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Discussion Starter #1 (Edited)
Hi there,
I have Comps #904 1.550 springs installed at 1.960 so they are 130 seat pressure and 360 open. Max rec lift .600

I was planning using these heads with my Isky 274 Mega hyd flat tappet, but dont know if the spring pressure is on the high side for a flat-cam?

Brodix use this springs on their heads for hyd roller and flat tappet if I have understand everything correct. What do you think?

Thanks
Matt
 

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The Mega 274 is a circle track cam with 226/226 @ .050" and .490" lift with 1.5 rockers. Here's the cam card: Mega-274
Isky recommends the Isky #6005 spring, 1.430" OD and 275lbs/in which has 135lbs at 1.750" installed height and #285lbs open. That comp spring is better suited for a roller and exceeds Isky's spec by 75lbs.
300 lbs is about the upper risky limit for street flat tappets if you don't have Nascar saavy and money. With all this about lowered zinc in oil, it's an important consideration for cam/tappet longevity.

The installed height you have now would be excessive for the Isky spring. You'd need to use thicker spring seats and/or shim it up to get the installed height. Without looking at it I'm not sure exactly what you should do but I wouldn't run those springs on that cam.
Here's the Comp Cams troubleshooting guide in PDF. Basically it says use the same seat and max pressure the cam grinder recommends.

Why don't you run a higher lift roller cam and take advantage of the flow capability of those heads?
 

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Discussion Starter #3 (Edited)
Thanks Paul,
Thats what I've thought... It would be risky running the flat tappet with those springs. Brodix says they are first for hyd roller, but could be used even with flat tappet cams.

Yes, I know these heads need more lift to perform their best. The 274 cam was kinda emergency solution 'till I got some cash and step up to a roller. Well, those heads werent cheap and I already had the Isky cam & lifters here on the shelf. Thats why I first intended to use it untill I could afford a roller cam.

Anyway, I've got most of the parts for my engine, including a bored and decked 4 bolt block. I guess I can wait some more time before I'll assemble the plant, sell the Isky and buy that roller instead.

Do you have any tips on a good hyd roller that would work nice with my combo? I guess Im looking for one with pressed on "iron" dist gear, I better pick a small base, even though I dont think the clearance issue will be that hard coz of my stroker clearanced rods, but anyway...

Any tips would be appreciated, when it comes to bumpsticks, there's a jungle out there! Note, this car is intended to be used on the streets ;)
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Combo:
Engine: Chevy 350 bored .030 and stroked to 383
Rotating assembly: (Internal balanced)
Crank: Scat 3.75 stroke crankshaft
Rods: Scat Premium 7/16 ARP bolts I-beam 6” bushed connecting rods
Pistons: SRP forged piston & pins (inverted dome -16cc) around 9.8-10.2 cr
Rings: Sealed power 1/16 1/16 3/16 moly piston rings
Bearings: Clevite P rod & main bearings

Heads: Brodix RR 200 Alu heads with 64cc CNCd combustion chambers & 1.550 springs.
130 seat pressure 360 open .600 max lift
Intake Manifold: Brodix dual plane intake
Carb: Holley 750 HP carb

Exhaust: 1 5/8 under chassi headers connected to 2 1/2 dual exhaust (sidepipes)

Transmission: TH350 transmission with B&M Holeshot 1900 converter
Gears: 3.55 posi

Vehicle: 1963 Chevy II/Nova 3200 pounds with driver


Note; If needed I will buy another converter with higher stall, maybe even go with bigger primaries headers.
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Thanks for your help Paul
Matt
 
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