bnoon

I've got a list of parts coming in for the T.A. over the next few weeks and I need some opinions on my cam selection. The cam I've selected is:

Summit racing cam SUM-K1104

224/224 at .050 lift
.465/.465 lift int/ex
114* lobe separation

I've got a good flowing 3" custom exhaust on there and an exhaust cut out on the way for when max power is needed. I've also got SLP runners with a planned P&P on the plenum and stock base to match, plus adjustable FPR. Basically stock 305 TPI auto and torque converter running to a 3:23 rear. Custom chip will follow as more time allows. My question isn't about lift, rather, did I go to high on the lobe separation? To me, it just seems I may need a vacuum canister if anything...

BuckeyeROC

Yeah, that's a lot of duration for a stock TPI intake, whether on a 305 or 350. The lift numbers are on the small side though. To put it in perspective, I'd use about a 224/224 (but with higher lift) in a 383 w/ a SuperRam. I also think with that cam you'd want a 2800-3000 or so stall converter and some 3.42/3.73 gears.

If it's not too late, I'd keep looking at other cams. I'm not too sure what is working for the 305 guys though. Maybe the LPE 211/219 or an SLP 206 212 .480 .486?

kevinc

That's a lot of duration for a 305, even with the wide 114deg LSA.

With small-runner 305 heads I believe you risk holding the valves open too long and underfilling the cylinders as the charge reverts back out the intake valve...when the cylinder has more pressure than the intake runner and the valve's still open, reversion happens.

On the exhaust side, same pressure differential can bite you if the valve is held open too long...exhaust will be pushed back down the exh valve into the chamber if pressure in the exh runner is greater than pressure in the cylinder.

Personally, I'd go smaller on the cam.

bnoon

After talking with the Summit Racing techs, I think I may have actually made a good choice in cam. The 224 @ .050 (270 advertised) isn't that radical and can be used with the stock converter, though it is at it's limits and would perform better with a slight stall increase (nothing above 1,800-2,000 since it's not a racer) and/or gear swap. The increase in duration will not have to worry about reversion or blow by as much because of the lobe separation. The low lift will keep idle quality on the smoother side of rough. Overall, he said it's a very strong midrange cam. Should work well with the TPI manifolds and some tuning.

86 IROC

iTrader: (3)

The LSA is good, I think I'd step down one cam at the bare minmum - it will be split pattern. I think a split pattern cam will compliment the stock heads better. Take it FWIW.

bnoon

The cam is now sitting on my doorstep at home. Oh well, it'll still be better than the peanut cam. Not spending any more money on it to make a 305 try to go faster on parts I couldn't carry over to a larger motor. Just thought I'd change the cam since I have to pull the intake anyway to cure an oil seepage leak. The Summit cam was CHEAP and that made it my first choice from what I could remember about TPI's not revving to high.

Ed Maher

224 @ 0.050 in a 305 is like 234 @ 0.050 in a 350. In other words, it is most definitely what most people would call radical. It will defiitely at least 2400 or more stall, and in a heavy car like an F-body will also want more gear than 3.23s. You will still have reversion issues because that is dependent on the intake valve closing, which will be very late with that much duration and lobe seperation. And low lift has absolutely nothing to do with idle quality, the aformentioned late intake closing will take care of that.

In other words, you managed to talk to a summit tech that had no idea what he was talking about. While i'm sure it will work better than a peanut cam, something with 10' or so less intake duration would have been much more suitable. Especially if you think converters and gears are for race cars.

bnoon

Thanks Ed. I know gears and converters aren't only for race cars, but they aren't for cars that you don't want to spend a lot of money on either. With all of the cam talk going on earlier this week when search was broken, you'd have thought I could have memorized the recommended 305 TPI cams at the time I actually ordered it! Oh well... I could have gone really radical and gotten the 260+ duration and 550 lift cam my '70 vette had in it! LOL!

BadSS

Oh man,, twenty years of building engines, swapping cams, and tuning cars and all I had to do was call the Summit tech guy? What a rip. Anyway,,, Summit advertises the 1104 as a 282/282 cam ----- not 270.

You need to take a hit on the return postage and get the 1102 which is 262/272 – 204/214 –112 if you’re going to run the TPI. The 224/224 –114 cam in general is a real DOG – even in a 350. If you want to go “big” for the TPI you might have a snowball’s chance at being remotely happy with the 1103 – 272/282 - 214/224 –112. I don’t care if you take the advise (mine and others) or not,,, no skin off my nose. I just hate to see you back in here after the cam swap asking why your car isn’t running “right” or why you don’t have the performance you think you should have with the 282/282 cam.

bnoon

Believe me, after the stink this cam choice has made, there won't be any wonder left at all. The cam isn't going back though since the intake gasket fix is going in this weekend, which promted the cam change in the first place. Only has to last me a year anyway so that I can buy a new car outright instead of making payments... It's going to be hard though... these cars are fun to mod!

Ed Maher

I haven't heard that exact cam in a 305, closest was a 280 magnum in an L69 (230 @ 0.050, 110 LSA). That thing made like 12" of vacuum idling somewhere OVER 1000 RPMs and still cackled like a pro stock car. Granted what you're trying is a little lower in duration, but that wide LSA is going to put the intake closing so late that my feel is the idle will be still be as relatively unstable. It will also definitely have big reversion through the whole intake tract, even probably affecting the MAF.

BTW, low end will probably be junk too. The big cam 305 i mentioned above had a 2400 stall and 3.73s and it still came out of the hole like a dog.

In other words, you are actually going pretty far over the line on what works OK with fuel injection without major tuning efforts. And in the case of the MAF you might never get a decent idle because of the reversion. At the least you'd need to get in the chip and set the idle speed way up and probably play with MAF code thresholds too.

IMO it's very worth your while to not use that cam. Chances are good it will be nothing but headaches.

GofasterFirebird

iTrader: (3)

I have money down that it gets slower. Send it back and wait a week to do it!!

Vidman

Hi guys....

Not that I know what I am talking about but, I am switching to a 350 and the guy that is helping me with the motor called Crane and they said the biggest cam they'd recommend with a TPI is the Crane cam #113901 which has 204/216 @ 0.050 and lift of .427/.454 so we decided to go with that one and go with 1.6 roller rockers. Don't know if this will help, but that is what Crane said.

IROC315

iTrader: (9)

I have the 214/224 cam and am quite happy with it. My 305 isn't quite stock though. It's bored .060 over with ported 601 heads that have 1.94/1.50 valves. I had this on a carbed setup and it revved to the moon. I switched to tpi and it actually ran better within the lower rpm range. I've had some idle issues that come and go but I don't think it has to do with the cam.

Hawk92z-TDZ

Oi, that cam is almost the same as the one a friend is putting in his LG4 5-speed, 224/224 .470 .470 LSA 110

I take it a 305 TPI set up wont handle a cam thats size as well as a carb? Or is he in for abit of trouble? I thought TPI was better.

IROC315

iTrader: (9)

With the carb I felt it killed the much needed lower rpm torque. The tpi seemed to make up for it I guess.