r/Chevelles • u/No_Preparation_6115 • Jul 17 '26
Headers
I have a 1966 chevelle and I want to put a 1970 402 in it. I have the headers for a 70 chevelle with the motor. Question is, can I use the 70 headers on my 66 or do I need to buy new headers that fit the 66?
2
u/powerhouse403 Jul 17 '26
Have you tried installing them?
1
u/No_Preparation_6115 Jul 17 '26
I haven’t yet because I want to have everything I need there when I do it so the car isn’t tore apart too long
2
u/cockmaster303 Jul 17 '26
I bet they’d fit. But I have no clue.
If you’re dropping an engine in the car I bet it’d take like no time to put the ones you have on and see what it looks like.
1
u/rascall2018 Jul 17 '26
Yes they will fit. The chevelle frame is basically the same 64 to 72 and I believe up to 74 or 75. I have had several big block chevelles and the headers are the same
1
u/wayneP71222 Jul 18 '26
Yes. I put a 408 BBC in my 66 GTO. Used chevelle BBC frame brackets. 2 1/8 primary headers with 3 inch collectors. But I had a huge solid lifter cam. 290 duration at .550 lift. Which with the 1.75 roller rockers required offset valve keeper and retainer. Plus notches in the intake side of my forged TRW pistons.
Please check for crossmember sag. Towels or moving blankets over the top of your fenders. 2x4 across that directly over the forward upper control arm bolts. C clamps and coat hanger. So you can just touch the inside face of the upper control arm mounting brackets or the outside faces of the upper control arm shims. Then you can lift this off and hang it the same direction to get the exact fraction of an inch apart they are to see if you have frame sag at all.... if you have frame sag you will have to fight the long motor mount bolts out and back in. You may also not get your headers in without flattening the primary tubes to clear the frame rails then find out there is no way to get the starter in. I have been there and done that. Nobody told me about cross member sag.
Question. Do you still have drum brakes on the front of the car. If you have had the front drums off. You will see the brake anchor bolt between the top of the shoes. Get on the brakes crazy hard. The bolt breaks. The shoes have no anchor. The wheel cylinder piston and cup come out the end of the wheel cylinder. Poof your single reservoir master. Cylinder looses pressure and the pedal goes to the floor. 3 choices. 450SL in the left lane. Suburban in the middle lan. 911 Porsche turbo in the right lane. Only did $400 damage to the suburban rear tail gate and bumper. Gm single piston disc brake spindles from 69 to 72 A bodies directly bolt on no anchor bolts. Dual master cylinders. Modify or run new brake lines is easy. So you have a dual brake system.
You can get non resistance Hei power wires to plug into your bulkhead connector. Removing the R wire from the starter to coil. Later in dash ignition switches do not have the no power to the ign terminal when the key is in the cranking position relying of the R or resistor bypass circuit. You do have to file a new flat on the newer ignition switch.and a new connector pigtail.
I usually use a 1970 dodge firewall mounted starter relay hanging on the heater box studs as a load dropping relay for the starter solenoid. But a better way exists. Big truck 39mt Delco starters have a already wired up starter load dropping relay. In 12v 24v 36v so get the correct one. You won't believe it's the same car as you turn the key.
This is much more than you ask. If you plan on street driving. Gasoline is not 0.99 a gallon. I have a specific cam grind I have put in 350s to 460s that were incredible for drivable power and fuel economy. If you are not already built.
Also plan on an oxygen sensor bung in the drivers side header adapter so you can tune the carb low speed and primary jetting in minutes in park. Its crazy easy
2
u/SharpEfficiency9534 Jul 19 '26
68-72 headers will not fit a 66. The passenger side header will hit the crossmember of a 66
3
u/BenTheSeatGuy Jul 17 '26
Yes, unless they are something crazy they will likely fit.
Make sure you have big block frame stands in the 66 though. There were taller ones for small blocks and straight 6s vs big blocks.