Hi folks,

Just about to pull my engine for a bit of a refresh. I can't really call it a build because I am using oem parts but it's having a new ported head and other bits for a NA build (I'll post up the progress in a build thread)

What I need is a few pointers for pulling the engine and rebuilding.

Q1. Do I need to remove the bonnet to pull the engine & gearbox or can I just prop it higher than normal?

Q2. When honing the bores what grit stones should I use? My hone came with 180 grit but I can also get 230 if needed.

Q3. I assume 60degrees is a good angle for the crosshatch in the bores

Q4. How much material can I realistically remove when skimming the head before the cam timing becomes retardedly retarded?

Q5. Are ACL non race bearings any good. They don't have to be ultra strong seeing as I'm only na.

Thanks in advance.

 

I can only answer #1, and that is no, you don't need to remove the hood. You will need to take the radiator out though.

And what was that, did you say NA build on a website called miataturbo.net?

 

To me, in the context of Miatas:

NA = chassis
n/a = opposite of turbo

About #1, I've always removed the hood. Sure, you could leave it on, but it's only held on by 4 13mm bolts...

 

Pulling the hood is very, very easy - mark the brackets with a sharpie so you can easily align it when you are done. It's worth pulling just for ease of access.

Depends on the rings you are using - ask a machinist or the manufacturer of the rings.

Don't assume anything - ask a machinist.

Factory spec is .008 - someone else will have to comment on the effects big head shaves have on cam timing. I've built a pair of motors and never had to deck a head - start with a good running motor.

 

Thanks for the replies guys. I'll see how I get on without removing the bonnet, I always have a real hard time lining the ******* up again.

Sav, the only reason I am skimming the head is to remove some dings and scratches. The head was second hand and the previous owner had had it lying around for a while face down! It also serves to bump the CR up to compensate for my polishing and valve de-shrouding in the chamber.

Koto, sorry for the confusion n/a it shall be from now on.

Yes yes I know, I would like a nice shiny snail I really would but unfortunately in England the insurance companies levy a ridiculous premium for modifying your car because it increases the risk that you pose to Joe Public. By doing an NA build I can get away with just declaring it as a new Intake and tubular exhaust header which is quite cheap.

Oh and here's a sneak preview of what's to come.

Intake port



Intake mani made from billet 6082 runners TIG welded to 6082 plate then milled flat.



View down intake.



Throttles and mani



These were taken while still in the process of head & manifold porting so nothing is quite finished yet.

 

Ibtl

 

Don't be a h8r

 

I'd agree on the hood, pulling it is easy and putting it back on is also pretty easy if you mark it like Sav said.

For the rings, the spec should be on the info you get with the rings. It varies by ring material so be sure to check. Here's a good article on cylinder bore refinishing... http://www.spearsenterprises.com/pdf...gFinishing.pdf

As for the last question, I recall my '97 book saying .004 being the max. You can restore the cam timing by using adjustable pulleys.

 

How do they find out, or do you just need to claim it lest the insurance company find out after a wreck?

 

I was wondering the same thing. I would think you could probably do a full Mazdaspeed Miata conversion and call it a "factory" feature, thereby getting past the whole modified thing.

 

Would you feel better about his motor if you knew pistons came from me and were previously in a car that had its motor removed by fmowry to put in an LS motor and before that had seen boost and water injection?

 

Yes the pistons have indeed been tempered for me by y8s and his rod bending efforts! Thanks again Matt for the fine "gift"

Anyone have any comments on the porting job? This is the first port job I have done on a car rather than a bike engine, but I have a friend who used to do lotus racing heads guiding me. I just love how you can snap open the throttles and see the valves

They use any excuse not to pay out after a wreck.

I knew someone who was left without a car for weeks because the insurance company were trying to argue that his non-standard wheels with wider tyres were a contributing factor to the accident!!

They also keep a database of **** like this so if they do find out that you withheld information then the other insurers will know and you will be penalised when you come to renew.

Imagine if Hitler had won WWII and was currently a pissy old man, Insurance companies in the UK would be about on a par with the Gestapo.

 

That is a pretty good port job. Did you remove any material for a larger port, or did you do a clean up job?

 

Yes.

Actually, I have no problem whatsoever with his engine. I've just been around here long enough that after a picture of ITBs was posted I figured there'd be an onslaught of hate from some members. That hasn't happened, so there's no impending thread lock for me to in before. (everyone here does realise, of course, what "ibtl" means, right?)

I do like the portwork, OP. Being that your experience with porting is on bikes (which rev fairly high) and your friend's is with Lotus racing engines (which rev...fairly high), has there been any consideration in your porting for mid-range torque or is this to be a high-RPM engine?

 

Can't say that I do. Help a brother out.

 

I think it's fairly safe to say it will be a screamer. Lots of material came out in order to straighten the port run in to the chamber. Looking at all the shavings on the floor you'd think I'd removed 2 kilos of ally! But most of it was from the runners in order to get the nice oval to round shape. Whilst this is a ghettotastic setup I didn't want to be another clubroadster fanboi clamping motorcycle itbs onto a chopped stock mani and wondering why I had vaccum leaks.

 

Do you plan to do an aggressive diff gear change? It really made my car wake up. Most people here go to a tall gear, but tall gears makes our n/as worthless pigs. I went with the 4.44:1. I should have gone lower.

 

Not really sure what I have now. What ratio did the jdm s-spec specials come with? It has a torsen. I do at some point want to find a six speed, mainly to reduce the cruising revs so I will have to sit down and think about what diff gear to go for then calculate speedo gears etc. Any reccomendations?

 

At least in US spec boxes 6th gear is actually shorter than 5th in the 5speed... so a 6speed conversion raises cruising rpm rather than lower it. The factory 6 speed diffs use 3.9 gears.

 

Let me google that for you