351c good date code or just another toad?

[keith1562]

I've own a 72 Mach 1 Q code. When I bought it the seller said it had the original engine (351 cj). I also talked with guy the seller bought it from, he also said it had the original engine. That was 2 years ago & I've learned a lot since then. I found out that the engine block was cast in fall of 69, which means it's not original & it probably has two bolt mains. The mains are not really important as the car will not be seeing any time at the track. I think 2 bolt mains are adequate for a street engine with less than 400 h.p. at the fly-wheel. Anyway I got to thinking, if the block was cast in 69 what about the heads? The other day I pulled the valve covers and found the casting date "9J18" which seems to correspond pretty close to the block's born on date. Am I correct about the heads likely being from a 69- 70 car and if so does that mean it has closed combustion chambers? (It does have 4v heads for sure, it has a large 4 in front corner) I could not find any more informative numbers anywhere (DOAE...etc.) Also if it has closed chamber heads what will that do to the compression? I had my mechanic install flat top pistons & it runs good on pump gas.
I welcome any & all feedback, negative, positive, informative, or just to say "Keith you're dumber than a box of rocks".
Thanks,
Keith

[ylwhrse]

For what it's worth I am at work and don't have my identifying book, however as far as the ( DOAE) code which does identify the head it is on one of the intake ports runner on the bottom side of the head. You would have had to look at it while the head was off. Depending on the flat top piston used IE what compression height of piston pin, and what type of valve relief if any, if it is indeed a closed chamber head you should be somewhere between 9-1/2 to 10-1/2 to one at the most. To get any more compression you would have to use a pop up or dome style piston. If it is indeed an open chamber head you will fall somewhere between 8.25 to maybe 9-1/2 to one at best. Even the 10-1/2 to 1 should not be a problem for most clevelands, but somewhat depends on the cam chosen and where the timing is set. Worst case you may have to run premium unleaded. Just be sure that even if you don't here detonation or pinging to pull and look at your plugs occaisionally for any signs of detonation. Hope that helps.
YLWHRSE