Author Topic: Pump Gas Cam Selection  (Read 5527 times)

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Riderjeff

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Pump Gas Cam Selection
« on: September 17, 2019, 04:32:52 PM »
Howdy all.
New poster here, looking for specific recommendations for a street cam.  I'm resurrecting a '65 T-Bird that's been hiding in my garage for too long.
It's currently got a truck motor under the hood; don't know exactly what it is but it's a 2-barrel carb and a large snout crank from 1971.  Probably a 360/361 but it's just a donor block.

This will be a cruiser, not a racer, unlikely to ever go to the strip except for fun.  It will need to be an economy rebuild, either a 390 or 410. I've got a Streetmaster for the intake, and some C4AE-G heads on the shelf that will probably be rebuilt with stock valves and springs appropriate for the cam. I plan on a set of FPA headers, but that's about it for performance parts.  T-Birds need vacuum, and this will have the stock brakes & vacuum accessories.

The thing is, I'm looking at appx. 9.8 or maybe 9.5/1 compression with dished pistons.  I want to avoid the expense of forged and/or custom pistons.  I'll spend my money on good machining, so I'll have a stock bottom end put together right. 

The question is how much cam will I need to avoid detonation on pump gas? If the block is decked to allow good squish, what do you think would be the best compromise cam for good street manners and no octane problems?  Locally all we get is 91 ethanol blend.

I'd appreciate specific recommendations, rather than numbers, if that's not asking too much.

Thanks in advance.

plovett

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Re: Pump Gas Cam Selection
« Reply #1 on: September 17, 2019, 04:36:21 PM »
What rear gear and what converter is it going to have? 

paulie

Riderjeff

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Re: Pump Gas Cam Selection
« Reply #2 on: September 17, 2019, 04:40:50 PM »
I'd have to double check the build plate, I think it's a 3.0 rear and I plan on keeping the stock converter and Cruise-o-Matic MX trans.

plovett

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Re: Pump Gas Cam Selection
« Reply #3 on: September 17, 2019, 04:44:35 PM »
Compcams 268H, based on what you have said.

But Wait for more advice.

paulie

Riderjeff

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Re: Pump Gas Cam Selection
« Reply #4 on: September 17, 2019, 05:03:38 PM »
I like the Comp 268H, but was/am worried about too much cylinder pressure. Was thinking a little more duration would be a bit friendlier, but still need all the accessories to work.  Maybe the 270H?

plovett

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Re: Pump Gas Cam Selection
« Reply #5 on: September 17, 2019, 05:06:32 PM »
Building a 410 would make the 270H more viable.   The extra 20 cubes would soak up some of that cam.   

plovett

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Re: Pump Gas Cam Selection
« Reply #6 on: September 17, 2019, 05:07:57 PM »
A little more gear would help, too.  Is a 3.25 or 3.50 too much? 

plovett

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Re: Pump Gas Cam Selection
« Reply #7 on: September 17, 2019, 05:19:17 PM »
When I put the 268H in the dynamic compression calculator in a 390, with 9.8:1 compression and installed on a 106 degree intake center line, I get a dynamic compression of 8.08:1. 

That is not crazy high.  The heavy car, high gears and stock converter hurt you there.  91 octane will help.

9.5:1 would be better.  0.3 points of compression will net you an almost unmeasurable power difference.  But detonation will be noticeable at some point, if it occurs. 

paulie
« Last Edit: September 17, 2019, 05:21:59 PM by plovett »

Drew Pojedinec

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Re: Pump Gas Cam Selection
« Reply #8 on: September 17, 2019, 05:21:20 PM »
There has never been a camshaft, carburetor, or torque converter that I would buy off the shelf.
In any of those cases I would contact an expert, pour all the details out to them, and have them make a custom piece for my application.

Riderjeff

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Re: Pump Gas Cam Selection
« Reply #9 on: September 17, 2019, 06:10:14 PM »
Thanks, but as I said in the original post this is an ECONOMY rebuild.  Pretty much everything will be off the shelf!   :)

fastback 427

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Re: Pump Gas Cam Selection
« Reply #10 on: September 17, 2019, 06:29:29 PM »
You can get a custom camshaft from one of the three builders here for roughly the same price as a shelf cam...
I did.
Jaime
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Sand hauler

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Re: Pump Gas Cam Selection
« Reply #11 on: September 17, 2019, 07:01:51 PM »
Ditto on what fastback said. And it will be worth it in the long run that I know. Lessons learned the hard way
Bobby-   Carlsbad, NM

blykins

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Re: Pump Gas Cam Selection
« Reply #12 on: September 17, 2019, 07:07:52 PM »
A custom flat tappet will run you about $65 more than a shelf cam, but it’s definitely worth it.  There are lots of cams that are universal.  The 268H, 270H, etc., are great cams but they share the same specs for every single engine family.  Different engine brands and even different engine families require different specs. 

One beauty of a custom flat tappet is that we can grind them with more lobe taper to help with cam break in. 

You are wise to keep an eye on the duration with the shorter cams.  It can bite you with a tall gear and heavy car.
Brent Lykins
Lykins Motorsports
Custom FE Street, Drag Race, Road Race, and Pulling Truck Engines
Custom Roller & Flat Tappet Camshafts
www.lykinsmotorsports.com
brent@lykinsmotorsports.com
www.customfordcams.com
502-759-1431
Instagram:  brentlykinsmotorsports
YouTube:  Lykins Motorsports

Riderjeff

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Re: Pump Gas Cam Selection
« Reply #13 on: September 17, 2019, 07:09:13 PM »
Ditto on what fastback said. And it will be worth it in the long run that I know. Lessons learned the hard way

Can you guide me to who these builders are?  I'm such a newb.. ::)

plovett

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Re: Pump Gas Cam Selection
« Reply #14 on: September 17, 2019, 07:43:22 PM »
It's the 3 Bee's!

I am against advertising on the main forum, but I don't think this is that.  They are all gentlemen and won't take advantage.  I think this is just providing information. Jay can decide. 

Anyhoo,

The 3 Bees are:

Brent Lykins

Barry Rabotnik

Blair Patrick

Just google their sites and contact them.  It is funny that the three most prominent FE guys are "Bees", but that is what happened.  :)

paulie