340 Head/Cam upgrade before vs after with results

-
R

RAMM

Well-Known Member
Joined
Nov 22, 2010
Messages
2,634
Reaction score
3,424
Location
Ontario, Canada
Without trying to make this any longer than necessary, here goes:

This 340 is an older build done by another reputable shop 10-15 years ago, owner never had it dynoed and drove it on the street in a Barracuda '67-'68 notchback I believe for some years. He is in the process of re-vamping his 'Cuda (Alter-K frontend) etc.. Earlier this summer he decided to bring the engine in for dyno testing as it was. The engine performed well for a 344 cube engine with some time/miles on it. (Very little blow-by, good oil pressure, smooth, consistent).
After the dyno session the customer decided he wanted the engine to be somewhat stronger and a plan was hatched once he sourced some head castings online--this snowballed into a cam/lifter change to a solid and some 273 mechanical rocker arms as well as a 650 HP dbl pumper. He entrusted me to work the heads, pick the cam and make it all fit, then re-dyno it.

Old build 340 .030" Old school TRW slugs, 915 J heads or X heads--(customer took them off at home ) Big Mopar .508" 292/292 108 hydro cam, LD4B intake, 3310 750 Vac carb, 1/2" open spacer, Compression ? runs great on 91 pump. Dyno peaks of 365.8 hp @ 6200 rpm and 357.9 tq @ 4700 rpm--Not bad really. To be cont'd J.Rob

340B.JPG
 
New build: Same bottom end , un-opened except for cam change, oil pan did not come off, Comp solid 294S 248/248 @ .050" .525" 110, Properly worked heads ('576 or something) 2.05/1.6 11/32" valves -flow 248-251cfm @ .500" , 273 rockers, Comp pushrods, Holley 650 HP dbl, same LD4B cleaned up.
Assembled and put back on dyno. 410 hp @ 6500 388.9 tq @ 4900 rpm. Love solid flat tappets, and tests like these. J.Rob

340A.JPG


340beforevsafter.JPG
 
Good stuff, and accurate.
I dyno'd an kb .030 9.5 340 w/.528 solid, stock x heads flowed 218-225 cfm int , ld340 untouched, 750dbl pump. whole motor had 12k miles on it.
made 392hp around 6400 rpm.
 
It would have been stronger with 1.88 intake valves...lol.
 
Think you would have picked up much with a 750 DP? I would think a cam with that duration would respond to more carb. I'm also curious if you think a solid roller would be worth the investment in this case. I imagine you would be able to get same lift with less duration, or more lift with same duration, pickup some extra horsepower? I wonder if an intake change would be worth it as well. Hmmm

What static/dynamic compression did you end up at with the new heads/cam?

Inquiring minds. As I'm thinking of having my J heads ported into the 260 range and going with a solid roller this winter.
 
Lustle said:
Think you would have picked up much with a 750 DP? I would think a cam with that duration would respond to more carb. I'm also curious if you think a solid roller would be worth the investment in this case. I imagine you would be able to get same lift with less duration, or more lift with same duration, pickup some extra horsepower? I wonder if an intake change would be worth it as well. Hmmm

What static/dynamic compression did you end up at with the new heads/cam?

Inquiring minds. As I'm thinking of having my J heads ported into the 260 range and going with a solid roller this winter.
Click to expand...



I'm not a fan of solid rollers on Pcar heads. Hard to get enough lift and spring. It's hard to net .600 lift and get a spring for a solid lifter. Let alone a roller. And then, you have to correct the geometry. Add valve length and you just about have to add blocks, which is a bunch of work, and you still have a Pcar head.
 
RAMM said:
New build: Same bottom end , un-opened except for cam change, oil pan did not come off, Comp solid 294S 248/248 @ .050" .525" 110, Properly worked heads ('576 or something) 2.05/1.6 11/32" valves -flow 248-251cfm @ .500" , 273 rockers, Comp pushrods, Holley 650 HP dbl, same LD4B cleaned up.
Assembled and put back on dyno. 410 hp @ 6500 388.9 tq @ 4900 rpm. Love solid flat tappets, and tests like these. J.Rob

View attachment 1714985700

View attachment 1714985701
Click to expand...


Almost no reason to run a HFT in anything but a stocker. The solid makes more power everywhere.
 
yellow rose said:
I'm not a fan of solid rollers on Pcar heads. Hard to get enough lift and spring. It's hard to net .600 lift and get a spring for a solid lifter. Let alone a roller. And then, you have to correct the geometry. Add valve length and you just about have to add blocks, which is a bunch of work, and you still have a Pcar head.
Click to expand...

I just love the solid roller ramp rates, area under the curve and increased lift with no increase in duration. It's really a win win. Is it a pain? Maybe. Does it cost a lot more? Yup. But have to make sacrifices somewhere. Besides, nothing cooler than a solid roller street motor. Of course there's just no reason not to run solid these days. Unless you're a guy who just doesn't like to look at his engine. The myths behind solid cam's needs to die. I know lots of guys running flat and roller solids and they check their lash every 3 months and it's almost always the same. Cam's are different these days. Learn to work on your car.

As for valve sizes? I wasn't going to touch that one. I've been telling people for over a decade that the whole valve too big thing needs to go out the window along with its cousin"3/4 race" cam and "solids are too much maintenance".
 
RAMM: Head gaskets after? Any idea on the before head gaskets? Just looking for thickness. Tnx for the good data points!
 
Lustle said:
Think you would have picked up much with a 750 DP? I would think a cam with that duration would respond to more carb. I'm also curious if you think a solid roller would be worth the investment in this case. I imagine you would be able to get same lift with less duration, or more lift with same duration, pickup some extra horsepower? I wonder if an intake change would be worth it as well. Hmmm

What static/dynamic compression did you end up at with the new heads/cam?

Inquiring minds. As I'm thinking of having my J heads ported into the 260 range and going with a solid roller this winter.
Click to expand...

As YellowRose states--solid rollers don't make much sense in a production head. Intake change would probably be worth some--not a huge fan of these intakes. Pretty sure an RPM would fare better.

No idea on what the comp was before, I didn't take heads off and CC them. These heads are 68cc though comp still comes in well under 10-1 comp. J.Rob
 
Lustle said:
I just love the solid roller ramp rates, area under the curve and increased lift with no increase in duration. It's really a win win. Is it a pain? Maybe. Does it cost a lot more? Yup. But have to make sacrifices somewhere. Besides, nothing cooler than a solid roller street motor. Of course there's just no reason not to run solid these days. Unless you're a guy who just doesn't like to look at his engine. The myths behind solid cam's needs to die. I know lots of guys running flat and roller solids and they check their lash every 3 months and it's almost always the same. Cam's are different these days. Learn to work on your car.

As for valve sizes? I wasn't going to touch that one. I've been telling people for over a decade that the whole valve too big thing needs to go out the window along with its cousin"3/4 race" cam and "solids are too much maintenance".
Click to expand...
Or setting the valves once a year and wishing I had left the valve covers on. This year I was naughty and didn't set them. A little clatter cold and barely clatter at temp. Just a 4 barrel 273 and I only put a thousand miles or so on it every summer.
 
yellow rose said:
Almost no reason to run a HFT in anything but a stocker. The solid makes more power everywhere.
Click to expand...
Totally agree to a point.
HFT's have their place just not in anything that you want to rev much above 5800-6000rpm--and a stock stroke 340 is known for their love of RPM's NO? Seemed like a waste to have a HFT in something like this to me. J.Rob
 
nm9stheham said:
RAMM: Head gaskets after? Any idea on the before head gaskets? Just looking for thickness. Tnx for the good data points!
Click to expand...

No idea what the head gaskets were before, this engine now uses Fel-Pro 540SD which I believe are about .045-.050" torqued. You're welcome. J.Rob
 
Last test after setting lash and adjusting float levels and idle mixture a little closer. J.Rob

Lasttest340.JPG
 
Lustle said:
Besides, nothing cooler than a solid roller street motor. Thinking about embarking on a build this winter that makes zero sense. Yes it will have a solid roller, possibly Ti valves as well, 321 cubes as well--LOL.

As for valve sizes? I wasn't going to touch that one. I've been telling people for over a decade that the whole valve too big thing needs to go out the window along with its cousin"3/4 race" cam and "solids are too much maintenance".
Click to expand...

Big valves don't hurt torque unless the throat/bowl is wrong. J.Rob
 
yellow rose said:
Are those your dyno headers or the actual headers the car will run??
Click to expand...
Sorry forgot to answer--they are actually Hedman headers for my '83 150 P-U. As for actual headers I have tried everything from sprint car stepped to TTI 1 3/4" to the usual smashed under the steering headers and they don't vary more than a couple of points here and there--especially on a low comp, mild, smaller cube deal like this. J.Rob
 
RAMM said:
As YellowRose states--solid rollers don't make much sense in a production head. Intake change would probably be worth some--not a huge fan of these intakes. Pretty sure an RPM would fare better.

No idea on what the comp was before, I didn't take heads off and CC them. These heads are 68cc though comp still comes in well under 10-1 comp. J.Rob
Click to expand...

Any reason for under 10-1? I would think with that cam you'd be safe at 10-1.

RAMM said:
Big valves don't hurt torque unless the throat/bowl is wrong. J.Rob
Click to expand...

Yeah that's what I'm saying. That the whole big valve thing is a myth. Up there with 3/4 race cam and solid cams being too much work.

Your 321 build sounds interesting. I like the builds that sound stupid, but make stupid power.
 
RAMM said:
Thankyou Jim. J.Rob
Click to expand...
Most welcome, love following your stuff. Especially with the iron heads. We don't get to build the short block but I'm waiting to see what this small block, 340/440ci with ported stock 340 iron intake, ported 596 heads with 11/32 x 2.02 intakes flowing 278 @ .500" and a custom solid flat tappet, will do. It is an undercover stock look even using stock 340 cast iron exhaust manifolds.
 
Last edited:
You must log in or register to reply here.
-

Back
Top