve the top end but didn't have the budget for heads, intake, etc.
I'm now in the process of changing the stock .390 cam to a Lunati 60101, 213/219, .454/.468, but wanted to keep the other top end parts stock.
Recent threads, however, seem to indicate I may be in for a big disappointment. True??
If so, I may reach for the money to go with RHS vortec heads and performer intake and choose the 60102 cam.
Would appreciate some input before I put this torn-down engine back together.
Tks
My car is an '80, stock 350, 4-spd that was ovrhauled a few years ago with balanced crank, flat top pistons but no change in heads or cam. Don't know the CR but est. 9-9.5 to 1. The A.I.R. pump has been removed and true duals with headers added.
Performance still lacking, I decided to improve the top end but didn't have the budget for heads, intake, etc.
I'm now in the process of changing the stock .390 cam to a Lunati 60101, 213/219, .454/.468, but wanted to keep the other top end parts stock.
Recent threads, however, seem to indicate I may be in for a big disappointment. True??
If so, I may reach for the money to go with RHS vortec heads and performer intake and choose the 60102 cam.
Would appreciate some input before I put this torn-down engine back together.
Tks
Instructor
Joined: Aug 2009
Posts: 112
Likes: 0
From: Caledon Ont
that's all great but your build is incomplete, basicaly you have no flow...at minimal a cam should have been done on the rebuild but your on track with those vortec heads, if you want cheaper speak to a good machinist he may able to help on the stock heads...just keep in mind no machine shop can duplicate the 3 valve angle of a vortec head
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
I can't comment on the cam without knowing about your trans and diff ratio, but a .450 lift cam is in the ballpark. The flow on your existing heads tops out at about 180/125 @ .400 lift - so a cam change with those heads buys you exactly dick 
You'll definitely need a head change to make significantly more power. You do NOT want to invest a single penny in those heads...and just having them overhauled is around $450+ which is in striking distance of a decent stock-replacement class iron head.
Vortec heads are a perfect budget choice, depending on your existing CR, but will require a new intake as well.
You'll definitely need a head change to make significantly more power. You do NOT want to invest a single penny in those heads...and just having them overhauled is around $450+ which is in striking distance of a decent stock-replacement class iron head.
Vortec heads are a perfect budget choice, depending on your existing CR, but will require a new intake as well.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
I know there have been many thrds on this subject and, having read most of them, I'm having second thoughts on my current project.
My car is an '80, stock 350, 4-spd that was ovrhauled a few years ago with balanced crank, flat top pistons but no change in heads or cam. Don't know the CR but est. 9-9.5 to 1. The A.I.R. pump has been removed and true duals with headers added.
Performance still lacking, I decided to improve the top end but didn't have the budget for heads, intake, etc.
I'm now in the process of changing the stock .390 cam to a Lunati 60101, 213/219, .454/.468, but wanted to keep the other top end parts stock.
Recent threads, however, seem to indicate I may be in for a big disappointment. True??
If so, I may reach for the money to go with RHS vortec heads and performer intake and choose the 60102 cam.
Would appreciate some input before I put this torn-down engine back together.
Tks
My car is an '80, stock 350, 4-spd that was ovrhauled a few years ago with balanced crank, flat top pistons but no change in heads or cam. Don't know the CR but est. 9-9.5 to 1. The A.I.R. pump has been removed and true duals with headers added.
Performance still lacking, I decided to improve the top end but didn't have the budget for heads, intake, etc.
I'm now in the process of changing the stock .390 cam to a Lunati 60101, 213/219, .454/.468, but wanted to keep the other top end parts stock.
Recent threads, however, seem to indicate I may be in for a big disappointment. True??
If so, I may reach for the money to go with RHS vortec heads and performer intake and choose the 60102 cam.
Would appreciate some input before I put this torn-down engine back together.
Tks
Thread Starter
Instructor
Joined: May 2007
Posts: 130
Likes: 0
From: Houston TX
Thanks for the frank comments....it's pretty much what I expected.
As shown above, the transmission is the stock 4-spd and rear ratio is 3.08. SO....almost any cam upgrade goes begging due to the restrictive stock heads.
If I go for the RHS Vortecs there are two valve combos and three runner sizes. What's my best choice....and should I step up the cam size????
Thks, again
As shown above, the transmission is the stock 4-spd and rear ratio is 3.08. SO....almost any cam upgrade goes begging due to the restrictive stock heads.
If I go for the RHS Vortecs there are two valve combos and three runner sizes. What's my best choice....and should I step up the cam size????
Thks, again
Melting Slicks
Joined: Jul 2006
Posts: 2,285
Likes: 487
From: Salmon Arm, BC
With those freeway gears you'll want to boost your low end torque as much as possible. keep the intake runner small (180), this keeps air velocity up and enhances cylinder filling, and use small valves 1.94/1.50. the larger valves will only help above 5000 rpm
Yes, With the better flowing heads the 60102 would be a great choice. It will give you nice street manners and when you stick your foot in it will reward you with POWER.
Yes, With the better flowing heads the 60102 would be a great choice. It will give you nice street manners and when you stick your foot in it will reward you with POWER.
Last edited by OMF; Aug 9, 2009 at 02:10 PM. Reason: cam comment
Thread Starter
Instructor
Joined: May 2007
Posts: 130
Likes: 0
From: Houston TX
My mistake....the runners on those heads are 170cc. It's the combustion chamber that comes in three sizes, 64, 67, or 76cc??
Picking the 1.940/1.50 valves I'm guessing the choice would be 64 or 67cc. What's the deciding factor??
Picking the 1.940/1.50 valves I'm guessing the choice would be 64 or 67cc. What's the deciding factor??
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Thread Starter
Instructor
Joined: May 2007
Posts: 130
Likes: 0
From: Houston TX
Duhhh...on checking Summit, the RHS 12407 heads with the 1.940/1.50 valves comes with 64cc comb chambers. 
I chose the RHS over the GM Vortec based on flow tests shown in the Graham Hansen Car Tech book on HP Cyl Heads. However, those tests were with the larger valves. Anybody know the expected difference. Larger valves, lower velocity but highr pressure...any major perf difference??
Finally, I'm not a racer, so want higher torq at low rpm...good street performer.
Cheers..
I chose the RHS over the GM Vortec based on flow tests shown in the Graham Hansen Car Tech book on HP Cyl Heads. However, those tests were with the larger valves. Anybody know the expected difference. Larger valves, lower velocity but highr pressure...any major perf difference??
Finally, I'm not a racer, so want higher torq at low rpm...good street performer.
Cheers..
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Here is a nice set of low mileage heads at a fair price that would meet your needs with the bigger cam. I wouldn't worry about the 2.02 valves. The 4 speed will allow a little more cam and heads with those gears than an automatic. Hard to find a decent flowing performance head with the small valves.
http://forums.corvetteforum.com/c3-p...70cc-67cc.html
http://forums.corvetteforum.com/c3-p...70cc-67cc.html
Last edited by 63mako; Aug 9, 2009 at 02:32 PM.
Thread Starter
Instructor
Joined: May 2007
Posts: 130
Likes: 0
From: Houston TX
Here is a nice set of low mileage heads at a fair price that would meet your needs with the bigger cam. I wouldn't worry about the 2.02 valves. The 4 speed will allow a little more cam and heads with those gears than an automatic. Hard to find a decent flowing performance head with the small valves.
http://forums.corvetteforum.com/c3-p...70cc-67cc.html
http://forums.corvetteforum.com/c3-p...70cc-67cc.html
From the flow data they don't look as good as the RHS Vortec but the perf/price looks much better...if they're in good cond.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
I wouldn't get too wound up about maximizing flow with the power targets you're seeking; the GMPP Vortecs are likely your best budget purchase if you're going to invest in a new intake. This leaves you with no more than .475 lift so the cam choices narrow out a bit. With 3.08's, an "RV" or "4x4" cam will make more power down low by giving up a bit over 5K...but with a 4-speed if you like rowing the gears this doesn't matter quite as much.
As an aside, if you really want some "grunt" consider upgrading to 3.70 gears - this will make a huge difference seat of the pants.
Used heads are always a gamble to some extent - especially if they've had machine work done. Just IMHO.
As an aside, if you really want some "grunt" consider upgrading to 3.70 gears - this will make a huge difference seat of the pants.
Used heads are always a gamble to some extent - especially if they've had machine work done. Just IMHO.
Thread Starter
Instructor
Joined: May 2007
Posts: 130
Likes: 0
From: Houston TX
I wouldn't get too wound up about maximizing flow with the power targets you're seeking; the GMPP Vortecs are likely your best budget purchase if you're going to invest in a new intake. This leaves you with no more than .475 lift so the cam choices narrow out a bit. With 3.08's, an "RV" or "4x4" cam will make more power down low by giving up a bit over 5K...but with a 4-speed if you like rowing the gears this doesn't matter quite as much.
As an aside, if you really want some "grunt" consider upgrading to 3.70 gears - this will make a huge difference seat of the pants.
Used heads are always a gamble to some extent - especially if they've had machine work done. Just IMHO.
As an aside, if you really want some "grunt" consider upgrading to 3.70 gears - this will make a huge difference seat of the pants.
Used heads are always a gamble to some extent - especially if they've had machine work done. Just IMHO.
I have considered the gear change but maybe only to about 3.55 to keep the cruising rpm reasonable. Thks
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Billa has some sound advice on the heads. The 256 cam is a great driver, Ive used it. Good idle and gobs of torque at a range youll use all the time.
Did an el cheapo build (which I dont like but his $) on an IROC. $895 10:1 shortblock, crappy Edelbrock heads, the 256 Voodoo, ported TPI and some shorties.
Suprisingly the car pulled like a mild stroker; in 2nd gear the car would push you back, hold you there and keep pulling;roasts the tires at will.
Not bad for a lo-budget pos
Did an el cheapo build (which I dont like but his $) on an IROC. $895 10:1 shortblock, crappy Edelbrock heads, the 256 Voodoo, ported TPI and some shorties.
Suprisingly the car pulled like a mild stroker; in 2nd gear the car would push you back, hold you there and keep pulling;roasts the tires at will.
Not bad for a lo-budget pos
Thread Starter
Instructor
Joined: May 2007
Posts: 130
Likes: 0
From: Houston TX
Thanks for all the input.
I found out my heads are casting #14022601, 267, 305 HO, 80-85, 58cc, 1.84-1.5, 7 bolt ex. The CA "smog" heads are #14014416 which has nearly equivalent specs. The stock '80 350ci head is #462624 which has 1.94/1.50 vlvs, 64cc.
billla is right, these heads are the main restriction and gotta go!!
I'm going to check out some reman shops. There are several pretty good looking sets of 2.02/1.60, 76cc reman heads available...half the price of new. Anyone have experience or know a reliable shop??
Thanks, again, for all the input.
I found out my heads are casting #14022601, 267, 305 HO, 80-85, 58cc, 1.84-1.5, 7 bolt ex. The CA "smog" heads are #14014416 which has nearly equivalent specs. The stock '80 350ci head is #462624 which has 1.94/1.50 vlvs, 64cc.
billla is right, these heads are the main restriction and gotta go!!
I'm going to check out some reman shops. There are several pretty good looking sets of 2.02/1.60, 76cc reman heads available...half the price of new. Anyone have experience or know a reliable shop??
Thanks, again, for all the input.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Thanks for all the input.
I found out my heads are casting #14022601, 267, 305 HO, 80-85, 58cc, 1.84-1.5, 7 bolt ex. The CA "smog" heads are #14014416 which has nearly equivalent specs. The stock '80 350ci head is #462624 which has 1.94/1.50 vlvs, 64cc.
billla is right, these heads are the main restriction and gotta go!!
I'm going to check out some reman shops. There are several pretty good looking sets of 2.02/1.60, 76cc reman heads available...half the price of new. Anyone have experience or know a reliable shop??
Thanks, again, for all the input.
I found out my heads are casting #14022601, 267, 305 HO, 80-85, 58cc, 1.84-1.5, 7 bolt ex. The CA "smog" heads are #14014416 which has nearly equivalent specs. The stock '80 350ci head is #462624 which has 1.94/1.50 vlvs, 64cc.
billla is right, these heads are the main restriction and gotta go!!
I'm going to check out some reman shops. There are several pretty good looking sets of 2.02/1.60, 76cc reman heads available...half the price of new. Anyone have experience or know a reliable shop??
Thanks, again, for all the input.
http://www.summitracing.com/parts/TFS-30300001/
Last edited by 63mako; Aug 10, 2009 at 04:30 PM.
Thread Starter
Instructor
Joined: May 2007
Posts: 130
Likes: 0
From: Houston TX
63mako...thks for the tip and link. I have looked on ebay and there are several possibilities. One is a set of #462624, 1.94/1.50, rebuilt w/springs for .510 lift and is the correct head for an '80 350 (ex CA). I think the (orig) comb cham is .622.
Wouldn't this work as well using the right gasket thickness to maintain a 9+:1 Cr??
Wouldn't this work as well using the right gasket thickness to maintain a 9+:1 Cr??
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
http://forums.corvetteforum.com/c3-p...all-block.html
Last edited by 63mako; Aug 10, 2009 at 10:46 PM.