92GreyGT

Did you put different valve springs on the heads? Stock Explorer valve springs aren't going to work. Your fuel pressure is a little low but not low enough to keep the engine from going above 4900. It sounds like a timing issue or valve springs to me.

the new nos/man

are your cats glowing red?

i got a 88 bronco here with the same prob .

im going to check and make dam sure the timing chain didnt jump a tooth. its a used p.o.c. i just got to sell. i had to change the pass side head gasket ran great '
than in 2 weeks it wont barley rev over 4g cats where glowing red i gutted them,. same thing im going to put it on #1 and pull the cap ,and see if it lining up with the #1 termail,when it quits raining here..
if it all good then im going to change the fuel filters.
let us know

2 kwik

I like to know his fuel pressure @ 4k

kilby94

Me too! But haven't got gauge yet.

kilby94

Yeah its got new springs and 1.6 rollers. The motor only has around 7000 miles since it was put back together.Runs very strong at low rpm!! I dont think they are P heads though, but i cant find any identifiable marks on them so who knows?