Your thoughts please on how to go forward

kiwicar · Post by **kiwicar** » Sat Apr 26, 2014 8:10 am

Hi
I am sat at home, rained off racing today and my thoughts drift back to what is the next stage in engine for the slingshot probably to be started over next winter.
To define what I want from a "next stage" first I would be looking for a substantial increase in power. . . how much is a bit difficult to define and will come later. I am also looking for a bit of a difficult to define "coolness/interesting/ unusual factor but that should become apparent from what is being considered. Finally it must be based on a stock chevy block.
First thought strip the existing 383 engine replace the rods with ally ones and add nitro to the fuel, about 25% to 30%, and fit a new scroll in the metering block for the injection and new jets. Easy to do, about £800 to £1200 for the rods they would need replacing every other season and about £25 a run for the nitro. A bit debatable on the "coolness" factor Nitro is cool, but the motor looks basically the same (well until it runs

) should give about another 200 bhp
Option 2
buy a set of these http://www.araoengineering.com/chevysmb.htm and fit. 4V with push rods cool, not a huge increase in power but I could add 20% nitro without needing the ally rods and that would give a total increase of about 25%. . .

Option 3
stick a whipple supercharger on it, run about 22 psi boost apart from the actual blower there is little to do to the engine, it would need blower restraints and a kevlar sump "nappy" thing and a full transmission and converter shield but obviously and another £300 in injection bits. Very cool and probably 1400 bhp out of the engine. it would probably mean a re-shell for every other weekend of running.
Option 4
build a "budget" big block using the very cheep head castings off ebay (£400 a set)and go shopping appart from that a similar spec to the small block as far as cam and valve gear (but not cheeper rockers).
I have a big block chevy block in the garage, a 4.31 bore at the moment but it would go to 4.375" bore, then the choice is crank, do I go 3.75" stroke for a 7.4 liter screamer (9k rev limit) or go for a long stroke torque monster with a 4.350 bore and a 4.5 inch stroke, about 8.8 liters about 7k max revs and add 20% nitro for about 950 bhp but a lot of the bits would come over from the SBC and a big block chevy is by definition cool.
Thoughts please, ideas I have not thought of, the budget is an additional £5k ish but that is not for the whole engine as I have the injection system, dry sump system and can fabricate a lot of stuff.
The slingshot is on a "steam punk" theme so all the above (well to me anyway) seem expropriate to that clash of olde/ very high tech I am looking for.
best regards
Mike

Ian Anderson · Post by **Ian Anderson** » Sat Apr 26, 2014 8:26 am

Avoid Arao engineering 4 valves like the plague

Your money will disappear and you will never see the heads
See
http://www.gt40s.com/forum/feedback-buy ... eware.html

Ian

Ian Anderson · Post by **Ian Anderson** » Sat Apr 26, 2014 8:30 am

Mike
What speed are you wanting at the end of the 1/4?

What gearing have you got?

What revs are needed to do that speed?

Then you know what engine revs you will need and can build a bulletproof one to match.

If it is anything like GT40 we expect to spend twice the engine cost on the transmission to handle the extra power

Ian

Blown v8 · Post by **Blown v8** » Sat Apr 26, 2014 9:05 am

Go with the Whipple,
Coolness guaranteed !

bigaldart · Post by **bigaldart** » Sat Apr 26, 2014 4:08 pm

Keep it old school Mike, Roots style blower all the way, even a 6-71 would be good for 1000hp, 8-71 easy 12-1400. Set up is way easier than N/A and methanol a hell of a lot cheaper than nitro, 1400hp in a small block with steel rods is no issue and a reshell every season would be only a precaution. Only issue is learing to drive while looking sideways because you won't see much in front, then again a Whipple is even bigger than a roots. What fuel pump do you have?

Alan

JJMclure · Post by **JJMclure** » Sat Apr 26, 2014 5:59 pm

twin turbos mounted on the front wings! then the cold side piping will be so long there'll be no need for intercooling! only joking about the mounting what about if you had them hanging off the side facing forward? if you're running meth no intercooling. get some on3 76mm ones off ebay will leave you spare change

topcatcustom · Post by **topcatcustom** » Sat Apr 26, 2014 6:09 pm

I thought you were keen on a straight 8 lump as well Mike! Although you would spend your £5 grand on a custom crank for it...

How about dual SBC's in parallel with an over-engineered gear drive on the rear to connect them, and a blower running off the nose of each!

kiwicar · Post by **kiwicar** » Sat Apr 26, 2014 7:26 pm

Hi All
thanks all for the replies so far.
Ian thanks for the warning I will take note.
With a small block red line would be about 8.5k revs on a blower, with 1400 bhp then a low sevens should be doable and that equates to 195 to 205 mph across the line, 12% slip on the torque converter flat out and 33 inc tires works out at a 3.65 ish gear set (not allowing for tire growth it puts the stock case power glide on it's upper limit so a deadenbear case would probably a good investment and a bolt together converter.
JJ, turbos were a thought but are a bit of an unknown to me with mechanical injection, I know it can be done but I think it is not as simple as with a blower.
Al
I would probably need a new pump with a blower, the current one is tagged as 3.6 gph I also have a 150A that I think is a little bigger but I am sure I would be better off with something around 6 or 8gph with a blower the bottom end should be fine, the crank is rated at 1500bhp and it has H beam forged rods to match with lightweight forged pistons. I might go with a set of steel splayed bolt main caps.
As for which blower, I see littlefield high helix 8-71s come up from time to time on Ebay and Eurodragster, even new they are not ridicules money. The 5 liter/ rev Wipple is about $4500 new but they really appeal to me as a design and piece of engineering.
is it only me who likes the thought of a bit of Nitro.
Tom the straight 8 would have to be in an altered to look right (well to me anyway) and a twin engined dragster while a neat idea seem to have a very low success rate at being finished
best regards
Mike

mgbv8 · Post by **mgbv8** » Sat Apr 26, 2014 7:38 pm

Fresh slicks !
Fit the front wing !
Fit the Parachute !
Perfect the burnout procedure !

Then it WILL look cool when it runs an 8 on the strip

Then you can add lots of copper rivets or have them airbrushed on?

Then think about more power when the engine is maxxed out NASP on Methanol. Thats when a GM blower will be needed for max coolness

Everyone loves a car driven by a bloke who cant actually see where he's going because of the huge charger on top of the engine

topcatcustom · Post by **topcatcustom** » Sat Apr 26, 2014 7:58 pm

I concur Pel!

kiwicar · Post by **kiwicar** » Sat Apr 26, 2014 8:12 pm

Hi Pel
I agree with you on all you have said, also get some track time and practice opening the throttle but as I started the post, it was raining and I wanted to cheer myself up a bit.
I think the burn out I tried just before the near tree felling incident actually showed promise as I am pretty sure I had the wheels spinning for quite a bit longer that time.
I must confess If the current tires are not gripping soon I will be buying some fresh ones.
Mounting the wings is a project for the next few weeks, the front especially will be a challenge.
I can have the chute mounted in about 2 minutes the cable release also is not a big deal it just needs routing through and and a p clip pop riveting to the cover packing it however looks tricky.
Best regards
Mike

mgbv8 · Post by **mgbv8** » Sat Apr 26, 2014 9:03 pm

"" it was raining and I wanted to cheer myself up a bit.""

Then try Babe Station or Ebay Roulette !!!

Ebay Roulette can be good fun if you like surprises ??
This involves 5 pints of beer and then logging on to Ebay.

This is why I own a stuffed Tarantula, a mounted Deer head and a life sized Zombie Baby

JJMclure · Post by **JJMclure** » Sat Apr 26, 2014 11:22 pm

damn stupid ipod double posting for me
sorry please continue

unstable load · Post by **unstable load** » Sun Apr 27, 2014 6:29 am

Option 4
build a "budget" big block using the very cheep head castings off ebay (£400 a set)and go shopping appart from that a similar spec to the small block as far as cam and valve gear (but not cheeper rockers).
I have a big block chevy block in the garage, a 4.31 bore at the moment but it would go to 4.375" bore, then the choice is crank, do I go 3.75" stroke for a 7.4 liter screamer (9k rev limit) or go for a long stroke torque monster with a 4.350 bore and a 4.5 inch stroke, about 8.8 liters about 7k max revs and add 20% nitro for about 950 bhp but a lot of the bits would come over from the SBC and a big block chevy is by definition cool.

There aint no replacement for displacement.

DaviesDJ · Post by **DaviesDJ** » Sun Apr 27, 2014 7:22 am

Hi mike - hate to add to the woes but you would have had a ball yesterday - the afternoon was bright and the track was quiet.

I am completely with Pel - it seems that you have yet to unlock the considerable potential already in the slingshot - so I wouldn't do this over this winter. But hypothetically IMHO Twin turbos would look fantastic - be very unusual in a slingshot and surely be not a great deal more complex then a blower - as long as the pressures are matched to what is supplied by your mechanical induction - the pipe work to the turbos which could right at the front could be very 'steam punk'.