340 dynoed

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Babyblue66

Babyblue66

Cool dude
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In an apartment, MN
Got my 340 on the dyno.
It's a 70 block, forged crank, balanced, line honed, ARP rod bolts, slightly used heavy old TRW forged pistons. Calculated out to 9.7 to 1. J heads I ported a little. 2.02, 1.60 valves. Clay Smith 292 240 @ .050 .472 lift on a 108 lsa installed at 106 solid flat tappet single pattern "Chevy grind" according to the know-it-alls on here. 1.5 Mancini roller rockers. LD340 intake and a 750 double pumper and a 1 inch tapered 4 hole spacer. Dyno guy had 1 3/4 headers, although I'd rather have used 1 5/8.
Stock recurved electronic distributor. Nothing exotic. The rockers were by far the most expensive parts.

Best of 395 hp at 6300 and 377 tq at 4900. Runs very smooth and pulls past 6k with ease.
I was hoping for close to 400 hp so I'm happy with it.
 
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Made several pulls with different spacers. This is the best average pull. I also tried 3 carbs. Mostly to know if they were jetted correctly. Spacers made a difference on this engine. Adding about 10hp and torque. A 4 hole just shifted the torque down a little lower, cloverleaf made more than the 4 hole , but the tapered 4 hole made the best torque and HP. Not bad for a cam that has .454 lift after valve lash and not a ton of valve spring pressure.

20250313_194152.jpg
 
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Babyblue66 said:
Got my 340 on the dyno. The one, according to some of my new friends on this site, that I was so grossly unqualified to build.
It's a 70 block, forged crank, balanced, line honed, ARP rod bolts, slightly used heavy old TRW forged pistons. Calculated out to 9.7 to 1. J heads I ported a little. 2.02, 1.60 valves. Clay Smith 292 240 @ .050 .472 lift solid flat tappet single pattern "Chevy grind" according to the know-it-alls on here. 1.5 Mancini roller rockers. LD340 intake and a 750 double pumper and a 1 inch tapered 4 hole spacer. Dyno guy had 1 3/4 headers, although I'd rather have used 1 5/8.
Stock recurved electronic distributor. Nothing exotic. The rockers were by far the most expensive parts.

Best of 395 hp at 6300 and 377 tq at 4900. Runs very smooth and pulls past 6k with ease.
Click to expand...
Nothing wrong with those numbers. Nice cam that makes good power without eating her pigs.
 
What kind of garbage is that... That engine from the 2000's with an xe268H and stock heads did almost the same... And I'm being totally sarcastic about this. Yours is another example that the dyno debry 340 test is BS.

Nice engine making good power. I usually run an open spacer on dual planes as they tend to like em. Probably would have run to 6500 and get a 4 handle on HP. Should be a blast to drive with the 1500 rpm spread max tq to hp, good solid range.
 
crackedback said:
What kind of garbage is that... That engine from the 2000's with an xe268H and stock heads did almost the same... And I'm being totally sarcastic about this. Yours is another example that the dyno debry 340 test is BS.

Nice engine making good power. I usually run an open spacer on dual planes as they tend to like em. Probably would have run to 6500 and get a 4 handle on HP. Should be a blast to drive with the 1500 rpm spread max tq to hp, good solid range.
Click to expand...
The cloverleaf was the most open and it lost torque to about 5000 and didn't pull any higher peak numbers than the 4 hole tapered. So I saw no reason to try the regular open.
 
I have run a lot of Camshafts and the Clay Smith Camshafts always
perform the best with similar lifts. Never had one go flat either.
Wish I could say that about some of the others I have tested!

I would not hesitate to run 1 3/4 Headers on a 400HP 340 with a
2 1/2 exhaust system.i

30 years ago, we ran in 10's in our 340 Demon stocker with a 460/470 cam
and the heavy TRW pistons in a heavier car... you will like how your car performs.
 
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GTX JOHN said:
I have run a lot of Camshafts and the Clay Smith Camshafts always
perform the best with similar lifts. Never had one go flat either.
Wish I could say that about some of the others I have tested!
Click to expand...
That's good to know. Also it has only 135lbs on the seat and we'll under 300 over the nose. Easy on the cam and everything else.
 
Babyblue66 said:
That's good to know. Also it has only 135lbs on the seat and we'll under 300 over the nose. Easy on the cam and everything else.
Click to expand...
I see you started at 4,000. Any torque numbers lower? It would probably be in the 350-375 range at 3, 000. It should pull nice.
 
to bad you didn't put a Hughes cam in it, would have been over 400 hp. Dave is the man when it comes to camshafts.
 
Everything in that engine was available in the 70"s and 80's. Nice to see a solid old school build. You don't need all of the trick of the week parts to make good street power.
 
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A little more lift would have found that few missing hp for the 400 goal. No big deal. Nice street engine.
 
Nice build! Got to be some special satisfaction getting a good number like that when you put some sweat into the porting. I just finished a little hotter build that used some newer/lighter parts for 458hp, but I have a spare 340 block, crank, 2.02 J-heads, heavy forged pistons, etc still left over that were collected over the years. When I get caught up, I want to put something similar to yours together if nothing else, just to play with. I guess I need to talk to Clay Smith about a cam too. I missed him when I was looking for a grind a couple months ago.

What's the motor going into?
 
Nice numbers!

Is that R&R in Minnesota?
The reason I ask is I’ve seen dyno sheets from an R&R out there, but the sheets looked different.
New dyno data acquisition system perhaps?

Edit- I did some “googling”.
The logo on your sheet looks the same as the shop I was thinking of.
That place does a lot of dyno work.
 
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