Race 1 Answers Your Questions About the GM 602 and 604 Crate Engines
Disclaimer: The following information is merely a small part of your maintenance / engine start up procedures. Race 1 assumes no responsibility on incorrectly following these procedures. Further, this information is by no means an exhaustive list of everything that may need done to YOUR engine. Throughout the off season and during race season Race-1 rebuilds many engines, as well as the initial start up on other engines. These are the procedures that we follow when rebuilding and starting our customer’s new engines or their freshly rebuilt engines.
Proper Oil Level for GM 604/602
With the use of more expensive and exotic oils some racers have a false sense of security and do not check oil on a regular basis. This is a dangerous practice and it is stongly recommended to put the following procedure into your weekly maintenance schedule or pre-race prep.
1) Using the oil level inspection plug located on the left side of the 604 oil pan —make sure you can see that oil is near the hole.
2) Reasonably level the engine front to rear and side to side
3) Warm the engine to operating temperature
4) With the engine level, warmed up, and running at idle remove the oil level inspection plug and measure oil level.
We recommend the level to be 3/8 to 5/8 of an inch below the female threads of the inspection hole.
**SPECIAL NOTES**
On tracks with extremely long straight-aways 1 additional quart may be needed to maintain a safe level.
Over filling under normal conditions will overheat the oil and cut power significantly.
Engines with oil coolers MUST be checked running
The inspection plug for the 602 is on the right side of the pan and both 604 and 602 inspection plugs are higher than the centerline of the pans.
Do not confuse the inspection plug with the drain plug as they both have a 9/16 wrench head.
New Engine Start-Up
The following is recommended for all new crate engines from GM
1) Remove all the rocker arms, check that the rocker studs are tight in the head (604) and reinstall the rockers properly adjusting valve lash and properly securing the posi lock-(see valve lash procedure).
2) Prime the oiling system with a pressure tank or a drill operated primer that installs in place of the distributor. It is highly recommended that one of the above mentioned are used for the initial prime. Spinning the engine over with the starter is NOT recommended and may cause early engine failure.
3) We recommend priming the engine with a 10w30 non synthetic engine oil for the initial start.
4) After the prime is complete, starting the engine as soon as possible is recommended.
5) Start the engine, check for oil pressure immediately and check for any leaks immediately.
6) Check that timing is near 32 degrees, final timing adjustments should be made after the engine has reached operating temperature (see 604/602 TIMING).
7) Run the engine at varying rpms between 1200 and 2200 RPMs until water temp is over 180 degree. (cover the front of the radiator to speed the warming time).
TURN ENGINE OFF then proceed to #8
8.) Drain the oil and change the filter, this quick oil change removes the assembly lubes and also helps to remove any small debris that may have been hidden during the final cleaning before assembly.
9) We now recommend you fill the crank case with Joe Gibbs BR Brake in oil and use a Wix oil filter. The break in oil is to be run for one race only. Past that we recommended to use a semi synthetic oil for an additional race or two this will complete the break in process and insure the best possible ring seal known to us. We recommend Joe Gibbs XP7 for this.
10) Now a full synthetic oil should be installed. We recommend a mixture of Joe Gibbs XP3 and XP6.
Note: Proper oil level is always critical Call with any questions
604 and 602 Valve Adjustment
Roll the pushrod between your finger and thumb as if it were a cigar, at the same time begin tightening the adjuster nut.
The INSTANT that you feel an increase in resistance to roll the pushrod -STOP- that is zero lash.
NOTE this does require a certain amount of “feel” by the time you finish your first set you will be a pro.
Next: Tighten the adjuster nut 1/4 turn more.
Next: Tighten the set screw (allen).
Next: With your hex key (allen wrench) and your 5/8 wrench turn both into the stud another 1/16 to 1/8 turn, this secures the set screw from backing out.
**Positioning of the valve for adjustment**
When the intake valve is closing–ADJUST THE EXHAUST.
When the exhaust valve just begins to open — ADJUST THE INTAKE
There are other methods but we have found this to work on all engines and leaves less room for mistakes.
**NOTE** If you follow the firing order you will only have to turn the crank a 1/4 turn between valves once you get #1 in postion.
604 and 602 Timing
1.) We recommend that both these engines be set at a TOTAL timing of 32 degrees. NOTE different amounts of timing may be benificial due to different fuels, exhaust designs and carburetor choices. However, unless dyno testing is available or controlled race track testing we advise 32 to be the number.
2.) For dirt late model applications we recommend that the advance curve be locked out.
3.) The balancer is marked out in degrees and we highly recommend using the marks on the balancer and NOT a high tech timing light with dial up advance. (keep it simple). **NOTE** the small white paint mark that is near the “0″ groove in the balancer means NOTHING. The groove is 0 (TDC) and actual degrees are marked on the balancer.
4.) Total timing is set with the engine hot and at an elevated rpm (even with a locked distributor). The timing actually will retard and this is due to timing chain stretch, be sure to increase rpm until the timing marks become steady.
**SPECIAL NOTE FOR MSD DISTRIBUTORS**
After the timing is set, align the timing marks with the engine shut off, then remove the dist. cap and validate rotor phasing. The rotor should be pointing directly at either #1 or #6, if the rotor is pointing between terminals, then the pick up coil wires are reversed and must be corrected and the timing reset.
BROKEN FLYWHEEL BOLTS
We have seen several engines with broken flywheel bolts in recent years.
The blame is immediately placed on the bolt, and that is partially correct.
The actual cause in most cases is the length of the bolt and not the grade or quality.
A common length bolt to be used is 1 ¼ inches in length and when used with a Bert flywheel and no shims will be too long.
Even with a washer under the head of the bolt, in most cases this will be too long.
In ALL installations the bolt length should be verified to be correct.
1) begin by measuring the depth of the hole and the thickness of the flywheel–add those two dimensions and subtract .100” (little less than 1/8”)
And verify the total thread length from your calculation.
2) Double Check:
Install the flywheel and torque the bolts to 65 ft. lbs.
Remove the bolts and inspect the first thread on the bolt.
If the bolt has a drag when being removed –chances are it is too long.
If the first thread is mushroomed chances are the bolt is too long.
A bolt that is too long by 1/16 to 1/8 of an inch will appear to be tight but in actuality is not, and will shear (break) because of constant side loading.
*******NOTE********
Manufactures have many different tolerances and styles—the example given above is what we have found for a BERT flywheel used on a GM crate engine that is externally balanced (602–604)
ALWAYS VERIFY YOUR PARTICULAR APPLICATION!!!!
