help with Cam selection on modified engine
Thread Starter
Advanced
Joined: Dec 2021
Posts: 63
Likes: 9
help with Cam selection on modified engine
Car is 77 Vette
I have submitted the cam request form at Comp Cams and have called a few times and seem to just be on hold FOREVER giving up each time..... I am not a knowledgeable cam guy so I apologize in advance for stupid questions...lol
I want to possibly put a different cam in the engine than I have now - I have the XE268 in it now and it lopes a little more than my wife likes at idle. the description on website said it had a smooth idle, but also says it has a range of 1600 to 1800 - so not sure if really have the best cam for the car - what should the idle be set at - I had it set as low as I could in the 800 range.
Brief engine build data:
Basically want as much HP as I can get with a smooth idle - not gonna race the car, but want it to fun (fast) when I hit the gas pedal. any recommendations?
TIA
Michael
I have submitted the cam request form at Comp Cams and have called a few times and seem to just be on hold FOREVER giving up each time..... I am not a knowledgeable cam guy so I apologize in advance for stupid questions...lol
I want to possibly put a different cam in the engine than I have now - I have the XE268 in it now and it lopes a little more than my wife likes at idle. the description on website said it had a smooth idle, but also says it has a range of 1600 to 1800 - so not sure if really have the best cam for the car - what should the idle be set at - I had it set as low as I could in the 800 range.
Brief engine build data:
- flat top pistons,
- aluminum heads with
- 64 CC combustion chamber
- 185 cc intake runner
- 62 cc exhaust
- 2.02" intake valves
- 1.6" exhaust valves
- 0.575 max valve lift
- edelbrock performer intake
- stock style hydraulic flat tappet lifters
Basically want as much HP as I can get with a smooth idle - not gonna race the car, but want it to fun (fast) when I hit the gas pedal. any recommendations?
TIA
Michael
Thread Starter
Advanced
Joined: Dec 2021
Posts: 63
Likes: 9
Started shopping Holley Carbs and ended up purchasing an EFI kit that I am in the process of installing (along with doing a TON of other work on the car). figured while the engine was out the car would be a good time to go with a different cam.... thinking I need a lower RPM power band since I don't race the car -
Race Director
Joined: May 2006
Posts: 18,692
Likes: 2,572
I honestly don't recall - its been a long process - had the original quadra jet rebuilt (sent off) and I followed the instructions he provided - i remember getting a vacuum gauge and using it as part of the process. Car had a good hesitation off the line then took off really well, but the hesitation drove me nuts - so I took to a local guy and he basically rebuilt it again stating things that should have been done that werent. When I got it back from him, hesitation was gone but the car didn't seem to have the same power. Ran car like that for a couple of years before it literally started running like crap after a really hard take off one day. Said screw it and bought a new edelbrock - car ran perfect with it other than it had lost a lot of the power.
Started shopping Holley Carbs and ended up purchasing an EFI kit that I am in the process of installing (along with doing a TON of other work on the car). figured while the engine was out the car would be a good time to go with a different cam.... thinking I need a lower RPM power band since I don't race the car -
Started shopping Holley Carbs and ended up purchasing an EFI kit that I am in the process of installing (along with doing a TON of other work on the car). figured while the engine was out the car would be a good time to go with a different cam.... thinking I need a lower RPM power band since I don't race the car -
Race Director
Joined: Mar 2017
Posts: 11,923
Likes: 4,495
From: Virginia
A Holley Sniper EFI system plus a new cam could cost more than a junkyard LS swap (which gives you EFI and a roller cam for free!). All the fuel tank work you need to do is the same either way.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,153
Likes: 9,283
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Dont forget all the special swap parts, getting rid of the unwanted wiring and the cost of tuning, plus the O2 sensor and all the other sensors you will need....
As for the tune, set your idle at 900, dont bother trying to get lower. Set your timing at 16 degrees at idle and then look for 36 degrees all in at 3000 rpm. Then add in your vacuum advance with a soft and medium spring to no more than 50 degrees all in. after that reset you idle back down to 900 and start looking at your AFR. You will need to rent borrow or buy and AFR gauge and see what your idle, transition, cruise and wot is.
As for the tune, set your idle at 900, dont bother trying to get lower. Set your timing at 16 degrees at idle and then look for 36 degrees all in at 3000 rpm. Then add in your vacuum advance with a soft and medium spring to no more than 50 degrees all in. after that reset you idle back down to 900 and start looking at your AFR. You will need to rent borrow or buy and AFR gauge and see what your idle, transition, cruise and wot is.
Le Mans Master
Joined: May 2007
Posts: 5,018
Likes: 1,118
From: North tonawanda NY
I think we are failing to see the point, OP wants the car to idler and drive smoother. it almost seems counter productive to the list of upgrades but... anything below a 268 cam is more or less an RV truck cam. I had a 262/268 lunati cam in my car and it behaved much like a stock motor
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
Advanced
Joined: Dec 2021
Posts: 63
Likes: 9
Thread Starter
Advanced
Joined: Dec 2021
Posts: 63
Likes: 9
I think we are failing to see the point, OP wants the car to idler and drive smoother. it almost seems counter productive to the list of upgrades but... anything below a 268 cam is more or less an RV truck cam. I had a 262/268 lunati cam in my car and it behaved much like a stock motor
Thread Starter
Advanced
Joined: Dec 2021
Posts: 63
Likes: 9
Thread Starter
Advanced
Joined: Dec 2021
Posts: 63
Likes: 9
Dont forget all the special swap parts, getting rid of the unwanted wiring and the cost of tuning, plus the O2 sensor and all the other sensors you will need....
As for the tune, set your idle at 900, dont bother trying to get lower. Set your timing at 16 degrees at idle and then look for 36 degrees all in at 3000 rpm. Then add in your vacuum advance with a soft and medium spring to no more than 50 degrees all in. after that reset you idle back down to 900 and start looking at your AFR. You will need to rent borrow or buy and AFR gauge and see what your idle, transition, cruise and wot is.
As for the tune, set your idle at 900, dont bother trying to get lower. Set your timing at 16 degrees at idle and then look for 36 degrees all in at 3000 rpm. Then add in your vacuum advance with a soft and medium spring to no more than 50 degrees all in. after that reset you idle back down to 900 and start looking at your AFR. You will need to rent borrow or buy and AFR gauge and see what your idle, transition, cruise and wot is.
Le Mans Master
Joined: May 2007
Posts: 5,018
Likes: 1,118
From: North tonawanda NY
do you still have the stock l48 station wagon cam? I assume it was an L48 because an L82 stock cam would have even rougher street manners than the 268 cam from what ive read (im not trying to be difficult here, just trying to be realistic about putting things in perspective) Is it the cam your wife doesnt like or is is in other aspects of what it is... (no overdrive -higher rpms in drive and so on)
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,153
Likes: 9,283
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
If it's idling like **** with efi then it doesn't like your intake. I bet it's a dual plane. Find a low rise single plane and I bet all your issues go away. I ran an old tarantula and it idled fine. Other than that you are going to be stuck where you are because it's a fuel distribution issue. You can still bump up the Idle and hope it smooths out but you are going to fouling some plugs while others are lean
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,032
Likes: 4,387
From: Marlton NJ
That Comp Cam is kinda mild. You should be able to hear a little lope, but that's about it. Couple things to try:
- If you wife doesn't like it, it could be the mufflers. What kind do you have on?
- It will lope less if you raise the idle a little, you said you have it low, try +50 or +100. It makes a lot of difference at that range.
- Do you have the vac can on manifold vac, (not port) That makes a huge difference at idle, 10* adv vs 25* , more smooths it right out.
- As mentioned check your idle screws for best vacuum, and lean / rich roll off (-50rom) And AFR if you can. That also could make a difference if it's running rich or lean.
Thread Starter
Advanced
Joined: Dec 2021
Posts: 63
Likes: 9
Thanks for all the input guys - really appreciate it! just to clarify, I am in the MIDDLE of an EFI install so I haven't run the car on the EFI and can't really make any CARB adjustments as I have moved on from the carb - I was just thinking I could maybe try a different cam while I had the engine out.
I think I am going to stick with the XE268 cam and see how it runs after the EFI upgrade - I am doing the tremac 5 speed and a new quieter exhaust too - so that maybe enough so the wife will ride it in with me again. If not, then I can readdress the intake or cam...
Thanks again and glad ya'll talked me out of the swap for now!
MD
I think I am going to stick with the XE268 cam and see how it runs after the EFI upgrade - I am doing the tremac 5 speed and a new quieter exhaust too - so that maybe enough so the wife will ride it in with me again. If not, then I can readdress the intake or cam...
Thanks again and glad ya'll talked me out of the swap for now!
MD
