390 build -What have I done wrong

[Aussie Rob]

Found the box my cam kit came in and the spring pressures are different to what my machine shop told me. They are comp part # 924-16, Seat Load= 112lbs @ 1.90 installed, Open Load= 355lbs @ 1.20. Alternative upgrade (which I know about now) part# 26120
Seat Load= 155 , Open Load=355 , just a little better than the E/brocks, there is every chance that this where the problem is.
Why do manufacturers and suppliers not tell you these things up front so you can make the best choice without having to go the long way round to get the right outcome. I work away so I have to shelve things now until I get back in about 2 weeks or so.
 I have a tool to change springs with the heads on, do you recommend doing it that way or pull them off for accuracy?
Should I use the Edels or spend more money on the comps?
 thankyou all for your help and advise I'll let you know when I've changed them over.

[Barry_R]

The Comp 26120 is a beehive spring that would work very well on your package.  But you will need the matching retainers and locators as well.  Its a fairly expensive combination - but a good one.  We alternately use a PAC racing 1924 here, a double spring which catalogs at a seat pressure of 144 lbs @ 1.900, and open pressure of 403 lbs @ 1.300

[My427stang]

That 924 is a very common flat tappet street build spring, not enough for heavy hyd roller stuff

If it were mine, I wouldn't spend a penny until I saw what my actual installed height and spring pressures were, you are likely to be even lower than what the paperwork says

Then I would go with something like Barry said, or if the budget is less forgiving, a high quality standard spring with damper that that matches your installed height and lift. 

The factory Edelbrocks may be good for this application too, but you have to measure installed height, calculated or measured lift, and the resulting pressures. 

Sounds like a lot of work, but less than an hour of work for the machine shop if you showed up on his door with one head.  Even less time if you measured installed height on the car and calculated the rest, then he just measured spring pressures for you

[mike_burch]

What sort of X-Pipe is used?  Is it a name brand, or something an exhaust shop fabbed up?  Sometimes, exhaust shops will TRY to build them, and either use crush bent pipe or simply run one pipe through the other.  If they do this, the merge area is often the same as, or less than the diameter of ONE pipe.  These might sound "cool" but create a horrible restriction in the exhaust that will keep the engine from making power. 

What size exhaust is on the car?  What sort of bends?  If it is crush bent pipe that's 2.5" or less, and has some tight bends...  that can keep it from making power when revved up as well. 

As a test, I would uncork the exhaust, and take it for a drive.  If it runs significantly better, you've found a bottleneck.

Good Luck!

[Aussie Rob]

Thanks for the replies, I won't be taking anything for granted in the future, I'll be assessing the individual parts supplied in any kit I use.
As this was delivered directly to the machine shop I'm pretty disappointed in him as well(spent plenty there over the years-as well as recommendations). After several emails to comp they tell me I need better springs ,go figure, so I let them know my thoughts. They are telling me the same as you guys, the supplied springs are even less than advertised. I'll probably have to save a bit and go with the beehives. The x pipe is a Summit product and the pipes are coming off for a dyno run next time I'm off shift, he's not charging me for this one. Thankyou all for your tech expertise, it would be easy to dig a bigger hole without it.

[CaptCobrajet]

Standard issue at my place is the Comp 26120 beehive for anything up to .600 lift in a hydraulic roller, as long as 6000-6200 is the max rpm.  Past that lift, or rpm range, I have seen that the conical springs are better.  The beehive is head and shoulders above "regular"  springs, and the conicals are even better.  Less resonance=more rpm,  less weight=more rpm, and also more control of the valvetrain with significantly less required open pressure.  A typical dual spring and retainer usually weighs double what the conical weighs, and almost double what the beehive weighs.

[Aussie Rob]

Hi everyone, I've decided to replace the 924-16 springs with the 26120's as suggested and need some help to ensure I order the correct locators to fit the edelbrock heads. The vehicle is 400 miles from where I'm working so I can't carry out any measurements . I am unsure of the inner ID to fit over the guide. Part # are 4696, 4697 and 4698. Also would the installed height of 1.880 giving 155 seat and 355 open be appropriate pressure wise, this still leaves .110 before coil bind with my lift. If I order the parts online now they will be there when I get off shift.  Thanks Rob.

[Barry_R]

The 4696 is the best bet with a .570 ID.
Helpful if they have a lathe nearby - sometimes you'll get heads with a larger guide in them
Easier to open the ID hole up than it is to shrink it...