67 Cuda: disappointing dyno numbers, need some advice!

[PRH]

and your sources are good. Big block version in '90 catalog but the small block version was gone.

My source for that was from someone who said they’d used that cam before(who I had faith in them knowing what they had)......... and that story was being stored in the aging gray matter.
If the 455/455 SB cam was gone by 1990...... it doesn’t sound like it fits the build timeline of 1995(unless it was sitting on someone’s shelf for a while).

 

[Mattax]

My source for that was from someone who said they’d used that cam before(who I had faith in them knowing what they had)......... and that story was being stored in the aging gray matter.
If the 455/455 SB cam was gone by 1990...... it doesn’t sound like it fits the build timeline of 1995(unless it was sitting on someone’s shelf for a while).

Its not on the 1995 price sheet, but that's the only price sheet I saved. Those were occasionally useful for items not in the glossy catalog. Pretty sure that was how I knew there were still a few 20:1 steering worms available in '89 - '90.

 

[72bluNblu]

Sounds right, I think I will put the rockers on tho shouldn't hurt and might help a little?

Changing the rockers won't do anything you're going to notice.

Honestly I'd leave it alone until I had time to pull the heads and really see what was in there. Or until I could afford to replace the heads, if they're 308's then they're open chamber and you can boost the compression with a set of closed chamber heads.

Probably in the 8.5-9.0 CR range.

Just run it til the season is over.
Here’s my thoughts on what is likely in the motor...... based on the mid-90’s build timeline.....

“Trw flat tops”, Trw used to have those. Stock replacement forged piston for like a 71 360. Flat, no valve pockets, down the hole about .090”.
I used them in a 360 for my father in 1990.
That build was 8.8:1.

“455 MP cam”, From what I’ve been told, Mopar used to have a .455/.455, 272/272-112 cam for the small blocks.
It disappeared from the line up somewhere in the late 90’s, early 00’s....... but was available for the BB for a while longer.
I bet that’s whats in there.

Sounds about right to me.

Some of it will depend on the machine work done on the engine and heads, maybe the OP will get lucky and the pistons aren't that far down and the primary culprit for the low compression is large head chambers.

Either way, the results of the dyno make perfect sense with that kind of compression. There might be a little more power there with a better matched cam and some tuning. But if a bunch more horsepower is desired, it's going to take some work. If it's got open chamber 308's on it maybe the head chambers are large and the fix can be just a set of closed chamber aluminum heads. Of course if it doesn't have open chamber heads on it and the pistons are way down in the cylinders it might take a full tear down to really address that compression.

 

[Brandt Fonda]

Changing the rockers won't do anything you're going to notice.

really? shoot! How about some tuning? I don't know how much you can tune a holley sniper 4150 but maybe that would be a little more pep.

 

[PRH]

That pull seemed like it kinda took a while........

You said you have the OD trans?

Did you test in 3rd or 4th gear?

 

[Brandt Fonda]

That pull seemed like it kinda took a while........

You said you have the OD trans?

Did you test in 3rd or 4th gear?

yeah the OD tranny, pull was in 3rd, 3.91 rear gears

 

[PRH]

Okay...... just seemed to take a while.

Do you know if it’s an inertia dyno or a load cell dyno?

If it’s a load cell dyno, then the rate of the pull is controlled/programmed.

If the rockers you bought are 1.6’s..... they might make a few more hp.

 

[Wyrmrider]

Have AJ run the numbers for you now that you know your compression, 308 heads which should have slightly smaller chambers than X or J
he'll have to add 10-12 degrees to the MOPAR timing to make his computer program work right maybe even close to 20 degrees to go from .008 to .004
update figure 16-18 degrees from MP to .004 so almost a 290 cam the way Crane measures cams
As said above not much to do if FT pistons way down the hole
maybe not this thread but BTW the 4 eyebrow Pistons are so they do not have to make Lefts and Rights

 

[Brandt Fonda]

Okay...... just seemed to take a while.

Do you know if it’s an inertia dyno or a load cell dyno?

If it’s a load cell dyno, then the rate of the pull is controlled/programmed.

If the rockers you bought are 1.6’s..... they might make a few more hp.

I don't know which kind of dyno it was but he said he had to set the roll speed or something before he did any pulls and he did a couple of low speed runs and adjusted the dyno a few times before the real pulls. He also said the rwhp numbers were calculated at a 25% loss. (which seems high, I thought it would be 15% since it is a manual 2 wheel drive car?)

The rockers I bought were 1.5 because I thought the heads would have to be worked so the pushrods didn't rub/bind?

 

[Brandt Fonda]

Have AJ run the numbers for you now that you know your compression, 308 heads which should have slightly smaller chambers than X or J
he'll have to add 10-12 degrees to the MOPAR timing to make his computer program work right maybe even close to 20 degrees to go from .008 to .004
update figure 16-18 degrees from MP to .004 so almost a 290 cam the way Crane measures cams
As said above not much to do if FT pistons way down the hole
maybe not this thread but BTW the 4 eyebrow Pistons are so they do not have to make Lefts and Rights

ok cool, should I just shoot him a message?

 

[sireland67]

I am a firm believer in if it is not broke dont fix it.
Without tearing the whole top end off the engine, and measuring everything, there is no way to tell if your new rocker arms will clear the pistons.
It would really suck, to jam a valve down into a piston, even though I dont think you would, but I am not a gambling man, so I have to know, I do know that the factory rocker arms are all over the place, so you may be changing the valve train clearance more than you think.