Disappointing dyno results

[jawbone]

My 340 was broke in and put on dyno. It's a 340 with mild cam 214/218 @ .050, 110 LSA, .440/.450 lift. Carb is a period correct Carter AVS which was rebuilt by Woodruff Carburetor.
Results of dyno was disappointing. A/F ratio indicates extremely rich condition. scfm low as well. Engine guy making noise that carb is too big but that particular carb came with engine from Chrysler. My time on dyno is limited so need to resolve this as soon as possible. Any ideas would be appreciated.

 

[jawbone]

1968 specs	318 V8	340 V8
BHP	230 @ 4400 rpm	275 @ 5000 rpm
Torque	340 @ 2400 rpm	340 @ 3200 rpm

 

[MidnightSwinger]

Your cam is killing that combo, check out the duration on a stock 340 cam.

68 340 4 speed cam:

276°/284° duration
.444"/.453" lift

Int open: 26° BTDC
Int close: 70° ABDC
Exh open: 78° BBDC
Exh close: 26° ATDC

Overlap: 52°

Per the 68 factory service manual...

 

[jawbone]

Wanted to ad has iron heads and stock iron intake.

 

[jawbone]

Your cam is killing that combo, check out the duration on a stock 340 cam.

68 340 4 speed cam:

276°/284° duration
.444"/.453" lift

Int open: 26° BTDC
Int close: 70° ABDC
Exh open: 78° BBDC
Exh close: 26° ATDC

Overlap: 52°

Per the 68 factory service manual...

Want to run on pump gas. Check link. Almost same specs.

https://www.hughesengines.com/Index...&level2=SHlkcmF1bGljIFJvbGxlcg==&partid=30210

 

[jawbone]

My duration is 264/268

 

[MidnightSwinger]

My duration is 264/268

in your initial post you stated 214/218 @ .050, which is what the link to that roller cam states. Did you convert to a roller cam?

All factory 340’s ran on pump gas.

 

[jawbone]

in your initial post you stated 214/218 @ .050, which is what the link to that roller cam states. Did you convert to a roller cam?

All factory 340’s ran on pump gas.

No it's a flat tappet. Do I need a smaller carb?

 

[MidnightSwinger]

No it's a flat tappet. Do I need a smaller carb?

Check the link that you provided for me, make sure that’s actually the cam you have. You linked a roller cam.

 

[toolmanmike]

Want to run on pump gas. Check link. Almost same specs.

https://www.hughesengines.com/Index...&level2=SHlkcmF1bGljIFJvbGxlcg==&partid=30210

Is that the cam you are running? I am no cam wiz but I would like to see more duration especially with a 340.

 

[jawbone]

Check the link that you provided for me, make sure that’s actually the cam you have. You linked a roller cam.

Was using the roller cam as a comparison to mine. Same specs other than mine is not a roller and my lift is not a much.

 

[A56]

Check the link that you provided for me, make sure that’s actually the cam you have. You linked a roller cam.

lol, ya treed me and beat me to it.

 

[jawbone]

Is that the cam you are running? I am no cam wiz but I would like to see more duration especially with a 340.

Changing cams at this point is not an option. Was considering smaller carb to correct A/F ratio and scfm. I'm not a cam guy either. Cam was picked by provider.

 

[toolmanmike]

Your carb running rich won't cut horsepower that low. You need to go back to the basics and look at each component. The wrong pistons can lower compression. Your small cam isn't helping at all. Was the dyno run with headers?

 

[MidnightSwinger]

Was using the roller cam as a comparison to mine. Same specs other than mine is not a roller and my lift is not a much.

Yeah, you can’t do that. A roller vs a flat tappet cam specs is like comparing apples and orangutans.

If you truly put a cam with only .450 lift and 218 duration, that is your answer. Yes the carb is too big for that cam. Not too big for a 340, but that cam is garbage(no offense intended).

 

[jawbone]

Your carb running rich won't cut horsepower that low. You need to go back to the basics and look at each component. The wrong pistons can lower compression. Your small cam isn't helping at all. Was the dyno run with headers?

Yes on the headers.

 

[A56]

Changing the carb may correct your A/F but it may not eliminate your disappointment in HP gain.

 

[toolmanmike]

Yeah, you can’t do that. A roller vs a flat tappet cam specs is like comparing apples and orangutans.

If you truly put a cam with only .450 lift and 218 duration, that is your answer. Yes the carb is too big for that cam. Not too big for a 340, but that cam is garbage(no offense intended).

I would agree. The cam is going backwards compared to a stock 340 grind. I would put that cam in a 318 and make it happy.

 

[MidnightSwinger]

I would agree. The cam is going backwards compared to a stock 340 grind. I would put that cam in a 318 and make it happy.

I would put that cam in the garbage can and make myself happy. If I went through the trouble of building a 318, it would get at least a 340 cam.

 

[toolmanmike]

I would put that cam in the garbage can and make myself happy. If I went through the trouble of building a 318, it would get at least a 340 cam.

Ya, that's for another thread. In fact there are a couple 318 cam threads up right now.

 

[jawbone]

I would put that cam in the garbage can and make myself happy. If I went through the trouble of building a 318, it would get at least a 340 cam.

I was at the mercy of the cam supplier. As I said, not a cam guy. Got tired of reading comments on cams so did the best I could. Still at a loss and don't know what to do. If I were to purchase another cam would be the same story. Thanks for your comments.

 

[MidnightSwinger]

Ya, that's for another thread. In fact there are a couple 318 cam threads up right now.

Y’all don’t want me in there!

 

[jawbone]

So what is a 340 cam?

 

[jawbone]

If I were to change carbs, can you suggest one.

 

[mcodecuda]

A simple jet or metering change can correct your air/fuel ratio issue. If your “engine guy” is suggesting that the stock carb is too big then ask him why did he select components that resulted in an engine that made less horsepower than stock.