Let's see how much m20 heads suck.

[So Live]

John, you guys ever play with plastic work on the floor of the intake ports? In my opinion it looks like there is some room for improvement in the top of the port but volume is already borderline too large for a 2.5 from what I gather. So why not clean up the top of the port, fill the floor slightly to maintain volume, and also benefit from increasing the ssr at the same time?

Cheers,

[ForcedFirebird]

A little. Problem is, if you want to make real power with an m20, you ditch the stock intake (where most of that would benefit). With the understanding that I do this for a living, I don't always take the time to prefect stock situations. I am often at my shop before 7am, and rarely get to leave much before 9pm - many a nights I work all night and take cat naps. Too many walk-ins and interruptions during the day to get much done. I have two very part time subs, but the majority of the hands-on work that goes on is done personally. I was in front of the bench for 12hrs straight yesterday. :/

[So Live]

Gotcha. That's all very understandable. Was mostly curious for those of us trying to optimize stockish set ups.

Cheers and keep up the good work!

[ForcedFirebird]

Gotcha. That's all very understandable. Was mostly curious for those of us trying to optimize stockish set ups.

Cheers and keep up the good work!

Read back the thread, all the stock numbers are shared, we even mix and matched stuff. I know the photobucket thing is messed up right now, from here on out, it will be uploaded to r3v direct.

[dvallis]

Use this Chrome plugin to unblock Photofucket. Works ... for now. All my new posts use Imgur.

https://chrome.google.com/webstore/detail/photobucket-embed-fix/naolkcpnnlofnnghnmfegnfnflicjjgj?hl=en

[digger]

John, you guys ever play with plastic work on the floor of the intake ports? In my opinion it looks like there is some room for improvement in the top of the port but volume is already borderline too large for a 2.5 from what I gather. So why not clean up the top of the port, fill the floor slightly to maintain volume, and also benefit from increasing the ssr at the same time?

Cheers,

if you looking to do that it might be easier to start with a 731 or 200 head they already have the smaller volume, plenty of meat to create a nice short side radius. i know people who have machined in the squish pads to accommodate the m20b25 piston or you can use a flat top piston which is much simpler

[harry02]

Bottom line is , with 885 " dont waste your money , just do a 3 angle job "

[ForcedFirebird]

Bottom line is , with 885 " dont waste your money , just do a angle job "

What angles? Many times a head gets ruined with a poor machinist running a top notch machine (Serdi), with cutters we provide, simply because the guy wasn't paying attention and put the valve face 100's of an inch too deep. :(

[harry02]

@ForcedFirebird let me reformulate it : so if i have 885 head, i just need a mild porting and polishing (exhaust side) ?

[digger]

So, I'm flowing a stack of stock heads to hand-pick Spec30 cores. Yesterday and AMC casting came across the bench. Didn't go beyond the second port, it was as bad as the first, and don't think the others would be far off. Test 1 is port #5 on the previous head for comparison sake (accidentally deleted #6 but it wasn't far off). Basically this shows the flow in the AMC is 73% as good as stock at .4" of lift. :/

[ATTACH]116136[/ATTACH]

i'm not surprised it is that bad.

its funny pipemax says you only need 130cfm for 170bhp with port size of 30mm. of course the assumption is with proper intake/exhaust and cam parameters

[ForcedFirebird]

@ForcedFirebird let me reformulate it : so if i have 885 head, i just need a mild porting and polishing (exhaust side) ?

Depends on who does the porting. Read back the thread about polishing ;)

[ForcedFirebird]

i'm not surprised it is that bad.

its funny pipemax says you only need 130cfm for 170bhp with port size of 30mm. of course the assumption is with proper intake/exhaust and cam parameters

I don't think it's the flow numbers that make them bad. The ports make an ear-piercing noise at .200" - which usually means it's stalling. I can see why they are used as a base to modify with the thicker castings, but that comes with a price. The casting and machining quality is sub-par.

[digger]

that amount of flow from the size is pretty bad.

[jeffnhiscars]

A little. Problem is, if you want to make real power with an m20, you ditch the stock intake (where most of that would benefit). With the understanding that I do this for a living, I don't always take the time to prefect stock situations. I am often at my shop before 7am, and rarely get to leave much before 9pm - many a nights I work all night and take cat naps. Too many walk-ins and interruptions during the day to get much done. I have two very part time subs, but the majority of the hands-on work that goes on is done personally. I was in front of the bench for 12hrs straight yesterday. :/

Well then I won't interrupt. Ill just see you Monday with my 731 & intake and we can see how much this puppy sucks :)

[ForcedFirebird]

Well then I won't interrupt. Ill just see you Monday with my 731 & intake and we can see how much this puppy sucks :)

I was able to recover the database!

Test 1: Stock 885
Test 2: AMC
Test 3: 731 port #6 with 885 valves? (didn't measure) DIY porting
Test 4: same except port #5
Test 5: 731 port #5 repeated with 323 DIY ported manifold, "i" TB pinned open (note: plenum not bored to match TB)