Alright, as some of you may recall I could not get my 454 to pass emissions. I finally took the valve covers off and found out I have 781's. Don't know what has been done, but I had 120psi cranking compression. I was told by the speed shop that the cam is way too big for themotor and there is so much overlap that the CO will never be low enough to pass. So would a comp 280H (230/230 .520.520? on a 110LSA work with these heads? Any ideas on sorting this mess out would help greatly.

Thanks,
Joe

Joe,

What speed shop are you dealing with? What cam do you have now and what compression? 120 psi cranking is pretty low. What rpm and vacuum does your motor idle at now? Just my opinion but 110 lsa will be hard to get through emissions.

Regards,
Gary Anderson

It sounds like you have flat top pistons and 781 heads, not a good match. That compression sounds like about the 8:1 range. You might do better to change heads to closed chamber if you do indeed have flat tops.

Without knowing what the static compression ratio is or the current cam specs in the motor are it will be difficult for anyone here to give you a recomendation. If you post your complete combination that would help, I see it is a 4 speed car. what gears? intake, carb, exhaust system, usable rpm range, etc. Was the compession 120 for all cylinders? 150-180psi for pump gas would be ideal IMO. With flattop pistons and the large combustion chamber of the 781's you may have a very low compression engine, I bet it runs fine on 87 octane as it is, but down on power. If the engine does have flattop pistons you may want to consider swapping the heads for some closed/small chamber models to bring the compression back up. Also a leakdown test would be a good idea just to verify the rings and valves are sealing properly before dumping money into a cam or heads.

Right now I do not have cam specs as I did not build the engine. If I remember correctly the vacuum idle was pretty low....maybe 8-9"? Correct me if I am wrong, but the 781's are ggod heads. I would rather swap for some domed pistons and raise the compression and add a decent sized cam. The other components which will be replaced are a torker intake(will be replaced with a performer rpm) and a holley 650 which will be replaced with a 750 with mechanical secondaries. Gears currently are 3.07's, but I will be swaping in 4.11's. I guess maybe a complete rebuild may be the best bet because I think I may be having a bunch of mismatched parts. Gary the speed shop is the Carb shop on National Ave. May have NVR or Kilpatrick build me a motor if need be. I think are 1 time emissions are so leanient that a 110LSA will pass no problem.

-Joe

As you mentioned,an RPM is a great choice for an intake.
For heads,any 390's,215's or 063's (all closed chambers) would get you up to 9.0 to 1 or so
Stick with a cam that will build cylinder presuure too..something in the 220-230 ish duration @ .050 and ground on a 110 or 112 LSA..stay away from a 114 LSA with low compression.

Joe,

Since you don't have a "pentastar" I would avoid Kilpatrick. My stuff has come from NVR for years. Tom has been building engines for 30+ years and has the gray hair to prove it. Just be honest with him about what you want and trust his advice. He hates someone telling him how to build an engine.

I assume you are getting a "Collector" plate? If so my understanding is the car must pass a one time emissions test for the standards of the model year of the car. If you want more than a moderate driver engine you may have to use a smaller cam to pass emissions and then swap to a "real" cam afterwards.

My current motor idles at 15-16" vacuum @ 1000 rpm, cranks 210-220 psi and I would bet isn't even close to passing a snif test. It has '781 heads, 9.8 compression, small domed pistons, Crane street roller 234/244 @ .050 on 112 lsa, Performer RPM and a 750 HP Holley. It made 550+ HP on Tom's dyno and 440 on the chassis dyno at one of Kilpatrick's dyno days bashes. If I was to change anything it would be a little more compression (10.25-10.5) and a cam with a little shorter seat timing and around the same .050 timing. The Crane is kinda lazy in this respect but I had it sitting around so I used it.

Regards,
Gary Anderson

Gary,
I already have the collector plates, but didn't pass the 1 time test. I will maybe just lean towards a rebuild as I don't totally know what I have in my motor. I am basically looking for a motor that will push my 70 into the 12's and keeping the revs to about 5500. How is NVR price wise? Would it be better to pull the motor and take it there or give them the car and let them have at it?

Joe,

I'm sure his preference would be just bring in the motor, but I'm sure he could arrange to do the R&R ($$$$) if you wanted.

If you just want to run 12's that is no big deal. My car ran 12.90's at 8.0 compression and a small hydraulic cam. If you want to go 12.0 that is another story. And remember the IHRA cutoff for a roll bar is 11.49 so unless you want to get into that can of worms that is something to consider as well.

For a high 12 second deal a hydraulic cam and Rhodes lifters might get you through emissions and never have to touch it again.

Regards,
Gary Anderson