67 Cuda: disappointing dyno numbers, need some advice!

[PRH]

It is a fun car and reliable atm, maybe best option is to concentrate on some other areas and save up for a crate engine from a reputable builder with build sheet and engine dyno already done.

Obviously....... those are all factors in deciding what, if anything, is to be done.

On another note......
Looking closer at the pic of your springs..... what little bit of the rocker and shaft are visible........ they look pretty rough.

 

[fishmens67]

Good information and advise is given out. but you still really don't know what's under the hood. Head work, pistons ?
It is best, before you spend another dime, pop the heads and take a peek.
It might reveal some shortcomings.

 

[crackedback]

JMO, that's a 350ish HP engine on a good tune up unless the heads are exceptional on performance. With the 450 lift, bad lifter angle and rockers that are rarely at the true 1.5 ratio, the valve is likely seeing something in the .420-.425 range

About where it should be for RWHP is my guess. Might scratch a little more out on the tune up.

Steel crank??? All 360 factory cranks for that time period are cast. Usually when that "term" is thrown around it implies a forged unit which is highly unlikely in this engine.

Heads, intake and camshaft are ares to investigate to get the RWHP where you want it.

Agree with PRH, somewhat new build and the rockers look like they've never seen a hot tank.

 

[mopowers]

That sounds about right, my low compression 340 has 9.0 static, measured, and 160 psi.
It still runs decent for a street car.

What cam are you running?

 

[Wyrmrider]

He has a DC 268 cam- about the same seat to seat as a 275 comp or 280 crane
do the compression test as we are all just stroking ourselves
IMHO forget the roller rockers and new cam till you get results
If cam is new will Hughes swap out with different cam if needed? no reason to put new cam in and make it "used" just for curiosity
Agree with YR if you do get 1.6 rockers and B3 kit and need a different cam go solid millions of 273's out there and they work better and little maintenance
Whats the bottom line on the manifold not 50 HP methinks
meanwhile look into the B3 kit so you know what you are getting into Shafts, pushrods lifters etc
I do not like roller cams with rollers on the shafts- It takes heat treated (not induction hardened) shafts do do that
the rockers are not going to make 50 hp difference either
good choice on the headers- so no big split on the exhaust duration- opens exhaust early and hurts power and mileage and also makes more heat in the ex

 

[Brandt Fonda]

JMO, that's a 350ish HP engine on a good tune up unless the heads are exceptional on performance. With the 450 lift, bad lifter angle and rockers that are rarely at the true 1.5 ratio, the valve is likely seeing something in the .420-.425 range

About where it should be for RWHP is my guess. Might scratch a little more out on the tune up.

Steel crank??? All 360 factory cranks for that time period are cast. Usually when that "term" is thrown around it implies a forged unit which is highly unlikely in this engine.

Heads, intake and camshaft are ares to investigate to get the RWHP where you want it.

Agree with PRH, somewhat new build and the rockers look like they've never seen a hot tank.

it is a 74 block but it was built around '95ish, talked to him again today he says pistons are TRW 9.5:1, forged and crank is forged. also heads are closed chamber? Not sure if 308's were closed chamber? He drove the engine in a Demon till wrecked, then he put it in Cuda. The Cuda sat after he put the motor in it for about 15 years why it looks rough in those pics. Before I got it back running I sprayed seafoam in each spark plug hole till full. Let sit for a couple days then turned engine over by hand. It turned very smoothly for several rotations changed the oil and fired it up. Since then I have changed the oil 2 more times in less than 1.5k miles. Maybe corrosion throughout the engine could be a problem?

 

[Brandt Fonda]

I already bought the roller rockers, the cam and some new lifters about 4 months ago. I really don't think they will take them back tho wont hurt to ask. I was quoted 600$ for the install of those items. I could go with a different cam pretty easy, it was only 170$ so not worth breaking crap over.

 

[Brandt Fonda]

do the compression test as we are all just stroking ourselves

Ill try to have the compression numbers on Friday

maybe one of you guys could get a close guess of compression ratio with 360la block bored .30 stock stroke, 308 heads with I think 73cc ?

I did a compression ratio chart online and got 10.33:1
values I used:
bore size: 4.07 stroke: 3.58 Gasket bore diameter: 4.18
compressed gasket thickness: .039 combustion chamber: 73cc
0 for piston dome and piston deck height.

 

[yellow rose]

it is a 74 block but it was built around '95ish, talked to him again today he says pistons are TRW 9.5:1, forged and crank is forged. also heads are closed chamber? Not sure if 308's were closed chamber? He drove the engine in a Demon till wrecked, then he put it in Cuda. The Cuda sat after he put the motor in it for about 15 years why it looks rough in those pics. Before I got it back running I sprayed seafoam in each spark plug hole till full. Let sit for a couple days then turned engine over by hand. It turned very smoothly for several rotations changed the oil and fired it up. Since then I have changed the oil 2 more times in less than 1.5k miles. Maybe corrosion throughout the engine could be a problem?View attachment 1715358816

Welp, this is a bit of a mess isn't it? You can look at the balancer and tell if it's a forged crank or not...usually.

I'm sure that 9.5:1 was with at least a zero deck...maybe.

If it is a steel crank, it's a Mopar performance part. It never came in a car.

I'm to the point where now, if it was me, I'm yanking it out and ending the guessing game. Then you'll know exactly what you have.

 

[RustyRatRod]

the purple cam is the old grind .450/455 268/272 , I thought with the stamped rockers I may not even be getting a full 1.5 ratio and not seeing all of current cam. My exhaust is TTI 3/4 step headers into 3" TTI X pipe into dual 3" all the way out.

it is indeed the aluminum m1 dual plane. I'm starting to see a general consensus that my heads may be sub par, though I have heard that the 308's flow better than x, j heads. The engine was built by Barnes and Reece in NC. which I have heard is a reputable builder, however they may have just put the engine together how they were asked and may or may not of ported them. ​

Sub par for what? Just because the builder didn't build it a certain way doesn't mean it's not a good engine. I'm quite sure they weren't looking for some forum expert's opinion of their work. They probably built exactly what was asked of them. Just because some guys on a forum don't think it's "all that" ( I am not among them) doesn't mean a thing. Sounds like it's a pretty good engine to me. I bet with some tuning and no parts changes at all it would wake up pretty good.

Just remember, there's always more than one way to do something.

 

[PRH]

I’d probably be inclined to leave it alone til the season is over.
Then pull it out and apart....... see what you have........ come up with a plan after you know what you’re working with.

Just looked up the new cam specs.
Fundamentally, it should be fine, but there will be some work required to the heads to facilitate the use of the correct springs.

Here’s a 9.8:1 360+.030, bowl ported 2.02 J heads, roller rockers, LD340, 750DP, 1-3/4” headers, small solid cam:

 

[72bluNblu]

it is a 74 block but it was built around '95ish, talked to him again today he says pistons are TRW 9.5:1, forged and crank is forged. also heads are closed chamber? Not sure if 308's were closed chamber? He drove the engine in a Demon till wrecked, then he put it in Cuda. The Cuda sat after he put the motor in it for about 15 years why it looks rough in those pics. Before I got it back running I sprayed seafoam in each spark plug hole till full. Let sit for a couple days then turned engine over by hand. It turned very smoothly for several rotations changed the oil and fired it up. Since then I have changed the oil 2 more times in less than 1.5k miles. Maybe corrosion throughout the engine could be a problem?View attachment 1715358816

308’s are open chamber heads. 302’s were closed chamber, but they have the smaller 1.78/1.50 valves and the smaller 318 sized ports.

Only way to get 308’s to be closed chamber is to mill the living crap out of them.

Ill try to have the compression numbers on Friday

maybe one of you guys could get a close guess of compression ratio with 360la block bored .30 stock stroke, 308 heads with I think 73cc ?

I did a compression ratio chart online and got 10.33:1
values I used:
bore size: 4.07 stroke: 3.58 Gasket bore diameter: 4.18
compressed gasket thickness: .039 combustion chamber: 73cc
0 for piston dome and piston deck height.

There’s no point in messing around with compression calculators with what you’ve got. You’d be guessing on almost everything. Could easily be anywhere from 8:1 to 10:1 based on the info you have. You don’t know how far down in the cylinders the pistons are. You don’t know how big the valve reliefs are, which changes the volume. You don’t know how big the head chambers are.

And on that note, 308’s can be anywhere from 65cc’s to 72.

 

[RustyRatRod]

If that thing has a forged crank, send it to me. I'll eat it.

 

[sireland67]

I dunno about "lots", but more. Mine's .513"/.533", advertised 276/284, duration @ .050" 234/242, 110° lobe separation, RPM 2200-6400

Calculated static is 9.8:1, dynamic with that cam is 8.2, and I still pull a couple degrees of timing to keep it happy on 91 octane in the summer with those iron 308's.



I would suspect that has a fairly small cam too yeah?



Nothing wrong with the M1. I don't think you're going to find a ton of compression to warrant some big single plane intake and a big cam for a big high end number. I like the Eddy Air Gap better than the dual plane M1, but it's not a huge difference. Not worth swapping over I wouldn't think.



"doesn't have anything past 5,100" is probably a few things

First, the operating range of your cam is 1,500-5,800. So, not a giant cam to expect a big top end number, it's supposed to be all in at 5,800. I'm assuming this is the MP cam you've got- .450"/.455", advertised duration 268/272, duration @ .050" 228/231, 110°. The MP cams are ok, but there are newer grinds that perform much better than the old "purple cam" grinds. I like the Lunati Voodoo cams personally, but people are funny about camshafts.

Heads are next. You still have the small valves so 1.88/1.60, plus maybe some kind of porting that might actually be hurting you. A badly ported head will flow worse than stock. "Some porting" for me is code for "some previous owner screwed around with a dremel". Maybe not. But if it was professional they usually give you a number. IE, stage II porting, flows 264 cfm @ .500", that sort of thing. And if someone payed for that they usually know what they got. Anyway, if they left the small valves in there they probably didn't do much porting either.

The valve springs are singles with dampeners. There's a few varieties with varying spring pressures, but any of the singles are going to be kinda borderline with that cam. The Lunati I listed above that I run in my 340 requires doubles and more seat pressure than any of the MP singles with dampeners can give. The video didn't sound bad like you had a ton of valve float, but they may not be helping your situation either.

Compression ratio. You obviously don't have an 11:1 static. If you put 11:1 pistons into a 360 and they sit close-ish to the deck and then you use a set of heads with 67cc chambers (which the 308's could easily be), well, your compression ratio isn't even 10:1. The 308's on my 340 are 65cc chambers after everything was done and the heads were cut, and the pistons I run are .018" proud of the deck. And I'm at 9.8:1. If you don't have a ton of compression, you don't want a bigger cam to blow off more compression.

Report back after the compression check, if it doesn't crank at 160 psi or better you're going to have some work to do if you want add a bunch of power.

Cam is a lunati 703 voodo, so yes small cam, but has a strong bottom end until redline, nice street engine.

 

[Wyrmrider]

were all looking for the compression numbers
do check your retainer to seal dist B 4 putting in larger cam

 

[furrystump]

I like PRH idea, enjoy it over the summer. Winter you can pull it apart and measure everything. It doesn’t cost a ton to measure what you need. I bought a bag of ten 60cc plastic syringes on Amazon for like $20. A plastic square and some grease. You can measure chamber volume. A deck bridge is $20-$30. A harbor freight dial indicator maybe $15. Measure EVERYTHING! That way you can get better answers if problems arise. In the end It takes a bunch of head work to get a cast iron head to make “significant” power. My car weighs 3445 and runs 116mph, what is that 350-380 at the wheel? X heads almost full effort, but stock pushrod location.

 

[yellow rose]

I like PRH idea, enjoy it over the summer. Winter you can pull it apart and measure everything. It doesn’t cost a ton to measure what you need. I bought a bag of ten 60cc plastic syringes on Amazon for like $20. A plastic square and some grease. You can measure chamber volume. A deck bridge is $20-$30. A harbor freight dial indicator maybe $15. Measure EVERYTHING! That way you can get better answers if problems arise. In the end It takes a bunch of head work to get a cast iron head to make “significant” power. My car weighs 3445 and runs 116mph, what is that 350-380 at the wheel? X heads almost full effort, but stock pushrod location.

That's about 425-430 at the crank at your weight. There is nothing wrong with that, at all.

Depending on the dyno, your wheel HP is pretty close. I'd say 360 at the wheel is pretty close.

 

[MopaR&D]

Ill try to have the compression numbers on Friday

maybe one of you guys could get a close guess of compression ratio with 360la block bored .30 stock stroke, 308 heads with I think 73cc ?

I did a compression ratio chart online and got 10.33:1
values I used:
bore size: 4.07 stroke: 3.58 Gasket bore diameter: 4.18
compressed gasket thickness: .039 combustion chamber: 73cc
0 for piston dome and piston deck height.

A 360 bored .030" over would be 4.03" bore, also flat-tops always have a little bit of "dish" volume due to the valve reliefs typically 7-10ish cc. I also highly doubt your pistons come up exactly to zero deck.

It kind of sounds like the OP is intending to have a shop do all the checking and parts-swapping? This kind of situation is why I do all my own engine stuff... Pulling apart an old-school pushrod V8 and measuring things yourself is not hard. I'd at least do that and then once you know what you have take it to a shop for assembly if you feel the need. You're really shooting blind trying to get hop-up parts when you don't know for sure what is currently inside your engine.

And I agree, those HP/Tq numbers are pretty accurate for the combo you have now, I'd drive it and enjoy it until you're ready to have the car inoperable for a month plus (could be less if you know what you're doing and get it done quick).

 

[lead69]

You need to put a gauge on that thing like these guys have said, knowing your cam specs its pretty easy to get a solid ballpark of static compression at that point. The fact he said it had trw forged pistons isn't a great thing. The only production trw for a 360 was a stock replacement style with no compression height and a bit of a dish, the last 360 I had with trws the pistons were .100 or so in the hole and needed thin mr gasket head gaskets and 64cc chamber to get 8.8 compression. If you use the hughes cam you will need better springs and get the installed height right and that means pulling the heads and machine work. I agree with those that said run it or if you really want to make some changes be ready to rebuild it completely. Once you open that can of worms there is no going back. Somebody designed that thing the way it is and imo they did a decent job, but to change one or two parts you wont really gain anything significant until you redesign the whole dam thing.

 

[Brandt Fonda]

You need to put a gauge on that thing like these guys have said, knowing your cam specs its pretty easy to get a solid ballpark of static compression at that point. The fact he said it had trw forged pistons isn't a great thing. The only production trw for a 360 was a stock replacement style with no compression height and a bit of a dish, the last 360 I had with trws the pistons were .100 or so in the hole and needed thin mr gasket head gaskets and 64cc chamber to get 8.8 compression. If you use the hughes cam you will need better springs and get the installed height right and that means pulling the heads and machine work. I agree with those that said run it or if you really want to make some changes be ready to rebuild it completely. Once you open that can of worms there is no going back. Somebody designed that thing the way it is and imo they did a decent job, but to change one or two parts you wont really gain anything significant until you redesign the whole dam thing.

Im going to try and get some cranking compression this next week. Looks like I may have some roller rockers and a random cam for sale

 

[lead69]

Im going to try and get some cranking compression this next week. Looks like I may have some roller rockers and a random cam for sale

Keep them for later, if you already spent the money why not, you may use them down the road or to sell when it comes time for a solid flat tappet and trickflows lol.

 

[Brandt Fonda]

Ok did the compression check today, and they are all right at 140

 

[PRH]

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.

 

[Mattax]

“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.

P4286671 ..hydraulic cam and tappet package for light competition applications. Offers good mid-range torque and good power 272-272-48*, valve lift .455, centerline 112*

only other cam with 455 lift that year

P4452761 ..hydraulic cam and tappet package for light competition. Offers good mid-range torque and good power 268-272-50*, valve lift .450/.455, centerline 110*
1989 Mopar Performance Catalog. Small block camshafts p. 80, 81.

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

 

[Brandt Fonda]

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