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Thread: Everyone needs cam help? So do I
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12-06-2020, 09:28 PM #1
Everyone needs cam help? So do I
So I'm building my 96 LT4 corvette into a 383stroker with some spray see build here https://www.instagram.com/silver_surfer_lt4/ I got a set of 195cc heads and ordering the eagle 11:1 forged stroker kit as soon as the motor is out. I am trying to keep compression around 11.0-11.2:1 and stock RPM range and gears. But whats stressing me out the most is cam selection. So I'm hoping to get some input.
Originally I was looking at the comp cam XFI 07-468-8 https://www.summitracing.com/parts/cca-07-468-8 But my engine builder told me its to big with out me re-gearing that he wanted to put in the XFI 07-467-8 https://www.summitracing.com/parts/cca-07-467-8 I know almost nothing of cams. talking to others it ws suggested I get the zz409 cam https://tpis.com/products/6_cam160?v...28342563799112 or even 226/232 .578/.574 110 LSA. – 1900-6200 RPM from http://elliottsportworks.com/?page_id=32 anytime I talk to someone about the Comp cam my engine builder suggested I get "Thats an ok cam" I ask what they reccomend and they just say go with what your engine builder wants to put in. Someone told me with that cam I will be around 400whp with my build. I was shocked at I was shooting for about 50 more without spray. I am pulling out the engine tomorrow and its crunch time and I'm stressing over this. I have no idea what kinda gains between all these cams or how they respond comparatively or if there is something else I should try. Any input would be great.
ThanksLast edited by silver_surfer_lt4; 12-06-2020 at 09:31 PM.
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12-07-2020, 08:36 AM #2LTX Member
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Personally, I have found cam information from many sources to often be not the best choice, for me. This includes some high reputation engine builders locally here in Minnesota. I think what happens is that folks don't take a good look at the intended use of vehicle closely enough to fully understand what is best for the owner, and of course are tainted by their own preferences of use and the ever presence of the "more hp is always the best". Engine builders, I have found, almost always recommend more cam that than what I settled on after testing a few in use. Matching all the other things counts big in cam selection as the cam can't really do anything about not enough or too much stall, wrong rear gears, trans gear ratios, manual or auto, spray, turbo, supercharger, E85, good or bad quench, and all the other things, if they don't match among them all.
An immediate question for me would be how the spray is going to be used. Is it to get a under geared setup of the line quicker or is it to get more top end once the traction is better so not going to fry the tires? Shift points? Tires? etc. Dose the engine need to be comfortable to drive in a the typical slow cruise around a big car show? Does it have to be OK to drive 300 miles on the freeway without driving you crazy?
I just went through all this again, for the first time in many years as I sold off the the hotrod a while ago, for the engine I am building for my 96 RMW which is a heavy, summer use as my only vehicle, go to the home center, vehicle that I also want to be a bit more fun but still comfortable to drive anywhere and any distance. The most common recommendation I got was a cam that was way too aggressive, 3.73 gears, and a 2500 stall converter. This would make the car quite unsuited to my desired purpose. I currently have the heads out getting done, block machining to follow when I get them back and get final chamber CCs. It will be done at a race engine based shop that does very good work. It has changed to new owner since I last used them, but the owner was very receptive to listen, just as the old owner was very interested in matching to application. He is in the process of looking at the cam/piston/valve spring/ etc combo as a final confirmation, but he was onboard with the use pattern and first impression was it would be a good match. It will be a custom grind, which really don't cost much more than a stock grind, so I can get just what I wanted. Being able to chose individual lobes and separation angle gives you lots variations in design to be able to get the results you want for your particular application. By biggest unknown is exactly how the reverse flow cooling actually affects the selection of parts as there is very little real testing out there to look at, but once I get it together I will have a much better idea.
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12-07-2020, 10:08 AM #3"The Rock"
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I'm an idiot when it came to cam specs. I simple called LLOYD and discussed what I wanted, explained what I had, set up wise... and he told me what I should do... I wish I could provide more help, but the best I can say from my experience, was talking 1 on 1 with L.E.
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12-07-2020, 08:02 PM #4
thanks for the input
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12-08-2020, 09:53 PM #5Long Live the Opti
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Just my $.02 from my experience. That 242/248 you're looking at is too big to be able to run to high RPM with those small heads on a stroker.
Look for a 10-12* split I to E duration. Your heads are going to be the limiting factor on your motor.......195 CC isn't going to feed a 383 in the higher RPM band. A huge cam won't make up for that and will cost you power under the curve.
I'd shoot for something like a 218/230 or 224/236 using the the comp cams profiles as a base. You start getting too big on duration you're going to cut your bottom end without getting a countering gain on the top end due to the heads.
Or call Lloyd Elliott and have him do you a cam up.
Again, this may not exactly be "technical" information, just a hand full of years worth of experience on the platform.
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12-10-2020, 07:57 AM #6Xtreme Member
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Supporting Membercall lloyd elliot. with the small head i dont see much more than a 228/236 in the upper .5xx/low .6xx lift range on like a 110lsa.
on the impala before i sold it to popo i had shoved a 228/236 592/592 on a 110 cam in there with a 3k stall but no gears. car sounded awesome but was a slug. popo put 4.10's in it and it woke the car up big time.
i think you need to do atleast 3.73's and a small stall. driveability was fine and i daily drove the car when i owned it, and popo daily drove it as well. WITHOUT the gear change, it did have some cam surge down low.Last edited by SSlowBoat; 12-10-2020 at 07:59 AM.
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1994 Firebird Formula 381 stroker - Carrying the torch! - 9.90 @ 134.3mph on a 200 shot
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12-10-2020, 09:34 AM #7LTx Guru
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Couple questions..... do you need to pass tailpipe emissions? Is this basically for street fun, favoring good bottom end torque, or a track car looking for HP on the top end? How much nitrous? The larger the shot, the more you need to reduce overlap. You can lose a lot of nitrous with blow through. You may need to open the exhaust valve sooner and stay closer to 112-114 LSA. And follow Sean's advice on increasing the I/E split to 12°. Bottom line, make sure the person who designs your cam knows the answers to the above questions.
I believe your C4 has a 3.45 rear (wasn’t the LT4 only available with the M6 trans), and the ZF gear ratios are similar to the T56. I would strongly agree with Shaun's comments regarding a small stall (if itsactually an auto trans) and gears of 3.73 (or whatever is available for the C4 rear) and higher.
I'm not on Instagram, so I couldn’t look at your build. What are you referring to as 195cc heads. The factory LT4’s are 195cc. Trick Flow makes a 195cc. Are you using them “out of the box”, or having them worked by someone like Lloyd Elliot?SOLD - GONE TO A (VERY) GOOD HOME ! - 94 Formula A3+1: 381ci forged stroker - Callies Stealth, Oliver 5.85 billet rods, BME nitrous pistons / CNC LT4 heads / CC solid roller / TH400+GearVendors OD / 4.11 Strange 12-bolt / 300-shot N2O / Spohn Suspension / roll bar / MoTeC M48 Pro engine management system /a few other odds 'n ends.
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12-13-2020, 07:21 AM #8Xtreme Member
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I looked at your IG and see the heads are 195 AFR Eliminators. Getting enough air through the motor is going to be a challenge as the 195's seem a little down on CFM. I think 450whp is a little unrealistic without more compression and the biggest hydraulic roller cam you can find, more unreasonable than the 468. You wouldn't have to work as hard with a better cylinder head.
Might be apples to oranges, but I can give you some #'s from my motor to compare. I made 414whp SAE or 425whp STD if you wanna be a cheater. Loose 383 intended for FI, 9.5:1 CR, Lloyd's 226/239 0.565/0.587" 114LSA cam, AFR 210 Eliminators. The 210's have a significant advantage on the intake side at equal lift (301 vs 280 CFM @ 0.550"), but I don't know how they compare beyond 0.550" because AFR specs stop there for the 195's. I'd imagine the gap keeps widening. I didn't make peak power until 6.1k and don't shift until 6.5k which is beyond the stock rev range.
If you're looking for a true 450whp, I would dump the 195's for something better like the 210's/227's or LE Trickflows and go with a cam a little bit bigger than mine on the int with a tighter LSA. I'd also boost the CR up around 12:1 if you have 93 in your area.96Z M6, ERE-383 #60, AFR 210s, LE cam, 9", Procharger D1, ???whp
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12-19-2020, 08:19 AM #9
Hello everyone thanks for all the input! My engine builder, tuner and comp cam all suggest the 230/236 cam. I spoke with Lloyd he did suggest a cam in the 22x/230x area however he cant do custom cams right not as everyone is out of cores. I went with the 195 afr heads listed here https://www.airflowresearch.com/195c...cylinder-head/ as I was trying to not get all crazy with RPM's. was originally shooting for stockish rpm range. looks like im looking at 6500rpms now. only 300 more then stock. as for compression ratio. My engine builder and I have been going back and forth for weeks now. Originally I wanted 11-11.5 which he advised was not a good idea as we apparently have shitty gas here after explaining lt4 vs old SBC differences . I am now shooting for 11.5-11.8 c/r he said he wont build me a 12:1 unless I am doing something about fuel and not running pump gas. Back to the heads AFR suggested that head as I originally wanted the 210cc they said was too big for what I was doing then I was all about the 195 competition heads. Which for the money everyone suggested it wasn't worth it for my build. So I donno. Other info you guys asked for I am doing a 150 shot of spray, stock gears 3.45 on a manual trans.
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12-19-2020, 08:20 AM #10
Llyod was very helpful. The 24x cam is competently out of the question now.
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