[torqjunki]

Scott...Is this a street car? THats a lot of compression if your trying to run it on pump gas. Also a lot of compression for a pretty small cam. Not sure if you will ever be able to tame this combo without race gas. A bigger cam with some overlap will help, but a bandaid really. I am in Magnolia, TX and would be happy to help you out with the tune. 281-389-6150 David

[chiphead]

That engine will ping itself to death if it's really got 11:1 compression and that small of a cam. I would expect cranking compression numbers over 200 PSI with engine warm, plugs out and throttle wide open. That would verify combo of compression and small cam.

A cam with a later intake closing event, about 10-15* more duration and 112-114 LSA would reduce dynamic compression and make more power. That would be complimented by an RPM intake and Q-JET.

We could make timing recommendations, but the timing may be retarded on purpose to prevent detonation. Setting it where it should be may be a bad thing, depending on how sensitive the engine is to detonation. I suspect retarded timing why its so down on power and hot. Check what you have now and post back. We need to know timing at idle and at 3000 RPM.

The engine temps at 220 is too high. It's either water flow, air flow, radiator size or tuning. What are engine temps at cruising? What is the oil pressure at idle and at 3000?

[PontGuy]

As stated all of your symptoms are typical for too much compression - too little cam. A compression test would help confirm this.

Curious though, the numbers that you give for .050 duration didn't sound right so I looked it up and Crower lists the cam at 221 int 229 exh. It doesn't change your situation but are you getting the numbers from the cam card?

[67drake]

Originally Posted by PontGuy

Curious though, the numbers that you give for .050 duration didn't sound right so I looked it up and Crower lists the cam at 221 int 229 exh. It doesn't change your situation but are you getting the numbers from the cam card?

X2. That is the cam I run,and some of those specs are different than my cam card. Might want to double check what cam you are running,or at least the specs.

[screamingchief]

I doubt the CR is @ 11.0:1 here,not unless the short block was zero decked and the heads had been shaved some before being shaved that .012" this time.

The common pistons for these 400 engines sit down in the hole like .020" on average,so that typically puts the CR closer to 10.0:1 when used with most any of the common small chamber big valve heads like those 670's.

Most of those small chamber big valve heads will be over 72cc when "virgin",typically they are closer to 75cc or so,so that .012" mill just puts them 2cc or so closer to the "nominal" 72cc spec that we all know so well.

Besides,there can be a lot of explainations for those sorta symptoms,many of them are related to common tuning chores,others are often related to minor problems like vacuum leaks or such.

I can see a few things I'd change in this combo,but most of what's going on with this is likely things that are only loosely related to those items I would wanna change.

In the right hands,I bet this could be "whipped into shape" in no time.

2¢ FWIW

Bret P.

[PontGuy]

I doubt the CR is @ 11.0:1 here,not unless the short block was zero decked and the heads had been shaved some before being shaved that .012" this time.

Maybe, maybe not. I do know that I ran a similar cam with RA heads in a 400 years back and though it ran OK I had similar issues- pinging, dieseling, heat soaking, etc. I installed a much bigger cam, one of the old Crane Fireballs, and the engine was a lot happier. But that was on a 4spd car with a big gear and no power brakes, so I could get away with the "racy" cam.

We are all just guessing, and compression numbers would help tell where this one stands.

Though the intake/carb combo, no vacuum advance etc. are not the way I would go and are probably not helping the situation.

[screamingchief]

Originally Posted by screamingchief

I doubt the CR is @ 11.0:1 here,not unless the short block was zero decked and the heads had been shaved some before being shaved that .012" this time.

Well,lots of times when folks say two cams are "similar",they really are'nt all that similar.

The only way to compare two cams is by looking at all the info for both cams and looking at what the valve events are like with both cams.

Beyond that,I never assume anything about cams,there are just too many people that just look at the basic cam info without really understanding where the real differences in cams lie.

You may know what cams you had in that combo,but I have absolutely no idea what they were unless you tell me exactly which two cams you are refering to.

Then I might be able to compare those two cams to the OP's Crower #60242 cam.

Originally Posted by PontGuy

We are all just guessing, and compression numbers would help tell where this one stands.

I dunno about guessing,,,I'm not really guessing about anything I said...

I know I have a pretty good idea what I'd expect to see from any compression test results,if he is infact @ 10.0:1 I'd expect the cranking compression to be around 150 psi (give or take 5-10 psi or so) with that #60242 cam,and if it were indeed up @ 11.0:1 I'd expect it to be closer to 170 psi (again give or take say 5-10 psi).

Now there are a lotta folks out there that would say he should easily be able to run trouble free with those sorta cranking compression numbers,but that's just not always the case,as there are numerous other factors that affect that situation beyond just what psi it cranks out,so honestly looking at those compression test numbers are only going to tell a person if he's way off the mark.

There are combos out there that crank over 200 psi that run trouble free,and the flip side of that is there are also combos out there that only crank 130 psi and they ping like crazy,so there is no "magic" cranking psi that is going to ensure trouble-free results.

A lot of that depends on not skipping over "details" in the build itself,as well as the overall skill of the tuner,and the quality of his work.

Now there may be some info that the OP neglected to mention here,so yeah there is some "grey area" in all this where certain things needs to be taken for granted till he clarifies those further,but the SCR situation is'nt really one of them.

Even if he had that combo zero decked,with a 72cc head that still only gets him to 10.5:1 CR.

And in order to get it to an honest 11.0:1 CR,it would have to be zero decked and the chambers in those 670 heads would need to be like 68cc or so.

That stuff is'nt a guess,that's pretty cut & dried really.

Originally Posted by PontGuy

Though the intake/carb combo, no vacuum advance etc. are not the way I would go and are probably not helping the situation.

I agree with most of ^^^^ that.

I did'nt go into specifics,mostly because I wanted to make the point that the CR was'nt likely as high as was being quoted by the OP,and being discussed amongst the others here.

But I did indeed point out that there were some things that I too felt were not helping this.

Yeah,the first thing I'd do is pitch the non-vacuum advance uni-lite distributor,mainly because I dont care for the uni-lite distributors,and second because I've rarely ever seen a vacuum advance hurt a "street" car in terms of improved performance and driveability.

That mostly relates to the "tuning" end of things,as I mentioned earlier.

Get the timing dialed in and then you can start to figure out the rest of the tuning needs.

Also,the car could almost certainly use some more converter,even with the 3.08 rear gear that cam is gonna want a bit more stall than many "stock" converters will give.

Another thing is that I'm not a fan of the performer intake either,especially with the square bore holley carbs on them,as the Edelbrock dual flange intakes can be prone to vacuum leaks around the carb base with the square bore carbs on them.

I dont really have a problem with the 650 holley DP per-se,as that can be easily made to work by someone with the proper carb tuning skills.

Hands down I'd take the Holley 650 DP over any of the Ecarb AFB clones.

And the cooling system sounds like it may need some indepth attention as well.

But I'd probably double check the electrical guages accuracy by installing some mechanical gauges to get another more accuate reading of the OP & WT.

Though things like high coolant temps and low oil pressure can easily be caused by lots of other things.

Same with things like pinging and dieseling.

Lotta that stuff is often related to one another.

If it's running rich and hot as SOP right now,odds are there is a $#!t ton of carbon build-up in the chambers and on the tops of the pistons,and understand that all it takes is one small piece of that carbon to glow red hot and that'll certainly cause those sorta pinging and dieseling issues.

That sorta thing often has absolutely nothing to do with the static compression ratio...

And proper plug choices plays into this as well,if too hot a plug is being used that could explain some of those sorta problems as well.

And if one is running a thinner wt. oil with a fair amount of miles on it,well a "warm" running engine likely is'nt helping the oil pressure much either.

Not to mention if he's running way too rich,it's entirely possible that the oil is getting fuel contaminated as well.

Or even worse yet,maybe he has a Fram oil filter on it that has collapsed internally or such.

Again those would not necessarily have anything to do with the static CR.

Sure sometimes there is indeed a cause-effect relationship to those sorta things,but sometimes it's just coincidental too,so one is often best served by trying to keep an open mind,and working thru these sorta deals before just going out and throwing more parts at the problem trying to fix it.

All I'm saying here is this:
Often it's a failure to get all those simple things "right" that causes the biggest problems.

FWIW

Bret P.

[torqjunki]

Well said Cheif....Thats why I avoided any real detailed info....this car needs to go to someone who knows Pontiacs and tuning..... Go see the Screamin chief or someone who can methodically diagnose and fix it. Money well spent.