Author Topic: 355 HP...really  (Read 4431 times)

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Offline rockhouse66

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Re: 355 HP...really
« Reply #30 on: September 27, 2018, 07:17:10 am »
I have been involved in two very stock builds that came out in the 350-375 HP range through manifolds (not headers).  That is a very mild cam and I think your 355 result is typical.  Some tuning could certainly be done to improve it a little though, from the looks of things.  That drop off at the higher revs is not typical.
Jim

'69 Grande CJ

Offline markharvey9077@gmail.com

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Re: 355 HP...really
« Reply #31 on: September 27, 2018, 11:26:57 pm »
just spoke with builder...cam is .214/224 duration 50 thousands....valve lift is .520/546 lob 110...(hope i copied that correctly) and the dyno was run with headers...comments? recommendations?

Offline 69scj428

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Re: 355 HP...really
« Reply #32 on: September 28, 2018, 07:29:34 am »
I would have to ask why the compression is so low if it is in fact 9:1. I have run 10.5:1 on the street using super unleaded for years without and detonation issues. I do have to keep my
timing from being too advanced, but that is not an issue for the horsepower difference. Valve springs are a concern as stated above. They need to match the cam to ensure the valves open and close properly without valve float. I have, however, used factory springs in a 428cj before with a crane .561 lift 290 duration cam without an issue. I am not sure why your dyno sheet shows as if the valves are floating--strange to me!! I think you need to start from scratch with the cam, springs, and check out the carb. Is the carb a Holley street avenger by any chance?? Just curious because I have seen low performance before from those particular carbs. Another recommendation is to use hardened rocker arm shafts as I have had them break before with high lift cams. Who degreed the cam shaft?? Was it done in accordance with the cam card or did the builder use a stock type timing chain without multiple key indexes?? A retarded camshaft outside of the manufactures' specs could also cause the issue that you have. Your engine makes good torque which is what really makes a street car fun. I think it would run okay, but for reliability purposes, I think you should check out some of the recommendations made in these posts. Most notably, I would be concerned about the valve springs and the stock rocker shafts if you re-used them. Just my 2 cents--hope it helps-------Donald :) :)

Offline 69cobrajetrugae2

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Re: 355 HP...really
« Reply #33 on: September 28, 2018, 08:12:15 am »
As we know every one of our engines squeezes and swirls the burning fuel charge differently, some better than others.  Higher compression does not guarantee success, in fact through the years one of the engine masters here has tried to steer us away from that sort of dinosaur logic.

 When Bob built the first version of the 428 CJ the engine surprised everybody.  As I recall, a mismatched intake head gasket or something along those lines created tremendous port velocity down in the dirt which might have gone unnoticed if the compression was higher.

A higher compression ratio has no effect on power production until the piston is about 10 degrees of TDC.  At that point the rate of burn is increased which increases the temperature which increases the pressure which does make more power as compared to a engine with a lower C/R at least on paper.  In reality the fuel is also consumed faster so the peak cylinder pressure might not jive with the optimum crank angle resulting in greater pumping losses.  Add more fuel and less advance is a partial solution but what about the high temperature of compression and the fuel auto igniting?

 As the piston progresses in it's power stroke the rate of burn has increased so much due to the temperature of high compression it may detonate.  Quench at TDC is tight fit between part of the piston crown and the head which does what the word implies, it puts out part of the burning charge to avoid detonation but since some burn temperature is lost in the quench so is the pressure and so is some of the power.

 Carbon in the combustion chamber and piston crown hinder heat transfer creating a hot chamber.  When the relatively cool fuel charge is drawn in and then rapidly heats up, less of the charge can enter before the valve closes but even so that charge is potentially power packed.

 A guy that knows this can pull back his total advance and play with the A/F ratio and make more power but if he leans it out too much he'll know it because the engine will perform better than ever at the top end.  If he's experienced steps will be taken to back off the power, which is to back off the temperature and therefore the pressure to "save the hardware".

  Unless leaded racing fuel is used and one is a master engine fellow, high compression ratios is very poor judgment in my opinion.  Look elsewhere for high temperatures and pressures that are not so destructive and unpredictable.

Offline 428 CJ hardtops

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Re: 355 HP...really
« Reply #34 on: September 28, 2018, 08:55:29 pm »
Wow headers probably added 25 to 40 hp over manifolds .Yes something isn't right but it explain bigger jetting .
had many 428 CJ and SCJ cars over the last 30 years.I currently own a 68 1/2 coupe and a 69 R code SCJ Coupe and a 70 R code SCJ Cougar Eliminator .I am looking for a 70 428 coupe if anybody knows of one for sale.

Offline markharvey9077@gmail.com

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Re: 355 HP...really
« Reply #35 on: September 29, 2018, 01:33:53 am »
talked to the builder...and he tells me this is a compcam ...and I looked up on the website ahd the 926-16 is all that comes close...and he used Manley springs...but I will get part numbers to confirm he had a match..why would he not buy the cam/springs in a kit...?  When I get the part number ...what spec on the springs am I looking for...the seat load...etc...what would be a number that would cause me to change them....I found a local dyno shop that I may have him change out the springs.  What would be a fair price to have them change them out....

Second...as for the cam...I was not looking for a racing cam...just a non smooth idle...is this the correct one or should I upgrade...to what...

Do I reduce the jets to 66/79 stock? ....this is a 735 cfm original rebuilt.

Offline RoyceP

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Re: 355 HP...really
« Reply #36 on: September 29, 2018, 08:44:18 am »
Google is your friend -

https://www.jegs.com/i/COMP-Cams/249/926-16/10002/-1


talked to the builder...and he tells me this is a compcam ...and I looked up on the website ahd the 926-16 is all that comes close...and he used Manley springs...but I will get part numbers to confirm he had a match..why would he not buy the cam/springs in a kit...?  When I get the part number ...what spec on the springs am I looking for...the seat load...etc...what would be a number that would cause me to change them....I found a local dyno shop that I may have him change out the springs.  What would be a fair price to have them change them out....

Second...as for the cam...I was not looking for a racing cam...just a non smooth idle...is this the correct one or should I upgrade...to what...

Do I reduce the jets to 66/79 stock? ....this is a 735 cfm original rebuilt.
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Offline 428 CJ hardtops

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Re: 355 HP...really
« Reply #37 on: September 29, 2018, 09:18:20 am »
I think the installed height is higher than those springs are rated at .Closer to 2 inches than the 1.8 they are measured at .Would make a huge difference in performance .
had many 428 CJ and SCJ cars over the last 30 years.I currently own a 68 1/2 coupe and a 69 R code SCJ Coupe and a 70 R code SCJ Cougar Eliminator .I am looking for a 70 428 coupe if anybody knows of one for sale.

Offline markharvey9077@gmail.com

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Re: 355 HP...really
« Reply #38 on: September 29, 2018, 02:46:52 pm »
so ...I find the part number of springs he installed and see if they compare to the 2" 415 recommended...if that is the correct cam....and upgrade myself...???

The dyno guy I talked to wanted $1000 for a before and after dyno ...with me changing the springs...seems a bit high...and wanted $4k more to change the cam/springs....but he did say a 224 cam would drop off after 4200...seems a little weak....

Wish I had the sense and tech to go here first...and direct the builder to install the right cam...


Offline RoyceP

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Re: 355 HP...really
« Reply #39 on: September 30, 2018, 08:21:12 am »
The stock cam is a real snoozer but it runs up to 5500 before it starts falling off. Your cam is slightly, and I mean very slightly, more than a stock cam. It ought to perform a little better than a stock cam, provided everything else is proper.

I've never seen spending money on dyno runs as very cost effective. I would get the timing and carburetion squared away and go to the drag strip. Lots more fun for a lot less money. You might be pleasantly surprised at how much difference it will make getting the advance back where it should be.


so ...I find the part number of springs he installed and see if they compare to the 2" 415 recommended...if that is the correct cam....and upgrade myself...???

The dyno guy I talked to wanted $1000 for a before and after dyno ...with me changing the springs...seems a bit high...and wanted $4k more to change the cam/springs....but he did say a 224 cam would drop off after 4200...seems a little weak....

Wish I had the sense and tech to go here first...and direct the builder to install the right cam...
1910 Model T Ford Touring Red
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1968 Mercury Cougar XR-7 GT-E Green 427 W Code
1968 Mercury Cougar XR-7 428CJ R code 3.91 C6

Offline geraldt52

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Re: 355 HP...really
« Reply #40 on: September 30, 2018, 02:31:07 pm »


...Wish I had the sense and tech to go here first...and direct the builder to install the right cam...

Your builder's selection of cam, which isn't bad at all, would not explain the way the engine is dying from 4K on up...you need to figure why that's happening, and it isn't the fault of the cam based on its specs.  You've gotten good suggestions regarding checking lifter preload and checking spring heights/forces...which would seem the most likely snafus.

Before I did anything further though, I'd disconnect the vacuum advance and put a timing light and vacuum gage on the engine and gently run it up to a bit over 4K looking for either the vacuum or the advance to go erratic.  It's possible that the advance is bouncing all over the place above 4K and killing the power.  Then I'd remove both valve covers and turn the engine over just looking to see that the valve train is operating as expected.

Offline markharvey9077@gmail.com

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Re: 355 HP...really
« Reply #41 on: October 02, 2018, 04:06:07 pm »
I think I found the issue....I got the part numbers and the cam may not be right...but the springs are...Cam is a 33-238-4 (218 intake/224 exhaust, lift ast .513/.52 110 deg separation...lob lift at .298.)  This shows as a heavy towing in 428 with gears...that sounds like a truck engine and explains the high torque and low HP...springs are 926-16 as specified.  Not sure if he is feeding me a line as he said Manley springs the first time.

I believe a 33-226-4 with 224/224, 519/519 is better suited at a minimum....the next higher cam shows aftermarket stall issue...at 230 duration.  How high could I go without stalls and an excessive rough idle.

I am capable of the cam change...is this worth it...

Comments please

Offline crossboss

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Re: 355 HP...really
« Reply #42 on: October 02, 2018, 04:18:25 pm »
As Royce and many others (including myself) had mentioned, a stock cam will go to 5,500. FIRST, I would ditch the junk Pertronix with a reliable and quality electronic ignition like the OEM Ford Dura-Spark set up. SECOND, make sure your springs/installed height is correct. THIRD, check for lifter preload/valve train geometry. FOURTH, and most important, make sure EVERYTHING is with in spec. Remember, just because you purchased a 'new' cam, that does not mean it is good. I had a very similar situation with a bad cam grind. Good luck, and keep us posted!
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Offline rockhouse66

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Re: 355 HP...really
« Reply #43 on: October 02, 2018, 05:43:24 pm »
Note that the cam card for the cam you have now says it is good to 5500 RPM, so you really need to figure out the issue with the drop off in power so early.  As mentioned, valve spring setup (not just the spring rating), ignition timing, etc.  Yes, the 270H would be a step in the right direction IMO.  Especially if you plan to run headers on your car (do you?).  The "stall" comment is related to automatic transmission cars - is yours an automatic?
Jim

'69 Grande CJ

Offline geraldt52

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Re: 355 HP...really
« Reply #44 on: October 02, 2018, 07:46:45 pm »
That cam has slightly longer durations and higher lifts than the factory 428CJ cam.  There is really nothing wrong with it, and I surely wouldn't waste my time/money changing it out at this point. 

Besides, you really need to figure out why the dyno run fell off so dramatically over 4K, or you may change out the cam and end up right back where you are.  Something is wrong that needs fixing, but that cam selection is not the culprit.