Opinions on a destroked chevy?

[Guest Anonymous]

Hi all. I've finally got a few 240's sourced locally and I'm getting ready to start my project. For a powerplant I wanna use a SBC but I still would like to get some high end out of it. I'm considering destroking a 327 and building a 302. Think the car will wanna break loose any worse than another SBC because of the motor wanting to rev so quickly? Or will the 302 not produce enough torque to make that a factor. So far it seems like this may be the way to go. Just throwing it out there. Any opinions, suggestions, comments?

[patzky1]

As a real quick reply, destroking the 327 will (depending on what else you do) make the engine have less torque, the "wanting to rev up more quickly" part you mentioned, but it will be a little more high rev accepting of course. I think what you mention would be a great motor but why not just use the 327 platform as it is? They're already great engines and if it ain't broke don't fix it. I really think the amount of high end power you gain won't overcome the lost torque since 327's aren't really torque monsters and with good tires you can make a good Z launch and that's what Z's do best, launch.

 

I hope some of my B.S. has helped in some way.

Pat

[grumpyvette]

there several factors to keep in mind,the first is as the engines rpms double the stress on parts squares, to give you a better grasp on that theres about 8 times as much stress at 8000rpm as there is at 2000rpm, and after about 6500rpm- 7000 rpm the cost of reliable parts doubles every 1000rpm, the most hp per dollar spent in a sbc is going to be a properly built 377-406cid engine,it comes down to the most effective use of the sbc as far as cylinder head air flow limitations,piston speed and part costs all point to building the largest engine that will not require super expensive custom parts and spinning it no faster than 4000fpm of piston speed if you intend on letting it live a long health life,while a 302 0r 327 looks great on paper the valve train useing stock style parts limits you to about 6500rpm, so if your limited to that rpm you might as well get the largest engine that maintains a piston speed under 4000fpm at that rpm also and thats a 406 with its 3.75" stroke, a 377 will give you another 650rpm but will require more expensive parts, trying to use that extra 1500 rpm that a 302 seems to provide will cost you about $2000-$4000 extra if you intend on reliably buzzing that engine to 8000rpm.

also keep in mind that the cams,light weight valves, and intake systems necessary to pull the effective hp from an engine spinning 8000rpm are not well suited to daily driveing while an engine that turns almost 6500rpm can be built with much less expensive parts and can be tuned to work fairly well in the 2000rpm-4000rpm range, something an engine set up to run 8000rpm efficiently will not do. the short answer here is that the greater displacement, wider torque curve and less expensive parts all make a 377-406 a much cheaper and easier engine to build yet still retain the same or greater hp levels of a high rpm engine.

[Mike C]

I agree with Patsun. If you have the 327 just go that way. Dollar/power/performance it is a LOT cheaper, especially if you want forged pistons since your only options with a 302 are expensive forgins if you want flat tops. You'd be surprised at how fast even a 355 will rev with a good set of heads, narrow lobe centerline and a moderate amount of compression (9.5-10.5:1) My 355 had solid flat tappet cam in it, 265/265@ .050 and .540 lift on 106 lobe centers. From 3500-7500 before you could blink! Didn't do squat below 3500, but man did it rev! Just look at the Nascar 358" engines that turn nearly 9000 rpm! A Nascar truck motor (9.5:1) would be the ULTIMATE max effort street car motor! 358" and ~600 hp!

[grumpyvette]

those NASCAR ENGINES that spin 9000rpm all day long cost $26,000-$30,000 last time I checked and a cheap stock car claimer type engine will not last long in a street car nor will it turn 9000rpm, yes a 327 can be built that revs to 7500rpm fairly cheaply but hold that rpm for more than a few seconds and something will break, perhaps not the first or the 100drth time but much sooner than you might think. stress is cumlative its just a matter of time REMEMBER theres a HUGE differance in letting the tach hit 7000 for a fraction of a second on a shift and trying to reliably produce hp at 7000 plus rpm.

 

look http://www.gaerteengines.com/latemodel.html

 

IF THEY COULD BUILD AND SELL DEPENDABLE HIGH RPM ENGINES ANY CHEAPER THEY WOULD!!

[Mike C]

I understand all that Grumpy, but their just isn't anyway to hold a STREET CAR motor at high rpm for that long and actually be using it for something. Those NASCAR motors also have about $18,000 of that money in the heads which is about power and not RPM durability. The short blocks are really good parts and really good assembly but could be closely replicated for about $5000 using a truck block, forged crank, H-beam rods and lightweight forged pistons. $1000 for solid roller valvetrain and a set of the Pro Action ported cylinder heads for $2300 that flow 300+ CFM and you have the recipe for a 7500 rpm motor that should provide quite a few years of service. A 355 engine can be built that will easily withstand 7500 rpm usage on the street for a long time if quality parts are used. It will rev quickly and be fun to drive. If you want big time rpm with stock parts than the short stroke will be much easier on GM forged connecting rods.

[grumpyvette]

even that combo your discribeing will cost about $10,000-$11,000 by the time you add a good carb,intake,rev. kit,oil pan,windage screen tray,headers, oil cooler, roller rockers, valve covers,high volume oil system designed for those higher rpms,cam gear drive,hardened push rods,flex plate and ARP bolts everyware, as stock parts won,t work that well.

 

"about $5000 using a truck block, forged crank, H-beam rods and lightweight forged pistons. $1000 for solid roller valvetrain and a set of the Pro Action ported cylinder heads for $2300 that flow 300+ CFM and you have the recipe for a 7500 rpm motor that should provide quite a few years of service."

and those "GM forged connecting rods" can,t be trusted for constant 7500rpm use. even you suggest (," forged crank, H-beam rods and lightweight forged pistons.")

 

please understand I am in no way trying to start or win an arguement , I am trying to point out that if you keep the engine rpms under 6500rpm and use the largest stroke that keeps the piston speed under 4000fpm (3.75" like in a 383 or 406 sbc)that results in the largest displacement for the size block your useing the engine you build can keep mostly stock type parts and give you far more hp per dollar spent!! its just that a 406 that turns a max of 6500rpm can be built to give you 475 reliable hp while that extra 1000rpm-1500 rpm gains no real hp but costs you at least $2000-$3000 more to get and maintain

[Mike C]

I agree. I was responding to his post that he wanted big RPM. You just can't do it as well with a 3.75 stroke as a 3.48 but obviously it won't do it as well as the 3" stroke, but the $600+ for 302 forged pistons is absurd. I still think the 350 is the best way to go if you do small blocks, regardless. 6500 is a nice range for a street motor and that's why mine has the little Comp steet roller now (236@.050)instead of the monster mechanical cam. I ran a 331 in the Camaro before the 355, (the 331 lives in my Jimmy now, 100K miles since it last spun the tires in the camaro, with 35" tires and all, but with a Crane 266 cam now, and does an admirable job towing my 3500# boat/trailer combo.) and the 350 revs every bit as well, no, actually better, but then again it has MUCH better cylinder head prep than the 331 did. It's just hard to go wrong with a 350, especially if you are replacing another small block and you don't have to shell out for a balancer and/or flywheel/flexplate.

[Guest Anonymous]

Hi guys,I do agree with grumpy in regards to the fact that V-8's tend to not like it when they are sustained over 7000 RPM. I spawned a topic a few days ago asking an opinion about a 302 chevy. Originally I posted that I wanted to destroke a 327 motor but I failed to mention why. Which may have pushed on the RPM subject. I didn't really want a motor that pushed 7K. Basically I just want a quick motor and the thought was I would make a decently quick motor by destroking a 327. Not to say it's nessicaraly a fast motor, but quick. I'm relativly new at engine building. Sorry if I'm off topic or if I confused anyone.

[grumpyvette]

if your just looking for a quick reving engine the main factors are overcomeing the enertia of the rotateing assembly and compression ratio and air flow through the cylinder heads,and cam timeing, so ... get the lightest crank, flywheel,rods,pistons and the highest compression ratio the fuel your useing will allow with a cam thats in the 240-250@.050 lift duration range and almost reguardless of stroke length(yes the shorter stroke will be somewhat faster at building rpms but not POWER) the engine will climb the rpms like a rocket . but TRUST ME JUST A LITTLE BIT HERE WHEN I SAY THIS, (IF THE RULES ALLOW IT AND A RATIO OF CUBIC INCHES OF DISPLACEMENT TO WEIGHT IS NOT A FACTOR ALMOST EVERY KNOWLEDGEABLE ENGINE BUILDER WILL BUILD AN ENGINE IN THE 377-427 CID RANGE (SBC ENGINES) IF MAX HP IN A SET CAR WEIGHT IS THE GOAL) THE ONLY REASON ANYONE BOTHERS RUNNING 302-360 CID ENGINES IN COMPETITION IS CLASS RULES MAKE IT MANDATORY. THERES NOT A SINGLE NASCAR TEAM THAT WOULD NOT RUN AN ALUMINUM BIG BLOCK ENGINE OF 525-565CID IF THE RULES WOULD ALLOW IT, ITS JUST A FACT THE MORE CUBIC INCHES OF DISPLACEMENT EQUALS MORE POTENTIAL HP! BTW once you engage the clutch or transmission and the engine is working against the car weight and gearing its the RATE at which TORQUE PER MINUTE can be applied to the rear wheels that counts and that almost totally depends on effectively useing the largest possiable displacement efficiently if your looking for the most effective combo!

NOTICE NOT ONE HIGH HP ENGINE IS UNDER 350 CID and most are over 400cid!

LOOK HERE,just some info/options

the 400 can be bored and stroked to about 427-440 cid look here,and NOT ONE OF THESE ENGINES NEEDS TO SPIN OVER 7000rpm,BTW some of these guys are running over 1200hp http://www.theengineshop.com/engine5.shtml http://www.amerspeed.com/engine_prices.htm

http://www.shafiroff.com/434_sportsengine.html

http://www.lingenfelter.com/packages/427TT.htm

http://www.golensengineservice.com/engineDetail.asp?engine=85

http://www.geocities.com/monty_williams/

http://www.skulte.com/turbo.html

http://www.grapeaperacing.com/GrapeApeRacing/

http://www.turboclub.com/aturbo.htm

[Guest Anonymous]

Grumpy,

 

How much more power / torque will a 383 /406 make over a 350 on a...

 

$3,500 Budget

$4,000 Budget

$5,000 Budget

$6,000 Budget

 

I have read "many" dyno results, from your posted links and most are done with a 350. It seems that a 350 with 195 AFR heads and a good cam intake ets is good to 525 at 6500 rpm. What would the 383 / 406 make with the same parts and these or larger heads.

 

What about overheating on a 383/406 vs a 350?

Why did chevy not make more of these engines and put them in Hi Po applications?

 

I am leaning toward a 383 / 406 for my 91 Camaro, but the above are my concerns.

 

Thanks for all your help. I spend hours reading your posted links.

[Guest Anonymous]

Thanks Grumpy,

I've got questions, You've got answers! I like it! You ever consider getting into pit crew stuff. You sound like you could turn out one hell of a competitive engine. Anyways, Thanks again. I'm gonna keep reading and see if I can learn some more.

~John

[grumpyvette]

there are no repeat no overheating problems with properly built 383 engine anymore that with similar 350 engines, the 400-406 engines do tend to run slightly warmer because of the siamesed cylinder walls but they too if the engine is built correctly with the steam holes properly drilled in the heads and gasket run just fine with no OVERHEATING PROBLEMS. you can reasonably expect a 350 - 406 engine to make about 1.1 hp per cubic inch of displacement for $3500-$4000 1.2 hp per cid in the $5000 range and 1.3 per hp in the $6000 range with no nitrious now Im sure not saying you cant make more than that but thats about average, in DAVID VIZARDS book {max performance CHEVY small blocks on a budget} he gets 500hp from a 350 for $3000 and 550hp from a 406 for $3000 but it takes carefully checked swap meet parts deals lots of careful hand labor, carefully picked used parts and lots of knowledge of what works and what won,t and days of cylinder head porting,your best rought is get the very best flowing heads you can afford on the largest displacement engine you can build for the money you want to spend and a cam that matches your combo and intended use, look here at these sites its a good starting place for combos,but notice all the high hp engines have good high dollar heads and in most cases roller cams.

http://www.ryanscarpage.50megs.com/combos.html

 

http://personal.clt.bellsouth.net/clt/m/g/mgervin/chp/chp.htm

 

http://www.findarticles.com/cf_offrd/m1185/n4_v31/19168096/p1/article.jhtml

 

http://www.airflowresearch.com/ (look at the dyno tests) but remember DART PRO 230cc heads, IRON EAGLE 215cc-230cc)HEADS and CANFIELD 220cc heads can give quite similar hp numbers too if properly matched parts and correctly done head work is done!(those big hp numbers almost never are from (out of the box heads from any manufacturer)(in most cases you can do your own head work but if your not up to it,heres a good head port guy btw,

http://www.ondoperformance.com/

 

heres a good intake and injection system guy

http://fuelinjectorclinic.com/

 

heres crane cams tech line

386-258-6174 Tech Line

[Guest Aaron]

Grump, do you have any links to good tutorials on DIY head porting? That is something that I have always been interested in.

[Pop N Wood]

Good to see someone else going round and round with Grumpyvette on this one... I've done my turn!

 

I originally wanted to put a 327 or 302 in my Z. In the past I have had several people tell me that the light weight and narrow tires (without flares) of a Z really limit it’s ability to handle a lot of low end torque. One guy even told me his 283/auto trans equipped Z was faster than his son’s 350/4 speed Z because the smaller engine was so much quicker off the line.

 

But a couple of things have combined to change my mind. First is the availability of aftermarket parts. The way I see it, if you want a 302/327 the options are to get a 60-70 vintage junk yard engine OR custom order a rotating assembly. Maybe these items are easy to get at swap meets but there aren’t a lot of internet sites stocking 302 cranks as standard items. Most places do stock 383 stroker assemblies thus their prices are much more competitive.

 

The other thing that changed my mind were several comments from Grumpyvette. Build a 350 with higher RPM HP in mind and get more HP with the same low end torque of the smaller engine. Most crate engine designed for street cars use things like dual plenum intakes to boost low end torque and are being marketed with heaver cars in mind. And from what everyone on this posting is saying, a 350 can be made to rev just fine!

 

One question for the experts: for the longest time every car magazine out there was publishing articles about modifying a 350 to use longer rods (I think 6 inch instead of stock 5.7 inch). What are the draw backs of NOT doing this and wouldn’t a 327/302 already have the more favorable rod geometry?

[blueovalz]

Sometime we hate to see the truth. I'm currently going to a 289 vs the old 302, but in the process, I'm using a domed piston with .020" deck height vs the old .005" flat-top. Compression was, and still is 10:1. I was concerned about the increased quench thichness at this ratio, and this read (one of the previous links) only verified my fears. KB pistons has a good write-up on the value of a thin quench thickness too.

[grumpyvette]

sure.

 

http://www.findarticles.com/cf_offrd/m1185/n4_v31/19168101/p1/article.jhtml

 

http://www.sa-motorsports.com/diyport.htm

 

http://www.sa-motorsports.com/diyguide.shtm

 

http://www.ws6transam.org/ported.html

 

http://racerhelp.com/article_racing-10.html

[Guest 1fastz]

my engine is a 383 chevy built right on a budget

 

4340 elgin steel forged crank 3.75 stroke eagle H beam 5.7 rod wich alows for a off theshelf trw forged piston wiht standard ring package .

 

350 4bolt maine block half filled with concreete ..

 

flat top piston using dart conquest < now known as the pro 1 > heads fully ported with a unported team G intake and a 750 carb..

 

crane cams custom roller with no rev kit just a real good set og 1.55 valve springs

cam is 255 intake 265 exhaust with 633 lift across. 109 lobe seperation

 

589 horses and pulls to 7200 rpm shift point all day long

 

cost ? about 7000 dollars. compleat ready to run carb to pan to distributor..