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Discussion Starter · #1 · (Edited)
I've done a search here and read a good amount on milling E7's but I guess I want to make sure this gets done right. Here is the situation:

I have a headgasket leak or head crack/warpage. Either way, the heads are coming off and I'm putting some rebuilt ones on. I have some spare E7 heads with probably 100k on them. They are going to be taken to the machine shop for a complete rebuild (valves, seals, springs, etc). I want a fresh flat surface on there so I'm going to get them milled .030.

- Does the lower intake need to be milled?
- Will the stock pushrod length work?
- Will stock replacement springs work with the higher compression?
- How much HP is actually gained from raising the compression to 9.5:1?
- Is there anything I should be aware of with raised compression (timing, octane, etc)?

The intake ports will be cleaned up and the exhaust bumps will also be removed.

Forgot to add my current engine mods:

19lbs injectors
75mm MAF
65mm throttle body
Cobra intake manifold
stock headers
Offroad H-pipe
Magnaflow mufflers
 

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- Does the lower intake need to be milled? most likely not, never had a problem. you will know if you have unmetered air and wont idle or start fast. Just eyeball it when installing the lower manifold.
- Will the stock pushrod length work? yes
- Will stock replacement springs work with the higher compression? yes
- How much HP is actually gained from raising the compression to 9.5:1? 3 1/4
- Is there anything I should be aware of with raised compression (timing, octane, etc)? no

What I would do {this is me} check the heads to see if they are warped you might not even have to get them milled. Install a cam when you have the motor apart. Install some 80 dollar comp cam springs. And seals if you want. If they only have 100k on them then they are good to go. Dont put money into stock heads. They last forever. and you will still have a few bucks left over to fill the tank and go racin!
 

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Discussion Starter · #3 ·
Well, the machine shop here will do a valve job and resurface for $150 (both heads). I figure if the resurface is already included, just pay him a few bucks more to mill them for some compression.

Would it make a difference (all-around performance and driveability) on those heads if I were to have stock replacement springs installed or do you think I won't even notice it? I've heard it'll feel like a new car.

It seems like it would be the right time to do the cam but unfortunately my budget doesn't permit that right now. Thanks for the suggestion though, I didn't even think about that.
 

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old springs do get weak but there is not a noticible difference if you have the stock cam. Maby a little more stable up a the rev limiter. I would not replace the stock springs with more stock springs especially if they have around 100k
 

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Compression & Springs...

I think raising the compression will indeed make the engine more susceptible to ping/knock - which *could* require either less timing and/or more octane.

As far as valve springs go, it they are worn/weak - you're likely to encounter valve float at high rpms. (Really won't notice anything on the low-end.)

FWIW - my '86 longblock had 254,000 miles on the stock valve springs. Not that it made any power past 5000, but I once ran it to like 5200 and it sounded like it was coming apart - pop, backfire, surge, miss, buck - it was horrible. When I did my E7 head swap, I went with the Trick Flow spring kit (Summit) and so far they've really worked well with my stock cam and 1.7 rr. (I've had it to about 6000 several times and it runs real smooth...) Good luck! Mark
 

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I want to get some E7's im porting, milled .030 also. Im running an E-cam. I should still clear fine?

My thoughts: They are'nt hitting now, im sure there is more than .030 clearance.
 

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Your stock pushrods will still work, but you will probably need a set of shims for your pedestal rockers. This would be a great time to drop in a set of used Crane/Cobra 1.7's if you are gong to retain your stock cam and can find an extra $125-$150 in the budget.
 

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You're in a spot where finding a set of budget 3-bar GT40 irons would be great. You are willing to rebuild a set of iron heads, why not add 30 RWHP for the same amount of work if you can budget it? It would be a bonus if you can find a set someone has freshened up. You might be even up financially. Just a thought...
 

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Well, the machine shop here will do a valve job and resurface for $150 (both heads). I figure if the resurface is already included, just pay him a few bucks more to mill them for some compression.
You're in a spot where finding a set of budget 3-bar GT40 irons would be great. You are willing to rebuild a set of iron heads, why not add 30 RWHP for the same amount of work if you can budget it? It would be a bonus if you can find a set someone has freshened up. You might be even up financially. Just a thought...
I agree better heads would be better, but $150 (springs not included) would be hard to beat.
 
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