Can stock J heads make the same power as stock C’s
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What about variations in castings? During the golden era of stock, racers would flow many sets of heads looking for CFM variations in head castings. To have a head to head comparison between stock heads would not the heads have to have the same valve and seat angles, same valves and the valves be set at the same depth in to the head/seat?
Lots of reasons for different heads. First off when they added rotators they had to change the spring pocket depth. The F and D heads had one of the center exhaust ports NOT tied to the cross over. While I haven't published the data, the F heads seem to have something done to the ports to change their flow compared to the E head. But I bet most of the head changes are for cooling. Meaning there are directors cast inside the head to direct coolant flow where the designers want it to flow. My OEM background had a lot of changes to the heads for cooling and not for air flow. This is a bigger deal than most people realize. jerry
Other things to consider would be the change from 45 degree lifter angle to 39 degrees would need changes to the push rod holes for push rod clearance. Rocker arm attachment holes went from 5/16-18 threads to 7/16-14 over the years. Wouldn't this require more material inside the head ?
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"YES"
Let me answer your question with a example;
490 TQ X 2.48 X 4.88 = 5930
550 TQ X 2.48 X 3.73 = 5087
To answer your question, you can see there's a drastic difference in TQ to the rear tire, you can see engine TQ can never overcome gear ratio TQ multiplication, but the more gear/converter you run, your RPM range has to be extended. This is why the power is ALWAYS trying to be moved up as far as racing is concerned.
Let me answer your question with a example;
490 TQ X 2.48 X 4.88 = 5930
550 TQ X 2.48 X 3.73 = 5087
To answer your question, you can see there's a drastic difference in TQ to the rear tire, you can see engine TQ can never overcome gear ratio TQ multiplication, but the more gear/converter you run, your RPM range has to be extended. This is why the power is ALWAYS trying to be moved up as far as racing is concerned.
Last edited by VORTECPRO; Jul 10, 2025 at 07:33 AM.
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"YES"
Let me answer your question with a example;
490 TQ X 2.48 X 4.88 = 5930
550 TQ X 2.48 X 3.73 = 5087
To answer your question, you can see there's a drastic difference in TQ to the rear tire, you can see engine TQ can never overcome gear ratio TQ multiplication, but the more gear/converter you run, your RPM range has to be extended. This is why the power is ALWAYS trying to be moved up as far as racing is concerned.
Let me answer your question with a example;
490 TQ X 2.48 X 4.88 = 5930
550 TQ X 2.48 X 3.73 = 5087
To answer your question, you can see there's a drastic difference in TQ to the rear tire, you can see engine TQ can never overcome gear ratio TQ multiplication, but the more gear/converter you run, your RPM range has to be extended. This is why the power is ALWAYS trying to be moved up as far as racing is concerned.
I honked the horn when I drove my slow Oldsmobile through your state last year (after hitting 6 tracks).
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There is a fairly simple answer. Engine castings are cast in an assembly line situation. One set of cores and patterns were not used to cast all the parts In the case of cylinder heads, they would have maybe 100 sets of cores and patterns. The cores and patterns would vary slightly among them. Thus, flow could vary slightly.
I would be inclined to believe this.
Other things to consider would be the change from 45 degree lifter angle to 39 degrees would need changes to the push rod holes for push rod clearance. Rocker arm attachment holes went from 5/16-18 threads to 7/16-14 over the years. Wouldn't this require more material inside the head ?
I would be inclined to believe this.
Other things to consider would be the change from 45 degree lifter angle to 39 degrees would need changes to the push rod holes for push rod clearance. Rocker arm attachment holes went from 5/16-18 threads to 7/16-14 over the years. Wouldn't this require more material inside the head ?
but wouldn’t the addition of valve rotators or pushrod hole mean a change in the MACHINING instead of an entirely different casting?
Never mind, I guess if the existing casting doesn’t have enough meat to change the machining, then a new casting would be needed.
Obviously, there has to be a reason.
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but wouldn’t the addition of valve rotators or pushrod hole mean a change in the MACHINING instead of an entirely different casting?
Never mind, I guess if the existing casting doesn’t have enough meat to change the machining, then a new casting would be needed.
Obviously, there has to be a reason.
Never mind, I guess if the existing casting doesn’t have enough meat to change the machining, then a new casting would be needed.
Obviously, there has to be a reason.
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The 455 Olds is undervalved, and crossectional area is far from optimal. The fastest class an Olds 455 runs in is D/SA, they do not run J heads. I can't speak for Jerry, but I do believe if I tested the J head back to back with a C head, both stock I believe the C head would prevail. The bigger intake valve combined with more cross section would allow the engine to make more power @ a higher RPM. My last 455 build the customer wanted a stroker, I advised against it, my argument was: A Edelbrock head can't support a 455 much less 500 inches. My question to this forum:
Which is quicker down a Dragstrip
Engine 1. 500 HP @ 7000 RPM 490 TQ
Engine 2. 500 HP @ 5400 RPM 550 TQ
Which is quicker down a Dragstrip
Engine 1. 500 HP @ 7000 RPM 490 TQ
Engine 2. 500 HP @ 5400 RPM 550 TQ
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I'm not saying the J head is better than a C head. In a "stock like" 1970 W-30 configuration the J heads make slightly more power than the C's and a decent amount more torque. I have made in the mid 450's with stock C heads prepped for adjustable valvetrain. I don't think we'd get to that point with a J head. But J is NOT junk by any means. Sure the flow numbers are far from stellar, but there is more to a head than flow, and the J's do well in a stock engine trim. The dyno data proved it. Hell, the E heads made significantly more power than a C head in a stock form engine. But based on flow numbers you would pick C.
In the end there is no correct answer, it depends on what you want to do and there are parts to this that are not understood, at least by me. If you want a 400 HP engine, a J head will do just fine in stock form.
jerry
In the end there is no correct answer, it depends on what you want to do and there are parts to this that are not understood, at least by me. If you want a 400 HP engine, a J head will do just fine in stock form.
jerry
you shouldn’t make a blanket statement like that about the E head.
Last edited by CANADIANOLDS; Jul 10, 2025 at 07:26 PM.
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Not enough data. It depends on gearing and what the power curve looks like, what transmission. A heavy car with a powerglide would benefit from engine 1 if the power curve was flatter and not as peaky, as the RPM's wouldn't put you too far out of the power band of the engine. It's a question that can't be answered in it's current form.
jerry
jerry
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As far as helping you cope, what you need is a Dale Carnegie course on how to meet and influence friends.
https://www.dalecarnegie.com/en/cour...ale%20carnegie
Last edited by 66-3X2 442; Jul 10, 2025 at 08:25 PM.
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Probably because he's actually done something in the Oldsmobile world. Myself, I liked his 307 production Olds build, I also liked his test car, maybe someone can post up pictures of it. A link to his 307 build would also be nice.
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I couldn't care less about what he's explaining. I'm old, I'm tired & I ain't building any more cars, so why should I care?
As far as helping you cope, what you need is a Dale Carnegie course on how to meet and influence friends.
https://www.dalecarnegie.com/en/cour...ale%20carnegie
As far as helping you cope, what you need is a Dale Carnegie course on how to meet and influence friends.
https://www.dalecarnegie.com/en/cour...ale%20carnegie
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Everyone needs to be held to the same standard. Thats a staple in any functioning group.
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I couldn't care less about what he's explaining. I'm old, I'm tired & I ain't building any more cars, so why should I care?
As far as helping you cope, what you need is a Dale Carnegie course on how to meet and influence friends.
https://www.dalecarnegie.com/en/cour...ale%20carnegie
As far as helping you cope, what you need is a Dale Carnegie course on how to meet and influence friends.
https://www.dalecarnegie.com/en/cour...ale%20carnegie
I still have the will to learn and figure stuff out. better with age. I still love going to the track
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I’ll let you try to figure it out. I’m not going to give you the answer.
one more time, you can’t make a blanket statement about the E intake port when there are two very different ones…so it’s not true
Last edited by CANADIANOLDS; Jul 11, 2025 at 08:01 PM.
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Hell I haven't given up. I do something everyday & I still build and restore tri carbs. I'm 73 with one leg and I still cut my own grass. I learn something every day but I get tired of hearing you and the Chevy guy run everybody in the ground. I have no doubt ya'll know what you're doing but it gets really tiring hearing about how great and wonderful ya'll are. I've done my time @ the track and loved every second of it but the older you get the drive isn't as strong. If only we could see you and the Chevy guys private correspondence we could really learn something.
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Hell I haven't given up. I do something everyday & I still build and restore tri carbs. I'm 73 with one leg and I still cut my own grass. I learn something every day but I get tired of hearing you and the Chevy guy run everybody in the ground. I have no doubt ya'll know what you're doing but it gets really tiring hearing about how great and wonderful ya'll are. I've done my time @ the track and loved every second of it but the older you get the drive isn't as strong. If only we could see you and the Chevy guys private correspondence we could really learn something.
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What I have learned from this thread.
The big block Oldsmobile cylinder head does not flow enough air to support a (Performance) 455 build.
Increasing the stroke to an engine that already struggles to move air is not ideal.
That there are other production engines that move air more efficiently.
The big block Oldsmobile cylinder head does not flow enough air to support a (Performance) 455 build.
Increasing the stroke to an engine that already struggles to move air is not ideal.
That there are other production engines that move air more efficiently.
Last edited by Bernhard; Jul 11, 2025 at 09:05 PM.
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Last edited by 66-3X2 442; Jul 12, 2025 at 07:16 PM.
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Ok-i'm going to get Yacavonne on this, he's another old timer, not surly though. We're going to get to the bottom of this, and who you are, and what you've done. Although some of the higher classes you post up in Stock are dime rocket type cars, still there's some ingenuity that goes into racing them, but not my cup of tea.But at least you've done some real racing! I would sure like to see any and all pictures of your NHRA Stock cars you've raced, And if you don't mind, what did the NMCA Olds run?
Last edited by VORTECPRO; Jul 12, 2025 at 10:48 PM.
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OK-investigation complete, here's the scenario: as an old time racer, you feel you had some success, and fancy yourself a "stick" racer with this 3x2 car which is long gone, you now only have memories of your hay day in racing, which makes you very intolerant of people like myself that are still out there doing it, trust me I get it, I'm getting old myself, its not easy. As an old racer, really you should be allies with people like me, because people like me really care about your racing days, in fact I've taken in more than one old NHRA racers that were down on their luck.
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this show you came to was started by me ….I’m not even mad you’re talking about your old memories which has nothing to do with C&J heads.
