wjsullivan

I picked up a set of freshly rebuilt 186 heads for my 1970 LT-1 engine project. Only problem is the guy had them rebuild for use in a hydraulic lifter setup and I'm building a stock solid lifter motor.

His note is below:
The Cylinder Heads have been set up for a Hydraulic Roller Tappet and Lifters, Maximum Effort Retro Fit, Hydraulic Roller and are not for use with a Flat Tappet Cam.

What do I need to change on these heads to convert them back to run with solid lifters and a flat tappet cam?

gerry72

Nothing other than the springs, but maybe not even those. Depends upon how much seat and over the nose pressure they have and how closely they match the cam you'll be using. If this is a stock LT-1 type cam, then the springs may be too heavy for them. The factory LT-1 springs were pretty soft with 120 lbs seat pressure.

You'll have to find out the spring specs to know for sure. There is no difference otherwise (valves, guides, rockers, seals, retainers and locks don't know what cam you're using)

Lt1er

As a fellow Lt1 owner my advice is: find out like Gerry said, about what the exact spring pressure is. You need a spring pressure checker and you need to know the max lift possible before coil bind.

Your warning about not to be used on flat cams was intended for H-flat not solid flat cams

H-roller are generally around 130-140 pounds seat and for just below .600 lift. Which would be perfect for a higher revving solid lifter.

When I built my Lt1 I hat shop P&P my 186 casting heads, install screw in studs and guide plates, Manley Proflow valves, higher than required springs, and chromemoly retainers with 10 degree locks. I bought Oliver forged 580 gram lightweight I-beam 6 inch rods Ross forged bushed flat top pistons. Balanced the motor with the stock forged crankshaft. ARP main Studs. All assembled by "gkull" here on the forum over 14 years ago, nearly 60,000 miles, and still kicks butt! 3.55 rear and 4 speed aluminum flywheel

The orginal LT1 cam is crap from yesteryear Without going to a solid roller I looked around and got some advice on solid flat cams. Crane cams has this nice solid cam 238/248 and I use 1.6 roller tip rockers. It is a no BS 400+ hp build that can be driven around town and run on the local 91 super unleaded





Part Number: 113841 Grind Number: F-278-2 (REPLACES CC-278-2)
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1957 1987 CHEVROLET 8 FAIR IDLE, MODERATE PERFORMANCE USAGE, GOOD MID-RANGE HP, BRACKET RACING, 3400-3800 CRUISE RPM, 10.0 TO 11.5 COMPRESSION RATIO ADVISED. BASIC RPM 3000-6500
Engine Size Configuration
262-400 C.I. V
Valve Setting: Intake .022 Exhaust .022 HOT
Lift: Intake @Cam 320 @Valve 480 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 3334 @Valve 500
Rocker Arm Ratio 1.50
Cam Timing: TAPPET @.018
Lift: Opens Closes ADV Duration
Intake 29.0 BTDC 69.0 ABDC 278 °
Exhaust 82.0 BBDC 26.0 ATDC 288 °
Spring Requirements: Triple Dual Outer Inner
Part Number 96877
Loads Closed 126 LBS @ 1.850 or 1 27/32
Open 304 LBS @ 1.400

Recommended RPM range with matching components
Minimum RPM 3000
Maximum RPM 6800
Valve Float 7400
Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 10.0 BTDC 48.0 ABDC 109 238 °
Exhaust 63.0 BBDC 5.0 ATDC 119 248 °

wjsullivan

Thanks guys.

I've got the invoice from all the work done at the machine shop which includes part numbers, etc. I believe the springs are COMP Cams 986-16

These were picked to go with COMP Cams 12-422-8 - COMP Cams Xtreme Energy Retro-Fit Camshaft and Howards Cams 91160 - Howards Cams Maximum Effort Retrofit Hydraulic Roller Lifters.

So it sounds like I'll need to change those once I pick a cam and lifter combination.

Lt1er

Actually if you look them up in the spring chart .PDF on comp cams site they are good to go. That is if you measure them and they have been installed at 1.750 to 1.800 to the bottom of the retainer which would give you 117 - 130 pounds closed and the ability to have .600 or .550 max valve lift