HLA conversion?

[manga_blue]

2 or 3 of my HLAs are stuffed. It's time to get rid of them. I've hated the HLA setup for years anyway. This is for an NA8 but the NA6 ones are almost identical.

I've heard of a couple of options, neither of them free of problems:
- replace them with solid NB8A buckets and shims. OK, but you need a shim grinder and/or lots of bigger shims. If you do need to go bigger then there are known issues with them throwing shims at speed and wrecking the head.
- buy Mazdaspeed solid buckets and lash caps. http://www.miataroadster.com/mazdaspeed_motorsports_development/mazdaspeed_motorsports_development_solid_lifters/mmdb6n71218316/i-407708.aspx. Lightweight, but you have to get them from the States and then wait again for the right lash caps after you've measured up the buckets. Also $US296 all up.

Has anyone just tried gutting the original HLAs and replacing the valve assemblies with solid shims? This looks too easy. Am I missing something?



The outer piston is 13mm diameter, the inner is 10.00mm. It seems to me that you can remove the ball, the small spring, the valve holder and the large spring and replace them with a hardened 10mm diameter disk shim of around 3mm thickness. It takes about 15 seconds to gut them. Precision Shims Australia sell 10mm diameter shims in 0.02mm increments from 1.50mm to 4.00mm and 0.05mm increments up to 5.00mm, covering the size range that I think is needed. They're $7 each. It's a full cam out and in job to measure up for shim sizes but at least they're in stock in Oz.

This would effectively convert it to a shim-under equivalent. Total weight would come out to about 50g per bucket. That's much the same as the old HLA, a bit heavier than the NB8A's 47g and a fair bit more than the Mazdaspeed's 35g. The car only spins to a bit over 7000, but it does spend long periods up there.

[wozzah1975]

2 or 3 of my HLAs are stuffed. It's time to get rid of them. I've hated the HLA setup for years anyway. This is for an NA8 but the NA6 ones are almost identical.

I've heard of a couple of options, neither of them free of problems:
- replace them with solid NB8A buckets and shims. OK, but you need a shim grinder and/or lots of bigger shims. If you do need to go bigger then there are known issues with them throwing shims at speed and wrecking the head.
- buy Mazdaspeed solid buckets and lash caps. http://www.miataroadster.com/mazdaspeed_motorsports_development/mazdaspeed_motorsports_development_solid_lifters/mmdb6n71218316/i-407708.aspx. Lightweight, but you have to get them from the States and then wait again for the right lash caps after you've measured up the buckets. Also $US296 all up.

Has anyone just tried gutting the original HLAs and replacing the valve assemblies with solid shims? This looks too easy. Am I missing something?



The outer piston is 13mm diameter, the inner is 10.00mm. It seems to me that you can remove the ball, the small spring, the valve holder and the large spring and replace them with a hardened 10mm diameter disk shim of around 3mm thickness. It takes about 15 seconds to gut them. Precision Shims Australia sell 10mm diameter shims in 0.02mm increments from 1.50mm to 4.00mm and 0.05mm increments up to 5.00mm, covering the size range that I think is needed. They're $7 each. It's a full cam out and in job to measure up for shim sizes but at least they're in stock in Oz.

This would effectively convert it to a shim-under equivalent. Total weight would come out to about 50g per bucket. That's much the same as the old HLA, a bit heavier than the NB8A's 47g and a fair bit more than the Mazdaspeed's 35g. The car only spins to a bit over 7000, but it does spend long periods up there.

I converted my engine, but only because of the very large cams.

To be honest, unless you're planning on fitting big cams and turning it over 7500-8000rpm on a regular basis you're better off just getting complete replacement HLA's. They'e not expensive and for what you'r intending to do they'll be fine. My last race engine had 280deg .400" lift 240@50 cams and HLA's and worked fine for 2 years at 8000rpm (and still goes!)

If you do intend to go ahead with a bucket/shim converion, then the easiest option would be to find a donor head and swap them over. NOTE: you will need to swap the cams as well, the profiles are completely different to one another. I recommend you buy new shims, not regrind the second hand ones

Cheers
Woz

[manga_blue]

Thanks Woz. I'm a bit surprised that you'd need to swap cams though. I thought you could use HLA profile cams with solids but you just wouldn't get the benefit of faster lift rates. The problem came when you tried solid profile cams with HLAs cos the HLAs couldn't take it.

[wozzah1975]

Thanks Woz. I'm a bit surprised that you'd need to swap cams though. I thought you could use HLA profile cams with solids but you just wouldn't get the benefit of faster lift rates. The problem came when you tried solid profile cams with HLAs cos the HLAs couldn't take it.

I'm not saying that it wouldn't run, but it certainly wouldn't run very well. There is alot of difference in the profiles. You need to change both if you're going to do it.

Woz

[manga_blue]

Buggar! Anyway FWIW I just went looking for solid cam profiles and found this from Maruha:

Maruha Clearance Collar, which works as a shim under bucket (SUB), is the best choice to save money for upgrading your car.
The product replaces the MIATA brand HLA plunger (Picture 1).
There are 40 sizes available to choose, from 11.0 mm to 13.0 mm length by every 0.05 mm(total 40size) .

[evil_weevil]

So thinking out loud here - swapping the head to an NB type with solid lifters and cams could be an option for us NA8 owners if the lifters are on their way out?

[manga_blue]

That's true. You'd still need to factor in head cleaning, testing and machining into the price. But it's a good option. I was in Craig's NB engined NA8 at Wakefield last week. It was using all the NA8 sensors and ECU with std headers and a cold air intake. I've got to say it pulled very strongly and it felt much much better in an NA than in the average NB (but doesn't everything? ). Later in the day he was staying with me on the back straight and along the first half of the main straight.

The NA8 head on my car is in very good shape, apart from the lifters, and it's making good power. A bit of porting, matching, unshrouding, valve angle cuts and big springs go a long way. Nevertheless I'll be picking up an old NB8A head somewhere over the next year or so as part of the next engine build. That engine may be an 8500rpm screamer. It's not critical but part of solving the current HLA problems could mean finding a solid lifter setup than I can port across later.

[wozzah1975]

So thinking out loud here - swapping the head to an NB type with solid lifters and cams could be an option for us NA8 owners if the lifters are on their way out?

It would be, but far simpler to just change all the cams and gear into your own head. A bit of mucking around measuring shims, but still simpler and much cheaper than swapping a whole head.

Woz

[evil_weevil]

Cool, cheers Wazza - this is what I'll do then

can get a hold of NB cams - just need the solid lifters and away I go? that simple? even with standard ecu?

sorry to hi-jack thread manga!

[wozzah1975]

Cool, cheers Wazza - this is what I'll do then

can get a hold of NB cams - just need the solid lifters and away I go? that simple? even with standard ecu?

sorry to hi-jack thread manga!

To be honest I don't know hat the fuss is about wanting to convert them to mechanical for the reasons I stated earlier in the thread. New lifters are cheap and easy to replace, but if you have your heart set on it then I can't see it being a huge problem on your ECU if you do convert it. The difference in the cam specs is minimal.
You will need
-solid buckets
-shims
-cams
All from a mechanical head, then you'll have to measure the clearances and order new shims to suit, or have the old ones ground to suit.

Cheers
Woz

[93_Clubman]

can get a hold of NB cams

Chris, from memory cams in NB8A & NB8B were different as a result of going from NB8A VICS to NB8B VVT.

[project.r.racing]

the valve stems are different length from memory. if you plan on swapping cams and lifters, you'll also need to swap the valve also. Only been told of the length defferences. So someone that has actually done it might chime in yo comfirm this.

[sailaholic]

Have been told by an engine developer that the NB solid lifters don't contact the full width of the cam lobes. He also said that the hla's are fine for street use/cams

Sent from my GT-I9100 using Tapatalk

[datfreak]

To be honest, unless you're planning on fitting big cams and turning it over 7500-8000rpm on a regular basis you're better off just getting complete replacement HLA's. They'e not expensive and for what you'r intending to do they'll be fine. My last race engine had 280deg .400" lift 240@50 cams and HLA's and worked fine for 2 years at 8000rpm (and still goes!)

regarding that race engine with the HLAs
I've done piles of reading about running solid lifters with high lift (10mm) lift cams but not many mention keeping the HLAs.
Is there much gain going with solids over hla for 260-270 degree 10mm lift cams, changing at 7500rpm?
Does it effect power or drivability?

btw I like mangas idea of gutting the hlas and using 10mm shims under them - cheap alternative to SUBs

[greenMachine]

After I belatedly found that my stuffed welded up camshafts had also damaged the buckets in my racecar SUB setup (NB8A head), I replaced them with gutted HLAs. It was a PITA getting the shims right, and I still have a set and a bit down in my workshop somewhere, but nothing that a feeler gauge, a micrometer and a truckload of patience couldn't fix. Mind you, the valves were already set up for SUBs, so it was just a case of getting the right shims to get the clearances right. I have never tried to convert the factory shim-in-bucket to SUB, so I don't know what (if anything beyond the new buckets) extra that might entail.