Bowtie Phase 2 heads modification advice
Thread Starter
Racer
Joined: May 2020
Posts: 498
Likes: 167
Bowtie Phase 2 heads modification advice needed
Ok, I’ve decided to turn lemons into lemonade with my bad intake valve. I’ve decided to keep my heads and modify them. I’ve never ported heads so I’m thinking might as well give it a shot... Here’s what I am thinking and please provide advice with parts and porting.
Here’s what I know about Bowtie Phase 2 heads:
2.02 intake 1.60 ex
184cc intake
64cc chambers
I’m going to replace everything valve guides, springs, valves, etc
My goal is to get 250 cfm at around .500 lift and 200 cfm exhaust, which appears very do-able with these heads.
The short block is standard ‘70 LT1 specs except for the cam. Yes the mechanical cam was removed. The only problem is I have no idea what the cam specs are. All I have been told is it’s a hydraulic cam that was considered the hottest hydraulic cam you could buy in the late ‘80’s... But that’s it...
I really don’t want to replace the cam, because I don’t want to pull the engine. I feel this could snowball fast into a bigger project.
So, any advice on valve train and porting???
Thanks in advance
Here’s what I know about Bowtie Phase 2 heads:
2.02 intake 1.60 ex
184cc intake
64cc chambers
I’m going to replace everything valve guides, springs, valves, etc
My goal is to get 250 cfm at around .500 lift and 200 cfm exhaust, which appears very do-able with these heads.
The short block is standard ‘70 LT1 specs except for the cam. Yes the mechanical cam was removed. The only problem is I have no idea what the cam specs are. All I have been told is it’s a hydraulic cam that was considered the hottest hydraulic cam you could buy in the late ‘80’s... But that’s it...
I really don’t want to replace the cam, because I don’t want to pull the engine. I feel this could snowball fast into a bigger project.
So, any advice on valve train and porting???
Thanks in advance
Last edited by JC 1975; Feb 16, 2021 at 09:37 PM.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Id run a solid lifter cam that can work those heads unless you really like the one thats in there.
Think those were somewhere between 215 and 220cfm stock
Id get the best valve job you can and focus on the bowl/short turn area....port entry not so much that can kill velocity..
Go little at a time, keep your speed down and have fun.
Your profile doesnt list your location.
Think those were somewhere between 215 and 220cfm stock
Id get the best valve job you can and focus on the bowl/short turn area....port entry not so much that can kill velocity..
Go little at a time, keep your speed down and have fun.
Your profile doesnt list your location.
Thread Starter
Racer
Joined: May 2020
Posts: 498
Likes: 167
Unfortunately, I don’t have a degree wheel and too cheap to buy one for only a one time use and not 100 percent confident I would do it right... Which is why I would pull the engine and take to a place to install the cam.
Thread Starter
Racer
Joined: May 2020
Posts: 498
Likes: 167
Id run a solid lifter cam that can work those heads unless you really like the one thats in there.
Think those were somewhere between 215 and 220cfm stock
Id get the best valve job you can and focus on the bowl/short turn area....port entry not so much that can kill velocity..
Go little at a time, keep your speed down and have fun.
Your profile doesnt list your location.
Think those were somewhere between 215 and 220cfm stock
Id get the best valve job you can and focus on the bowl/short turn area....port entry not so much that can kill velocity..
Go little at a time, keep your speed down and have fun.
Your profile doesnt list your location.
https://www.speedwaymotors.com/SD-SS...es,412529.html
Le Mans Master
Joined: Apr 2001
Posts: 5,941
Likes: 281
From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
Do you have a flow bench? If you really want to do a good job at porting you need it. Otherwise you might screw up the heads. There is more to porting besides cfm. You also need to watch air velocity.
Le Mans Master
Joined: Oct 2010
Posts: 6,937
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
Bowl work and a good valve job. Check for shrouding around the valves. Some minor port clean up. You should be inn good shape.
Nothing wrong with a hydraulic flat tappet cam.
Nothing wrong with a hydraulic flat tappet cam.
Le Mans Master
Joined: Mar 2004
Posts: 7,500
Likes: 1,508
From: Little Rock AR
You can clean up the sharp edges and abrupt transitions in the valve pockets and get most of the easy stuff without needing a flow bench. Just need to be careful not to nick a seat with the tools.
Cam is unknown so that is a problem. Compression and cam work together so you need to know something about both in order to move forward. Spring spec and cam selection is up in the air without more info.
Cam is unknown so that is a problem. Compression and cam work together so you need to know something about both in order to move forward. Spring spec and cam selection is up in the air without more info.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
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
Thread Starter
Racer
Joined: May 2020
Posts: 498
Likes: 167
You can clean up the sharp edges and abrupt transitions in the valve pockets and get most of the easy stuff without needing a flow bench. Just need to be careful not to nick a seat with the tools.
Cam is unknown so that is a problem. Compression and cam work together so you need to know something about both in order to move forward. Spring spec and cam selection is up in the air without more info.
Cam is unknown so that is a problem. Compression and cam work together so you need to know something about both in order to move forward. Spring spec and cam selection is up in the air without more info.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Installing one straight up shouldnt cause a problem at all
Sure a degree wheel is ideal but most times you dont need it esp for a FT cam over 220
Not familiar with that brand, probably generic chinese stuff.
Sure a degree wheel is ideal but most times you dont need it esp for a FT cam over 220
Not familiar with that brand, probably generic chinese stuff.
Last edited by cv67; Feb 17, 2021 at 01:37 PM.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I'd find a book on porting. I ported a set of 292 heads. The smallest flow point below the valve shrouding the seat is the biggest gains. I rounded it to the seat metal and then had the machine shop bore out the seats for larger 2.055 valves with multi angle valve job with manley. 100 longer valve stems.
What is your max rpm? Because 100#seat is only for sub 5000 rpm
What is your max rpm? Because 100#seat is only for sub 5000 rpm
Thread Starter
Racer
Joined: May 2020
Posts: 498
Likes: 167
I'd find a book on porting. I ported a set of 292 heads. The smallest flow point below the valve shrouding the seat is the biggest gains. I rounded it to the seat metal and then had the machine shop bore out the seats for larger 2.055 valves with multi angle valve job with manley. 100 longer valve stems.
What is your max rpm? Because 100#seat is only for sub 5000 rpm
What is your max rpm? Because 100#seat is only for sub 5000 rpm
Thank you! Good to know! Yes, definitely going over 5,000 rpm.
What’s your feelings on this set up?
And what do you think about just using a degree wheel? Not the entire kit?
https://www.summitracing.com/parts/rhs-12972-01
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
When youre ready let me know, pm'd my #. Got plenty of extra supplies you could make use of.
Have to see if I have extra carbiides but got tons of cartridge rolls, cant hurt iron with those.
DIY is always funI bet you can get 250/close to it and 200 exh without too much trouble.
Have to see if I have extra carbiides but got tons of cartridge rolls, cant hurt iron with those.
DIY is always funI bet you can get 250/close to it and 200 exh without too much trouble.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
You need "tree" style fluted carbide bits to port, especially on Cast Iron.....
I use a wide flute tree for initial shaping, then a finer tree to touch it all up........
If you have a deft and steady hand....sanding or "tootsie roll" abrasive discs are not needed......they are for making it look pretty........
Rule is, you can take more off but you can't add it back.......don't try to change the overall shape of the port, just round off and finesse what is there.
Buy a book on porting as stated and start with a junk head to get the feel.
You can buy carbide burrs here:
https://www.mcmaster.com/carbide-bits/burs/
Jebby
I use a wide flute tree for initial shaping, then a finer tree to touch it all up........
If you have a deft and steady hand....sanding or "tootsie roll" abrasive discs are not needed......they are for making it look pretty........
Rule is, you can take more off but you can't add it back.......don't try to change the overall shape of the port, just round off and finesse what is there.
Buy a book on porting as stated and start with a junk head to get the feel.
You can buy carbide burrs here:
https://www.mcmaster.com/carbide-bits/burs/
Jebby
Le Mans Master
Joined: Oct 2010
Posts: 6,937
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
I always found port work rewarding but haven't done any in over 30 years but I swear every time I hear a grinder I think I can still taste the. Iron.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Nasty stuff....Op make sure you wear great eye protection..any dust in your eyes can really ruin your day.
Breathing it in, same thing. Jebbys right on rolls...they dont do a lot for function most times in fact I rarely use them on my own stuff.
However if youre afirst timr theres a lot less chance to hurt something with rolls til you get a feel for the tool
A decent electric grinder with a Foredom $39 pedal to regulate speed helps a LOT. Slow and steady is the way to go there.
I ruiend a lot of heads figuring that stuff out, having them flowed til I figured out what did what. Got laughed out of many a machine shop. lol
Breathing it in, same thing. Jebbys right on rolls...they dont do a lot for function most times in fact I rarely use them on my own stuff.
However if youre afirst timr theres a lot less chance to hurt something with rolls til you get a feel for the tool
A decent electric grinder with a Foredom $39 pedal to regulate speed helps a LOT. Slow and steady is the way to go there.
I ruiend a lot of heads figuring that stuff out, having them flowed til I figured out what did what. Got laughed out of many a machine shop. lol