Genhero

iTrader: (3)

I've finally got enough money to finish off my engine build but before I order the parts I would like to get a person that is more experienced to read it over, thank you.

It will be a 383 (.030 over, 3.750 stroke... yatta yatta)

Bottom End Kit
Forged Aluminum Pistons +7cc
Two Valve Reliefs
Connecting Rod Material is Forged 5140 steel
Connecting Rod Beam is I-Beam

Top End
I'm buying a complete Trick Flow Kit because I am not so good at matching cams with heads. "Trick Flow 490 HP 23 Degree Engine Kits for small Chevy"

Combustion Chambers are 72cc
Intake Runner is 195cc
Intake/Exhaust Valve - 2.020 in. / 1.600 in.

Head Gasket
Bore 4.200 in.
Gasket Material PermaTorqueMLS
Compression Thickness is 0.61 in.

That will produce a CR of about 11.02:1

I am going Carb(just to get it underway this summer) until I can afford a DFI setup next summer.

Cam Specs
Hydraulic Flat Tappet Camshaft(Its a 1986 block and I did not want to retro-fit)
246/254 degree duration at .050, .495/.510 in. lift, with 1.5 ratio rockers and a 112 degree lobe separation.



My questions are what size Carb should i use? Does that cam seem like a pretty good high performance cam for a 383 or is it a bit "small"? And the last question is i've heard AL heads can handle up to 11.5:1 CR on pump gas because of the way they disperse heat, is this true? As stated above my CR will be about 11.02:1 so I should be able to run 93-94 octane, is this correct or did I read a bad article?

Just a little more info, this car is not my daily driver and is a fun summer car only. The only thing is, I do not want to have to mix in a racing fuel additive for a higher octane than pump gas. Thank you.


-Russ

five7kid

iTrader: (14)

Without doing the calculations, that CR sounds too high for the parts you're talking about. Perhaps more like 10:1.

A 750 Holley would be a good carb choice.

Viprklr

iTrader: (5)

I've also heard that aluminum heads can handle a higher compression ratio due to better heat dispersion. True? Don't know.

I'm not so sure on your 11.02:1 CR. It does sound too high for what you have. 72cc chamber? Wow that's big. .61 compressed thickness? You probably mean .061 which is still a nasty quench. Why not run a thinner head gasket to raise your CR a tad and drop your quench to a more reasonable number?

Genhero

iTrader: (3)

yeah i meant .061 on the gasket. I chose the 72 cc chambers and gasket based on virtual engine calculators info. I might be putting in the wrong deck height though. Im hoping for 11:1 CR so Ill have to take another look at the calculator. But what do you think about the cam? Thanks for the replies.

-Russ

Sonix

iTrader: (1)

I love engine build threads, there so exciting - especially if you seem serious about the build - and you do.


Ok, something in your numbers is out to lunch. I used ;
http://kb-silvolite.com/calc.php?action=comp

And attached the pic. 72 cc is a big chamber head, flat top with valve relief pistons with 7cc reliefs. I assumed you didn't deck the block, and used that colossal head gasket.

First thing I notice - is a .061 head gasket is a joke. Something there is wrong.

Here's what i'd recommend, see the 2nd attachment - zero deck the block, and use a normal .041" gasket. That'll set you right at 10:1 (give or take a smidge).

AL does dissipate heat faster, which means it can tolerate more compression (or you can think of it as it needs more compression, your call). However one full point is optimistic, I think. So instead of 10:1, you can run 10.5:1 or so. 11, or 11.5 is not what i'd rely on.

That's a big cam, even in the 383, it'll feel like a big cam. You'll need all the compression you can get to have that run right. If I was in your shoes i'd take one step down on the cam.

As is, you don't have quite enough compression for that cam, and the heads (195cc) I think are a tad small for the cam. I'd just bring the cam down. If you do what I mentioned in that second attachment everything else will line up, or fall into place nicely
-good quench due to the zero decked block
-perfect compression ratio
-Can use a basic head gasket, no need for the pricey exotic ones. If you blow a head gasket this perk pays for itself more than once.
-Then it'll be a bit more driveable as well.

What part # is that cam? If this is carbed, 383, and not a daily driver, i'd bring the LSA closer. That's more of an FI or forced induction type of cam. I'd go down to a 107-108 LSA for max power. (according to vizard...)

Hope thats some good thoughts for you to chew on.

Stekman

When you say +7cc for the slugs, you're saying they're domed slugs, right? Also, are you planning a 0 decked block? 7cc dome and 0 deck gets the 11:1 SCR.

I agree with the above on the compression. Also, personally, I prefer to stick to the major cam companies when it comes to camshafts (Comp, Crane, Crower, Isky, Bullet/Ultradyne, etc.) as they're lobes are generally more "up to date." I don't know how ancient (or new, for that matter) TF's lobe profiles are. Can't really get a good idea of ramp rates, either as TF doesn't list. However, looking at their listed specs for their rollers, they look a little "off" comparing to what Comp has to offer so I would expect about the same from their flat tappets.

I'd go for the mid-low 10:1 compression range and toss something along the lines of the XE274H or XE284H (Comp Cams Xtreme Energy) in there. Another good look for a cam would be the Lunati Voodo 60104.

Genhero

iTrader: (3)

Stekman, the piston type according to summit is still "flat" but with +7cc. The deck will be 0 though, the block is at my friends machine shop right now.

Thanks for all the info Sonix, I did a bit of homework but all the cams available make it a bit overwhelming. I did check out the two cams that Stekman suggested and I do like the XE274H because of its RPM range but I would like some of your input on it, here are the specs.


Cam Style:Hydraulic flat tappet
Basic Operating RPM Range:1,800-6,000
Intake Duration at 050 inch Lift:230
Exhaust Duration at 050 inch Lift:236
Duration at 050 inch Lift:230 int./236 exh.
Advertised Intake Duration:274
Advertised Exhaust Duration:286
Advertised Duration:274 int./286 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:0.487 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:0.490 in.
Valve Lift with Factory Rocker Arm Ratio:0.487 int./0.490 exh. lift
Lobe Separation (degrees):110

I also took your advise on the CR and gasket specs and will go with a CR between 10-10.5:1 but closer to 10. That cam that I showed the first time did not have a grind number because it was part of a top end package, but Im going to just get the top end seperate (IE heads, cam and intake seperate).


I noticed you said .041 for a gasket would be normal, how would a .028 sound? It would bring my CR to 10.186:1 (I know I'm really go for strange gaskets numbers but I would like to push the CR a bit higher then 9.879:1 or so). Would that size be a good idea or just stay with .041? Thanks.


-Russ

SpitotRs305

if you are zero decking the block you wont want a gasket smaller than .039 in a street car...the .041 will be best for quench if the block is zero decked with a flat top piston... as quench wont come into play with a dished piston

that cam is good i might like to see a little more lift out of it

Sonix

iTrader: (1)

With 10:1, or thereabouts, the compxe274 is a proven performer (haha, I sound like a magazine ad), Stekman knows his stuff.

Since it's a flat top with valve reliefs, that 7cc is probably the size of the valve reliefs, and not an actual +ve number as in domed pistons. Just my guess.

And yea, .040" is optimal quench, don't go lower, you run the risk of hitting the heads with your pistons.
Stay away from those custom sized $$$ gaskets!

Stekman

Is there a part number for the slug? Personally, I would find a good slug that would work with a 64cc chamber and run their 64cc version of the 195 as it has slightly better low-midrange airflow compared to the 72cc version. Comparing the 64cc head to the 72cc head, the 64cc yields slightly more desirable usable airflow than the 72cc. I know there are plently of pistons in the world, so there is bound to be something that yields a good compression ratio. The low-midrange airflow (.250-.500") of the 64cc is a bit better (not by much, but when it comes to airflow, every little bit helps. The chamber size probably aids in velocity as well.)

If you like the RPM range of the Xe274, I would look to the Lunati Voodoo 60103. Roughly the same RPM range, little less duration, little more lift. As a generalization, find the duration that suits you best, then find the cam that yields the most lift. Whatever you find, pair it with a good set of 1.6 rockers and get in the .500's lift and take advantage of the midrange airflow that the TF heads have to offer. Use that with the 64cc and you're starting to get a more well balanced motor.

What transmission is this motor getting?

Genhero

iTrader: (3)

http://store.summitracing.com/partde...0&autoview=sku

ESP-B13055L030 is the part number incase the link doesnt work(its an eagle setup)

Stekman, that is the part number to the pistons, its a rotating kit but I checked out some other pistons and there is a set put out by Wiseco(anyone know if they are any good) and they are -8cc forged pistons. Which would bring my compression to 10.73 (give or take with 64cc heads). Would I be better off going with that combo?
There is also a set of Hypereutectic Aluminum with -12cc which would be roughly 10.27 CR on 64cc heads.


BTW just a little warning the United Engine and Machine Co. seems to be bugged for negative cc's it just make the compression go up as if it was positive.

http://www.race-cars.net/calculators...alculator.html

This one seems to work for negative cc's.

I would have to say that is a big 10-4 on the voodo 60103 and the .041 gasket, I dont mind pushing up the rpms a bit more from the xe274 to the 60103 and the lift would be nice with a set of 1.6 rockers as stated by Stekman.

This engine will be getting a T56(which I know is more of a cruising tranny) but if anyone has any suggestions on what may be a better fit for this build I'm definitly open for ideas(especially since I want to put the tranny and rear end gears in two weekends from now). I would like something that is pretty easy to install and that will be easy to go from automatic to standard(sense I am a computer science major and can only go so far with fab work and time is very limited ), which is why I was looking at the T56 from 93-97 (pretty much a direct fit with a little work to the console and I could grab the slave cylinder and clutch pedal off the donor).

Oh yeah one more thing, does that 60103 cam have a provisions for a mechanical fuel pump. I was thinking of running the mechanical pump(sense they are a hell of alot easier to change) for normal use and run a switch to the dash for a on/off for the in-tank pump or an in-line pump. Is there an easy way to tell by looking at them? Ill go look it up but if you get back to me before I find it that would be great!

I appreciate all the help, thanks again.

-Russ

Stekman

Ok. So when they list 7cc, they are definitly talking about 7cc as being the volume of the valve reliefs. Just had to get rid of the confusion there.

Since you're piston shopping, does that mean you're not particularly locked on buying the rotating assembly as a pre-assembled kit? Wiseco makes pretty good pistons, JE, SRP (division of JE), Ross, BME, CP, Diamond, and a few others are really good pistons, hard to go wrong with any of those, but they're also the ones you pay for. TRW makes some decent budget slugs (forged and hypereutectics). What's the budget for this motor?

I've never seen an aftermarket cam that doesn't have a fuel pump eccentric.

Sonix

iTrader: (1)

Yea, I had the 60103 briefly, I wiped 4 lobes off it. Nothing against Lunati, and I did the break in dead on perfect, I just got unlucky. And yea, of course its got the mech fuel pump lobe.

I think it's closer to the compxe268 than the xe274. The advertised is closer to the 268, the @.050 is closer to the 274. Actually it'd be exactly inbetween. So no, it'd be a lower RPM cam than the 274. With 195cc heads, I think you could use the 274, or the 60104. Your call though, they're all pretty close.

Depends on who you're talking to, if they want to say +7cc or -7cc, everybody considers it differently, and calculators are the same way. Its silly, you just have to know what the piston cc refers to. The 12cc is probably a dished piston, so put it in to the calculator such that it lowers the overall compression ratio. Just adds confusion because no one can agree on negative or positive.

I didn't realize the difference there on the 64 vs 72cc heads. The only reason I agreed with you on doing the 72cc heads (I assumed they flowed identically), is that you can use a tight flat top and get the CR you want now. But if you decide to use a blower/turbo later, $400 for big dish pistons will drop your CR to 8 or so, and you can keep your larger chamber heads. Rather than having to rebuy both. But, assuming you don't plan that in the future, 64cc heads are great because they'll also work on a 350 with normal flat tops quite well.

That's damn good advice, that's exactly what I follow. That led me to the Voodoo since it's got the most lift per duration (super fast ramps). Makes it easier to wipe lobes off it though.

Last piece of advice - With the T56 (a wicked tranny BTW), you can go to a very steep rear end, and still have a good low cruising RPM. With a nice steep rear, no torque convertor to futz around with, you can go to a bigger cam, with the least amount of hassle.

five7kid

iTrader: (14)

+xx cc piston = reliefs or dish. -xx cc piston = domes.

I haven't seen it used any other way (but I probably haven't seen everything).

intex1982

iTrader: (2)

----------
lol - + duh

Genhero

iTrader: (3)

Nope, Im not locked into any pre-assembled kit, I have been saving everything I like in one folder and will just buy it all at once when I think Im happy enough with all the parts(hopefully this to next month ). So if +7cc is the valve relief then on the calculator the "piston dome in cc's" would be 0?

Sonix I'm not adding a supercharger/turbo to this build. I was either going to do a 350 single or twin turbo or a 383. Although I am not on a budget for this build it will take me longer to get it all together if I add a turbo to the 383(with piping, BoV, wastegate, better spaced headers... etc). I just helped my friend rebuiild his engine and turbo his nissan 240 and it really wasnt that bad pricewise but it was alot of extra piping and I would need new headers and such. So I dont mind going to the 64cc Heads. I thought they flowed the same between the 72 and 64 too, but hey... learn something new everyday

Thanks on clarification on the fuel pump lobe.

I should probably say that the rear gear will be 3.73(If I do stick to my original swapping to standard) otherwise it will be 3.42(unlikely).

I have done a bit more research on cams and I think I understand them alot better now and I used your advise and went through some cams closely matched to the ones we previously spoke about. I think the voodoo 60105 has a bit too much duration for me but I do like the 60104(which I think I will stick with). Which, just to recap, is 2,200-6,400 and .504 int/.525 exh with 1.5. So if I used 1.6 it would be (if my calc. is correct) .538 int/ .560 exh would that be to much or could I run that on the street/strip?
Thanks for the help.

-Russ

SpitotRs305

that doesnt sound bad for lift but what duration.. that is what will determine street manners

Genhero

iTrader: (3)

The 60104 has these durations:
Duration at 050 inch lift: 233 int. / 241 exh.
Adv. Duration: 276 int. / 284 exh.

which after reading the tech article about Cams, it looks like this cams intake duration runs best with low 10.5-11 CR. correct?

-Russ

Stekman

It should be just fine on the street, perform equally well on the strip. It's got roughly the same advertised as the Xe274, with a little more aggressive .050" duarations giving it more aggressive ramp rates. That will cut down on the effective overlap, making it 'decent' on street manners.

The lift I think will be a pretty good fit with the 195's. Should be a pretty good motor. One thing to consider - I always prefer buying cylinder heads bare and assembling them with the correct (correct meaning matched to the cam/valvetrain) components. I've never been a fan of running the springs that come on the heads if you buy them assembled. The retainers, locks, and valves are fine - but be sure to get a good set of valve springs.

Genhero

iTrader: (3)

Thanks for the info, I will just do the springs myself. I just wanted to make sure, an appropriate piston for this build would be -12cc for CR, correct? That would be combined with the 64cc heads and .041 gasket. Thanks

-Russ

Sonix

iTrader: (1)

oh, if you mean my tech article, take that compression suggestion with a grain of salt. I was just trying to show that a 202/210 cam and 12.5:1 CR is terrible, and 8.5:1 and 245/252@.050 is also bad. You're in the ballpark, that cam would like 9.5-11 sorta range, more is usually better.

Genhero

iTrader: (3)

thanks for all the help guys!! Ill post pictures once I get it all done(with the rate that things are going it will take longer to build/install then it was to get the cash.)

-Russ