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Old 08-19-2019, 11:42 PM
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Default 1970 Ram Air 3 400 camshaft advice

Hi, we are building a 1970 YZ Ram Air 3 400 in a 1970 Trans Am for a customer. He wants it to remain basically numbers matching and stock as far as block and heads go, but stated he would like maybe a bit of a camshaft upgrade to get a little more out of it, but nothing too radical.

It is a YZ block, stock #12 Heads, factory rods, and cast "8" eyebrow pistons with no markings, but it appears the bore is .020 over when measured with a caliper. The pistons appear to be around .040" in the hole as well. The camshaft that is currently in it is unknown. The only stamping I can find on it is the letter "A" stamped in the rear on the camshaft, along with "MAP" stamped in the rear as well. There is nothing else anywhere on it, front or rear. I would like to talk him into letting me replace the pistons with normal Flat Tops, and try and get it atleast close to zero deck, either with the pistons, or having the block decked. I am going to also try and talk him into letting me replace the factory 50 year old rods with a better set of 5140 rods, this build doesn't need 4340. Compression should be up around 10-10.2 I believe, if I were to do those upgrades, and I was thinking about using the Crower 60916 camshaft, but then I suppose that would require an adjustable valvetrain?, so the cost just keeps climbing for him. This is just a street restoration project, so he doesnt really want to go all out with this build, which is understandable, although he did say he wouldn't mind a few upgrades. We are also thinking of buying the carb kit and Jets/Rods from Cliff to build the Qjet, and maybe have someone put the factory Points distributor on a machine and set up a custom curve for it.

So my question is, what would be a good camshaft for this application on Pump Gas without running into problems with pinging and detonation, while using the stock, non adjustable valvetrain. The valve springs will be Crower 68404. I like the idea of the 60916, just wish it didn't require an adjustable valvetrain.

How much compression do you think it has in its current configuration, and what camshaft would you recommend for it with its current parts and compression?(just in case he wants to use what he already has.)

Thank You
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  #2  
Old 08-20-2019, 12:00 AM
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Summit 2801 or 2802. I like to think that the 2801 is a high lift version of the Pontiac 068, and the 2802 is a high lift version of the Pontiac 744. The Summit cams are the cheapest. Crower cams are the highest.

The Melling SPC-3 is similar to the Pontiac 744 cam, used in some early '69 RA3 stick cars. Has lots of adv duration, to help bleed off a little compression. It used the non-adjustable system. But, I along with most others, recommend an adjustable system.

https://www.amazon.com/Melling-SPC-3.../dp/B000C4PQA8

The Lunati 10511004 is similar, but has less dur @ .050 lift, a 110 LSA, & slightly more lift.

https://www.lunatipower.com/factory-...8-301-313.html

The Melling SPC-7 is similar to the Pontiac 068 cam.

https://www.autozone.com/internal-en...07135_705947_0

From what I've read, those pistons at .040 in hole should be detonation prone.

You can get a ruff estimate on the CR with this calculator.

http://www.wallaceracing.com/cr_test2.php

"...5140 rods, this build doesn't need 4340..."

With the current price of the 5140 rods, the $400 RPM H-beams are a much better buy, IMO. Lighter, stronger, & only a very few dollars more.

https://butlerperformance.com/i-3164...tegory:1234812

http://www.racingpartsmaximum.com/sa...elhbeam-2.html

Last edited by ponyakr; 08-20-2019 at 12:49 AM.
  #3  
Old 08-20-2019, 12:02 AM
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Those heads have pressed in studs??

Adjustable valvetrain is likely the cheapest mod you will make unless it has pressed in studs. The heads can get expensive real fast(seats/guides/valves/tap studs,etc).
Important variable in cam selection is rear/first gear ratio.

I always feel it is best to send your stuff to a machine shop and have them quote you what NEEDS done, see how that fits your budget, then decide how much is left for hot rodin..
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Old 08-20-2019, 12:12 AM
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Stock non-adjustable valvetrain pretty much mandates the use of a stock cam. I wouldn’t hesitate to run the same cam that this engine rolled off the line with, the 9779068 cam.
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Old 08-20-2019, 12:44 AM
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The #12 heads have screw-in studs. You can use poly-locks with those studs, or buy some cheap 7/16 studs, & use poly-locks with them.

Some seem to think you can't run poly-locks with the bottleneck studs. But I did it for years. Never broke a stud. But, for only around $30 or so, you can buy 7/16 studs. Or, if you have a good BBC friend, you may be able to find some used factory BBC studs, real cheap.
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Old 08-20-2019, 06:13 AM
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The 1970 casting number 12 heads have a 75 cc chamber and with how they where fitted off the show room floor with deck height and head gasket had a compression of only 9.43 to 1.

If a valve job has ever been done on the heads then you can add in another 1.5 CCs of chamber volume to the formula.

With what will likley amount to a compression of less then 10 to 1 I would go with something like a high lift version of the factory 068 Cam, especially if it's a 4 speed car without the 2 to 1 torque multiplication a torque converter to help out.
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Old 08-20-2019, 07:45 AM
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The only thing that .040 in the hole is helping is the comp. ratio.
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Old 08-20-2019, 08:02 AM
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When you pick a cam make sure that you know where you want the RPMs to be at when you create your best power. The bigger the cam the higher the RPMs where you get your best power. Decide on the RPM range that works best for you and how you want to drive, factor that in to your choice. If you don't want the best power above 4000 rpm then don't go big. I like my best power lower than 4000 so a big cam wasn't what I needed.
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Old 08-20-2019, 08:08 AM
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I wouldn't cut the block that far to tighten up quench. You'll start to run into other issues like intake fit, etc.

Those pistons also reduce compression with that much valve relief area. I'd get a taller and better piston to hang on your forged rods. Shoot for something that ends up .015-.018" in the holes instead to leave enough room for a nice clean-up and zero decking at the same time.

CC the heads and calculate the true static compression ratio. Then look at camshafts.

The last one of those engines I did here ended up at 10.4 to 1 compression and we found the Crower 60916 wasn't quite enough cam for it. It ran fine but we had to take a little more timing out of it than most to run pump gas, but still good end result but it could have been better. I know, I know, I should have just called Edelbrock and purchased their "RV" cam in it, and sent the customer out of here with a case of octane booster with instructions to put 1 can in it and time it by ear, then add another can if it pinged!....LOL

Seriously, it would be good news if you still have the original Ram Air carb, no problem putting a custom kit together for it with tuning parts once you nail down the final engine combo. If you have another part number I can also supply what you need to set that up. The points distributors don't need a lot of help. I replace the factory rubber bushing (if it's even there) with a stainless steel one, clean things up, zinc plate the parts if/as needed, and new vacuum advance. Most don't need much beyond that aside from a good set of points and condenser........Cliff
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Old 08-20-2019, 08:24 AM
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Thanks everyone, I appreciate the help and tips. Cliff, where is the best place to find the taller piston that you suggested? Thanks
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Old 08-20-2019, 08:29 AM
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Start with thinking about how you use the car. Work that into your cam choice. RPM where the power is at. THEN work on what compression you want to match that and your fuel choice.
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Old 08-20-2019, 08:34 AM
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Quote:
Originally Posted by Cliff R View Post

CC the heads and calculate the true static compression ratio. Then look at camshafts.
I feel that making the compression what you want it to be FIRST to match your camshaft and fuel choices is better than working backwards from a compression that can limit your choices.
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Old 08-20-2019, 09:12 AM
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I line what Cliff said, and agree with the last post;

Compression first, cam second.

I would get a better piston with less/smaller valve reliefs;
I would deck the block, but not worry about getting it zero decked - just freshen it up;
the stock 068 cam is a very good cam, and works good with the automatic;
I was going to suggest a 744, but that might not play well with the auto.

I would also look at what exhaust is there, or what might be going there before doing any modifications (i am a bit of a purist though)....
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Old 08-20-2019, 09:17 AM
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Quote:
Originally Posted by unruhjonny View Post

Compression first, cam second.

..
So you let the compression you find out the pile of parts you have makes then go from there?
I would do that if it was a mandated pile of parts, like the engine was built already.
But if you have all your choices on the table why not dictate the compression you want first then make a list of the parts that would help you attain that?
Pick a cam more dependent on what you want to use the car for, not for the compression your pile of parts dictated.
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Old 08-20-2019, 09:37 AM
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Quote:
Originally Posted by TransAm 474 View Post
Thanks everyone, I appreciate the help and tips. Cliff, where is the best place to find the taller piston that you suggested? Thanks
Speed pro makes a 4 valve relief piston that probably has a more desirable compression height. If you know your current piston manufacturer and part number you might be able to look it up and see what the CH is on the pistons. And then compare that to the speed pro advertised CH . Auto tech can make pistons to a desired CH but that would be more money but also a better piston overall. Basically just moving the wrist pin location up or down. The first engine I ever had done back in the 80's had 8 valve relief badger pistons.
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72 lemans,455 e-head, UD 255/263 solid flat,3.73 gears,,,10" 4400 converter,, 6.68 at 101.8 mph,,1.44 60 ft.2007
(cam 271/278 roller)9"CC.4.11gear 6.41 at 106.32 mph 1.42 60 ft.(2009) SOLD,SOLD
1970 GTO 455 4 speed #matching,, 3.31 posi.Stock manifolds. # 64 heads.A factory mint tuquoise ,69' judge stripe car. 8.64 @ 87.3 mph on slippery street tires.Bad 2.25 60ft.Owned since 86'
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Old 08-20-2019, 09:56 AM
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Quote:
Originally Posted by ponyakr View Post
The Melling SPC-3 is similar to the Pontiac 744 cam, used in some early '69 RA3 stick cars. Has lots of adv duration, to help bleed off a little compression. It used the non-adjustable system. But, I along with most others, recommend an adjustable system.

https://www.amazon.com/Melling-SPC-3.../dp/B000C4PQA8
That's what I have in my RA III
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  #17  
Old 08-20-2019, 10:19 AM
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Quote:
Originally Posted by scott70 View Post
Speed pro makes a 4 valve relief piston that probably has a more desirable compression height. If you know your current piston manufacturer and part number you might be able to look it up and see what the CH is on the pistons. And then compare that to the speed pro advertised CH . Auto tech can make pistons to a desired CH but that would be more money but also a better piston overall. Basically just moving the wrist pin location up or down. The first engine I ever had done back in the 80's had 8 valve relief badger pistons.
I think the 8-relief pistons had a 1.700 CH(I call it pin height). The Speed Pro L2262F pistons have a 1.714 pin height. So, that's .014 closer to the deck. Plus, they don't have a bevel around the top. like the sealed power pistons do.

https://www.summitracing.com/parts/s...w/make/pontiac

https://www.summitracing.com/parts/u...w/make/pontiac

https://www.summitracing.com/parts/slp-l2262f

I think the Icon pistons have a 1.720 pin height.

https://www.summitracing.com/parts/u...w/make/pontiac

https://www.summitracing.com/parts/u...w/make/pontiac

But, as stated, if budget will allow, the Auto Tec pistons are best. They're lighter & can have any pin height you need. Some of the price increase can be offset because of less deck machining needed, with the correct pin height.

https://shanonsengineering.com/produ...at-top-pistons

Last edited by ponyakr; 08-20-2019 at 10:41 AM.
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Old 08-20-2019, 10:34 AM
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Pretty much what Cliff described the short block is how I built my 70 RAIII.

I used old style TRW flat tops and as they come out of the box they are only .015" in the hole or there about. I then deck the block near zero. Think I left mine .004 or .005" in the hole and with a .039" gasket I end up with decent quench. Compression was 10.13:1 on mine with the #12 heads.

For me adjustable valve train is a must so I can set lifter preload to what I want or what the lifter manufacture recommends. Making them adjustable is a piece of cake. I simply swap over to big block chevy 7/16 rocker studs and the appropriate poly lock to fit. This also provides a little more valve train stability with the larger studs. I do it with every Pontiac here regardless of cam or spring pressure choices.

On cam I wouldn't hesitate to run something in the low 220's @.050 and the Crower 60916 is one of those choices I'd look at for an engine like this. I run the 068 only because I want to conform to a certain rules package. If it weren't for that I'd be looking at something else. I can tell you everything has to be spot on to run pump gas with this cam.

If you're really stuck with pistons .040" in the hole (that just makes me cringe) and you really don't want to make the valvetrain adjustable, then I'd just stick with an 068, call it done, and hope it doesn't have wonky tuning issues and pump gas problems with the horrible quench.

Here's how my bone stocker runs after paying attention to the little details, lots of tuning, and a 3850 race weight, 91 pump gas and a 3.31 gear.

https://youtu.be/er1z7PpqsnY

Last edited by Formulajones; 08-20-2019 at 10:50 AM.
  #19  
Old 08-20-2019, 10:47 AM
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"...I wouldn't hesitate to run something in the low 220's @.050 and the Crower 60916 is one of those choices I'd look at..."

https://www.summitracing.com/parts/c...xoCIuIQAvD_BwE

A Lunati 10510312 is in that range, and is a little cheaper than the Crower.

https://www.lunatipower.com/street-m...8-276-286.html
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Old 08-20-2019, 10:55 AM
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I would go with a set of #64 heads and the Summit 2801 cam. Little less compression so you don't have to concern yourself about the fuel.
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