cranking compression - Page 2

Jeff Lee · 09-09-2010, 12:20 PM

IF dyno numbers / comparison is accurate AND it picked up HP/TQ with no dips that were not present before, AND the peaks are at the same RPM, then it should be a quicker car.
If it is not, it must be something external of the engine. Does anybody disagree?
And a -3 MPH should be more than .100 increase on ET. Right?

What is different about the ring package and how did that show a benefit to you on the dyno? Less leak-down? More / less vacuum in the engine? How much difference to the old engine?
Is the extra ring seal creating more HP at the same time creating more demand from the carb(s) & the fuel curve or float / needles & seats, now under par in the car as opposed to the dyno?
Does this engine have a vacuum pump?

randy wilson · 09-09-2010, 12:23 PM

Sorry Mike, i didn't explain myself real well. The numbers were better all the way from last year. I know, how can that be and slow down. I'm at a loss.

randy wilson · 09-09-2010, 12:33 PM

We are up 3 sizes since dyno. It was real slow before that.

Mart Jeltema · 09-09-2010, 02:06 PM

Mike Taylor is correct. If the average is better, then look at the jetting. When my Brake Specific # looked good on the dyno and didn't perform on the race track thats where I head. I have found on a car with a hood scoop needed to increase the jet size. On my single carb 750 I had to increase the jets 3-4 #'s.

Jeff Lee · 09-09-2010, 08:15 PM

It's not always as simple as jetting. Are the bowls staying full?
Your MPH loss is not in the right relationship to the ET loss. I'm not sure what that means, but it means something.

Jeff Lee · 09-09-2010, 08:17 PM

Quote:

Originally Posted by randy wilson

We are up 3 sizes since dyno. It was real slow before that.

Then keep going bigger until it slows

junior barns · 09-09-2010, 09:40 PM

what happens when you have no scoop and not much hood to carb clearance?

SSDiv6 · 09-10-2010, 12:35 AM

Quote:

Originally Posted by junior barns

what happens when you have no scoop and not much hood to carb clearance?

You have reduced airflow.

randy wilson · 09-10-2010, 05:01 AM

We have been bigger on the jets, this is what it likes. Thanks guys, we will figure it out.

Mike Taylor 3601 · 09-10-2010, 07:50 AM

Randy,
As far as cam advance goes all I've seen on dyno is when advanced gain a few pounds tq lose few hp lower peak 100 or 200 rpm ,retard exact opposite lose few# tq gain couple hp raise peaks 100-200 rpm. IMO cam timing changes are better tested on track
my experience with stick cars is advanced cam timing does'nt seem to work well they sound better better response but just don't want to go anywhere,also when you opened lash you lost a little duration and overlap that can tell you some info about your cam,usaully it takes .005 increments to show try tighten intake .005 loosen exhaust.005 from recommened settings if that works I promise you have HP&TQ in cam change PM me if you do I tell you who will fix that cam for you.
Hood Scoops will sure mess with jetting,speaking of jets if useing holley jets DON'T they are not accurate you can change them and get no results or opposite of what you should.
Convert to Max Jet they are precise when you make change you get results.
One other thing dyno numbers are corrected hp &tq., second,do you know for sure #'s are'nt adjusted for desired results. PS manipulated #'s from correction factor usaully gain lots of tq.
Mike Taylor 3601

09-09-2010, 12:20 PM	#11
Jeff Lee VIP Member Join Date: Jul 2007 Location: Anthem, Arizona Posts: 2,766 Likes: 0 Liked 3 Times in 3 Posts	Re: cranking compression IF dyno numbers / comparison is accurate AND it picked up HP/TQ with no dips that were not present before, AND the peaks are at the same RPM, then it should be a quicker car. If it is not, it must be something external of the engine. Does anybody disagree? And a -3 MPH should be more than .100 increase on ET. Right? What is different about the ring package and how did that show a benefit to you on the dyno? Less leak-down? More / less vacuum in the engine? How much difference to the old engine? Is the extra ring seal creating more HP at the same time creating more demand from the carb(s) & the fuel curve or float / needles & seats, now under par in the car as opposed to the dyno? Does this engine have a vacuum pump? __________________ Jeff Lee 7494 D/S '70 AMX Last edited by Jeff Lee; 09-09-2010 at 12:25 PM.

09-09-2010, 12:23 PM	#12
randy wilson Senior Member Join Date: Jan 2007 Location: N/A Posts: 882 Likes: 0 Liked 22 Times in 22 Posts	Re: cranking compression Sorry Mike, i didn't explain myself real well. The numbers were better all the way from last year. I know, how can that be and slow down. I'm at a loss. __________________ don,t have one

09-09-2010, 12:33 PM	#13
randy wilson Senior Member Join Date: Jan 2007 Location: N/A Posts: 882 Likes: 0 Liked 22 Times in 22 Posts	Re: cranking compression We are up 3 sizes since dyno. It was real slow before that. __________________ don,t have one

09-09-2010, 02:06 PM	#14
Mart Jeltema Junior Member Join Date: Feb 2007 Posts: 37 Likes: 0 Liked 10 Times in 2 Posts	Re: cranking compression Mike Taylor is correct. If the average is better, then look at the jetting. When my Brake Specific # looked good on the dyno and didn't perform on the race track thats where I head. I have found on a car with a hood scoop needed to increase the jet size. On my single carb 750 I had to increase the jets 3-4 #'s.

09-09-2010, 08:15 PM	#15
Jeff Lee VIP Member Join Date: Jul 2007 Location: Anthem, Arizona Posts: 2,766 Likes: 0 Liked 3 Times in 3 Posts	Re: cranking compression It's not always as simple as jetting. Are the bowls staying full? Your MPH loss is not in the right relationship to the ET loss. I'm not sure what that means, but it means something. __________________ Jeff Lee 7494 D/S '70 AMX

09-09-2010, 09:40 PM	#17
junior barns Senior Member Join Date: Jun 2006 Posts: 541 Likes: 11 Liked 20 Times in 14 Posts	Re: cranking compression what happens when you have no scoop and not much hood to carb clearance?

09-10-2010, 05:01 AM	#19
randy wilson Senior Member Join Date: Jan 2007 Location: N/A Posts: 882 Likes: 0 Liked 22 Times in 22 Posts	Re: cranking compression We have been bigger on the jets, this is what it likes. Thanks guys, we will figure it out. __________________ don,t have one

09-10-2010, 07:50 AM	#20
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,368 Likes: 345 Liked 292 Times in 101 Posts	Re: cranking compression Randy, As far as cam advance goes all I've seen on dyno is when advanced gain a few pounds tq lose few hp lower peak 100 or 200 rpm ,retard exact opposite lose few# tq gain couple hp raise peaks 100-200 rpm. IMO cam timing changes are better tested on track my experience with stick cars is advanced cam timing does'nt seem to work well they sound better better response but just don't want to go anywhere,also when you opened lash you lost a little duration and overlap that can tell you some info about your cam,usaully it takes .005 increments to show try tighten intake .005 loosen exhaust.005 from recommened settings if that works I promise you have HP&TQ in cam change PM me if you do I tell you who will fix that cam for you. Hood Scoops will sure mess with jetting,speaking of jets if useing holley jets DON'T they are not accurate you can change them and get no results or opposite of what you should. Convert to Max Jet they are precise when you make change you get results. One other thing dyno numbers are corrected hp &tq., second,do you know for sure #'s are'nt adjusted for desired results. PS manipulated #'s from correction factor usaully gain lots of tq. Mike Taylor 3601