bisimoto A20 valves

[gp02a0083]

Now if they were something like sodium filled valves, now that would be awesome

that's what i was saying on FB lol. Cygnus has the same question that I have with this. First of all why 2 different metals being used? Why not just stainless steel for all valves. The heat capacity aspect and metallurgy of the valves are very important things. I am with Cygnus on this one, if the valves are not lighter and stronger there really isn't a point of buying them. If anything you would be better off spending the money and having the valves de-shrouded and the head cut / polished to give you better flow, then I would look into the valves at the same time the head work is being done. Our A20's have small valves and only 3 per cylinder. So its going to need a little bit of help to get the head to flow well. Plus i highly doubt bisi is doing the "R&D" at all for A series, i'm still skeptical about the valve springs they offer. the only dam thing that looks like it was engineered 1/2 way decent is the cam gear. Otherwise I have not found any reason to buy anything from him/them.

[Vanilla Sky]

I agree. Bisimoto is like K-Sport. It's okay, but it's not better than what you're replacing.

[apache07x]

When I was racing circle track my machinist would use the loopholes and do some killer things to a head. The rule book being too vague just said it had to be a stock head that could be surfaced up to 0.120 and stock valves with a stock head diameter. A person can find a lot lighter valves with the same head dimensions and a smaller stem both length and diameter. You'd be surprised what a few ounces in the valve train does to the performance of the engine.

I'd say research. It's out there. Valves from a Maserati may fit our head or an Opel as far as that goes. But if their lighter and will fit with minimal machine work why not if performance is what your after.

I'd lighten up cam pulleys, timing pulleys, crank pulleys anything that was rotating weight and cost very little money or just my time to do and run top 3 every week and have half of the money in my stuff looking like I pulled it out of the junk yard. People couldn't understand how I had a "stock" appearing car and run with them and their $6000 engine. Easy I worked on the little stuff. I didn't go to the store and buy a cam pulley that weighed 2 ounces more than my homemade one.

Anyways I'm rambling. What was the question again? lol


I guess the point I'm trying to make is you don't have to use A20 valves use what your budget will allow and you can make fit properly.

[lostforawhile]

what about the valve springs? are the bisi valve springs still the best upgrade? I can get brand new valves that are made by Melling, thats one of the few companies I would trust with valves or an oil pump, they sell them under a number of manufacturers names, the list of name interchanges is on their website, they are OEM quality. I plan on running that stage two cam with the upgraded springs and new valves, seats,guides etc, I was going to mill the head to run about 13-1 compression. I already have the golden eagle cam gear to offset the head milling, I even found a source for new rockers

[cygnus x-1]

what about the valve springs? are the bisi valve springs still the best upgrade? I can get brand new valves that are made by Melling, thats one of the few companies I would trust with valves or an oil pump, they sell them under a number of manufacturers names, the list of name interchanges is on their website, they are OEM quality. I plan on running that stage two cam with the upgraded springs and new valves, seats,guides etc, I was going to mill the head to run about 13-1 compression. I already have the golden eagle cam gear to offset the head milling, I even found a source for new rockers

13:1?! I thought you wanted to still run on pump gas? Or are you going to run E85? And I really don't think you will be able to mill the head enough to get to 13:1 static compression without breaking into the water jacket, or getting dangerously close to it anyway. Are you going to be using domed pistons or something?

Regarding the Bisi springs; I think that's the only upgrade available off the shelf.


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[Vanilla Sky]

You can double up and do some swapping. I know it's somewhere on the forum.

[lostforawhile]

13:1?! I thought you wanted to still run on pump gas? Or are you going to run E85? And I really don't think you will be able to mill the head enough to get to 13:1 static compression without breaking into the water jacket, or getting dangerously close to it anyway. Are you going to be using domed pistons or something?

Regarding the Bisi springs; I think that's the only upgrade available off the shelf.


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someone figured out already that you should be able to take up to 2 mm off the head, to get around that, I know 1.5 mm has been done and it works, I was going to run a meth system at higher rpms to avoid detonation issues, 13-1 should be able to be run on premium with spray at higher rpm. I found out I'm going to be getting some cash very soon, so it's time to start building this beast and getting it running, I'll try and find the thread again, very interesting discussion on compression ratios, meth isnt just for boosted setups,

[lostforawhile]

I might have misunderstood that, what am I looking at with 1.5 mm off the head and .5 mm off of the block? the 86 BS version of the A20 starts with stock 9-1 compression, I keep seeing different numbers about the CR on the A20s but the book states 9-1 is the starting baseline

[apache07x]

I might have misunderstood that, what am I looking at with 1.5 mm off the head and .5 mm off of the block? the 86 BS version of the A20 starts with stock 9-1 compression, I keep seeing different numbers about the CR on the A20s but the book states 9-1 is the starting baseline

Yeah that's what I would do with my race engines is take some off of the head and some off of the block too. Your cam lift is going to dictate a little bit on what you can take off of the block and head too obviously. Also you should be able to make other valve springs fit if you know the specs on them and do a dual spring setup or a stiffer OEM spring from another engine as I imagine longevity is important too.

[lostforawhile]

Yeah that's what I would do with my race engines is take some off of the head and some off of the block too. Your cam lift is going to dictate a little bit on what you can take off of the block and head too obviously. Also you should be able to make other valve springs fit if you know the specs on them and do a dual spring setup or a stiffer OEM spring from another engine as I imagine longevity is important too.

well Bisi makes the springs, several people have run them, little pricy but it's whats available, I think the issue on their valves is they are basically stock. I can get a melling made intake for about 11 bucks and an exhaust for about 20. vintage parts has new rockers available, I think the most important part of any N/A build is the head. The spray adds some horsepower and it makes a huge difference in intake charge temp, it's designed to be used above 4000 rpm, so a simple rpm switch is all thats needed to activate it. most of your detonation issues happen under load at higher RPM, when the spray is on. I looked at both snow and devils own, and devils own is much more flexible, they have many more jets available, and you can design your setup. They dont have a tank in their systems, but you can use a windshield washer tank, this also lets you use one with a low fluid warning switch

[apache07x]

well Bisi makes the springs, several people have run them, little pricy but it's whats available, I think the issue on their valves is they are basically stock. I can get a melling made intake for about 11 bucks and an exhaust for about 20. vintage parts has new rockers available, I think the most important part of any N/A build is the head. The spray adds some horsepower and it makes a huge difference in intake charge temp, it's designed to be used above 4000 rpm, so a simple rpm switch is all thats needed to activate it. most of your detonation issues happen under load at higher RPM, when the spray is on. I looked at both snow and devils own, and devils own is much more flexible, they have many more jets available, and you can design your setup. They dont have a tank in their systems, but you can use a windshield washer tank, this also lets you use one with a low fluid warning switch

Wonder how much room there is on our heads to put in larger headed valves? Then get ferrea or melling stainless steel valves with the correct stem diameter and length. Let it breath a little more.

[obd0driver]

I hear everything you guy are saying I just ask them when I order parts for a friend. they told me they can get them from the place they get there stuff from. That's really the info they had from they would tell me who made them but did say they have couple sets laying. so someone has to be making them for something. If we can get that info I'm sure its just a call away to have something made to the spec we want.

[cygnus x-1]

I might have misunderstood that, what am I looking at with 1.5 mm off the head and .5 mm off of the block? the 86 BS version of the A20 starts with stock 9-1 compression, I keep seeing different numbers about the CR on the A20s but the book states 9-1 is the starting baseline

The stock compression is different depending on which pistons you have. The '88-'89 fuel injected engines had less dish in the pistons so the CR went from about 8.8 to 9.1.

With the smaller dish pistons, 1.5mm off the head gets to 10.3CR. 2mm off the head is 10.8. 1.5mm of the head and 0.5mm off the block is 10.9, so basically the same.
The problem with taking material off the block is that now the pistons are no longer flush with the deck and are protruding into the gasket area. This is ok as long as the gasket doesn't hang over into the cylinder. This shouldn't ever happen but it's something to watch for. I've estimated the gasket thickness at a little over 1mm, so that's pretty much the limit of what you can take off the block.

If you have the larger dish pistons subtract 0.3-0.4 from what I just said.

The highest CR in my spreadsheet is 13.4:1. That's with 2mm off the head, 0.5mm off the block, and the combustion chambers welded up. Of course I had to estimate how much the weld would fill so it's a rough estimate. The thing is, if you really wanted to run that much compression you really would be better off having some custom made forged pistons with a dome instead of a dish. Welding up the chambers and milling them back down again (and getting them matched) is not going to be cheap. That much welding may also weaken the head casting. Forged pistons are also much stronger and will hold up better to the extreme heat and pressure. I think a custom set of pistons runs around $600.

Wonder how much room there is on our heads to put in larger headed valves? Then get ferrea or melling stainless steel valves with the correct stem diameter and length. Let it breath a little more.

Stock valves are 30mm intake, 35mm exhaust. The valves I got from SI are 32mm intake, 37mm exhaust. That's about the maximum you can go on the stock seats.


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[firefighterwhite89]

has anyone had any issues with the factory valves themselves failing? I'm asking because Melling makes both of them, one of the few aftermarket companies I would trust, now the valve springs from Bisi are one thing what about retainers? I know the 90 lude uses the same retainers, anyone know of a quality aftermarket one?

if you are just going to replace the valve springs or retainers and not the valves, you can do so without ever removing the head, which saves $$ on a HG.

-Take 1/4 cotton rope, 10 ft. long at least.
-Remove the spark plugs.
-Whichever cylinder you're replacing the valve springs on, feed between 6-9 ft of rope in the cylinder while that cylinder is a Bottom Dead Center.
-Turn the crankshaft pulley with a socket(Either 19mm or 17mm, can't remember) until the piston is nearly TDC or the pulley is hard toturn anymore.
-NOW, you can remove your valve springs/retainers without the valves falling or removing the head.


Just a neat trick i learned one day from a mechanic.

You'll have to remove the head to replace the valves though. There's no way around it.

[lostforawhile]

if you are just going to replace the valve springs or retainers and not the valves, you can do so without ever removing the head, which saves $$ on a HG.

-Take 1/4 cotton rope, 10 ft. long at least.
-Remove the spark plugs.
-Whichever cylinder you're replacing the valve springs on, feed between 6-9 ft of rope in the cylinder while that cylinder is a Bottom Dead Center.
-Turn the crankshaft pulley with a socket(Either 19mm or 17mm, can't remember) until the piston is nearly TDC or the pulley is hard toturn anymore.
-NOW, you can remove your valve springs/retainers without the valves falling or removing the head.


Just a neat trick i learned one day from a mechanic.

You'll have to remove the head to replace the valves though. There's no way around it.

I'm going to do extensive work to a head once I find a good core, I dont want to take a chance on messing up my only good one, bisi springs,brand new melling valves, cam, golden eagle cam gear, and of course the proper head work and head shaved to increase compression, I even found brand new rockers