Secondary Air Cylinder Heads

Just getting round to finishing the engine install in my P38 4.6 HSE 1997

The heads have the threaded holes where the secondary air injection goes, I have bought these separately as the car did not have an engine when I bought it

Can I just blank these off, or did the 97 4.6 (Gems) come with SAI?

Thanks

think them heads are off a old v8 classic carb model

I thought the secondary injection (not used in the uk) Was a THOR engine thing and it went in to the exhaust manifolds. So not sure what heads you've got. What's the number of head bolt holes?


Ignore that. Just looked at RAVE and it shows the cylinder heads have SAI adapters.

Yep, newer 4.0 and 4.6 heads had the SAI, just need to no what thread the adapters are so I can make up some blanks

5/8 unf 20 tpi

I just went out and had a look at mine. It's a 4.6 registered in 2002 and built very late in 2001. I've not got the fittings you have on your heads. Which leads me to think the SAI was only fitted to export models, probably bound for the USA. Just trying to figure out where your heads have came from.

Thanks, can't find anyone that stocks that size, it looks like it is earlier than UNF, BSCy was 20tpi from what I can find

The heads where a bargain buy from ebay, did not notice the bl**dy holes until installed on engine, they could be discovery heads, as these seem more common with SAI

Could consider someone welding the holes shut, but wonder if it can be done whilst on the car?

Shoreline said:

Could consider someone welding the holes shut, but wonder if it can be done whilst on the car?

Click to expand...

I would be nervous about that. Ally TIG welding, which would be the obvious answer, with its High frequency arc initation could play havoc with the BECM, unless you remove it completely from the car.

How about metal putty stuff ? not ideal but a thought.

get a thread gauge on it

The size I gave you came from the RAVE manual. It relates to the tap used to clean the threads during overhaul. Never thought about the Disco link could very well be where your heads came from. I've had a look for 20 tpi as well and it seems you can buy plenty of Taps for that thread but no actual bolts. So I started scratching my head and thinking well it must of been a pipe fitted to "that they're hole" So what I think your looking for is a pipe fitting. If you can get them maybe you can plug weld them then fit them. Be far easier than welding in the engine bay and you always have the possibility of to much weld going in the hole and then messing gas flow up.

20tpi is 7/8 or 1/2



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Yes it's very strange to have 20tpi on 5/8's. Normally 18. Which pointed me towards the pipe fittings. However I haven't found anything with 20 tpi. So either RAVE has a mistake in it or it's very peculiar fitting which screws in the heads for the SAI. At this point I'd nip off down my local machine shop and ask them to make me a batch of 8 plugs I could fit. Cost wise it maybe the cheapest option.

Right done some digging around RAVE again and I might have some good news. On the Disco 2 V8 engine RAVE refers to SAI adapters which once removed from the head must be replaced with new.However it only states 2 per head. They have a 9mm internal hexagonal drive and need to be torqued up on fitting to 33NM 24ibf.ft. So these parts must be available from the main dealers. Order 4 then weld up the hole and fit them job done. that surely must be the easiest way without removing the heads again?

They are available from dealers, £40 each and need 4. Wonder if any one has replaced theirs when removing them and have them left over. Will ask local eng company to see if they can turn 4 plugs on a lathe, Can't you tell I'm north of the border!

Other option is to get some close enough to wrench in threads, say UNF, which I think is 18 TPI and just torque it down with some washers until it seals.

Thanks for the replies

Good things come to those that wait, someone is sending me 4 adapters, so can get them welded up and the rest of the rebuild finished

TA DAH!!!! :5bhurray::5bhurray::5bhurray:

Applause to early, can't find any courier that I can send the guy in the states a shipping label, for him to send the parts. Anyone know of a service I can buy here that will pickup from the states?

Aramex shop and ship