I am starting to assemble the 327 for my TBI camaro. 327 are not set up for roller cams, so I'm planning to use a hydraulic flat tappet.

I am thinking 268 advertised duration is about as far as I should go for a street driven TBI car. I am looking at the comp XE 268 and the Lunati 60103. Both are fast ramp, 268 duration dual pattern cams.

I had a recommendation from Lunati to use a special version of the 60103 with 112 LSA instead of the standard 110 LSA. The regular 60103 specs are here http://www.lunaticams.com/CamSpecCar...rtNumber=60103

I notice comp has a special fuel injection version of the xe268 with 114 LSA instead of 110 LSA. The regular xe268 specs are here http://www.compcams.com/Cam_Specs/Ca...x?csid=86&sb=2

Does anyone have experience with the extra lobe separation angle version of either of these cams with a TBI system? What kind of idle would you expect?

327 + .060
9.9:1 CR
670 holley tbi on gm perf tbi vortec manifold
185 cc intake port, 2.02/1.60 valve vortec patriot performance heads w/ pocket porting.
probably 2500ish stall convertor
custom DIY tuning

The car is only for the street, just for the weekends, not a daily driver.

Thanks for your thoughts. The real question is - would these cams be a good fit for tbi?

 

To clarify, these cams would be fine with me in terms of performance, rpm range etc. The main question is if they would work well with custom DIY tuned TBI.

 

Here is my $.02. The 327 being that it has a shorter stroke and fewer cubes than a 350 will like to scream to make power. The 185cc intake ports and 2.02" intake valves will make this certain. You are looking in the right duration range IMO. The engine will want to turn to make its power, but I have a feeling you still have the 2.73 gears out back. You need 3.42s at a MINIMUM and really SHOULD run something like 3.73 or so. I am assuming you are running a tire around 26" tall or so. With the smaller cube 327 and lack of mechanical advantage from the shorter stroke, you will need the gearing help for sure. I would also look at the stall speed again. 2,500 rpm rating is behind a stockish 350 with very strong low-end torque. Behind the 327 you will probably be lucky to stall much over 2,200-2,300. A quality converter with a stall speed of 2,800-3,000 rpm is more in the ball park. Don't worry thoough, a properly built converter wil still be tight at part throttle and retain lockup at cruise.

If you have not already spent money into the 327 block, I feel you would be money and performance ahead to sell the 327 to a Nostalgia nut and get a modern "880" casting 350 roller cam block. The metalurgy advancements in the past 35 years are well worth it. Not to mention you get the 1 piece rear seal, roller cam provisions, better casting, 4 bolt mains, larger mains, etc. With the availibility of the 4 bolt main, roller cam blocks, I doubt I would build an engine without using this block. With ZZP deleted from modern engine oils, flat-tappet camshaft failures are common place and they tend to wear quickly. Roller cams are the way to fly, quite literally. More HP and TQ.

 

Thanks 355 - here's a little more background info. First, if I changed to a 350, I couldn't go by 327chevy anymore...LOL

Yes the late model 350 blocks are better metallurgy and technology. But...

I already had the 327 block from a previous project. I have already had the block preped (it didn't need much), already have the pistons, bearings, rings, etc. I just want to do this block. I already have it and it's a little different from everybody else to do a 327 in an 88 camaro. And everybody's dad pays attention when you say 327. I want to see if it really revs like they say.

You are correct on the metallurgy on the later blocks too - the nickel helps with durability. BUT - this car is not my daily driver. Probably going to be for cruising locally on Friday & Saturday nights only. So if we assume the older metallurgy would be good for at LEAST 50,000 miles on a rebuild (probably ok closer to 100k), that is 19 years at 50 miles per weekend. At 100 miles a week, I'm still good for 10 years.

I agree with you on the gears. I currently have the stock ones, but I will be upgrading. I was thinking 3.55 or 3.73.

Good thought on the torque convertor stall on a 327 vs 350.

And you are also right on the zinc in the motor oil. As far as I know, the zinc is still in the "racing" oil - that is what I plan to run.

And yet again you are right on the 2 bolt mains. But considering that the old 375 horse 327 corvette engines held together on 2 bolt mains - I am thinking mine will do the same on new arp bolts. I hope to be in the 375-400 horse range at the flywheel.

Anyway, not arguing with you, just sharing how I got to where I am on this buildup. (And how I rationalized the 327 decision.)

So, back to my main question...anybody have a feel for how these two particular cams would work with the TBI system (assuming custom tuning)?

Even better - has anyone actually run these cams with TBI?

 

Very good, was just making sure that you knew what you were up for. Like I said, if you haven't already spent money on the 327 block. If you were going to spend $$$$ into the short-block like a few 15-17 year old kids have decided to do in the past. But the 327 can definately be made to do what you want.

I have not run either of those cams, but I know of a crossfire vette owner that lost his crossfire for a 454 TBI assembly and runs the XE268 cam, not the XFI version either. He is running it in a 350 with a stick and has commented that the low-end under 1,800 rpm or so is NON-EXISTANT and thats in a 350. In the 327, its going to take an even bigger hit. Thats why I was trying to let you know what you are in for.

I have run the old L82 grind in my personal TBI 305. Its 291/287 @ .004, 224/224 @ .050, on a 114* LSA. I was able to make it run very well on TBI. Took some work dialing it in, but it ran well.

I am running a smaller roller cam now and it runs very well with my ported vortecs on my 350. Stock 3.08 gears, 29" tall tires, and 1,600 rpm tq converter BTW. Pulls crisply to 5,500 rpm with stock TPI runners. With a 454 TBI on a single plane intake manifold it would easily pull 6,000+ rpm.

 

I run that XE268! doggy under 2000 rpms but I do cruise in 5th gear at 1600 rpms and 58 MPH OK. Under 58MPH I need to shift to 4th and then tach shows 2100.. Engine wakes up 3400 rpms and I shift at 6000. 3.07 gears . manual trans. I would suggest you look at next one up on chart XE262 218/224 @ .05 with a 114 LSA. the 114 LSA makes it tunable.

ps yes I know I need gears(3.55).

 

I knew it was you, just did not want to single you out. I guessed you would post anyway.

 

Ronny - so you run the 110 LSA XE268 in a 350 with TBI? I am planning to set up my governor to shift @ 6000 rpm @ WOT. That puts me at about 3000 rpm after WOT 1-2 upshift on 700r4. You mentioned it comes alive at 3400 rpm, what's it like at 3000? I hear you on going one step smaller but I really want this thing to be tough...I will think about the 262 though. Do you happen to have any sound clips of your combination?

I am thinking that in my case, the automatic with 2600-2800 stall would help on the low end. Plus 114 LSA = less overlap and better low end than 110 LSA, all else being equal. Of course I do have a smaller engine...

 

Fast, can you clarify the differences between hydraulic flat-tappet and hydraulic roller-tappet? Didn't engines such as the LO3 have flat-tappet cams stock? And would an engine such as the LO3 have the ability to use a roller cam?

 

89RS, Flat tappet lifters are simply flat across the bottom. As the cam rotates under them, the lifters slide over the top of the lobes. Picture of flat tappet lifters http://store.summitracing.com/partde...0&autoview=sku

Roller lifters have a steel "wheel" on the bottom that rolls on the cam as it turns. Picture of roller lifters http://store.summitracing.com/partde...0&autoview=sku

In both cases, the force of the valve springs is pushing the lifters down against the cam.

Sorry for the ford pictures...thats what I found first.

So for a flat tappet cam & lifter set to survive, the oil needs to contain the zinc substance, which helps prevent wear in this "sliding" contact.

The zinc stuff is not needed for the roller cams because there is no sliding contact at the lifter. Only a rolling contact. Regular oil w/o zinc is not a problem for the roller lifters.

 

So the disadvantage of flat tappet is reduced longevity due to more wear and tear on the lifters correct? Other than that, roller lifters really don't have much of a performance advantage right?

 

This will be over simplified. Roller cam & lifters also have a greater performance potential than do flat tappet cam & lifters.

The reason is that due to the rolling contact, the ramps on a roller cam can be steeper than they can on a flat tappet cam.

Cam designers can use this in more than one way. Given the same advertised duration (time in degrees from point at which the cam just starts to lift the lifter away from the base circle to the time the lifter just returns to the base circle) on a roller vs flat tappet, the designer can:

1. Achieve greater peak lift with the roller design. The steaper the ramp, the higher you can open the valve before you have to turn around and start closing it.
2. Keep the cam open longer at a given lift. A common way to rate cams is at .050" lift. So if the two cam types started opening and also closed at the exact same point, the one with the steaper ramps would get to .050" lift sooner and would stay open to at least .050" longer. So the two cams would have the same advertised duration, but the roller cam would have greater duration @ .050" lift.

The performance is an "area under the curve" situation. Both how high the valve is lifted and how long it is open matter to performance.

To over simplify, the advertised duration is what the engine "feels" at low rpm (more is worse) but the .050" duration is what it "feels" at higher rpm (more is better). So another possible advantage with a roller cam compared to flat tappet is if they both had the same .050" duration (for higher rpm performance), the roller cam with the steeper ramps could have a shorter advertised duration. In this case the two cams could have similar high rpm performance, but the roller would idle better and have better low end torque.

 

Well i think I'll add my $0.02 to this aswell. I run the xe268 in a 350 tbi and my converter stalls at 2200 and I have 3.42 gears. The first suggestion I have is to go with a higher LSA. Tunning mine was a PITA. I have personally been looking to do a cam swap to the XFI268. More power at a lower rpm makes for better bottom end and it also has a 113 LSA which would seem to make tunning alot more friendly. Also dont forget the retro-fit roller set-ups.

 

I decided to go big. I got a Lunati Voodoo 268 cam (60103) for Christmas. It is similar to the XE268 that a couple guys here have discussed. I installed the cam, so now the 327 shortblock is almost complete.

I do understand it's big-ish for the TBI. And it does have the tighter 110 degree lobe separation angle. So it sounds like I'm in for some tuning fun. I knew I'd have to tune anyway due to other changes (displacement, heads, 670 holley, exhaust).

Can Colt45s or Ronny comment on the specific difficulties that the tighter 110 LSA poses compared to your suggested 114 LSA (given that I will be tuning anyway)? I'm not asking how to tune - I'll done some reading there and will save those questions for another thread. The question is in what way is the tight lobe separation making it more difficult?

(made up example answers: can't tune out a part throttle surge -or maybe- won't hold a steady idle)

Thanks guys.

 

What I did to improve idle quality is as follows:

1. I idle open loop. off idle is CL.

2. I idle somewhat enriched within open loop tables. Approx 5%. WB shows
.95-1.00 lambda.

3. I set my commanded stoich value at 14.2.

4. I raised my lean median rich 02 swing points about 10% higher to achive an enriched idle A/F. In fact that enrichened all CL operation. I cruise at 1.00 lambda CL.

Now I run 80lbs injectors at 20 lbs FP. I idle at 14 lbs or so. I reduced the proportional gains a tad due to larger injectors.