Very Disappointed
Posting Guru
Joined: May 2010
Posts: 1,867
Likes: 3
From: Alton, MO
Waitaminute..... you ran the rig on a chassis dyno, right? Those results can vary widely from dyno to dyno PLUS... that's rear wheel horsepower. The numbers you hear from people may result from an engine dyno or a chassis dyno so it needs to be an apples to apples comparison.
An engine dyno does not experience parasitic driveline losses like a chassis dyno. For example, an auto tranny is inherently less efficient than a manual transmission which transfers more HP to the rear wheels. Using the rule of thumb of 20 to 25 percent for parasitic losses, your estimate of 350 is in the ballpark for gross HP at the crank. An 380 ft.lbs. at the rear wheels is also decent.
The RPM is only 4700? That's low if, as I am assuming, it has a higher lift cam. However, ya might have found the line between lift/duration and how much the stock heads can handle.
An engine dyno does not experience parasitic driveline losses like a chassis dyno. For example, an auto tranny is inherently less efficient than a manual transmission which transfers more HP to the rear wheels. Using the rule of thumb of 20 to 25 percent for parasitic losses, your estimate of 350 is in the ballpark for gross HP at the crank. An 380 ft.lbs. at the rear wheels is also decent.
The RPM is only 4700? That's low if, as I am assuming, it has a higher lift cam. However, ya might have found the line between lift/duration and how much the stock heads can handle.
Logistics Pro
Joined: Jan 2011
Posts: 4,762
Likes: 54
From: Antelope Valley ,CA
72 HIGHBOY
hey neighbor , shoot me your exact engine specs , i checked your profile and you have no cam number listed and no valve sizes etc .
i will run your set up on desktop dyno5
who did the work ? AV bumper ? or ?
your rear wheel numbers don't look bad figuring 15% loss for driveline
hey neighbor , shoot me your exact engine specs , i checked your profile and you have no cam number listed and no valve sizes etc .
i will run your set up on desktop dyno5
who did the work ? AV bumper ? or ?
your rear wheel numbers don't look bad figuring 15% loss for driveline
Thread Starter
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Senior User
Joined: Jan 2012
Posts: 169
Likes: 0
From: Antelope, California
72 HIGHBOY
hey neighbor , shoot me your exact engine specs , i checked your profile and you have no cam number listed and no valve sizes etc .
i will run your set up on desktop dyno5
who did the work ? AV bumper ? or ?
your rear wheel numbers don't look bad figuring 15% loss for driveline
hey neighbor , shoot me your exact engine specs , i checked your profile and you have no cam number listed and no valve sizes etc .
i will run your set up on desktop dyno5
who did the work ? AV bumper ? or ?
your rear wheel numbers don't look bad figuring 15% loss for driveline
The shop i had rebuild it didnt give me the total specs on my engine This is also why i cant tell anyone the exact comp ratio or exactly how the heads were ported. This is the problem im running into now. I need to pull the engine apart and do all the measurements myself. Bad timing right now because im trying to move.
How far from Antelope is Antelope Valley? It looks like you have almost the same engine mods i do, there is a place here that will give you 3 runs on the chassis dyno for $75 and they are friends of mine. Let me know if you want to see what youre getting.
Oh and the engine rebuild alone cost me around $7k, the interior brand new was like $4.5k. Just FYI
Thread Starter
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Senior User
Joined: Jan 2012
Posts: 169
Likes: 0
From: Antelope, California
There is also a guy here in Roseville that is really good with the FE engine. I may end up taking it to him and seeing if he can sort this out. We called him yesterday and told him what was up and even he was surprised at the results. I will let yall know what his name is and his shop too so if anyone else has questions you can give him a ring. He does all the big engine rebuilds for the shop that i frequent so he is really good and very knowledgeable. He also has an FE in his race car...
Logistics Pro
Joined: Jan 2011
Posts: 4,762
Likes: 54
From: Antelope Valley ,CA
I am in Palmdale west side . engine builder should be able to give you specs on cam .
popping before 5k sounds like a problem that needs fixing first . for $7k you should have a bad *** motor . i built mine in my garage for $3k
popping before 5k sounds like a problem that needs fixing first . for $7k you should have a bad *** motor . i built mine in my garage for $3k
Logistics Pro
Joined: Jan 2011
Posts: 4,762
Likes: 54
From: Antelope Valley ,CA
opps (my bad ) guess we are not neighbors ,
didn't know there was an Antelope CA ... know now
thought you meant Antelope valley , aka Palmdale,Lancaster
didn't know there was an Antelope CA ... know now
thought you meant Antelope valley , aka Palmdale,Lancaster
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Thread Starter
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Senior User
Joined: Jan 2012
Posts: 169
Likes: 0
From: Antelope, California
My cam is a comp cams high energy, grind 268H 33-224-3.
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Senior User
Joined: Jan 2012
Posts: 169
Likes: 0
From: Antelope, California
I think the only way im going to get the specs for this engine is to pull it apart and measure it. The shop that rebuilt it is being very unhelpful in finding things out. I guess ill start on that tomorrow although honestly i dont want to put any more time or effort into this thing.
Anyone want to buy my truck? lol!!!!!!!
Anyone want to buy my truck? lol!!!!!!!
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
Like I said, I think your numbers are fine. I recommend ya do some research on chassis dynos vs engine dynos to be informed of the differences.
Step away from the truck and take a few days to think about other things. It sounds like you're really discouraged but let it wear off for a bit until you can come back with a clearer head
Personally, I wouldn't bother pulling the motor apart just to find out what the heck your machine shop did... all that matters now is that machine shop/builder stands by his work. If something goes awry, then it is his job to figure out what the heck went wrong with his workmanship.
Enjoy your rig.
Step away from the truck and take a few days to think about other things. It sounds like you're really discouraged but let it wear off for a bit until you can come back with a clearer head
Personally, I wouldn't bother pulling the motor apart just to find out what the heck your machine shop did... all that matters now is that machine shop/builder stands by his work. If something goes awry, then it is his job to figure out what the heck went wrong with his workmanship.
Enjoy your rig.
Thread Starter
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Senior User
Joined: Jan 2012
Posts: 169
Likes: 0
From: Antelope, California
I appreciate it fellas, i do, but the shop wont even get back to me and the specs are probably long lost. The shop that built it is 7-8 hours south of where i live now.
I did however find some paperwork and do some clever deducing. I found a compression ratio calculator online and put in all the values it asked for to the best of my educated knowledge. Ill lay them out so you all can confirm. Here it is:
--Static comp ratio first:
Cyl Bore : 4.080in
Stroke : 3.78in
Compressed head gasket thickness : .041in
Head Gasket bore diameter : 4.40in
Combustion chamber CC's : 72*
Piston Dome Volume : 10cc's
Piston Deck Clearance : .015*
*Estimated to the best of my knowledge and research.
*********9.486:1*************
--Dynamic Comp Ratio:
Rod length: 6.49in
Intake valve closes ABDC : 60 degrees
*********7.8:1**************
Oh and for fun i threw in Dynamic CR @ 6psi too; 11.1:1 DCR - This doesnt matter tho as i have no SC or Turbo on he truck.
I did however find some paperwork and do some clever deducing. I found a compression ratio calculator online and put in all the values it asked for to the best of my educated knowledge. Ill lay them out so you all can confirm. Here it is:
--Static comp ratio first:
Cyl Bore : 4.080in
Stroke : 3.78in
Compressed head gasket thickness : .041in
Head Gasket bore diameter : 4.40in
Combustion chamber CC's : 72*
Piston Dome Volume : 10cc's
Piston Deck Clearance : .015*
*Estimated to the best of my knowledge and research.
*********9.486:1*************
--Dynamic Comp Ratio:
Rod length: 6.49in
Intake valve closes ABDC : 60 degrees
*********7.8:1**************
Oh and for fun i threw in Dynamic CR @ 6psi too; 11.1:1 DCR - This doesnt matter tho as i have no SC or Turbo on he truck.
Posting Guru
Joined: May 2010
Posts: 1,867
Likes: 3
From: Alton, MO
Here is the start to your problem. Your cam is a 1500-5500 rpm range. Your manifold is idle-5500. They don't go together. You would do better swapping out the manifold for a Performer RPM manifold (1500-6500) yet they still wouldn't match quite right. While more work, buying the cam that Edelbrock designed to go with the manifold. You also have a manifold designed for torque not hp. I am betting on mismatched parts along with proper tuning. Just proper tuning will do wonders.