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quest for 340 at 450hp

74340

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So I just rebuilt a 73 340 my goal was to have some drivability but still make some good power 450hp is my goal. I really don't want to add nitrous or any type of boosted application looking for a naturally aspirated option.

My current build

New eagle crank ( stock stroke )
Sealed power Pistons 10 to 1 compression
Ignition system is an RT garage revenator with their distributor and coil currently have the rev limiter set at 6000
Intake is an Edelbrock air gap ported by huge engines
Heads are in Edelbrock RPM 63cc full CNC ported by Hughes engines they flow just under 300 CFM at 500 left
1.6 prw rockers
750 ProForm racing carburetor mechanical secondaries no choke
HVH 1 in spacer



Cam is .539 intake and 549 exhaust duration at 50 is 236

Lobe separation 107
cope racing transmissions 904
Ptc torque converter with a 3000 RPM stall

The rear is an 8 and 3/4 I have two center sections 2.76 and 3.91 both are sure grips Dana power lock. 3.91 currently in the car

I know that I would benefit from a much larger cam and I know that I would also benefit from a higher compression ... I just wanted to stay away from race fuel and keep a camshaft that's somewhat streetable. Do you think this combination is good enough for a 450hp horsepower goal? Without milling the head or a larger cam ?

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Cuda416

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Compression isn't all that it's cracked up to be.

450 out of that engine (heads sound wicked) should be doable in your sleep
 

74340

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They could actually get my heads to flow over 300 CFM but they required offset rockers and I already had brand new 1.6 prw rockers they sell the offset ones there would have been an extra $800 it was hard to justify because I just spent $1,400 in head work with the 208 valves I could have them milled down further to gain compression ( at extra cost) but I'd really like to avoid race fuel... Hoping it would be enough for my hp goals ... Maybe throw the 276 center section in for cruising then pop in the 391s for when I go to the track.
 

moparleo

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What engine builder gave you this combo ?
Are they doing the assembly ?
Clearances, ring package, etc...
Are they going to dyno the engine when done ?
There are so many variables on an engine. Every combination is different.
This question should be asked to the builder and answered before you spend $1.
Can you make 450hp with "some drivability" (what does that mean?)
Street build, low stress put on engine, drivetrain, low maintenance...get in, turn key go .
High hp = high rpm's, looser clearances, shorter valve spring life, constant maintenance especially if try to do the street and strip thing .
There is a compromise on any dual purpose application. Race cars make bad street cars and street cars make poor race cars.
Race cars only have to make power and stay together for a very short period of time. 1/8 or 1/4 mile adjustments made frequently.
Street cars go thousands to hundreds of thousands of miles between heavy maintenance.
Which are you more interested in ?
Small C.I motor= high rpms to make power.
Hi RPM = quicker wear/lower life of engine components.
 

74340

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Well actually the car will never be going down a 1/4 Mile or 8th mile track... This car will be a pro touring car ( road track car ) Hotchkiss suspension system will be added to the car in December hydro boost braking system has already been added along with four disc braking system . The 340 block was actually free when I originally got the engine it had no heads on it a friend of mine was upgrading to trick flow heads so he had given me these edelbrocks heads . As far as cost goes the only money I really have into it besides is the machine shop assembling the short block and balancing.. the heads were given to me for free however I did have them CNC ported which did cost 1400$ after tax the cam was also a freebie new in the box. Believe it or not this is kind of a budget build that I was hoping would hit 450hp the reason this combination was chosen was because mostly circumstance and free parts . As far as drivability I really didn't want to have to pay for race fuel. Or the need to turn my timing back just to run 93 for 450hp goal
 
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Steve340

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When assembly is done so long as they keep the internal friction down and it is tuned correctly my guess is very close or on 450 HP.
Torque in a street car is more of a factor than the bragging rights of a big HP number.
Your combo does sound pretty good.
 

moparleo

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The point was not how much you spend but spending anything before the combo is thought out. A bunch of free parts doesn't make the build better only more economical.
Pro=touring or Road Track car. Different.
HP vs Torque. I am sure you will let us know how your project turns out.
 

74340

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Yea I agree ... I'm sure I'll change the combo at some point... (One day) I know there are better combinations for power and torque it's just what I had at my disposal economically right now. ( Dumping the money in the suspension system right now) Obviously a stroker kit would make the most sense for high torque and in the future that may be what goes into the 340 I'll let you know how the build goes I got to see if there's someone in my area that has a dyno that maybe I could put the car on to get some numbers at the tires post the video let you know what happens ... This could be a total swing and a miss I got my fingers crossed.
 
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gzig5

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I think you should end up close to your HP goal. Really depends on the cam timing events and getting it installed with correct timing. Hydraulic or solid flat tappet? A 300cfm head should support 600hp depending on the other parts of the combo and what the mid-lift numbers look like.
I've got a similar build in the works for my 340 with the goal it being a road course type car as opposed to drag. I feel peak HP/Tq are less important in this situation than a solid low-mid range and maximizing area under the curve. You may end up changing the cam but I think you will have a good start on it.
 

74340

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Yeah it is a flat tap it hydraulic cam a buddy of mine had given it to me with some lifters that match it still in the box. I'll probably go with a much larger cam later on the springs on the heads will handle all the way up to 580 lift cam . ( I know that these heads would respond well to a much larger cam) ( probably even more cylinder pressure) then what I'm getting out of the sealed power replacement Pistons. Part of the reason I spent the money on the CNC porting was because putting in a camshaft is within my skill set to do on a weekend but CNC porting aluminum heads is not something I can do in my garage over a weekend. Which is why I put putting a larger cam in the car on the back burner. More or less it was the combination that I had in my pile of parts which a good number of them were free. Kind of hoping it wasn't a total swing and a mess .. fingers are still crossed the car is coming together within the next few weeks so I guess we'll find out.


















LiftStock
Full CNC
CFM Gain​
Stock
CNC Super Prep
CFM Gain​
.100​
71.0​
72.0​
1.0
55.0
87.8​
32.8
.200​
138.0​
149.0​
11
113.0
136.5​
23.5
.300​
188.0​
221.0​
33
150.0
153.0​
3.0
.350​
213.0​
245.0​
.400​
230.0​
266.0​
36
176.0
178.4​
2.4
.450​
236.0​
285.0​
49
185.0
184.2​
-.08
.500​
240.0​
296.0​
42.3
189.0
186.6​
23.3
.550​
249.0​
301.0​
44.6
195.0
188.7​
24.5
.600​
251.0​
303.0​
49.4
196.0
189.8​
25.0
.650​
250.0​
304.0​
52.3
197.0
190.1​
25.7
.700​
254.0​
-​
-​
305.0​
51
198.0
191.7​
26.7
.750​
259.0​
-​
-​
305.0​
46
 
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Rons340

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That is quite an impressive list of parts! However, the dyno is really where the rubber hits the road in my opinion. That is where you can make it all come together with the correct air/fuel ratio (carburetor) timing tweaks, cam timing as well as ignition timing, and confirming that all of those wonderful components are happy together. You should be in the ballpark of 450 hp though, but you may be able to hit it out of the park with a little help. Good luck!
 

74340

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Wow if you don't mind me asking what were your build specs on that was it a stock stroke motor? Similar head flow?
 

6PKRTSE

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I should have mentioned that it was a 416 stroker. Stock heads and intake but extrude honed.
 
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