'86 5.0 H.O question....


Jun 2, 2005
I have an '86 5.0 H.O in my '88 Thunderbird.It's a stock Speed Density engine (Mustang computer also) with an Explorer intake and 1 5/8 headers,true dual exhaust with H-Pipe,and a 58mm throttlebody (I had to get one from a Mark VII because my engine didn't have one).My questions are....What is the biggest throttlebody I can use without going too far?I have a 60 and a 65 in the garage.Are the 1 5/8 headers overkill?Are the 19# injectors adequate?Thanks.
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If you have an 86 block, you have E6 heads and flat top pistons. Until those are gone anything you are doing is moot.

E6 Heads flow like poo. Hence the 58MM TB and smaller E6 upperintake on a Stock 86HO.

Right now the headers are probably overkill, as is the explorer intake. 19's are adequate.

Right now the heads are the bottleneck.

Tear down the motor, notch the pistons, and slap on some different heads. then a 60 or 65MM TB and the rest of your combo. Big difference then.

86 was the 'teething" year for EFI 5.0s.

86's lost 25hp and 25lbs of torque, over the 87+'s mainly due to those heads.
Modular2v said:
the speed density is kinda limiting you on alot of aspects.....i wouldnt go much bigger than the throttle body you have now

Crap! Total Crap! LOL Just pickin on ya man. :D

Your real limiting factor at this point are the E6 heads. They're not so limiting though, that you won't find a gain from running a larger TB. If you've got a 65mm lying around then put it on. I've run as large as 70mm on E6 heads and stock cam and produced a dyno measurable gain from the swap. Don't expect miracles or anything, but you will find a gain there. The 86 SD cam is one of the most agressive of the 5 oh HO OEM cams and will make use of any additional air you can get into the combo. You'd be suprised how much you can wake up that combo with a set of TFS heads and that stock SD cam. On a stock motor... I'd hazard a guess that you're at roughly 75% of the potential for the stock cam (figure pulled out of my rear-end. Just a guess with no hard data to show for it).
I have a set of GT40's on the workbench.I hope to get them on soon.Will the headers hurt my engine (performance wise)?I just removed the factory Ford headers and put these on Saturday.The car isat the muffler shop right now geting the cats removed.
I replied to your PM about the GT40 heads but the short version is that you'll not be able to install those heads without either notching your 86 flat tops or swapping them out for a set of 87+ pistons. A bottom end rebuild kit may be in your future.