CID/RPM/CFM/HP

General engine tech -- Drag Racing to Circle Track

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skinny z
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Re: CID/RPM/CFM/HP

Post by skinny z » Sun Nov 05, 2017 9:47 am

swampbuggy wrote:
Sun Nov 05, 2017 8:58 am
Skinny Z-----what about considering a crate motor with warranty ???
I've been looking at shortblocks only as I intend (and is the point of this thread) to keep the heads.

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Re: CID/RPM/CFM/HP

Post by randy331 » Sun Nov 05, 2017 9:54 am

skinny z wrote:
Sun Nov 05, 2017 9:23 am
The question to be asked here is: Is a cam spec'd for a 353 suitable for a 390?
Sure it is. It's just as suitable for one as the other, just like the cam you have is. They will just have different rpm and manners.

I always get a laugh out of the comment "cam speced for my combo"

We tried 3 different cams in our EMC engine. We'd have won with any of them. Once your close a few deg here or there or a couple deg. LSA change won't make or break the combo.

Randy

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Re: CID/RPM/CFM/HP

Post by skinny z » Sun Nov 05, 2017 10:06 am

randy331 wrote:
Sun Nov 05, 2017 9:54 am
LSA change won't make or break the combo.

Randy
So, is that to say that a 110 LSA will not be significantly different in power and torque than one with 106 LSA provided the overlap remains the same?

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Re: CID/RPM/CFM/HP

Post by randy331 » Sun Nov 05, 2017 10:15 am

skinny z wrote:
Sun Nov 05, 2017 10:06 am


So, is that to say that a 110 LSA will not be significantly different in power and torque than one with 106 LSA provided the overlap remains the same?
In my experience no. At least not if both cams are of the same lobe family ( lobe speed and lift ) and installed on the same ICL. I think a lot of these types of changes just get cams put in as the cam card shows, so the 106 ends up advance and the engine likes the earlier IVC point and people see that and think it's the LSA that made the difference.

IVC seems to run the show for the most part.

Randy

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Re: CID/RPM/CFM/HP

Post by F-BIRD'88 » Sun Nov 05, 2017 10:49 am

Randy is bang on about this.. The next big player is the intake valve opening point and next is the intake valve lift at TDC.

If you have a 110LSA cam you MUST optimize the INTAKE valve open AND close points
and the intake valve lift at TDC as close as possible. Find the best possible sweet spot cam position that gets the intake vale events optimized as close as possible for THAT CAM you got.

Get the intake valve events RIGHT, FIRST again they are intake opening point, Intake VALVE lift at TDC and intake closing point.
Valve Lash change also effects all these.

Yes the exhaust valve events is a critical factor too. But for this type of motor
with a closed exhaust system that is less than optimum tuned and working with a "off the shelf" 110LSA street cam then getting the intake events right (or as close as possible) is your goal. Move the 110 LSA cam around and find what the car likes.
Forget the theory BS and let the motor and car show you what it likes best.
Advancing the 110LSA so that the intake events are more like what a 106 LSA cam (in at 102in C/L will act like.

Doing that results in a change in the intake valve closing point * (the start of compression) and ALSO makes the intake valve be open higher at TDC ( the start of piston decent and intake duct draw by the piston.
Moving the 110LSA cam does BOTH. Find that sweet spot cam position for both the intake opening point (and intake valve lift at TDC) and the intake closing point.. Find what the CAR LIKES. This needs to be optimized thru testing regardless of the cams ground in LSA 110,106 etc. Get the intake valve installed Centerline position right first.
Try it... You will find the typical 110 LSA off the shelf cam very "Tunable"
Yes ultimately a different cam LSA may be (or may not be) a bit better in the end but this will get your 110LSA cam close and as good as it can be in your car.

What works on the dyno and looks to be great with open headers often turns out to not be optimum at all OVERALL in the car thru a street closed exhaust system.

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Re: CID/RPM/CFM/HP

Post by F-BIRD'88 » Sun Nov 05, 2017 11:20 am

Is this the same 3650# 3700# pickup truck with the th700r4 vehicle?

is this the same 350 short block that you had such problems with detonation?
Such that you now by your stated 15% leak down has clearly "BLOWN the RINGS out of it" Detonation does that and a engine do not self heal.
This is why I warn and warn about building street motors with excessive high compression ratio... This is the result. Short engine LIFE and blow by . a worn out old engine years before its time.
If that is the case there the piston ring lands are probably now damaged
so a simple re hone an re-ring may not fix it. as the piston right lands are still distorted from detonation and ring seal will still be crap and Sometimes gets even worst..
If the engine compression test and engine leak down test improves a lot if with added oil in chamber on the retest then the rings and Piston ring LANDS are probably NOW fubared.
This can fubar a $800 set of forged pistons (or a $80/set cast piston) real quick making them now junk reguardless of what ring is used or what the cylinders look like. Detonation is a equal opportunity piston ring land destroyer.

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Re: CID/RPM/CFM/HP

Post by skinny z » Sun Nov 05, 2017 12:02 pm

randy331 wrote:
Sun Nov 05, 2017 10:15 am

IVC seems to run the show for the most part.

Randy
And overlap? Where do you slot that in?

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Re: CID/RPM/CFM/HP

Post by skinny z » Sun Nov 05, 2017 12:07 pm

F-BIRD'88 wrote:
Sun Nov 05, 2017 11:20 am
Is this the same 3650# 3700# pickup truck with the th700r4 vehicle?
I don't own a pick-up truck.

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Re: CID/RPM/CFM/HP

Post by F-BIRD'88 » Sun Nov 05, 2017 12:24 pm

It is the same 3700# car and transmission then.

Boy are you ever being illusive on this stuff.

This is that same car.... The one with the Detonation issues from before..
and now because of that and your flawed tuning efforts the detonation has killed the ring seal on this motor (15% leakdown). The motor is now pooched and you are all hot now for a 385cid SBC.
If you keep using the same FLAWED tuning theories you will end up in the same spot with a 385CID motor that is pooched way before its time.

The only bright sdpot is you are now In Edmonton Alberta at some 2200' elevation and the air tends tro be lower pressure and a bit cooler overall average.
The 10.37:1cr may not be a problem THERE as it was here before.
It may still be thou if used with a FLAWED tuning method in a attempt to get gas mileage. Gasoline is cheaper than multiple engine rebuilds.
How many engines are you going to build before you see the light?

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Re: CID/RPM/CFM/HP

Post by F-BIRD'88 » Sun Nov 05, 2017 12:48 pm

The intake valve opening point AND THE intake valve lift @TDC is more than 50%
of the "overlap equation" it is the MOST important half+++ of that equation on engines such as you are working with.
Stop looking at in terms of "overlap" and LSA as such and look at it more in terms of the intake valve action (event timing AND lift @TDC) and LESS about the exhaust event ( exhaust closing point . This is secondary to getting the intake events that matter, correct for the job.
Get the intake events right FIRST. Get the intake flow going ( intake valve lift @TDC) No (not much) flow if the valve ain't open some. Reguardless of what the exhaust is doing.

that intake valve opening lift @ TDC benchmark is adjusted by the cams installed position and The ROCKER arm RATIO and the valve lash setting if solid cammed.

Lifter bleed down rate if Hyd lifters...

The solid lifter gives you a tuning advantage. Allows you to +/- the lash to get the best possible valve events along with adjusting the cams position
to get it all right. (or as best as possible) Think about the intake valve events FIRST. Not the cam events,,, the INTAKE VALVE events. You cannot walk into a room if the door is closed. You have to get in before you worry about getting out of that room (exhaust).

This why on SBC's with 23deg heads they like it when you play with the intake rocker arm ratio and tend to be indifferent to exhaust rocker arm ratio changes.
Last edited by F-BIRD'88 on Sun Nov 05, 2017 1:08 pm, edited 2 times in total.

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Re: CID/RPM/CFM/HP

Post by skinny z » Sun Nov 05, 2017 12:52 pm

I'm really only being elusive with YOU Bird because you tend to come off as a little unsettled.
BUT, yes. The high compression (from before) has probably caused some irreparable damage.
As YOU stated, 10:1 is OK with the previous cam in question. Nearly 10.5:1...not so much. That was my point then and I'm in agreement with YOUR assessment then AND now.
So, if you don't mind, I'm in the middle of deciding my next move. ONE experience with ONE iteration of ONE engine isn't a game stopper. Even more so considering that that iteration came about totally by circumstance, not design. So, get over it. I have.
Now, I would like to move forward.
Thanks.

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Re: CID/RPM/CFM/HP

Post by F-BIRD'88 » Sun Nov 05, 2017 1:09 pm

Is this car a 70 to 80 Camaro or Firebird? with the th700r4 trans?

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Re: CID/RPM/CFM/HP

Post by skinny z » Sun Nov 05, 2017 1:17 pm

[quote="F-BIRD'88" post_id=697070 time=1509905399 user_id=3630]
Is this car a 70 to 80 Camaro or Firebird? with the th700r4 trans?
[/quote]
Is your username relevant to the car you drive?

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Re: CID/RPM/CFM/HP

Post by F-BIRD'88 » Sun Nov 05, 2017 1:23 pm

Not any more. I sold that car. Kept the whole driveline for a future project.
Will be a Very different car.

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Re: CID/RPM/CFM/HP

Post by randy331 » Sun Nov 05, 2017 1:32 pm

skinny z wrote:
Sun Nov 05, 2017 12:02 pm
randy331 wrote:
Sun Nov 05, 2017 10:15 am

IVC seems to run the show for the most part.

Randy
And overlap? Where do you slot that in?
It's just part of the compromises one has to decide on.
But, I think people believe they need more than they do.

I got one 383 with a 224*-244* on 110* LSA cam with 2.02" / 1.55" valves and 50* seats. It has very little flow around TDC and it is a very surprising running engine. Made a surprisingly good power curve on the dyno and drives around in a heavy car very nice.

Too much overlap is probably worse than not enough.

Randy

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