425 Super Rocket. Missing power?

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Old May 24, 2019 | 06:22 PM
  #41  
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In all honesty everything that you bought and used looks fine. I have no idea why people here do not like the Edelbrock carburetors, but if tuned correctly they will make just as much power as anything else, not that I really like them, I have always used Holley's as I understand them, but that should not be an issue. Cam at 224/234 may be a tiny bit on the smaller side, but going an extra 10 degrees is not going to make an additional 100HP. There is nothing in your parts combo that looks really off the wall. I would assume that the 9.66 compression ratio they gave you is because the actually CC'd everything and calculated it, they could have made an error here, but who knows. Unless the comprssion is really at 8:1 or less it should not be a place where you loose 100 HP. If they spent that much time on the dyno I would assume that they played with the timing and air fuel ratios to get them at the most amount of power that was possible.

There are 2 things I can think of that may be an issue, 1- the cam is way off, meaning it was either not degreed and they just “lined up the timing marks”(and the timing chain or cam itself is off), or whoever degreed it somehow screwed it up royally. 2- This engine has very low compression. 2nd is easy to check, do a compression check on the engine and see what you have.

I would start there, do a compression check on every cylinder and post what you get.

Last edited by 72442conv; May 24, 2019 at 06:38 PM.
Old May 24, 2019 | 06:36 PM
  #42  
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Would all of you please quit calling “lining up the timing marks” “straight up”? Please!
Old May 24, 2019 | 06:38 PM
  #43  
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Originally Posted by cutlassefi
Would all of you please quit calling “lining up the timing marks” “straight up”? Please!
Fixed, LOL
Old May 24, 2019 | 06:41 PM
  #44  
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Originally Posted by 72442conv
Fixed, LOL
For all, can someone, besides me, step up and explain what “straight up” really means?
Thanks.
Old May 24, 2019 | 06:42 PM
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The more I think about it, the more it seems that it is probably really low in compression. Normally if you have a cam that is advanced the low end torque goes up and the top end power goes down, if it is retarded the oposite happens. Since we seems to be low everywhere, the only thing that makes any sense to me is very low compression. I guess that the cam could be so far off that it kills power everywhere, but I have personally never seen that with new parts.
Old May 24, 2019 | 06:45 PM
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Originally Posted by cutlassefi
For all, can someone, besides me, step up and explain what “straight up” really means?
Thanks.
To me it has always meant that you put the cam in, and put your timing chain on and just line up the dots. You do not advance it or retard it.
Old May 24, 2019 | 07:23 PM
  #47  
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Originally Posted by 72442conv
To me it has always meant that you put the cam in, and put your timing chain on and just line up the dots. You do not advance it or retard it.
X2
I tried to hint at the fact it's a 45° block with 39° heads. Do you have the cam card? If so does it say it's a 45° camshaft? I doubt it would make 385 hp with a 39° cam but there is hp missing somewhere.
Old May 24, 2019 | 07:42 PM
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I thought that the 425 was made in both 39 and 45 degree CBA's. So who know what this one is. You could have hit the nail on the head with this one... Wrong cam and it will kill the power everywhere, and it will probably run like crap too...
Old May 24, 2019 | 08:13 PM
  #49  
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Gam

Regarding GAM. At the time they came highly recommended. I was trying to get Smiley to build my engine but he had recently moved/ retired. GAM builds some pretty sweet engines. Including, I believe, a car that finished 3rd in the Pikes Peak Hill Climb. When I do research on companies im considering doing business with i IGNORE the good reviews and go straight to the negative reviews. All that being said my experience with GAM was definitely not 100% positive.
Old May 24, 2019 | 10:55 PM
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Originally Posted by 72442conv
To me it has always meant that you put the cam in, and put your timing chain on and just line up the dots. You do not advance it or retard it.
"Lining up the dots" means the cam is installed with whatever amount of advance is ground into the lobe profiles. Most that I see have 4ş advance built in when the "dots are lined up" , so to install the cam "straight up" would mean to retard it 4ş relative to the dots being lined up.
Old May 25, 2019 | 05:53 AM
  #51  
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Originally Posted by Fun71
"Lining up the dots" means the cam is installed with whatever amount of advance is ground into the lobe profiles. Most that I see have 4ş advance built in when the "dots are lined up" , so to install the cam "straight up" would mean to retard it 4ş relative to the dots being lined up.
For all, IT HAS NOTHING TO DO WITH LINING UP THE FREAKIN DOTS OK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Technically speaking, if a cam is installed straight up it was installed at the same intake centerline as the ground in lsa. In other words if a cam has an lsa of 112, then "straight up" would mean it was installed on a 112icl.
"Lining up the dots" means the cam is installed with whatever amount of advance is ground into the lobe profiles" is wrong too because you have no idea how accurate your timing set is, was the crank ground at the right degrees from the keyway, and a host of other factors. I've "lined up the dots" and had them be as much as 11* off from the "ground in" spec, and that was on my own car.
72442- yes it most likely is low on compression. That's what I've been saying since the first post. Add to that I believe the op is in Colorado? Now take away just about another whole point of compression.
Hopefully everybody learned something here, and that should be YOU CHECK EVERYTHING, AND TAKE OTHERS WORDS AT FACE VALUE ONLY. CHECK IT YOURSELF.

Thank you.

Last edited by cutlassefi; May 25, 2019 at 05:57 AM.
Old May 25, 2019 | 11:50 AM
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All 1965 "Big Blocks" 425 A block engines and 400 B block engines were all 45° camshaft engines. 1966 425 D block were 45° except the Toronado 425 engines were 39° camshaft plus "big" lifters 0.921" and the E block 400 was also big lifters 0.921. I presently have four 1967 425's and had a few more over the years and all of them are 39° camshaft angle with standard 0.842, (might be 0.841) the smaller lifters. The 1967 E 400 also has large lifters. These are just from my experience. I haven't read about the thread starter's camshaft card or mention camshaft angle's. Hint, hint.

Last edited by Kennybill; May 25, 2019 at 01:22 PM.
Old May 25, 2019 | 04:13 PM
  #53  
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cam

I'll try to dig up the cam card, and check the compression soon. The engine sounded great on the dyno. Running and pulling strong from idle all the way to 6,000 rpm redline. I am going to look for the dyno sheet and cam card now. I the engine and the cam were definitely 45 degree. Wouldn't the engine grenade immediately if it had 39 degree components in it?? The elevation in Greeley is 4,000 plus feet above sea level. Which I imagine could have an effect on the dyno results. So I guess its possible it could produce substantially more at sea level.?
Old May 25, 2019 | 05:04 PM
  #54  
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cam and build sheet.

Sorry if I used the wrong terminology regarding the cam or anything else. This is why people like me pay and sometimes wrongly trust experts to build their engines.Unable to find the dyno sheet or cam card at this time. I did however find the build sheet. Until I can figure out how to load pictures on this site I will just give you some of the more important details DIRECTLY from the build sheet. Starting at the top of the page.
LAB;1005: ALIGN HONE 5 MAINS.
LAB7018: BORE V8 BLOCK AND FINISH HONE WITH TORQUE PLATE .
LAB3300EGREE CAMSHAFT 107 DEGREE INTAKE CENTER .
LAB1003: FILE FIT RINGS. 018TOP,.020 2ND.
LAB1003: MACHINE CRANK FOR PILOT BUSHING.
LAB6010:RECONDITION RODS IN SETS.
LAB300:BALANCE V-8.
LAB9025:V-8 COMPETITION VALVE JOB.
LAB9113: REPLACE INTEGRAL GUIDES(SETS).
LAB9105: CUT AND INSTALL SEATS.
LAB9116: SET VALVE SPRING HEIGHTS
VALVE SPRINGS SET AT 1.750.
LAB8408: SURFACE V-8 HEADS (PAIR).
LAB8477: CHECK CHAMBER CC'S. HEADS CHECK 81CC.
LAB1100: COMPRESSION RATIO CHECKED 9.66 to 1.
These are are the highlights from the first page of the more important details. Unfortunately any critical details beyond this are beyond my knowledge and comprehension. Thanks for taking the time to read this. Truly appreciate all the feedback, positive or otherwise. Thank you. Tom@4milefirebirds in Fairplay Colorado. Elevation 10,000 feet.
Old May 25, 2019 | 05:19 PM
  #55  
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Once you verify the piston and deck height then we can see what the comp ratio really is.
Old May 25, 2019 | 05:35 PM
  #56  
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piston and deck height.

How easy is that? I do have a compression tester/ gauge. Can the compression readings be directly converted to compression ratio? Or will i need to pull the heads. In my previous post the the heads were checked at 81cc's. Sorry this is my very first engine build. If I was an expert at all this i wouldn't have needed to pay someone. I do have a friend nearby that could do that for me. Thanks for the advice. I will check into getting that done.
Old May 25, 2019 | 06:27 PM
  #57  
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Simple, just verify two things, the part number of the piston used and whether or not the block was decked. I’ll take it from there.
Old May 25, 2019 | 07:51 PM
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Originally Posted by Thomas Richards
How easy is that? I do have a compression tester/ gauge. Can the compression readings be directly converted to compression ratio? Or will i need to pull the heads. In my previous post the the heads were checked at 81cc's. Sorry this is my very first engine build. If I was an expert at all this i wouldn't have needed to pay someone. I do have a friend nearby that could do that for me. Thanks for the advice. I will check into getting that done.
No, you can not equate the compression reading to compression ratio. There are too many variables. What a compression reading will do is tell you if there is too little compression, if you are where you need to be or if you have too much compression. Like if you have 120 pounds then you know that you have too little compression, but you can not say that 120 lbs is equivalent to lets say 7.5:1...
Old May 25, 2019 | 07:55 PM
  #59  
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cutlass efi. Compression verification.

Excellent. Heads were resurfaced. How much i do not know. I'm sure i can dig up the piston part number. Either through Summit RE where I puchased them. Or digging up a 20 year old SRE catalog. Which I do have. I can also get exact cam and head gasket information from the Mondello parts catalog where I ordered half of my parts. Thanks again.
Old May 25, 2019 | 08:11 PM
  #60  
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Compression. Again.

I will try to verify actual compression ratio. In my previous post of my actual build sheet you can see detailed information on the build. The dyno numbers were generated at 4,000 plus feet above sea level. I was cautioned to run at least 91 octane or better. I hear what you're all saying. Not that it may actually matter but GAM has been around a long time and are still around. I'm sure they have built thousands if not tens of thousands of engines. I may also be able to get more detailed information on the build from them.
Old May 25, 2019 | 08:23 PM
  #61  
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Compression yet again. Sorry.

At one point i seem to remember reading that the 1965 425 Super Rocket "ultra high compression" in stock form produced 10.5-11.25: 1 compression. True or not I can't say. If that is true I would assume that the compression would would have to be reduced, at least slightly, in order to run safely on pump gas.
Old May 26, 2019 | 05:16 AM
  #62  
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Originally Posted by Thomas Richards
At one point i seem to remember reading that the 1965 425 Super Rocket "ultra high compression" in stock form produced 10.5-11.25: 1 compression. True or not I can't say. If that is true I would assume that the compression would would have to be reduced, at least slightly, in order to run safely on pump gas.
Ironically at 4000’ you could run those types of compression ratio numbers with little to no problems. We need better info in order to move forward.
Old May 26, 2019 | 05:25 PM
  #63  
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camshaft.

Unable to track down my cam card. But did find my Mondello parts catalog that I ordered the cam from. Apparently my memory was way off on this one. Here are the exact specifications as they appear in the catalog.
Part number JM 20-22.
Intake lift .496
Exhaust lift .512
Adv. Intake Duration 266 degrees
Adv. Exhaust duration 274 degrees
Intake @ .050 226 degrees
Exhaust @ .050 230 degrees
Lobe separation angle 110 degrees
Advertised as "Semi-Hot" muscle car street cam. "Good power & Torque".
RPM range 1,400-5,800.

​​​​​
Old May 26, 2019 | 05:45 PM
  #64  
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Pistons.

Speed Pro forged 18cc dish .DurOshield coated. I was frequently poor. These seemed and probably were at the time the best bang for the buck forged pistons on the market.
Old May 26, 2019 | 05:51 PM
  #65  
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Pistons.

Just a side note on the pistons. Weighed them when they arrived. Surprised to find that they were all within 1 GRAM of each other. To me that implies at the very least quality control was pretty decent.
Old May 26, 2019 | 06:19 PM
  #66  
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Originally Posted by Thomas Richards
Since i lack the knowledge to completely rebuild an engine I had it professionally built. 8 hour dyno tune/break in. I have the dyno sheet. But not with me. Peak horsepower was 386 and change. Timed with degree wheel. Pretty sure that's mandatory. Spent $4,000 on machine work ,assembly, and dyno time. Torque was 444? and change. Approximately 300 plus foot pounds @ idle. It was gaining power on every single pull. Line honed and bored with torque plates. It may produce more once i get it on the road. I was hoping that after seeing 455's producing 450-550 horsepower that my engine would have produced no less than 400. The 425 is basically the same engine with a slightly shorter stroke. If you or anybody else out there has any suggestions of how to achieve or exceed 400 plus without spending thousands of dollars I'm open to suggestions. Thanks for the feedback.
The old "Bruce Yakatori" build. If you could post up the dyno sheet that would be a good starting point. Exactly what are your goals with this engine? I would also mention, in Greeley's 5000 feet elevation, 9.66 isn't a lot of compression. Also 385 corrected HP on GAMs dyno is really 289 observed, or in the room HP.

3700 pounds @ 100 mph = 285 crank shaft HP, 100 MPH/1320=13.20 ET

Last edited by VORTECPRO; May 26, 2019 at 06:30 PM.
Old May 26, 2019 | 06:24 PM
  #67  
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Just curious what did they weigh?
Old May 26, 2019 | 08:12 PM
  #68  
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Piston weight.

Purchased 20 plus years ago. Sorry, don't remember the exact weight. Could probably find the weight at Summit Racing. .030 over pistons. =4.155 bore on the 425.
Old May 26, 2019 | 08:25 PM
  #69  
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Dyno

Generally. Wouldn't high elevation horsepower be less than sea level horsepower?? That comment seemed backwards. Obviously the wheel horsepower would be less than the horsepower as measured at the crankshaft. If it was only producing 280 crankshaft horsepower it would only be producing 125- 150 wheel horsepower at 10,000' where I live. If that's the case i might as well kill myself now. I would get smoked by a first generation Yugo running on 1 cylinder. Sorry if I misread the comment. LOL?

Last edited by Thomas Richards; May 26, 2019 at 08:27 PM. Reason: Missing Yugo.
Old May 26, 2019 | 08:36 PM
  #70  
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Originally Posted by Thomas Richards
Generally. Wouldn't high elevation horsepower be less than sea level horsepower?? That comment seemed backwards. Obviously the wheel horsepower would be less than the horsepower as measured at the crankshaft. If it was only producing 280 crankshaft horsepower it would only be producing 125- 150 wheel horsepower at 10,000' where I live. If that's the case i might as well kill myself now. I would get smoked by a first generation running on 1 cylinder. Sorry if I misread the comment. LOL?
Bruce Yakatori's (GAM) dyno sits at 4700 feet, the 385 corrected HP (29.92 barometer, 60 degrees dry air) you got on his dyno will be down 20 % at 4700 feet altitude 310 HP observed. I can only guess, but your probably down 47 % @ 10,000 feet. Altitude ain't fun. Could you please post the dyno data?
Old May 26, 2019 | 08:52 PM
  #71  
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Dyno sheet.

I've got two copies. I will try to locate at least one of them tomorrow. I'm hoping its not that bad. Had a friend in Denver with a basically stock 69 GTO . Automatic. 400. Had no problem pulling 100 plus mph going UP Fremont Pass. Elevation 12,000' plus.Near Leadville, Colorado where I was living at the time. Pretty impressive if it was only producing 80- 100 wheel horsepower. Regardless. Appreciate the feedback. Still haven't been able to figure out how to load pictures on this site. My only internet access is on my phone. If you or anybody reading this post would like the exact horsepower and torque numbers to the tenth, I will do my best to post that information.
Old May 27, 2019 | 05:53 AM
  #72  
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Given the info presented I'll stay with my original comp ratio calculation, 8.75:1.
That's your first problem by far, especially being at 10,000'.
Old May 27, 2019 | 04:50 PM
  #73  
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Originally Posted by cutlassefi
Given the info presented I'll stay with my original comp ratio calculation, 8.75:1.
That's your first problem by far, especially being at 10,000'.
That compression is very possible. The work at GAM is OK, a 6 out of a possible 10, but I can guarantee you this, the owner couldn't give a sh-- about how your project turns out, especially if the owner supplied the parts. Not a big Bruce Yakatori fan here...........the automation on his phone should have been the first warning sign. I got stories if your interested.

Last edited by VORTECPRO; May 27, 2019 at 04:54 PM.
Old May 27, 2019 | 05:14 PM
  #74  
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"Just a guess-low compression engine build with a bad combo of parts?? What is a "competition valve job" consist of?"



Why is this thread still trying to figure it out? Mark at Cutlass EFI and others has pretty much addressed the issues at hand...You have some good parts, some not for your goals lets go and build the next one the way it should be based up on your goals and $$. Over and out!!

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Old May 27, 2019 | 05:30 PM
  #75  
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Originally Posted by therobski
"Just a guess-low compression engine build with a bad combo of parts?? What is a "competition valve job" consist of?"



Why is this thread still trying to figure it out? Mark at Cutlass EFI and others has pretty much addressed the issues at hand...You have some good parts, some not for your goals lets go and build the next one the way it should be based up on your goals and $$. Over and out!!

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I'am not trying to figure anything out............I just want to see the dyno data. I believe a competition valve job would consist of a former NHRA Stock 3 angle valve job, A GAM scam, baffle them with BS.
Old May 27, 2019 | 06:33 PM
  #76  
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Originally Posted by VORTECPRO
I'am not trying to figure anything out............I just want to see the dyno data. I believe a competition valve job would consist of a former NHRA Stock 3 angle valve job, A GAM scam, baffle them with BS.
Yes, that is what is normally meant by a competition valve job...
Old May 27, 2019 | 10:38 PM
  #77  
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Originally Posted by Thomas Richards
How aggressive could i go with the cam? Money permitting I'd like to upgrade to a hydraulic full roller set up. Edelbrock heads. EFI. And Tremec TKO 600.
Shoot for 11.0:1 or so if you’re going EFI and just do this once.
With a better EFI (Holley Terminator etc) it will enable you to pull timing as the baro and/or temps go up, giving you the best of both worlds.
If you’re not going EFI then shoot for 10.25-10.5:1, put in the correct tune and be done with it.
Otherwise you’ll just continue to throw good money after bad.

Last edited by cutlassefi; May 28, 2019 at 07:56 AM.
Old May 29, 2019 | 01:55 PM
  #78  
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BTW, There is no way you can run a 39 degree cam in a 45 degree engine without knowing it immediately. Did it once when I was young and stupid. I trusted the manufacturer saying the cam worked in a 66 425. Ran like a 300hp paint shaker. Scary.
Old Sep 24, 2024 | 12:06 PM
  #79  
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Originally Posted by Thomas Richards
Spent many years and dollars building my 1965 425 "Super Rocket ". .030" over pistons, .010 under crank, full forged internals, ARP everything, Edelbrock intake and 4bbl., .496/.512 cam," roller tipped rockers,competition valve job,etc... After all this and a full day on the dyno it produced only 385 horsepower and 440 lbs/ feet. According to the factory specs I only gained 10-15 horsepower and LOST 100 foot lbs. What happened or where did I go wrong?
Factory head gasket is .017 thickness, did you have the block decked or the heads too make up for the thicker head gaskets available today? Also a more modern grind roller camshaft might have helped also. Plus with a roller camshaft you don't have to be as careful with oil additives package like zinc levels.

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