| blykins |
08-22-2015 01:40 PM |
A hydraulic roller cam that big in a 427 would float the valves before it made any power and would be a turd the rest of the time...
I don't use hydraulic rollers that big in my 480-490 inch FEs...
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| DAVID GAGNARD |
08-22-2015 01:41 PM |
Quote:
Originally Posted by Bernica
(Post 1360093)
If that current manifold is a single plane it will explain a lot of things as well, especially street performance. I'm with the folks comments above. Starting to suspect cam and intake...:confused:
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Quote:
Back in 2009 the car was previously tuned at Dennis Olthoff''s shop in North Carolina and Olthoff's records have it making 450rwhp on their dyno.
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Quote:
The only variances from the build sheet are that it listed a Davinci 950 carb and Performer RPM intake. The carb on the car now is a 750QF and intake is a victor jr. The camshaft that is listed is a Comp Cam .576 intake and exhaust gross lift with 252 exhaust and 262 intake with 112 lobe separation. I hope the camshaft isn't anything proprietary....this is from 10 years back and its stamped all over the build information so it doesn't appear top secret. I was aware the car did have a Davinci carb on it but that it was removed....I'm wondering if the intake manifold listed on the build sheet is a typo as I undertand it to have always had a victor jr on it. This is purely to provide information based on peoples questions about the motor....not to debate someone's dy
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Seems like a lot of things have been changed on this engine since bought from the builder and Olthoff's tune and 450rwhp correspond with the builders dyno hp numbers.......now, some years later,parts have been changed and hp is down about 100..........makes me wonder just what is in the engine at this point in time and if it is still the same basic (short block) engine as was delivered originally....
If it were me, I'd be doing some serious checking into the engine to find out just what is in it and what has been changed......and if it is the original engine at all.......
David |
| Bernica |
08-22-2015 02:01 PM |
Quote:
Originally Posted by DAVID GAGNARD
(Post 1360115)
If it were me, I'd be doing some serious checking into the engine to find out just what is in it and what has been changed......and if it is the original engine at all.......
David
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A good lesson for all. Document EVERYTHING and when you did it. Right down to changing plugs and oil, let alone more significant mods. It not only preserves your memory but helps the next guy that puts his hands on it.;) |
| Gaz64 |
08-22-2015 03:12 PM |
Quote:
Originally Posted by blykins
(Post 1360071)
252/262 @ .050"?
If that's duration at .050", that's a very large camshaft for a 427. My engines that are around this displacement and use hydraulic rollers have about 12-14 degrees less duration and peak at around 6000-6200.
My guess is that the cam has been changed sometime in the car's life and that cam does not match the rest of the engine/car/goals. Your compression test shows low because the cam is so large and the numbers actually jive for a cam that large.
I'm thinking that if these are .050" duration numbers, the cam is so big that you have no bottom end and you can't run high enough in the rpm range where the cam wants to be efficient.
If those numbers are advertised duration numbers, then that would be a tow truck cam....
I'd change the cam....
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Yes, I agree also.
Either the specs the OP has quoted are incorrect, or the cam is way too big or way too small for the expected outcome. |
| Ace23 |
08-22-2015 04:49 PM |
Quote:
Originally Posted by blykins
(Post 1360071)
252/262 @ .050"?
If that's duration at .050", that's a very large camshaft for a 427. My engines that are around this displacement and use hydraulic rollers have about 12-14 degrees less duration and peak at around 6000-6200.
My guess is that the cam has been changed sometime in the car's life and that cam does not match the rest of the engine/car/goals. Your compression test shows low because the cam is so large and the numbers actually jive for a cam that large.
I'm thinking that if these are .050" duration numbers, the cam is so big that you have no bottom end and you can't run high enough in the rpm range where the cam wants to be efficient.
If those numbers are advertised duration numbers, then that would be a tow truck cam....
I'd change the cam....
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I will double check the build sheet that list the installed camshaft specifications as well as the sheet from Comp Cams. The previous owner had owned the car since 2009 but I cannot guarantee any changes prior to his ownership. I guess someone changin camshafts is as possible as anything else.
Quote:
Originally Posted by DAVID GAGNARD
(Post 1360085)
and the engine originally came with a dual plane intake and Davinci 950 carb.....now it has a Victor Jr. intake and another carb.....
Makes one wonder what else has been changed on the engine from the time it left the engine builder till now????????
David
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I swapped the carb to a QuickFuel. I have a 150 page binder from when the car was brought in to the states and literally every receipt for the build and any additional parts through the years. Personally I think the motor is exactly what it says it is but thats something we can verify as the wrenches start turning. I haven' found anything on the car that hasn't matched up with the receipts......it was also a local car to me so the current group of guys in the Cobra club know that it hasn't been touched since 2009 when it was bought by the previous owner. None of the information I was given is a100% guarantee but it is better than not having any documentation on the vehicle |
| Ace23 |
08-22-2015 04:52 PM |
I will update this thread as we go down the checklist on the possible issues. If we can't find anything we will pull the motor and then I guess we will all know for sure!:D
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| blykins |
08-22-2015 05:01 PM |
I don't think I'd pull the motor out....
I'd stick a piece of wire down a spark plug hole, verify the stroke is what it's supposed to be, verify the cam specs, and if they are what you say they were, I'd stick a hydraulic roller in there with 236-238° @ .050" and my bet is that you'd notice a ton of difference....
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| DAVID GAGNARD |
08-23-2015 05:48 AM |
Quote:
Originally Posted by Ace23
(Post 1360133)
I will double check the build sheet that list the installed camshaft specifications as well as the sheet from Comp Cams. The previous owner had owned the car since 2009 but I cannot guarantee any changes prior to his ownership. I guess someone changin camshafts is as possible as anything else.
I swapped the carb to a QuickFuel. I have a 150 page binder from when the car was brought in to the states and literally every receipt for the build and any additional parts through the years. Personally I think the motor is exactly what it says it is but thats something we can verify as the wrenches start turning. I haven' found anything on the car that hasn't matched up with the receipts......it was also a local car to me so the current group of guys in the Cobra club know that it hasn't been touched since 2009 when it was bought by the previous owner. None of the information I was given is a100% guarantee but it is better than not having any documentation on the vehicle
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What concerns me is the Olthoff's tune/rwhp numbers correspond with the dyno numbers of the original engine,then thru the years things were changed and the engine "lost" about 100 hp......
Like Brent said,check the stroke,check the cam and see where your at and what you've got.........
Another question I would have is why was the intake changed and if the cam is not the original,why was it changed?????
David |
| olddog |
08-23-2015 07:16 AM |
I do not recall any talk on what the timing and AFR is now, when skimming through this thread. You need enough fuel to not detonate, but not a lot more than that (some safety margin). After that the timing is where the power is at. You could easily loose a 100 Hp if the timing is not right. A gummed up mechanical advance in the distributor could be the problem.
PS
Pull the vacuum line (plug it) rev it from 2500 - 4000 and see where it quits advancing and what that timing is. Once it quits advancing, no need to rev any higher. If you are under 32 that is likely your problem and your engine may need as much as 36. The best way to find out how much timing makes the most power is on a dyno. Some engines make the most power at 30 others 38, it has a lot to do with the head design and compression, etc. I would guess your engine to need 34-36.
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| DAVID GAGNARD |
08-23-2015 07:45 AM |
Quote:
Originally Posted by olddog
(Post 1360183)
I do not recall any talk on what the timing and AFR is now, when skimming through this thread. You need enough fuel to not detonate, but not a lot more than that (some safety margin). After that the timing is where the power is at. You could easily loose a 100 Hp if the timing is not right. A gummed up mechanical advance in the distributor could be the problem.
PS
Pull the vacuum line (plug it) rev it from 2500 - 4000 and see where it quits advancing and what that timing is. Once it quits advancing, no need to rev any higher. If you are under 32 that is likely your problem and your engine may need as much as 36. The best way to find out how much timing makes the most power is on a dyno. Some engines make the most power at 30 others 38, it has a lot to do with the head design and compression, etc. I would guess your engine to need 34-36.
|
Quote:
When the car was tuned the tuner did exaclty as you described......I would say a good 3-4 hours was spent tweaking the carb and making timing adjustments while on the dyno.
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Olddog,they did do that, they changed jets and tried difference timing setting for 3-4 hours on the chasis dyno.....they seem to have gotten the most they could out of the engine as it is now......
David |
| madmaxx |
08-23-2015 10:53 AM |
my guess is the cam was changed in the past for a more street able tune. higher torque at the expense of horsepower.
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| olddog |
08-23-2015 12:34 PM |
Quote:
Originally Posted by DAVID GAGNARD
(Post 1360187)
Olddog,they did do that, they changed jets and tried difference timing setting for 3-4 hours on the chasis dyno.....they seem to have gotten the most they could out of the engine as it is now......
David
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Thanks David. I missed that. |
| Gaz64 |
08-23-2015 01:08 PM |
Quote:
Originally Posted by Ace23
(Post 1359745)
Figured I would follow up with some information from my records that came with the car. The superflo dyno sheets shows a max hp of 585 at 6100rpm and a max tq of 568 at 5000rpm.....the AFR ratio's are at 13:0 and climb to 14:3 at max rpm which was 7000. The only variances from the build sheet are that it listed a Davinci 950 carb and Performer RPM intake. The carb on the car now is a 750QF and intake is a victor jr. The camshaft that is listed is a Comp Cam .576 intake and exhaust gross lift with 252 exhaust and 262 intake with 112 lobe separation. I hope the camshaft isn't anything proprietary....this is from 10 years back and its stamped all over the build information so it doesn't appear top secret. I was aware the car did have a Davinci carb on it but that it was removed....I'm wondering if the intake manifold listed on the build sheet is a typo as I undertand it to have always had a victor jr on it. This is purely to provide information based on peoples questions about the motor....not to debate someone's dyno numbers and if they are accurate. With work being as busy as it is there has not been any time to start going down the checklist of to do items.
|
Quote:
Originally Posted by olddog
(Post 1360183)
I do not recall any talk on what the timing and AFR is now, when skimming through this thread.
|
This could be the reason for the power loss. |
| Ace23 |
08-23-2015 02:50 PM |
Quote:
Originally Posted by DAVID GAGNARD
(Post 1360171)
What concerns me is the Olthoff's tune/rwhp numbers correspond with the dyno numbers of the original engine,then thru the years things were changed and the engine "lost" about 100 hp......
Like Brent said,check the stroke,check the cam and see where your at and what you've got.........
Another question I would have is why was the intake changed and if the cam is not the original,why was it changed?????
David
|
The work on the car and tune from Oltoffs reflect the current condition of the car as all that took place in 2009. When the previous owner bought it he had it sent to Dennis to work through the car and get it right. According to the previous owner, records and local cobra guys...nothing on the car has been changed since it left Dennis.
Quote:
Originally Posted by Gaz64
(Post 1360229)
This could be the reason for the power loss.
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My numbers were quoted off the engine dyno sheet. I can post it up for review |
| DAVID GAGNARD |
08-23-2015 03:17 PM |
Quote:
The work on the car and tune from Oltoffs reflect the current condition of the car as all that took place in 2009. When the previous owner bought it he had it sent to Dennis to work through the car and get it right. According to the previous owner, records and local cobra guys...nothing on the car has been changed since it left Dennis.
Quote:
|
If everything is supposed to be the same as when Olthoff tuned and did the chassis dyno, then something has happened to the engine since 2009 that has made it "lose" about 100hp........ I don't think the compression numbers are it and with only 11,000 or so miles on it,it shouldn't be worn out and due for a rebuild........
You need to verify the cam/stroke and a few other things to see exactly what you have....
David |
| Ace23 |
08-23-2015 04:48 PM |
Quote:
Originally Posted by DAVID GAGNARD
(Post 1360244)
If everything is supposed to be the same as when Olthoff tuned and did the chassis dyno, then something has happened to the engine since 2009 that has made it "lose" about 100hp........ I don't think the compression numbers are it and with only 11,000 or so miles on it,it shouldn't be worn out and due for a rebuild........
You need to verify the cam/stroke and a few other things to see exactly what you have....
David
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David, I don't disagree. Previous post was just explaining the timeline and where the Oltoff work for in. We will definitely be verifying as we go through it |
| Jerry Clayton |
08-23-2015 08:16 PM |
Why don't you try it with a 950 carb again? 200cfm differance is a lot of differance--------
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| Ace23 |
08-24-2015 06:59 PM |
Just a quick note. I came across some pictures of the engine when it was on the engine dyno at Keith craft back in 2004. The intake in the picture is the victor jr that is currently on the car. Looks like we can rule out the intake being changed as previously thought. I guess the mention of the different manifold n the build sheet was a typo.
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| Jerry Clayton |
08-24-2015 07:13 PM |
950 carb?
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| Ace23 |
08-24-2015 10:03 PM |
Quote:
Originally Posted by Jerry Clayton
(Post 1360381)
950 carb?
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Originally tuned with Holley 750. Previous owner went to the Davinci and then to a vacuum secondary street avenger 770. I changed it to the QF 750 and had it dyno tuned |
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