Mr. Notorious

iTrader: (1)

So I've been talking to a comp cam tech about my 383 stroker build, they obviously suggested a small base cam to clear the rods. My block is the normal roller block 87-92 and I plan on running a hydraulic roller cam. However, it was then brought up that the small base circle cam needs taller lifters because the lifter falls into the bore too far and the link bars will hit the lifter bores. Which makes sense but as far as I could find comp cam only offers taller lifter with a vertical link bar so the price for the set of lifters is $600 from Jegs

That was way out of my original budget for roller lifters. Can I run regular height lifters, with just longer pushrods? Or will the dog bones bottom out on the lifter bores? Does everyone run longer hydraulic lifters for small base circle cams? Whats some options? Thanks!

vetteoz

iTrader: (13)

Confused.
If you have a roller block you don't need the retro fit linked lifters like you do for non roller blocks

In a factory roller setup ,the dogbones sit on a machined flat at the top of lifter bore; they can't go anywhere unless lifter drops below top of bore

Mr. Notorious

iTrader: (1)

Thanks for the reply. I understand what you mean. What I was trying to get across was my dillemma of aparantly needing taller lifters to make up for the small base circle cam. I wasn't sure if that was even true or not?

Then that brings up my next question saying that the only aftermarket lifters I found were ones with link bars, which are way too pricey and for retrofit applications. Are there any .300" taller lifters that don't have the vertical link bar?

Do people just build their 383's and log off this forum? (kidding)

88IROC350TPI

What makes you think you'll need a small base circle cam? I've built a handful of 383's and 400's and have never needed one.

Mr. Notorious

iTrader: (1)

I was the told the rod would swing up and hit the back side of the cam lobe in my application by comp cam. 4.03 bore x 3.75 stroke. Is that what you used for the 383 builds? 400s don't have the problem. Did you use 87+ roller blocks too? What rods did you use? I've read some are better than others.

wth

88IROC350TPI

the people working the phones at places like comp cams arent exactly experts and are more than likely trained to say all large stroke motors need small base circles just play it safe. The last 383 we built had 6" scat i-beams that are "stroker clearanced" from scat. even using a huge standard base cam there was a ton of room.

What rods are yo using? If the motor isn't together yet it'd likely be cheaper to buy clearanced rods or have the ones you already have clearanced than it would be to buy expensive lifters.

Also do you have a cam picked out? What are the specs?

vetteoz

iTrader: (13)

Most of the aftermarket rods with cap screws and not rod bolts with nuts clear fine
This style bolt arrangement

Guest

Supposedly there are issues with the stock lifter and bar arrangement and enough lift... which basically means the cam is a smaller base circle than stock. So if you buy a small base circle cam, I'd say you'd be guaranteed to have to run taller lifters or aftermarket style link bar lifters.

Werewolf SS

iTrader: (3)

Having just finished building my 383 and breaking it in I can guarantee you unless the cam is putting more than idk lets say .520 lift out the chances of the rod hitting the cam is minimal and it usually will only happen on one or two rods that would possibly need clearance. To clearance a rod you figure where the rod bolt is contacting the cam and then pull out a niffy to die grinder a grind the bolt at an angle till it clears with a little bit of space between the rod and cam. Or if you building the engine with new rods and pistons go buy a set of stroker rods. These rods come with cap screws the screw in from the bottom and lock the halfs of the rods together which means thier is not bolt head sticking out the top and that elemenates the problem all together. No matter what some clearanincg will need to be done with block as the crank is throwing a longer distance and this might me slight grounding on the bottom lining of the bores (for me it was just one).

That way you don't have to do anything special about small base circle cams and taller lifters and all that; you just get the right rods and your good to go.

Orr89RocZ

iTrader: (20)

I ran LS7 lifters on my 383 with small base circle cam and 87-99 roller block using factory dog bones/spyder. This was a rather big 286/306 230/245 .377/.383 lobe lift cam. (.603/.613" at the valve) Was close to my rods which were eagle h beams, but may have had plenty of clearance to run a normal cam. I never checked but there is no problem with running a small base circle cam with factory style lifters on those blocks. Plus it shouldnt cost any more money to get a small base circle over regular. My custom cam didnt and I beleive comp sells custom cams for same price as shelf grinds.

My SHP block is set up like GM 87-99 blocks and I still use the same LS7 lifters/dogbones/spyder setup on another small base circle cam for my 401" motor.

If you have an 87-99 roller block that has the dog bones/spyder setup like posted above, then get a set of LS7 lifters and run a small base circle cam. You dont need link bar lifters. There are aftermarket lifters out there without the lifter bars.

Mr. Notorious

iTrader: (1)

Awesome replies. Unfortunately the blocks rotating assembly is already all assembled. However I do have those 12 point style bolts on them. I purchased the block all assembled so I'm not sure if they are stroker clearanced rods, the build sheet for the motor doesn't specify.

To answer someone's question I'm getting part number 05-501-8, which is the XR264HR-12. If you have any input on it feel free to let me know. I'm going to order this cam up and yes custom grind cams are the same price for hydraulic roller cams.

After questioning the amount of taken off the cam for the small base arrangement a couple times, comp cams actually said a taller lifter isn't necessary (thank god).

Anything special with the LS7 lifters? Are they different than our 3rd gen stock lifters?

Thanks for a great thread! I'm sure someone that uses the search function will love all the information! Although it'll probably be too late for them too to buy clearanced rods unless they thought way ahead!

Orr89RocZ

iTrader: (20)

LS7 lifters are about the same as any thirdgen lifter except the pushrod cup may sit a little deeper. Other than that they are good to over 7000rpm and can handle a good amount of spring pressure. Plus, they are only about 120 bucks a set.

Why such a small cam? What compression will you be at?

Mr. Notorious

iTrader: (1)

10:1 compression, manual tranny. I'm going to take advantage of the Tuned Port by setting my powerband for torque from 1,200 to 5,200. It's just going to be a street stomper. Never will see the track or over 5,000rpm. I'm going to be doing a custom tune but it will be my first time tuning so I'm kind of keeping the cam mild. Do you have an additional suggestion I should look at? I was going to run their extreme energy 4x4 cams but none of them are computer controllable.

Orr89RocZ

iTrader: (20)

Cam doesnt mean computer controllable. You can run anything in these systems. Tighter LSA higher overlap cams may have problems running in closed loop operation with o2 sensor, but willl run ok at part throttle and higher rpms. When you tune you can mess with open loop without o2 sensors, or keep it closed loop.

What system you running, is it a MAF or speed density car? MAF will compensate for different conditions while speed density will take abit more tuning effort to run perfectly but still easily doable with that setup. MAF setup shouldnt take much more than stock tune with some timing changes and maybe a few open loop tweaks at first start up to run well.

You can run a medium small duration cam on a tight LSA and be fine with a 383. Those 4x4 cams arent anything special, just a tighter LSA. Infact I'd recommend one, as it will really boost the torque and mid range of that TPI 383. Should be a monster. Keep duration up in the 218-224 range and it will work great.

Mr. Notorious

iTrader: (1)

I'll be running a MAF setup. I planned on running closed loop, might as well let the sensors do the work since I bought them. I do want excellent idle to part throttle control and response of the motor. Maybe I'll check back over the specs of the 4x4 cam I wanted and see if I can find another one with less overlap.

You don't think I'd have any problem running a 4x4 cam without a dyno tune?

The Devastator

I ran a very aggressive cam in a 383 4 or 5 years ago and the cam lobes did hit the con rods. Lucky for me I lived in a family of machinists. Put the rods on a bridgeport and milled a little of the inside of all the rods and presto. Your machine shop should be able to do this for you.

Orr89RocZ

iTrader: (20)

I ran a very tight LSA cam on my car and it worked fine in closed loop. I just had one minor issue that I believe was due to o2 sensor not being ready (hot enough) to go into closed loop.

Since I had long tubes, that moves the o2 way down the exhaust path and the gases are getting cool by that point. The sensor was a heated sensor so it should get hot but i'm not sure it was.

Each time I restart the car after driving (Hot/warm restart) it would fire up fine, idle fine for a few seconds while initially in open loop then while switching to closed loop, it would start to go very lean and idle would drop to almost stall. Had to feed it gas to keep it alive. After about 20 seconds or so of that, it would be fine again. Just needed warmed up I guess.

I think i could solve that now by playing with the o2 ready timers. Number of seconds needed before switching to closed loop, or possibly one of the startup delay functions i'm not sure. Other than that minor issue, it ran great. I couldnt solve that issue after a week of tuning so I said screw this, go open loop and never looked back. Ran fine that way.

My cam was 230/245 on a 109 LSA and over .600" lift. Fairly big but not huge for a 383. Pulled to 6200 where it peaked and held power to 6600 or so. Any cam smaller than that shouldnt have an issue.

A local guy here, 2bfeard on this board has a 350 L98 with HSR/AFR 190's and 280XFI cam and that thing idles rock steady at 750 rpms in closed loop with MAF. No problems at all, infact its much more stable than my 383 ever was and thats impressive.

dimented24x7

iTrader: (2)

Which cam do you plan on running? Some of the smaller ones will work OK. The issue with tight LSA is that the more overlap there is, the more air will find its way into the exhaust at low RPMs. I ran CL with a cam, and it worked fine under normal driving, but the idle was always a bit rich due to the overlap.

Also, are you planning on the stock 3rd gen MAF setup? That will have some serious issues with keeping up. 255 grams/sec isnt that much airflow, and even a decent 350 turning at 5500 RPMs or so will exceed that limit. You might consider either running a MAF translator + LS1 MAF, which can allow you to trick the ECM into seeing more than 255 g/sec, or run speed density.

Your other option would be to run a later model GM SFI setup, but the cost can be prohibitive. Just the wire harness will run close to $700 or so.

Mr. Notorious

iTrader: (1)

Thanks for the replies. I was going to go with the XR264HR-12 which is what comp cams recommends for the TPI cars. Sounds a little like a stock one but the comp cams guy knew I was putting it in a 383, and I didn't want a hassle of tuning it. I was going to buy it today before my vacation tomorrow but now it looks like I'll be going back over some notes. Maybe I'll look for a 4x4 cam with 111 LSA.

I'm running eldebrocks 60859 alum heads, 52mm throttle body, siamesed runners, and a little port work on the stock lower base.

I'll look into that MAF translater setup you talked about. I never heard of it. I did figure I'd be pushing the limits of the stock one, but I also knew I was never going to hang out in the RPMs past 5000. Maybe just an aftermarket one will do, I haven't purchased any MAF yet.

Orr89RocZ

iTrader: (20)

When you max out the MAF, you just use PE mode to add in the fuel. My 383 killed the MAF by 4500 or so rpm, and I reved to near 7000. All PE mode adders.

NAASBC355

Speaking as a machinist that throws ballance off it's neccissary to do this but you need to get it ballanced afterward.

~Couch

Mr. Notorious

iTrader: (1)

Thanks for the replies. I can't do any machining since it's already assembled and internally balanced...

Do aftermarket MAFs work okay up to 5000rpm for a 383?

NAASBC355

internal/external ballance refers to how you ballance it not that it is in a state of ballance. Any time you change the rotating assembly weight you change the ballance.

~Couch