BoostedMeOtter

Have a BP4W head im looking at installing new guides in before having a valve job done by a machine shop. Already ordered a 5.5mm guide driver tool that fits an air hammer

I see there are several brands making bronze guides for Miatas. Do you guys have any recommendations ? Ive been looking at the ones from Miataroadster. Anyone use these ?

https://miataroadster.com/miataroads...i-1964290.aspx

Also any tips for removing and installing guides ?

technicalninja

Let the machine shop install the guides unless you have years of experience and the correct sized reamer.
This is not the place to "save money" by DIY.

LeoNA

The guides cannot be pushed out from the port side doing so will ruin the head. They have to be machined down on the spring side to remove the snap ring and then pushed out from the top.

BoostedMeOtter

Ive read that somewhere on here. But the factory service manuals say you can drive them out port side.



I think im going to have a hard time finding a shop that will take the time to drive them out from the spring side where im at. Part of what's making me want to do them myself and just have the machine shop ream/hone the guides

Can you tell me how it ruins the head?

LeoNA

They are installed and removed in the same direction. They are driven from the spring side to the port just to be clear. After the guides are run the end that protrude into the ports expand from the heat and use. If you push them out from the port side the cast iron will enlarge the bore in the softer cast aluminum head casting. All good shops do it from the spring side. Maintaining the the interference between the guide head is very important especially for the exhaust guides.

BoostedMeOtter

Playing with a junk NA head i have. Ive found its pretty easy to remove the circlips. Do you see any issue in just removing the circlips and having the guides pressed out spring side. Or do the guides still need to be machined down before being pushed out ?

LeoNA

Usually the circlips are recessed in a chamfer and are difficult to remove. Also the groove that they are in is sharp and may remove material. I use an aviation style cutter in an old guide and seat machine. What part of the state are you in?

BoostedMeOtter

Northern CA. Couple hours north of Sacromento

LeoNA

There are some good shops in the Sac area. Mike Haag, etc. One thing to note is that after installing the guides the seats have to be cut. The better the job installing the guides the closer the center line of the new guides will be to the seats.

BoostedMeOtter

Talked to Haag acouple months ago about having my block bored/honed. They said they only do complete engines. Do you personally have experience with a miata head being destroyed from removing them port side ?

The plan is to have a have a valve job done when guides are replaced

LeoNA

Over 25yrs of experience and my business partner has 35. I just asked him to double check. He said don't do it and don't just beat in new guides.