Engine Valve Spring Question

Discussion in 'Classic Mustang Specific Tech' started by 65-Fstbk, Mar 31, 2013.


  1. 65-Fstbk

    65-Fstbk Member

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    Ok so here's my dilemma. I had a set of aluminum heads (freebies) for my motor. They were from a buddy who was doing a TR6 and sold the project. Now that I'm doing the motor I have realized that the heads have been milled alot and the intake valve is sitting just up from the deck. Too much for my liking and my budget doesn't permit new aluminum heads at the moment.

    So I'm going to use the stock E7TE heads until I can afford the upgrade. The cam I am installing is the Comp Cam 281HR (35-440-8). I'm thinking the stock springs may be a little weak for the cam so I was thinking about using the spring of my aluminum heads which are heavier double springs but I have no idea what the specs on them is. I'm figuring the aluminum heads would have been used with a HP cam so it may be a good swap.

    Anyone have any input on this? The diameter is the same but the spring off the aluminum heads is heavier and they are a little taller. Think it'll work??

    Port Coquitlam-20130330-00438(1).jpg Port Coquitlam-20130330-00439.jpg Port Coquitlam-20130330-00440.jpg
     
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  2. horse sence

    horse sence Please don't call me Mom SN Certified Technician

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    what you will have to check is the valve height from the spring seat to the spring retainer for both heads . i dont think it will work because the aluminum heads are probably set up for taller springs for higher lift cams than the cast heads
     
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  3. 65-Fstbk

    65-Fstbk Member

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    I think you're right horsesense, thanks. The retainers on the aluminum heads are right at the top of the valve stems and the retainers on the stock heads sit approx 3/16" down the valve stem which makes that even worse.

    Wonder if there are performance springs for stock heads??
     
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  4. woodsnake

    woodsnake Active Member

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    Is it your first build? (serious question, not trying to be snarky.)
    Is your block already a roller block, or are you putting pieces together for the roller cam?
    You can take both springs to your local machine shop, and they can give you some specs. Like what the coil bind is, and the actual spring rate.
    A few things you need to be aware of here, are installed height, coil bind bind, and seat pressure.
    I have had a very painful learning curve regarding cams, springs and push rod lengths. And I will take every opportunity to try and talk you out of an Edelbrock camshaft. All of the valvtrain measurements are CRITICAL measurements. Especially now that most engine oils do not have the required lubrication that our cars were designed to live with. I am in the middle of this retro cam kit in my 69 351W..
    http://www.summitracing.com/parts/CCA-K35-424-8/
    I still need to measure for pushrods, and I think it will be ready after that.
     
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  5. 65-Fstbk

    65-Fstbk Member

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    Yes this is my first engine build so I'm a little overcautious about things which I think is probably a good thing.

    The block is already a roller. It's a 1987 5.0HO. Was a low mileage block and there was no ridge at the top of the cylinders whatsoever. Factory crosshatching still visible. Block checked out really good at the machine shop and I am planning on using the factory forged pistons in the original bore. Bought a 400grit Flex-Hone to remove the glaze from the cylinders and will be using new Sealed Power Moly rings. I am converting it to carb from EFI though and am using the timing cover from a 289. Will plug old dipstick hole, use the 50oz balancer, front sump oil pan etc. It was a bummer about my aluminum heads being milled so much and I am tempted to buy a set of the $600 aluminum heads from e-bay (which seem to have great feedback) even though it was not in my budget. If my wife discovered that I'd be sleeping in the Mustang though so I'd better not at this time.:doh:
    The cam I am using is a Comp Cam 281HR which has .512 lift. I had asked the guys at Comp Cam to recommend a good street cam for my set-up and this is what they recommended. I have seen this cam running in an otherwise stock Fox Body (YouTube) and it has just the right sound I want plus it generates good low end torque. The 281HR is done pulling by 5500rpm so I'm thinking a really nice fit. I think I am going to spring (no pun intended) for the matching Comp valve springs that work well with this cam in a stock set-up. Will check with Comp Tech first to get them right. Once all is installed I will use a solid lifter, set lash to zero and use a pushrod length checker to get the correct length.

    Does this sound like I'm on the right path? I REALLY appreciate all your help folks. Much appreciated.
     
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  6. woodsnake

    woodsnake Active Member

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    In order to measure for the correct push rod, you will need a pair of light weight springs, and an adjustable push rod. ONLY USE THE SPRINGS RECOMMENDED FOR YOUR CAM.
    There is a huge amount to know about valve train geometry! Please study up before you start it up.
     
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  7. Hack

    Hack Active Member

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    My advice is to buy the correct springs recommended by Comp for your cam - what Woodsnake said.

    Then take your heads and springs to a shop and have the springs professionally shimmed so they are all set up correctly.

    This isn't an area to guess or go with "close enough". You want the springs to be right. If they are too heavy you are likely to shorten the life of your cam. If they are too light you will get valve float.

    Edit: You should also take the aluminum heads to the shop and get their advice on what to do. They may be fine to use. Rely on an expert to tell you. I wouldn't even spend the price of new gaskets to run a set of E7s. You should at least be able to find some cheap GT-40s. Take a little more time now and get yourself the best setup you can. You'd be best off to sort out which head you are using for sure and then buy the appropriate springs and cam to match.
     
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