I pulled the intake on my 1986 w/ iron heads due to a coolant leak and have a NAPA replacement gasket set without EGR blockoffs (no coolant passage restrictors either but no worries with this). The original manifold base gaskets had blockoffs at the heads center EGR ports. The LH side is moot since the intake doesn't have a LH EGR passage, but the RH side blocked flow through the intake to EGR valve -- makes sense since there's an external EGR tube between exhaust port #8 and the intake (I know aluminum heads don't have EGR ports). Question I have is if it's OK to use the manifold base gaskets w/o an EGR blockoff on the RH side. I'm afraid of having too much exhaust gas supply to the EGR and mess up engine calibration/performance, and/or the internal EGR port bypassing the external EGR tube and tripping a SE light if there's too low flow/temp to actuate the EGR temp switch. I'm also afraid of re-using the old blockoffs (or making my own) in case they leak since they won't be 'integral' with the gasket, or having them shift during assembly. Is anyone running EGR flow through the heads and external tube without any problems?

 

It sounds like you have a mix match of parts. The '85 intake should receive exhaust through the head. Where the old gasket blocked passage. If YOUR intake gets the exhaust from the exhaust manifold, it sounds like you have an aluminum headed intake base. Regardless of where your EGR is set up to get the exhaust, I doubt it can accept gasses from two sources. Even if it can, it is the EGR VALVE that is calibrated to allow the proper amount of exhaust in. In short, I don't think the open exhaust passage in the intake gasket will pose a problem.

RACE ON!!!

 

Do 86-on intake bases in aluminum head motors have a (unused) internal EGR passage in addition to the external EGR pipe?

 

I don't know. I wouldn't think so. I also don't know how the external (aluminum headed) fed EGR gets it's gasses. Is that tube hooked up directly to the egr or to the manifold?

RACE ON!!!

 

External EGR tube joins the #8 exhaust manifold port with a flange/port on the intake near the distributor base. This intake EGR port runs through the manifold to the EGR valve supply, and the one from the right head does too. 1986 was a funny year, the manifold was apparently Al head ready but the Al heads weren't until the later part of the model year. Was wondering if they kept the same intake base manifold casting in later years. The 85 internally routed EGR also has a different EGR valve based on catalog part numbers, and all 86-91 EGRs were the same. So I'm a little worried about adding EGR through the head -- the 86 EGR valve may not properly meter the higher abundance of exhaust gas (in addition to potentially bypassing the external tube and tripping a fault w/o enough temp/flow through it). The best solution would have been to wait for OEM gaskets (65 + shipping) for an '86 w/ iron heads, but I didn't know the $20 NAPA ones would be this much trouble AND I wanted the car ready this weekend! I decided to re-use a blockoff plate from the old gasket, first glue it to the gasket with silicone to keep it in place, then install the manifold base. Should keep it from moving during instal and hopefully get clamped tight enough to stay in place for another 18-years.

 

That ought to do it.

RACE ON!!!