Thoughts on a new motor? 351, 302, or LSX?

[Cobra4B]

Curious as to everyone's thoughts on what they would do if they were in our position... i.e. FUBAR'd 302 and a car that we want to keep around TTS/ST2 specs which limit us to 8.7lbs/horsepower.

Option 1: 306ci Dart block w/ 4-blot mains (or FRPP Boss 302) with our exisiting heads/cam/intake/carb/exhaust (assuming salvagable). Would be a 6500 rpm motor and make approx 330-340 rwhp.

Option 2: 351 SBF detuned to 330-340 rwhp but with as much torque as we can make. Could re-use the intake/carb setup, but would probably need to upgrade the AFRs to 185s.

Option 3: LSX conversion. A stock LS6 makes 350-360 rwhp in a C5 chassis and I've had zero reliability issues w/ them over the years.

Option 4: Other?

Thoughts?

Leaning toward the detuned 351 SBF option and a new Painless wiring harness to 100% re-wire the car and re-do the dash/switch panel.

[Panoz26]

Biased opinion
LSx

[Blue Streak 21]

Go for the max torque (displacement) you can get, and de-tune for allowable hp. Torque will accelerate you out of the corners faster and make catching cars on the short chutes much easier. Our cars are not light weight, so making a torque monster will make the car more drivable. You also reduce engine stress and extend useful life by de-tuning to 340 HP. So which option gives you the max torque? Both LSX and the 351 can have displacement increased without letting costs get out of hand. The LSX motor has the added advantage of being lighter, and you have a lot of experience with it from your Vette efforts. Find a LS7 motor and drop that in... Can you say rocket ship?

[Cobra4B]

Haha.... Katech LS7 in the Panoz... I forgot to mention that this isn't an unlimited funds rebuild.

A stock LS1 would make the power... my red C5 vert makes 332 rwhp w/ just an air intake and mufflers. But then you have to get into the adapters and such to make it work with our driveline vs. a 351 that just slips right in.

[panozracing]

EXACTLY Brian - My vote is: dart 351 block stroked and detuned to the HP you want....hmmmm wonder where that idea came from.

Drops right in!

[Cobra4B]

Dont think I would have any need to do a stroker crank... only need 340ish rwhp.

[panozracing]

Torque

[NZGTRA17]

Originally Posted by Cobra4B

Curious as to everyone's thoughts on what they would do if they were in our position... i.e. FUBAR'd 302 and a car that we want to keep around TTS/ST2 specs which limit us to 8.7lbs/horsepower.

Option 1: 306ci Dart block w/ 4-blot mains (or FRPP Boss 302) with our exisiting heads/cam/intake/carb/exhaust (assuming salvagable). Would be a 6500 rpm motor and make approx 330-340 rwhp.

Option 2: 351 SBF detuned to 330-340 rwhp but with as much torque as we can make. Could re-use the intake/carb setup, but would probably need to upgrade the AFRs to 185s.

Option 3: LSX conversion. A stock LS6 makes 350-360 rwhp in a C5 chassis and I've had zero reliability issues w/ them over the years.

Option 4: Other?

Thoughts?

Leaning toward the detuned 351 SBF option and a new Painless wiring harness to 100% re-wire the car and re-do the dash/switch panel.

Brian, my thougths;

Option 1 - at 306 cubes it would be a waste of a good strong block, time and $$ which will also throw away a bunch of free torque available with this block by boring/stroking.

Option 2 - OK if you had a 351 powered car already but otherwise a waste of $$ when you have a bunch of new'ish aftermarket 302 gear already that you have paid good $$ for - 351 is virtually a complete conversion similar in scope to an LSX (except for engine mounts and bellhousing). You will end up with a heavier car with a higher C of G, that if you dont stroke and stay 351 cubes, will make no more power and be no more durable than Option 4 but will cost more (new sump, new dizzy, new heads, new inlet manifold, re-jigged exhaust etc etc). Sounds like a lose lose proposition to me Brian unless in the future you want to go over 375 cubes.

Option 3 - no comment..........its all been said before!

Option 4 - use a Dart SHP block (4 bolt on caps 2 - 4 so your current pan will fit and also accepts hyd roller cam/lifters) and combine 3.25" stroke with 4.125" bore. This "short stroke" 347 combo gives the best of all worlds - gudgeon pin below the oil rings, reasonable rod angle, reasonable rod/stroke ratio etc etc. I would have used this combo Brian but I need every (reliable) cube I can squeeze to try to match GT3 Porches. Hence my using a 3.4" stroke and 4.155" bore for 369 cubes. If you go to Detroit Competition Engines site, I think you will see that they are now selling a Ford 400 cube 8.2" deck Dart stroker combo. This type of combo illustrates how far things have moved forward from the days of people bagging 347's due to percieved weaknesses. The torque difference between a 302 and a 347 is like night and day. In my car it was a gear up for slower corners and still getting sideways during mid corner power on where as the 302 would not light the tyres up a gear lower.

My understanding is that the Ford Boss block has shorter bore skirts than the Dart and World Products blocks so is not as good in a stroker application due to piston rock as the pistons come out of the skirt further. I would look into this in detail (i.e. - actually measure the difference between these block skirts) if you were considering using one of these blocks Brian.

Use a forged crank, H beam rods and forged pistons. Use the cam/heads/intake that you have. You will make more power than you need for your class but will have a bottom end capable of taking lots more power if you choose to step up a class. I have seen this type of bottom end combo live to over 700hp if you are happy to rev it.

My 10c worth.............Kel.

[Cobra4B]

Thanks Kel.... I didn't know you could do a 347 and stil have the wrist pin in the correct location and good angles etc.

[eric1h]

LS6!!

you know them, reliable(get an accusump!), and its an easy swap!

but again, I'm biased!

[NZGTRA17]

Originally Posted by Cobra4B

Thanks Kel.... I didn't know you could do a 347 and stil have the wrist pin in the correct location and good angles etc.

Brian, the gudgeon intersecting the oil rings is a non issue. Ring sets these days have a support rail that eliminates any previous oil consumption concerns and this would not be a problem for racing anyway.

Regards rod angles, I have calculated these (prior to going down this path myself) and these are as follows;

Ford 302 = 53.8 degs 3" stroke
Ford 331 = 52.3 degs 3.25" stroke
Ford 347 = 50.9 degs 3.4" stroke
Ford 427 = 50.2 degs 4" stroke

383 Chev = 51.3 degs 3.75" stroke

As you can see from the above Brian, the most popular stroker engine in history (383 Chev) has only a marginally better rod angle than a 347 Ford. A Ford 427 has a worse rod angle than a 347 and these are lasting very well in race apllications as Brian G has experienced. Per illustration provided by the figures above, I would not place to much store in the stories people tout about rod angle and rod/stroke ratio. Most of the internet comment on this subject is ill informed rubbish and people do not even know what the figures are that they are comparing. They are simply parroting what some friend has told them. There are a number of top flight engine builders who have stated on the net that the value of rod angles and rod/stroke ratios are grossly overstated when it comes to making hp and building reliability.

One last note on the Chev LS option. If you spent more on this option than on a Dart short stroke 347 it would also be lose lose. You will not have an equivalent bottom end with an LS unless you spend the money on an aftermarket shortblock with a forged crank, race type rods and quality forged pistons. Also (equally importantly) you will not have a race prepped bottom end with the correct piston to wall (to allow for the temperatures and consequent piston expansion of a race engine) and bearing clearances (tailored to oil viscosity and with sufficient clearance to promote the required flow levels to keep the bearings cool) suited to racing.

You cannot compare a production type bottom end to a race set up for strength or reliability as they are prepped to achieve different engineeering goals.

Kel.

[wirewheel99]

[jmimac351]

Heard nothing but good things about this guy. Apparently sends race engines all over the world.

http://www.fordstrokers.com/dart-bas...-short-blocks/

[jmimac351]

Apparently that Detroit Competition Engineering place has a former Sprint Cup engine builder from Roush working there. I think the Roush cars are using "Roush Yates" engines out of NC so that makes sense.

http://detroitcompetitionengineering.net/About_Us.html