Good day, everyone. I am building a SBC 383 TPI for my '86 C4 automatic. I plan on using AFR 195 heads with 65cc chambers, SCAT rotating assembly with 6 inch rods and +7cc pistons. I need advice on a cam, street/strip, I guess. It will be my daily drive. What I want is when I'm coming out of a curve, I want to punch the pedal and take off like a rocket sled. I'm also looking around for an intake. Maybe larger diameter riser tubes or TPIS mini ram. With TPI, I know I give up some performance, but I keep my stock ECM.

 

When I was a 383, I ran a Crane Hydraulic roller 222/230. It was a good street/strip cam. I had a SuperRam intake and it was a terrific combination. With a SuperRam or Miniram you can use your stock ecm.

 

Mine is a Crower 221/230 under a SR in the 398.

 

id suggest you calculate the potential static and dynamic compression on that 383, with 65 cc combustion chambers I think youll find its high compression and use of pump octane gas might be an issues
the guys gave you good advice, but ID suggest you consider swapping to a 3.07:1-3.73:1 REAR gear and 2800-3000 rpm stall converter before you swap to a significantly longer duration cam discuss with the cam suppliers that you chose to deal with

http://garage.grumpysperformance.com...03/#post-76070

http://garage.grumpysperformance.com...94/#post-44299

http://garage.grumpysperformance.com...200/#post-4041

http://garage.grumpysperformance.com...09/#post-74581

http://garage.grumpysperformance.com...7/#post-103706

http://garage.grumpysperformance.com...41/#post-96863

http://garage.grumpysperformance.com...-2#post-102159

 

Or...Assuming you haven't bought heads yet, choose the 75cc heads.
Quick DCR shows 9.6 DCR using 228 duration cam...pushing 10:1 DCR on a smaller cam. Changing to 75cd drops compression around 8.6:1. That's only 10:1 SCR...definitely "safe" 65cc might work...if quench is done right. I remember 1 or 2 guys going 11:1 w/o detonation. Going lower means you're not strapped into certain gas stations.

 

Thanks, GEGGPENN, the 75cc head makes a lot of sense. Scat has an identical rotating assembly with 3.7cc pistons, With 75cc heads, the Summit CR calculator shows 10.19:1 with that combo vs 9.85:1 with 7cc pistons.
228 duration cam, what kinds of lift?

 

I don't know anything about their calculator. It seems suspect to add 10cc of cylinder head volume and only subtract 3 from the pistons -- to get higher compression?

I use the Paul Kelley calculator. Maybe you can still find/download it. That tool helped me decide I needed dish pistons after planing AFR heads to a 56cc chamber (before I changed direction from a 350 to a 383).

Note: I probably downloaded it here: http://cochise.uia.net/pkelley2/DynamicCR.html

 

Yes, if I use the 75cc heads, I can get slightly higher compression by using 3.7cc pistons.
Thanks for the other calculator.
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For anyone downloading the DCR calculator linked above, this short set of instructions may help.

FIRST, enter cam specs: Advertised duration (seat-to-seat not .005"), LSA, and ICL

After inputting cam info, press "Calculate". Results (cam events) will fill in.

Click on the left tab next (Dynamic Stroke). Fill in stroke length and rod length, press "Calculate".
Effective "swept volume" of the stroke will fill in. You need this for the Compression tab.



Fill in build specs, ending at piston volume, Click "dynamic stroke" box. It will pull the calculated number from the first tab.
Calculate button will reveal DCR.



Unclick "dynamic stroke" box. Re-enter the stroke YOU entered on the first tab.
Calculate button will reveal SCR.



Use info from advisers/builders/forum to decide desired compression. In general, sites will suggest 7.5 - 8.5 DCR for alum heads....1pt lower with iron. Good quench will create the best builds...and allow a bit of increase. Typically, you want to most compression as it increases efficiency, MPG, and power.

Note: I'm at 8.3DCR...which means I might have been able to go higher (than 10.2:1 SCR). Also notice, my quench is .045. I found .030-040" as the ideal range to shoot for. I chose a .040" gasket and asked my builder to zero deck it. Instead, he took it down to .005 -- saying he did me a favor -- in case of future build. You know...so the next one had room for another "clean" deck and .040/.060 over pistons. It turned out OK...no detonation.

 

I looked up that Crower and it looks like a great fit, thanks.

 

Before you settle on a CR for your build, you really need to nail down your choice of intake. The TPI is going to (seriously) limit power, and it's going to create a spike in cylinder pressures around the ~2800rpm torque peak that won't occur with other intakes. You have to select CR with that in mind, which is why you can't go too high with them when using a TPI. If you notice, even from the factory GM went with 10.5+ on the LT engines, which is what you can do after you ditch the TPI. If you want to keep the TPI, then you might also benefit from smaller-runner heads than the AFR195s. You won't be able to use the flow they add on top, and heads with smaller runners might flow better at the lower limits a TPI intake will impose. This would require research on your part, though.

OTOH, you can get away with closer to 11:1 with a short-runner intake, and you can take advantage of the flow the AFR 195 Competition heads provide. My 396 had heads that flowed very similar to those and 10.8:1 CR with a ported stock LT4 intake (much like a MiniRam). I had a custom Comp Cam with 218/224 at .050 and .570/.565" lift with 1.6 rockers on a 110LSA. This setup pulled hard through the midrange and would be glorious with a 2800rpm torque converter and 3.45 gears. It ran great on premium pump gas. However, as you mention this will be a daily driver, you might just want to look at the XFI 268 cam, which has a wider LSA. This will help you idle more cleanly with more vacuum, while spreading the power a little wider but less grunt in the midrange.

You can use your stock ECM for any of these, but it will of course have to be seriously recalibrated, no matter what route you choose.

 

Thank you MatthewMiller, a lot to digest there. The AFR 195cc heads flow 275cfm@.500 lift and 280 cfm @.550. I'm assuming the mini ram with 58mm TB can keep up with that flow rate. I'm thinking since the flow only increases by 5cfm at .550, I'm looking for a cam slightly above .500 lift. Maximum RPM at 4000 fpm piston speed is 6400 rpm, so red line rpm range for cam is 6400. I just replaced the fuel injectors with stock equivalents, would I have to change those?
Using these parameters, I am looking for a cam with around .550 lift and operating range from something to 6000 rpm. The something is what I will look at from the results of the cams that meet that criteria. As for the TPI, I know it will limit horsepower, but it will create tremendous torque and as to recalibrating the ecm, what would be involved? Is there a service that will do that for me?
Also, I plan on achieving a CR that would let me use 93 pump gas.

 

To clarify, I was referring the AFR 195 Competition CNC'd version that they sell, not the as-cast versions. The CNC heads flow 308cfm at .600" and are meaningfully better at .600" than 0.550". My ported LT4 heads were almost identical in flow numbers to those. This is a real difference to the as-cast 195s.
It should have no problems. My ported LT4 intake was similar, and my TB I think was only 52mm (I'd have to go back and look at my specs).

My cam was really good up to 6000rpm. With the heads I mentioned, the extra lift was certainly helpful. The engine will of course pull to 6400rpm redline, but for best speed wanted to be shifted a little lower than that. The off-the-shelf 268XFI option probably runs pretty well up to 6400rpm. These are just ideas, of course, based on what worked well in my car.

I would expect you would, yeah. I think I had 38lb Lucas injectors in mine.

So...I'm confused if as to whether you plan to use your TPI intake or a Mini Ram. Those are two different things. If you really use a TPI intake, you aren't going to get a sniff of 6000rpm, much less 6400rpm. You'll be capped at maybe 5000rpm on your best day, and a huge sacrifice of power. And you'll have to set a lower CR, probably around 9.5:1 if you want to run pump gas. If you use a Mini Ram then it won't limit your RPM at all and you can run 10.8:1 or more.

On your car, you have to have new calibrations "burned" into a new EPROM chip. I don't know who's doing that anymore.

 

I plan on using a mini ram. I thought TPI and Mini Ram we the same thing. Thanks for clearing that up. I'll try TPIS for the chip burning.

 

Not. Even. Close. In fact, you could argue they are diametrically opposed in concept! The TPI has very long runners and therefore resonance-reinforced torque peak around 2800rpm, but it also imposes a an out-of-phase resonance restriction on flow starting around 4000rpm, and just kills power above that. The Mini Ram has very short runners and has no meaningful resonance tuning either way: it neither adds nor impedes cylinder filling at any meaningful RPM.

 

383, crane compucam, scat crank, forged 10cc pistons , full toller 4 bolt block. 24 lb injectors, BBK/Edelbrock throttle body, daily driver. More power than i can use on the street.
remember, the more u build it, the more u have to play with it to keep it at it’s best.
remember these are not drag racers, but road cars. Everybody forgets that. 6000 rpm with that suspension, those gears, not for city driving because you are going waay to fast. unless you get gas every morning on the way to work, you are not going to get the most out of your combo.
nice to know the power is there. But after the first couple of weeks, with gas prices on the tise again, make it a balance of power and efficiency.
biggest problem is the 1-2 shift rpm drop. Your foot is in it or it’s a dog.

 

If only there was an affordable5-6 spd auto conversion that would be the cats azz!
Thats why todays cars are so quick. Renting a V6 charger...thing scoots due to it.
Never liked that drop either but what can ya do..

 

vader86, what size injectors and is it a stock ECM?

 

RPMs and valve control definitely don't get talked about enough. Guessing that's your reference here? And, things like redoing springs more often if building more radically.

I'm thinking it would be helpful (considering the number of suggested TPI stroker builds currently posted) to post your heads (cc), cam specs, and compression. Personally, I'm curious because you used 10cc pistons. Are those a shallow dish or flat-top?

Are you saying your tire patch won't stick well enough? I'm running 315's -- which help A LOT. And, yeah...running up to 6k rpm in the city isn't how most people drive. Plus, 6k rpm in 2nd is highway speed. Too many people only provide advice on how to build something they think will be a race car. This is a HUGE point NEVER discussed!!! Kudos for saying it.

There is a bit of consideration for efficiency...but not much (unless someone is building a 10-sec car - in which case they won't care). The number of cylinders and weight of car is a physics issue too difficult to "crack". In general, a build should land close to OEM MPG. Higher compression makes an engine more efficient. Having more power generally lowers it.

"Your foot is in it or it's a dog"? I think I get your drift. Mine is just as fun from 2nd-3rd...and even in 4th. Plus, it took WAAAY more than 2wks for the "fun" to change from euphoria to pride. LOL Gas prices could be a problem for awhile...maybe a long while? Building a V-8 to have more power will likely get more rare going forward. We know it's already less rare with kids building rice-burners to impressive numbers. Of course, it takes a V8 to SOUND like a V8!

 

Heads are mild ported 113’s, with the valves clearanced(unshrouded) , and the square under the spark plug contoured to aid flow. 59.5 cc’s.
cam advanced 4 degrees, running 4 18” C5 wheels, 10.5 wide, with C5 front brakes.
rear is a 3.07 dana 36 out of a 96. It had 12,000 moles on it, so it should outlast me😝.
trans is out of a 91 firebird with the tailshaft snd housing switched, swapped to a green vss gear. running a longer servo pin for more band grab.