5.8 head job
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Junior User
Joined: Jul 2007
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From: NW Ohio
5.8 head job
I have a 90 5.8 I asked about a few months ago with a bad headgasket on #2 cylinder (80psi). All other compression was 110-130psi, I'm going to do mild port work on the heads and port match the intake to the heads, also have the heads machined to clean them up. What is safe to machine off or the max I can go w/o worring about compression issues?
What else can be done to this engine to help it breathe while still keeping the EFI? I've heard that the speed density system dosent like bigger cams, is this true? I'm not doing a full build up, its just a get me through engine until I get the one I want built this summer.
So far the plan is mild port work, mill the heads, duel exhaust, and increase the fuel pressure, possibly an MSD ignition box. I dont see a reason to keep the air pump and hoses, or cats.
I have all the parts for this already so once I buy the gasket set I'll be all set.
What does everyone think?
What else can be done to this engine to help it breathe while still keeping the EFI? I've heard that the speed density system dosent like bigger cams, is this true? I'm not doing a full build up, its just a get me through engine until I get the one I want built this summer.
So far the plan is mild port work, mill the heads, duel exhaust, and increase the fuel pressure, possibly an MSD ignition box. I dont see a reason to keep the air pump and hoses, or cats.
I have all the parts for this already so once I buy the gasket set I'll be all set.
What does everyone think?
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Don't raise the fuel pressure, it's not necessary and won't accomplish anything in the long run, the computer will re-adjust and counteract any short term "improvements" this provides. You can run a cam in that motor and you will see power increases, the Crane 444232 is SD EFI compatable. Don't mill the heads any more than necessary, you'll just have to shim the rockers more to compensate. Port the blazes out of the exhaust ports in the heads but don't waste much time on the intake side, they are small but they're also easier to screw up. Definitely port match the lower intake to the heads. Good luck and have fun.
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Junior User
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From: NW Ohio
Ok Thanks, I figured that the extra airflow would require slightly more fuel, I had a similar problem with an old S10 I had... I dont have ANY experiance with Ford gas engines and ALL of my hot rod knowage is SBC stuff, so I'm trying to apply what I know to this truck.
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Yes, extra airflow requires more fuel, but the EFI system is setup to measure the A/F ratio in the exhaust and feedback that info to the computer so it can make the appropriate adjustments. You just have to make sure the O2 sensor is installed in the exhaust and is connected to the computer.
That said... the speed density system on your truck relies on a steady vacuum signal so it won't tolerate radical cams like those that produce a lumpy idle, but more lift is just fine. The stock fuel system will support 300hp give or take, so you do have some room to work, and no jet changes necessary... how cool is that.
That said... the speed density system on your truck relies on a steady vacuum signal so it won't tolerate radical cams like those that produce a lumpy idle, but more lift is just fine. The stock fuel system will support 300hp give or take, so you do have some room to work, and no jet changes necessary... how cool is that.
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From: Calhoun GA
One other thing, I wouldn't suggest an MSD ignition for what your looking to do...unless you're in need of a tune up and you have the parts laying around. You can modify your heads, install a better cam, headers and exhaust and the stock TFI system, in good working order, will operate fine.
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Junior User
Joined: Jul 2007
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From: NW Ohio
Thanks for all the responces, Yes I have an adjustable pressure regulator and an MSD 6al box sitting around from other projects over the years, They may find there way onto the truck eventually but I need to get it running first. I'm still debating the cam, thats just more money to spend right now that I dont have. Also I found some headers on Ebay pretty cheap but no EGR port, so can I just weld the EGR tube to the headder or is there a better way to do it? Also are the stock mustang 5.0 headers worth swapping onto this truck? I figure they got to be better than the OEM truck manifolds.
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Junior User
Joined: Jul 2007
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From: NW Ohio
Ok, I'm thinking about cheating a bit on the cam, I'm not going to replace it but I'm thinking about adding 1.7 roller rockers to get some more lift. My question is, what do I need to do to install these on this engine? And will they fit under the stock valve covers? My next choice is a roller tipped 1.7 steel rocker. It looks like I will just need to install studs in the head for the rockers to attach to. If this is all that I need to do, will it effect valve lash and will I need to set it any different with these rockers?
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
No need for studs with roller rockers, just buy pedistal mount versions and bolt them on like the stock rockers. If the heads or block has been machined you'll likely need some shims under the pedistals to achieve correct peload.
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Junior User
Joined: Jul 2007
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From: NW Ohio
Ok thats good to know...
Next issue! I have a cracked head, #2 cylinder between the valves. I'm looking for a replacement but I've found some GT40 heads reasonable. Other than drilling the headbolt holes bigger, does anything else need to change to use these heads?
Next issue! I have a cracked head, #2 cylinder between the valves. I'm looking for a replacement but I've found some GT40 heads reasonable. Other than drilling the headbolt holes bigger, does anything else need to change to use these heads?
