Visit The Dirt Forum for More Information

Author Topic:   400 sbc with 5.7 rods
racer038
Member
posted February 27, 2003 11:20 AM
What is the proper way to insure proper cam / block clearances when using 5.7 rods in 400 block and stock 3.75" crank. Old rod bolts and side of rods were ground. I'm freshening and using new Eagle SIR rods. Shouldn't rods be clearanced before I have the assembly balanced??


autoshop
Member
posted February 27, 2003 12:14 PM
I use a coupla three pieces of cardboard cut about 6in long----lay one end on the camshaft lobe and turn the rod past it. If there's no bind, OK! If the cardboard gets stuck between the rod and lobe, remove the piston and get the grinder! I like my "tool" better than a coathanger, because when there's a shortage of clearance,I don't chance scarring the cam.


racer038
Member
posted March 01, 2003 06:20 AM
Thanks for the feedback. In terms of thousanths, rod to cam clearance should be what....... 0.030", 0.060", 0.090". If I change cams, then I'd need to recheck clearances. Do you have to do this always with longer than stock rods? If I built a long rod 383, would I be doing this again. Most guys I know, change cams all the time with the engine in the car and NEVER check cam clearance.


racer1030
Member
posted March 01, 2003 10:16 AM
>050-.060" is needed. Most aftermarket rods today will clear 3.75 stroke with areduced base circle cam. Many will clear with a standard base circle.Check with your rod manufacturer. Its not the rod length thats the problem its the rod bolt placement and length.


racer038
Member
posted April 18, 2003 05:51 PM
UPDATE REGARDING CAM CLEARANCE
I was convinced that a small base circle cam along with the Eagle SIR 5.7 rods in the 400 SBC would not be a problem, so I had the assembly balanced without assembling and checking for clearances first. Guess what??? Only 0.030" clearance on #2 and #6. Now I have to disassemble, get the clearance, re-balance and start all over again. I should have paid more attention to you guys instead of the machine shop and parts sellers. I was anxious and just wanted to get the stuff done. Now I'm paying the price. Advise "Do it right the FIRST time.


Eljojo
Member
posted April 18, 2003 10:26 PM
Last bit of advice: Should you decide to degree your camshaft differently those clearance #'s will change!


jnewman44
Member
posted April 19, 2003 12:08 PM
I built a 383 with .515 lift cam strait up, stock rods w/ arp bolts. Grinding was nessasary but minimal, I use a matchbook folded,(or closed), when that clears you have about .050". The grinding will be so little you can probably get away without rebalancing. Ask around about this.


racer038
Member
posted April 19, 2003 05:56 PM
Borrowed a scale from work and weighed the piston/rod assembly before and after clearancing. Less than 0.5 gram weight difference. I'm grinding all the rods evenly and then going to put it together. If she comes apart, I'll post an update.


Back to the Archives