I have a all motor LS with 14.2:1 CR and Crower 62405A's. My compression test are coming out 210psi. I expected with a big cam and alot of overlap that they would be low, but not that low. With the same setup and smaller cams I got 260psi. My engine just seems to have something holding it back, but what. I had it tuned by a well known Honda tuner and all he could say is, "that's weird".

I have been searching and talking with some HT members I know and they are saying maybe that I have too much crankcase pressure. Could this be it???


Modified by dohcter g at 12:30 AM 6/11/2005

 

leak the motor down (without cams) and see how much leak you have at TDC for each cyl and BTC as well.

I used ot have Toda VTEC killer cam on my 15:1 compression motor and only did 205psi on 4 cranks with ITBs wide open.

may be fine, leakdown will sya for certain.

Greg

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dohcter g &raquo;</TD></TR><TR><TD CLASS="quote">I have a all motor LS with 13.6:1 CR and Crower 62405A's. My compression test are coming out 210psi. I expected with a big cam and alot of overlap that they would be low, but not that low. With the same setup and smaller cams I got 260psi. My engine just seems to have something holding it back, but what. I had it tuned by a well known Honda tuner and all he could say is, "that's weird".

I have been searching and talking with some HT members I know and they are saying maybe that I have too much crankcase pressure. Could this be it???</TD></TR></TABLE>

Large amounts of overlap would explain the lower compression test results. Are you sure the cam gears are dialed in correctly also? This would explain lower the usual compression numbers and dyno numbers. What kind of number did the setup kick out?

 

I did one before I installed the engine and it came out pretty good. I just pump air into the cylinders with an adapter. And listened fo leaks using my best judgment. How do you measure the % of leakage?

 

My first 2.0 had 13.0 cr and toda B's , it onky pumped 220 on cr tests...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid93Eg &raquo;</TD></TR><TR><TD CLASS="quote">

Large amounts of overlap would explain the lower compression test results. Are you sure the cam gears are dialed in correctly also? This would explain lower the usual compression numbers and dyno numbers. What kind of number did the setup kick out?</TD></TR></TABLE>

Yes the cams were dialed in to TDC when assembled. Now after it has been tuned they are +6 int. and -2 exh. which I know is causing more overlap.

 

Bump!!!

 

Very nice, I'm in the process of building a b18b(81mm) motor with PCT and going to use crower 405a also with the valvetrain package.

1. How much piston to valve clearence did you have after installing the 405a's?
2. DId you mill the head?
3. what head gasket are you using?
4. what is your redline at?
5. WHat engine management do you have or using?
6. Header?

Sorry for asking all these questions just trying to get some ideas since us all-motor B18A/B peeps are a rare breed

Check out my build.

https://honda-tech.com/zerothread?id=1256879


As for your build, dam those 405 didnt get you hardly anywhere. I think in another post somewhere you said they made only 4 more horses, I think? I know they are for a higher rpm then the 404's. I think you probably need to get yourself a good header or a port job form Brad(RLZ). Post up your set up if possible.

How do they feel from your 404's. Deos it pull more, idle differently, is the power band raise higher in the rpm range then the 404s?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by volcom40street &raquo;</TD></TR><TR><TD CLASS="quote">
1. How much piston to valve clearance did you have after installing the 405a's?
2. DId you mill the head?
3. what head gasket are you using?
4. what is your red line at?
5. WHat engine management do you have or using?
6. Header?
</TD></TR></TABLE>

1. It was around .070" int and 0.90" exh.
2. .090" milled
3. a four layer steel
4. 8.5k
5. A custom flashed eprom to my specs and SAFC
6. DC 4-1

404's idle like factory compared to these monsters. It is night and day diff. The car feels the exact same as my old setup which sucks. I have to idle these cams at 1.5k just to be smooth enough to run. The 404's were idled perfect at 900 rpms even with 450cc inj.

I can not believe my car did not gain tremendous power. I am still scratching my head.

 

ttt

 

I know milling the head set of the timing! Did you and Jack try adjusting the cams further than what you did?

I have read and been told that milling the head advances the cams so they must be retarded back to 0,0. To my understanding it is close to .5 degrees per .010" milled. If that is the case complete TDC for you to begin with should be both Intake and Exhaust cams retarded 4.5 degrees. This would set you cams at 0,0.


Honestly there is something wierd going on with your build. I understand that the 405a's are going to bleed alot more compression than the 404's but with your compression, you should be good. Is there anything that you may have overlooked that may be hurting your performance?

Here is a dynamic compression calculator. Use it to figure out exactly what your compression is.

http://www.rbracing-rsr.com/comprAdvHD.htm


Is it possible that that using lighter pistons can affect your power? His last build yield high compression alone(12.4:1 static) and weighed ruffly 327g per piston. Now he is using a piston that would yield him 10.7:1 static without the milling and they weigh less. So looks like to me he used a different pistons to ensure piston to valve clearance and milled the head to achieve his compression goals.

Also what about the .090" mill on the head. Could that much milling affect performance by reducing the size of the combustion chamber.


I am just as clueless as anyone else, however I am trying to think of several scenarios that may be the culprit!

 

I am still scratching........The cumbustion chamber in the head measured 36cc. I believe a stock LS is 46. The timing was correct. I think I had to skip a tooth on the timing belt to achieve TDC because of the milling. Good thing about a non-vtec Honda is that you can lock the cams in TDC with pins. So is almost impossible to get it wrong. When I clayed I got alot more room than I expected but crower says .90" piston to valve clearence, so I was a little worried cuz, I think my int was .70" or so.

 

Perhaps the small chamber in the head is not holding as much air as a larger chamber. This is all speculation but with your huge cams holding that intake valve open for a day and a half you might want to have some chamber work done to get back some lost volume. I know that will affect your static compression ratio quite a bit. A smaller chamber is not always better.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybrid_vtec &raquo;</TD></TR><TR><TD CLASS="quote">
I have read and been told that milling the head advances the cams so they must be retarded back to 0,0. To my understanding it is close to .5 degrees per .010" milled. If that is the case complete TDC for you to begin with should be both Intake and Exhaust cams retarded 4.5 degrees. This would set you cams at 0,0.

</TD></TR></TABLE>

very interesting - my b16 head is milled like a ****, .030 under minimum spec. someone told me the most you can mill is .050" so that puts me around .080 milled but i have a .074" head gasket to compensate.

will i still have to retard the cams to like -4º? or will the thick gasket compensate enough to stay 0,0?

 

Milling your head retards cams not advances them.

You would need to advance your cam around 4 degrees or so with your head. Check piston to valve clearence before doing so however.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dohcter g &raquo;</TD></TR><TR><TD CLASS="quote">I did one before I installed the engine and it came out pretty good. I just pump air into the cylinders with an adapter. And listened fo leaks using my best judgment. How do you measure the % of leakage?</TD></TR></TABLE>

pump air into each cyliner individually with no cams installed or each cam MUST be at exactly TDC per cylinder ... this will ensure all vales are closed, now check for leaks. you can pump 100psi in and the second guage will tell you how much pressure builds up, if its 70psi then you have a 30% leackdown, etc.

places to check when pumping air in cylinders are:
intake ports/intake manifold
exhaust ports or header/exhaust end
cylinder next door
radiator with water - check for bubbling


greg

 

Thanks for the response dohcter g, dam you are scaring me with these 405a's i have here laying on the ground . I think that maybe, as someone stated above, you might have shrunk the combustion chamber to small, but i dont know. Velocity is the only thing that really counts, making everything work in sync.

What I would do is try to get a really good header maybe its holding you back??? Look into a SMSP, ANR, RMP or something like that.


one other thing you said you are using a 4 layer head gasket and when you did a compression test it was slightly down. Lets see here you have 13.8cr and a 4 layer head gasket better not be leaking??? Just a thought. I dont know how you would check this though other than another compression test and leave it on a while and see if it leaks over time. When an engine is in the mist of running it could be leaking and could seal when not running and cold, but thats just a thought??


Modified by volcom40street at 6:43 AM 5/26/2005

 

bump for more info!

 

When I first assembled the engine I had leaks in about 4 intake ports and 4 exh. ports. So I took the head to Hendrins Racing and had a 5 angle valve job on the intake and 4 angle on the exh. Then redid a leak down and there was virtually no air exiting the ports and going down throught the rings. Sounded real good. That is why I dont really think this is the problem.

 

HMMMMMMMMMM!!! I'm stumped.


Bump for someone to lend some more advice!

 

Bump for info!

 

still scratching???

 

Do you guys think I need to make changes to my set-up like up the CR or decrease it. Or stick with what I have and work the bugs of it?

 

email me. If you want to give me your complete setup, that may help me see some other factors. If your setup id the same as last time other than the piston, machining and cams, then dont worry about it.

I am still curious is the dyno you last dyno on the same a dynojet? I remember onw time you dynoed on a mustang dyno, which reads 15% lower than a dynojet. If you dynoed on that same dyno then you came out with a good hp gain. If not then you only gained 4 or 5 whp and something isnt right.


What did you tune with? What were the weather conditions that day(humidity, temperature)?

I am just trying to help by covering all angles.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dohcter g &raquo;</TD></TR><TR><TD CLASS="quote">Do you guys think I need to make changes to my set-up like up the CR or decrease it. Or stick with what I have and work the bugs of it? </TD></TR></TABLE>


COME ON... dont be ridiculious, J/K, You have to stay with this set-up. We're going to fix this sh*t.

Since your compression is so high, you have to be using a high octane. What octane are you using maybe go a little higher with some aviation fuel. I know its probably expensive as hell but give it a try if you havent already.

You probably are because I dont think that thing would even run with pump gas. If so you are a tuner from hell.

So you did nothing except change to the 405a on your engine and it only gained about 5 hp or did you do the pistons with head milling and 405a at once?
This is a stupid question but are they in right, there not off bu a tooth or anything?


Like Hybrid said was it done on the same dyno, temp, humidity. I still think those cams should give you more Hp especially with that high compression. Those cams should LOVE IT. (scratches head)

Just trying to help. Lets get this solved