smoktire

I am on the way to built a 383 stroker.

I whant to get an 11.0:1 with 64cc Eagle competition rotating assemblie (made of sae4340 crank-sae4340 H beam rods- sae 4032 forged SRP piston).

I think that i will not have enough monney to buy aluminium head this season so i would re use the vortec ones and XE268 cam.

What octane should i use? is 94 is ok ?

I might add a 100-150 hp shot of nitrous...

This engine will see little street use and big strip use.



thankx

Stekman

11:1 is a bit much for iron heads. It is also a bit much for that cam. Not saying it can't be done....

smoktire

I know that is a bit to high but back in 1969 the L-48 350 got 10.25:1 with leaded fuel.If i got to im ok to use 100 octane aviation fuel

ME Leigh

The olden day motors also had huge seat-seat duration cams, to bleed cylinder pressure. And the leaded gas back then had a much higher octane rating than today.

Air_Adam

Yup, engines back then were fine with high compression because fuel octane was much higher (premium was around 104 i think) and the fuel had lead too, which helps deter detonation.

The monster cams they had also really helped, because they bleed off ALOT of the cylinder pressure. Thats actually the reason that compression ratios were so high back then... they needed the high compression heads/pistons to make up for all the pressure that those huge cams would bleed off.

Red Devil

No.

Tremo

Back in the days of leaded premium gas, a friend had 12:1 pistons on his 302 Z28 motor, and 2.02 iron heads. That engine used the old 30-30 Duntov solid lifter cam. He did not have detonation problems.

He was readjusting the valves monthly.

I always though he had too much carb on that motor. He was running an 800 double pumper on top of an early Torker intake.

Air_Adam

Thats why

Rockin-Iroc

Yeah, to some extent, a larger duration cam will bleed off cylinder pressure at lower rpms due to the overlap. You might get away with 10:1 with a big cam, especially at higher altitude, but not 11:1. You could try having the combustion chambers ceramic coated, then you might get away with 94 octane, but might still have to retard timing, and maybe avoid driving it on 90 degree days unless you put a witch's brew of race gas in with your pump gas.

I run 5 gallons of 118 octane race gas in with 15 gallons of 91 octane pump gas to run 11:1 on my Corvette's big block. Believe me, it gets old spending over $60 bucks per tankful! My friend went with a big cubic inch 540 Merlin in his GTO, which makes more power than my 427 and he can run pump crap all day long with his 9.5:1 compression ratio on aluminum heads.

I might suggest dished pistons, or larger chamber heads. But because of the excellent flow of the heads you've picked, I'd rather go with the dished pistons.

You could get -30cc pistons and then run a centrifugal supercharger through an intercooler! Just a thought.

ME Leigh

I'd have to say i agree, its not worth the added expense and issues for the little percentage gain in power.

smoktire

What about a aluminium head (victor jr) 355 with 11.0:1 with a XR286R cam With 1.6 rocker arms...248-254deg@0.050" & .614"-.620"lift.

Stekman

Why are you hell bent on 11:1 compression?

89RsPower!

this is a race only application right? If not your nuts to go with that compression ratio unless your rich and its just a toy... just think about how much racing fuel costs and then imagine your gas mileage with that engine... lets just say for fun racing fuel is 6 bucks a gallon.. thats what cam2 is around here.. now figure like 10 miles a gallon on the high side of things... that really ad's up.. if you got the money and its a weekend cruiser though its your call.. 60 bucks per 10 miles seems a bit high to me and thats just a guesstimate..

smoktire

I whant to run the maximum compression = more power ... ok 11.0 may be too high so what CR would be ok with aluminium heads and 92 octane pump gas?I will also add 100hp of juice.

Stekman

Compression, cam, all that crap aside, what do you want out of the engine. State that, THEN determine what gets you there.

Air_Adam

One point of compression isn't worth much on a street motor... like maybe 10hp.

IHI

iTrader: (1)

Well put, more compression is not a justifible power builder. Even though it's generic, play with a DDyno and see for yourself.

As already stated the reasoning for more compression is for use with bigger duration camshafts since overlap bleeds off cylinder pressure.

Bad examples to follow but point should be seen:
350 with 11:1 compression 240/250 actual duration cam will keep you close to the 10.75:1-11:1 static compression

Same 350 with 11:1 compression and a race driven high revving 300/320 actual duration cam would drop you into 9.75:1 terrirtory

Like I said, not true to life ratio's but you can see the point.

Is it possible to run 11.3:1, aluminum heads on pump gas-Yes, I do it all the time, 93 octane ethanol in fact since nobody in town carries 93 or 94 dino fuel.

Jack up the timing, add some nitrious you better have some 110 in the tank.

Another key when wanting to run high compression and lower octane fuel is to jet it fat and keep the motor really cool, lean conditions and heat will exagerate pre-ignition. Also you must be sure to have the right heat range spark plug also. Too hot and it'll want to pre-ignite also, too cold and it will load up and make street driving terrible-I also know this first hand too

Dont try to reinvent the wheel with your motor, do alot of research and try to put together a combo that works in synch with all the other parts/combo your going to run for the most bang for the buck.

A side note, if this is going to be a bracket racer, most guys will agree that until you start stepping into the high 13:1-15:1 compression and running alcohol-that's when the engines start to get less affected by atmospheric condidtions. 13:0 and under on race fuel they're more supceptible to air changes and you just have to learn your cars habits when the air changes.

ridecamro

i was going to be runing 11.1:1 comp ration with vortec 062 casting heads. so by using your method would i be able to still run 93 octane gas

Red Devil

I think you misread his post and its intention.

IHI

iTrader: (1)

You'll have some advantage using the Vortec with their effiecent design they usually make the most power in the low 30* timing range-seems the "norm" is around 33* total, so that will bide you some room to play, BUT...running iron heads and trying to stay pump gas compatible try to stick with 10.5:1 being MAX compression 10:1 would be the best though.

It would be different if you already had the block with 11:1 or 11.5:1 slugs figures based on 64cc heads already installed, you could opt for thicker head gaskets as an easy low tech way to drop compression since most are figured using .039 compressed head gaskets, you could opt for the .042 and lose a little. Another method which would involve some math and a buret, would be to go and start opening up the chambers a bit to lose some gain chamber size which will drop compression, but you'd have to figure up how much compression would be lost per cc added to the chamber and go from there.

If you have'nt yet got the slugs and are going to run iron heads and want pump gas, 10.5:1 would be the most I would feel comfortable running given proper cam specs, 10:1 even better, unless everything in the motor was built around alllowing more compression and still pump gas friendly, but simply put there's not alot of power to be had by just running higher compression.

ridecamro

well the kit i will eb using is a power house kit. it's rated at 10.8:1 comp ratio with a 68cc head. the guy figured it to be 11.1 with vortecs and the thickest gasket i could go. how much would getting the heads mechined to make the cc bigger cost

IHI

iTrader: (1)

Your best answer is to call a machine shop in your area and tell them exactly what your situation is. I really could'nt begin to estimate since shop rates vary so darn much. Just a "rough off the hip figure" I would shott for about a 73cc chamber and that should put you pretty close to 10.3:1

Might also ask if it'd be cheaper to fly cut the pistons instead of doing the head work, I know that's done regulary and I wanna say it's roughly $5-10/piston

Agains that's a really rough figure but kind of the right direction.

Red Devil

Best answer is to ask for a substitution in that kit. I don't know anyplace that won't do it. :shrug:

Cruz'N Bruz'R

I'm running a 383ci. 11:1 with 64cc chambers, and I've never had detonation problems. The MSD is set for 38 degrees total and I've never run below 91 octane, but never above 94. I don't know why you guys think he'll have problems. I'm also running Pro Topline Iron heads as well. He'll be fine.

IHI

iTrader: (1)

Your always better to err on the conservative side, with the wrong combination of parts and tune a person could easily find themselves filling up to the tune of $5/gallon cuz they pushed the envelope-and did'nt win Again, with the cam he's talking about using, for no more power high compression is worth, it's just not worth pushing for extra compression-especially when he has'nt bought the parts as of yet and can nip this problem before it becomes one. Now if a purely race ground cam with big duration being used it'd be a little different, but the XE268 is not that cam. It would be alot happier in the 9.5-10.0 range.

Cruz'N Bruz'R

I totally agree. I now wish i had gone with lower comp. I can't add a blower or any kind of boost. It's kind of limiting. But I'm not running a rather huge cam. I'm running an XE276. I was just mostly commenting on the early statements of "no" and that iron heads are not good for high compression. According to the several shop builders/racers I talked to before building, those comments were completely reversed. Most high compression drag, dirt track builders prefer an iron head over an alum. Though the weight savings isn't there, the cast durability and maintained heat is.

IHI

iTrader: (1)

Retaining the heat is a big issue, we had a guy go from Dart iron eagles to Pro 1's of the same runner size, valve size, etc...basically only thing changed was the material and he slowed down almost a tenth.

Cruz'N Bruz'R

So I guess even the weight savings over the iron didn't help out.?

Streetiron85

A lot of guys buy stroker kits without doing any research... Don't B 1

The least expensive stroker kits out there come with flattop pistons, and guys think, "COOL! High compression, that means my car will be even faster!!! And it will cost less too!"

Then they find out too late that there's a downside to that if you want to drive it on the street.

TGO is a great resource for finding out what other guys experiences are, firsthand.
It's best not to make hasty decisions when choosing parts. What seems like a good deal, sometimes isn't.

IHI

iTrader: (1)

Nope, power lost was not enough to take advantage of the weight savings.

smoktire

I beleive that aluminum head combution chamber can run cooler due to the great heat dissipation of this alloy...so with less heat inside the combustion chambers the cr could be a litle more high before causing detonation...with iron heads 11.0:1 is too high most say 10.0:1 should be ok .With aluminum head is 10.3:1 would be consider as a nice ratio

Ok now most of you think that 11.0:1 does not worth the 10hp extra with the racing fuel pain in the *** so i will let down my 383 project in favor of a other project...

What about a 355 with
- aluminium head (victor jr)
-XR286R cam With 1.6 rocker arms...248-254deg@0.050" .614"-.620"lift and a
-super victor intake
-I still whant to use nitrous.

What cr would be ok for this to get the max hp on 91-94 octane

For the nitrous i will make a other fuel systeme with a little fuel cell so i will be able to put 110 octane just for the nitrous.

IHI

iTrader: (1)

Depending on LSA I would look to build it around 10.5:1 and no more, absoluetly no more than 10.5:. If your going to use nitrious and want to build some good hp try to get the LSA around 108* then just degree it per specs on the card.

Your going to want at least a 4000 stall and just so you have some left when spraying try to go with a 28" tall slick out back with a 3.90-4.11 gear. I think the 3.90 wouold be optimal as an all around gear if you plan to drive it on the street and if you want to get some more rpm out of it you can always step down to 27" and maybe if your chasis is working a 26". But with intensions to spray you want to be sure not to be all out of motor and be on the high side rev chip after the 1/8th mile mark.


Also be sure to check the springs pressure/clearance with the Vic Jr heads and wanting to run the 1.6 rockers since the cam will have a higher gross lift since they're figured with 1.5 rockers. Ya hate to buy all that then have to have the heads milled or springs changed just because of rocker arms.

smoktire

For the stall i was thinking to get a 3500 but i will search for a 4000.I alredy got MT ET drag 28x9x15 with a 4.10:1 gear.For the cam it is 110 lsa with .576"-.582" with 1.5 rocker i aleredy got Comp pro magnum 1.6 ones.....614"-.620"would be bether.You think that i will have valve to piston clerace problem?

Cruz'N Bruz'R

Depends what pistons your running, but you sure better check before finishing putting it all together.

IHI

iTrader: (1)

It's always good to check just to be sure. But typically unless your running a really cheap dome piston combined with a huge race inspired duration in the actual 290+ range, longer duration has the valves hanging open alot longer than normal and really becomes an issue with the timing event, sometimes you can get away with retarding the cam to compensate so the clearances are better when the piston comes upto TDC, otherwise you need to fly cut the piston to clear the valve.

Alot of the cheaper pistons are cast with not so much emphasis placed on quality control and keeping a tight design, and that can lend into issues when it starts getting radical on the build, but for the parts your describing you should be fine.

Cruz'N Bruz'R

IHI, in your optinion how big of lift cam go I go around. I'm running a set of Speed Pro ceramic coated hypers, flat top with two valve reliefs. Are these decent. Now, I'm running a XE276, but I really wanted to go with a solid roller in the +.600 range, but was afraid of clearance.

IHI

iTrader: (1)

The pistons your running now a really good piston, kind of middle of the road so to speak and there are alot of them out there. I know alot of guys running Speed Pro's with great results and long engine life-it's almost everybody's goal with cars to run as good as possible with as little as possible invested unless the pockets are pretty deep.

The big issue running solid rollers since they require such high seat pressures is to try and keep the lift in check, this will make the valetrain alot happier in the long run and not stress parts as quick, but if this going to be a motor you plan to freshen up at the end of the year, going all out is'nt as big a factor. Running a solid roller if you can keep gross lift under .630 you'll be in good shape as long as you run a good valve spring. Cam lift has less to do with power as does flow characteristics of your head and profile of the lobe since the time spent at max lift is very very short. A good head will start to flow very well starting as low as .200 lift to allow a good cylinder fill. Also of the medium range slugs have the valve relief roughly figured for 2.02 type size valves, so if your heads have 2.05"-2.08" you should really take a putty reading to make sure you wont clip the piston with the oversized valve.

Depending on your ultimate goal, sticking with the flat tops is a wise descion since it promotes better quench and is it's more effeicent than dome pistons, so milling the heads to up compression with the slugs you have will yeild better results than installing domed slugs. But then again your going to have to check valve clearance since the head is that much closer to the top of the block deck/pistons.

Given a off the hip assumption, you should be fine since the actual duration of the XE276 is on the smaller side. Couple that with a good 35-3800 stall/3.73 gear and you would be in business for a nice package. But, as always, there are too many variables with every situation and it never hurts to take the extra time to double check clearances so you dont ruin a fresh motor and waste time/money pulling engines and replacing parts.

89Warbird

I'm running 10.3:1 with Vortec heads and using my scanner I can tell you I'm at the ragged edge of detonation with 92 octane on a 90 degree day.

Increased compression ratio also improves overall engine efficiency, which means more power, less emissions and better fuel economy.

Aluminum heads dissipate heat so fast you should figure them to be worth a full point of compression.

All these folks that say they run 11.0:1 on pump gas with iron heads. I don't believe their compression ratio is accurate, I'd bet if it were actually checked it's lower than they think. Also I'd like to run a scan on their motors to see if it really has no detonation. Because I know my true compression ratio and I know that below 2000 rpm if I lug the motor I"m getting lots of detonation.

F-BIRD'88

Are you sure you have a true 11:1 cr?

A 383ci sb built with flat top pistons on a stock undecked block will actually be
10.45:1 with a felpro .039" gasket and 64cc heads. if you pistons are even lower in the block at TDC (.025" nominal spec) your cr will be even lower yet. An actual measurement of .055" below deck is not unusual with typical flat top replacement pistons and a stock block.
Unless your block is "0 decked" or you're using a domed piston your 383 motor is likely way under 11:1 compression.

It's a lot easier and cheaper in the long run to work within the laws of physics, than against them.
keep the motor around 10:1 for the street and concentrate on total engine airflow to get power.

Cruz'N Bruz'R

I bought my engine kit with the information of 10.7-11.0:1 with a 64cc head,depending on head gasket. I would love nothing more than to be low compreesion due to the fact that I really want to boost the motor, but am running too high comp. to do so.

F-BIRD'88

It's really only a piston swap away.

You would want to dissassemble the motor anyways, to increase the top ring gap, if you plan on "Blowin' it" with significant boost.

There are lots of low compression D dish pistons available..

Rockin-Iroc

A 355 would be fine, and if you can get 94 octane gas, 10.5:1 compression would be the very highest I'd go. However, you can build a lower compression 383. With the 5.7" rods, 64cc chambers, and -30cc dished pistons, I calculate 8.68:1 using a standard 0.039" head gasket, and 9.07:1 with a 0.015" steel shim head gasket. Either way, this would permit you to use a supercharger, or run low octane pump gas all day long.

This is the low extreme for a 383. You could get less of a dish and tailor that compression ratio up more. Still, if dyno2000's power numbers can be trusted, using the same Isky 270 Mega-cam hydraulic cam that I have (only just passes Colorado's emissions), and with a fully ported pair of heads with 2.02"/1.60" valves, the program is giving me the following power numbers with 9.07:1 compression:

416 lb-ft @ 4000 rpm
377 hp @ 5500 rpm

That's with a dual plane and a 750 carb. And that's on 85 octane pump crap you can buy anywhere. Now, stick a Holley/Wieand 177 roots supercharger on it and put the compression ratio back to 8.68:1 and you get the following numbers:

468 lb-ft @ 3500
440 hp @ 5500

That's not bad for a street motor that'll pass emissions and run premium pump gas all day long! That's kind of what I probably would be tempted to do. Those 177 blowers don't cost much!

Rockin-Iroc

This is interesting. I started thinking that in Colorado at least, I don't think you are allowed (by the smog police) to go backwards in technology. In other words, you can fuel inject a car that was always carbureted, but I don't think you can carburet a car that was originally fuel injected.

(Colorado residents, please correct me if I'm wrong).

But anyway, assuming I'd leave the fuel injection on the 383, with a Vortech V2 S-trim centrifugal supercharger, which is easier to package under the hood (but pricier), the peak numbers get even better on the above 383 engine:

502 lb-ft @ 4000 rpm
480 hp @ 5500 rpm

Although peak numbers are better, please note that the 177 roots blower had much better torque numbers below 4000 rpm. So you can decide if an extra grand is worth 40 extra hp and slightly more top end. I think I'd choose the compact 177 roots blower for a carbureted street car, but I'd go with the Vortech definitely on a fuel injected engine, just because of how much easier it is to package with EFI.

Cruz'N Bruz'R

I don't know how accurate DD2000 is. Mathmatically it is exact, but it doesn't allow for friction loss. Or engine efficiency. I got

514hp
489 lb/ft

when I plugged in my flow numbers and my cam. Thats NA, that would be awesome, but I'd take at least 10-15% friction loss off of that. Then another 10-15% driveline loss. And you should have your RWHP, roughly.

As for Colorado, here in Ontario, there no law on what you can't do to your car, but bottom line is it has to pass the set numbers no matter what.

Rockin-Iroc

Yeah, it seems a lot of folks like to go back to carburetion as a simpler way to get the upper rpm horsepower and revs, but I don't think that's legal where I live. Tuned ports respond to hotrod upgrades just like everything else. TPIS is in business because of that. But it's kind of funny when people swear you can't get performance out of a tuned port just because they couldn't.

Anyway, a friend of mine is putting a Holley Stealth Ram on a 406 because he didn't want to try a tuned port with that much CID, but he couldn't go back to carburetion either. It would've been a lot cheaper and easier, but he can't do it and keep it a street car.

I wish we could. I'd go with a carbed 177 blower set up on a 383 if it were legal to do that where I live. And it would save money over a centrifugal into the TPI.

ljnowell

Any monkey can get performance out of a TPI engine. Its still a SBC. You just wont get the performance that a carb is capable of. Ever.

VetNutJim

I think most 'monkey's run carbs because the whole ECM or 'computer' , woooooo........ is just to complicated for those monkeys.

Most of your higher order 'beings' understand what a computer can do for engine management EVEN if they don't understand all the details.

GM's TPI system is one of the finest computer controlled induction
systems ever devised.
Here we are TWENTY after it came out and theres a TON of them still running and running like the Energizer Bunny.
Like ANY system it has it's limitations but it's a heck of a nice system for anything but an ALL OUT purpose built racecar.

All modern induction systems are modeled after it.

LT1, LS1, LS6, Vortec, whatever. They are ALL TPI sytems of some sort AND computer controlled.

If you simply don't like GM TPI why don't you run one of the MPFI systems that resemble a carb?
They will FLOW and give you as much GO as you can possibly stand.

I've taken a survey and all the 'monkeys' in the know voted for computerized engine control.

It's not too late for you carburetor monkeys to come on over.

Sorry, didn't mean to hijack your thread.

Here's my vote on your compression:

11.0:1 = Too Much You Will Definitely Need A Computer Controlled System WITH a Knock Sensor To pull timing for you. You WON'T like that.... Gas sucks now-a-days. This is really in the 'danger zone'

10.5: 1= Maximum You 'May' run and you'll probably need to have the block decked AND run one of the .015 thick head gaskets to have a small enough quench
A thicker gasket (.039~.041) will actually be 'worser'.
Plan on Aluminum Heads

10.0:1= Getting more manageable and probably ideal.. much easier to build with. Throw it together and run it.
Aluminum Heads Would Be Nice

9.0:1 = Ok but not anything to write home about.
64CC Iron Eagles Ok

8.0:1= Supercharger level.... add cubic dollahs to initial estimate.

ljnowell

Typical response of a FI guy. I said TPI not aftermarket Multipoint systems. I would have one if I could afford. I sprecifically said TPI. GM TUNED PORT INJECTION. Dont try to make my posts out to be more than what they were.
If you really think that you can make as much power with TPI as I can with a carb, well, you remember what was said about monkeys.

VetNutJim

I would not take that bet.
Your engine will likely make more UPPER RPM Horsepower.

But I WOULD bet my TPI engine will run circles around the carbed engine in the day to day 'driveability' realm.
That includes engine responsiveness and fuel efficiency.

There's not many areas I can RPM max my TPI (without getting into a LOT of trouble) so I really like the power it makes down in the normal driving range.
I like the way it runs when it's cold, when it's hot, etc,etc. It just runs 'right'.

A carb is only 'right' about 3 times a year...
When the temperature, barometric pressure and humidity just happen to match where it is adjusted.

My old fuel injection engine gets updated thousands of times a second...

I don't think it's the carb that allows the power... it's the 'open' nature of the induction system.

I wasn't always a FI guy. I came up through the days of Carter AFB's, Holley Double Pumpers and Q-Jets.

Now, I only use one of those things for engine testing on my test stand.

On SECOND thought I have a TPI that I 'might' want to put up against your carb engine.
It's a little 348 CID Chevy with one of those long,round, TPI systems on it. It makes 405 HP.
I have another one that makes 305 HP.
They arent't the old type TPI but the new ones.

So how much HP are you making with that carb?

Oh, TPI IS Multi-Point FI, it's just a batch-fire system instead of 'real' SFI.

ljnowell

Why cant you stick to your argument???

1. I have never had a problem with a carb being unfriendly on the street. In cold weather, warm weather, you name it. If you know how to tune a carb, weather doesnt matter. Thats a mute point. My carbd engines are "Right" every day that I drive them.

2. The "open" nature of the system? Yeah, thats basically it. It can perform over the wall that TPI hits. Thank you for proving my point.

3. Why do you feel the need to bring in other engines and other manifolds? Once you change from the Stock TPI system, its no longer TPI. There is one type of "TPI" in this discussion.

4. I know TPI is a multi point FI, I dont need you to educate me, I assure of that.

Lets end this argument now, because it is not adding to the tech aspect of this thread. You feel your way, I feel mine.