It seems just too spendy to go through all of that. Especially given I already have an intake and a set of roller rockers from the original motor. I can (will) use a retrofit roller cam/lifter setup, which overall would still be cheaper in terms of added expense. I'm picking up a complete 350 with good block and 202 heads for 300 bucks. i don't think I'm going to touch a complete roller block for anywhere near that, if I can even find one.
Have you checked the price of link bar lifters recently? They've gone way up Have you checked www.car-parts.com for a roller block or engine?
I find it hard to believe that a factory roller block is more expensive than a roller cam conversion.
quote
Originally posted by Taijiguy:
I'm willing to spend some extra, but I have to be realistic about my cost/benefit. It's just too complicated, and not really worth it to me.
I find it hard to believe that a factory roller block is more expensive than a roller cam conversion.
Well, aside from anything else, I just see that 2 piece adapter as another potential point of failure. And yeah, from what I've been able to find puts the factory roller blocks at quite a bit higher than older blocks. Overall, it just seems that it's more cost effective to stay with an older block.
Not a lot of progress on the build at this point. I need to get the car out of the garage so I can have the room to build the engine. Plus, I'm paying cash as I go, so I'm trying to control myself. A lot going out to the machine shop, and buying up parts. I haven't really finalized what the end product will be, so I'm still considering all that and keeping my eyes open for parts. I prefer to buy some things used if I can so I'm trying to be patient and keep track of the ads on Craigslist. Did get a lot of stuff out of the garage, and have a guy coming to pick up a bunch of scrap metal, including the old block that isn't any good, and probably set of lame heads that were on a block I bought. Still trying to find a good set of heads- I have opened up to the possibility of going with vortec heads, but obviously that will require a different intake, which I didn't really intend to buy.
Well, aside from anything else, I just see that 2 piece adapter as another potential point of failure. And yeah, from what I've been able to find puts the factory roller blocks at quite a bit higher than older blocks. Overall, it just seems that it's more cost effective to stay with an older block.
Link bar lifters are way more expensive than factory style roller lifters also...
The rear main seal adapter isn't that much different than what GM did on the 1 piece rear seal blocks.
Although, I just found that there's a local u-pull-it yard that sells long blocks for 100 bucks. I'm going to go see what they have this coming Saturday. If they have a roller with vortecs then it's more than worth it.
The issue is (partly) that I already have a regular long block sitting on my stand just waiting to be rebuilt. Buying another engine when I already have one would (generally) be more expensive than just using retrofit roller cam/lifter kit. But if they have one then It will probably be worthwhile at that price.
Had a decent day today. The first thing I need to do is get the body out of the garage. It's been sitting on jack stands for the last 7 years with no cradle. Today I got a temporary cradle under it, got tires mounted and set it on its own four legs for the first time in a very long time. I'll push it out into the sunshine later this week.
I also picked up a 400 crank for the stroker build. It's an old cast crank, but it's been worked on by Lunati. I'm not exactly sure what they would have done to it, but it has their stamp on it. This would have been done back in the 70's. If anyone has any information on what they might do to factory cast cranks please let me know, as outside of maybe balancing it and/or polishing the journals, beveling the oil passages and whatnot, I'm not sure what else there would be to do. I was told that the 400 it came out of was in a Vega.
Haven't had too much to report over the last couple of weeks as I was patiently waiting for the right motor. I begrudgingly accepted that Will was right, and that a vortec would ultimately be the best choice because it would be a factory roller motor. The significance of that is that the lifter bores are somewhat longer which makes the lifters more stable in the bores. Also it would come with the heads I wanted. The boneyards would have been an OK choice, but after talking to them I decided it would just be a major pain in the ass to try to pull one, and was willing to pay a little extra to get one already out and disassembled that I could inspect it. I scoured Craigslist for the last couple of weeks and finally found one in town for 250 bones. It was exactly what I wanted, an 880 block with a roller cam and 906 heads.
Obviously it needs cleaned up, been sitting for a few years disassembled, but the lifter bores are smooth (outside of the surface rust) and the cylinders are going to get opened up .040 to accept a set of Sealed Power hyper stroker pistons. I also found a guy on CL selling a set of brand new Eagle forged 350 rods for 300 a set.
It will go to the machine shop for a little bath, then I'll bring it home with the 400 crank with 350 mains to clearance the rods, and check to see if it'll clear the cam. I'll also radius the oil returns and grind down any slag or casting marks and take it back to the machine shop for new cam bearings, line bore the mains with some ARP main bolts, and then a final bath. By the time that's all done I should have most of the parts I need to start putting it together.
Factory roller lifters. No reason to not reuse these, as these motors are generally good for a couple hundred thousand miles, so they must be pretty decent quality. I'm soaking them in solvent right now. I'll clean 'em up all nice and shiny and reprime them with fresh oil and they'll be good as new.
Vortec heads. Nothing special from the outside. These will get a light port job, new Lunati springs and retainers, and full roller rockers.
I hear it's really easy for someone who doesn't know what he's doing to screw up the Vortec heads, and even someone who does know what he's doing can't improve them much without cutting a LARGE amount of metal.
I agree with Will, the only thing I would do is set them up to handle .550 lift - that used to require machining the valve guides, but now I think you can use the LS(x) retainers and behive springs and get there w/o machining. Vortec heads flow quite well as cast, you just need a matching intake, camshaft, and exhaust to get the most benefit from them.
I primarily planned on just cleaning them up some, and smoothing the exhaust port. No gasket matching or hogging. I already have the spring part covered, Comp sells a tool that lets you use a drill motor to cut down the spring guides and create a pocket for more lift. It's like 40 bucks, much cheaper than a machine shop, so I'll be ordering one of those. I already have a set of Lunati springs but they aren't beehive type. I'm probably just going to go with those.
Been selecting my parts, as usual, the cam is proving to be the most difficult choice. I picked up a set of +.040 hyper flat top pistons which will give me somewhere around 10.5 or 11:1 CR using the vortec heads with 64cc chambers and more or less stock specs for deck clearance etc.
Even balancing the motor I suspect it'll have a top RPM of 6K or so, and I want it to be street-able. I'm considering this cam- Comp Thumpr roller-
Assuming everything else is even close, Desktop Dyno shows around 400hp at near 430ft/lbs torque with that cam.
[This message has been edited by Taijiguy (edited 08-21-2014).]
10.5 to 11.0 compression ratio might be a little high for a street driven car. I was able to run 10.2:1 compression on mine (Vortec heads as well) with 89 octane, but it was fuel injected. For a carbed setup, that compression might be a tad too high.
I don't know if he does older SBC applications, but Pat G might be able to custom spec a camshaft for $25-$40, then you get it made by Comp or other camshaft grinders. With your higher than ideal compression, you may NEED a cam with more overlap to help keep dynamic compression in the safe range and part of the custom camshaft spec includes dynamic compression ratio. http://www.guerragroup.com/#!camshaft-help/c1mq5
I know it's pretty high. And I paused before buying the pistons but based on a lot of research I saw it seemed it would be OK. Frankly, this is an interesting experience. The last time I built an engine this deliberately (meaning as opposed to just throwing a bunch of parts together and hope for the best), I was still buying gas with lead in it. This also the first 383 I've ever built from the ground up. I guess I have to admit to being pretty rusty, not to mention out of touch with how much things have changed in the last 30 years, and how much is available.
I like the Thumpr cam, so will probably stay with that, even if I end up reducing the CR, it only needs 9.5. I'll have to redo the valve spring seats to run it, but then, just about anything over .420 will need that anyway.
I'm not too proud to take advice. If anyone else has thoughts about the CR, or other suggestions, I'm certainly willing to listen.
Been selecting my parts, as usual, the cam is proving to be the most difficult choice. I picked up a set of +.040 hyper flat top pistons which will give me somewhere around 10.5 or 11:1 CR using the vortec heads with 64cc chambers and more or less stock specs for deck clearance etc.
Even balancing the motor I suspect it'll have a top RPM of 6K or so, and I want it to be street-able. I'm considering this cam- Comp Thumpr roller-
Assuming everything else is even close, Desktop Dyno shows around 400hp at near 430ft/lbs torque with that cam.
Like Guru said, that's a lot of compression for iron heads. If you keep your piston to head clearance not more than .040, pay attention to head gasket bore, etc. it may be streetable, but it will definitely be premium fuel only... and 91 may not be enough (I know 93 isn't available everywhere).
Are you sure that's a roller grind? Looks like the split between seat-to-seat and .050 duration is pretty wide; the sheet also says lumpy idle. Good profile selection should be able to keep the lope to a minimum without sacrificing much (or maybe any) power.
I also wonder if that is a roller cam. I think you would be happier with a 112 lobe sep. You will have a smoother idle, better vacuum and stronger mid-range performance. The exhaust duration seems excessive. Look at a Competition Products catalog for a wide range of cams. Try for more lift, 1.6 rockers are easier on valve springs, less lobe separation (around 112 degrees) and a 5 or 6 degree difference in the duration, somewhere around 230 at .050 on the intake, 236 on the exhaust. I think this is plenty of cam for a 350 cid motor. You can bleed off excessive cylinder pressure with a wide lobe angle but starting out with a better gas friendly ratio is really much better.
The thumper cams are factory rollers, but they mess with the valve events to make the idle rougher than needed and they are more about the sound vs. power.
The last SBC swap I did ran this cam (its a fuel injected cam so it will have a smoother idle and better vacuum, but it will still have an idle lope - especially with a carb). You might try running it in desktop dyno to see the difference. BTW - with 1.6 rockers, you need to machine the heads to run this camshaft. This camshaft will also need some strong valve springs with 1.6 rockers. http://www.compcams.com/Com...s.aspx?csid=209&sb=0
The thumper cams are factory rollers, but they mess with the valve events to make the idle rougher than needed and they are more about the sound vs. power.
<snip>
That was the appeal Although, 400hp at 400 plus torque seems pretty powerful to me.
Although, I'm kicking back forth how rumbly I want it to be. I really get a chubby over a lumpy idle, but then, the idea of a more subtle street menace also seems like it would be fun.
[This message has been edited by Taijiguy (edited 08-23-2014).]
Peak numbers are nice, but what you really drive on a day-to-day basis is the breadth of the powerband. The lumpy cam will unecessarily sacrifice low end torque and the breadth of the powerband to produce an engine that's peaky when it shouldn't be.
Peak numbers are nice, but what you really drive on a day-to-day basis is the breadth of the powerband. The lumpy cam will unecessarily sacrifice low end torque and the breadth of the powerband to produce an engine that's peaky when it shouldn't be.
Frankly I've run more cams through DD than I can count. Even been running Comp's CamQuest software, and there's really not a whole lot of difference on the numbers when comparing apples to apples. The one thing I liked about the Thumpr is that it starts at 1900 rpm, and I'm (for now) running the Isuzu 5 speed, which means the cam should be comfortable cruising at 70mph in 5th. If I use a cam that doesn't pick up until 2000 or 2200 then I expect it'll load up pretty good under those same conditions. I could drop to a less radical profile, but then HP and torque numbers drop way off. The XR282HR has really good numbers, but doesn't gather itself up until 2200 rpm. The Thumpr has similar numbers but picks up at 1900. The 4280 drops HP by 3 but picks up an extra ft/lbs on torque 461 up to 462 but drops the usable RPMs down to 1800. Both peak torque/hp at 4000/5000 respectively. I'd say overall I'm leaning towards the x4280HR or the Thumpr. I guess the ultimate determining factor would be how lumpy I want the idle. I'm expecting to run a vacuum canister regardless. Does anyone know offhand the cruising RPM (60-65 MPH) of the Isuzu 5sp with stock tire diameter? I seem to recall it being around 2000 or so....but then it's been over 10 years since I've driven my Fiero
Comp doesn't share their valve events at .050 lift on their website, just .006". All the camshafts have a suggested powerband, but overlap at .050" is really what will determine how well the car runs at low RPM's. The more overlap, the worse its low rpm manners (sub 2000 rpm). You might try googling each camshaft to find a thread where people share a picture of the cam card with the valve events at .050"
Thumper 283THR7 1900-5600 XR282HR (2200-5800) 280XFI HR13 (2000-6000) - this is the one I recommended and have used before.
Cruise RPM at 60 mph with the isuzu and 24.6" tires is right at 2000 rpm.
The 224/232 camshaft I run with my LS4 has 2 degrees overlap at .050" and will pull all the way down to 1300 rpm when under load. During very light throttle (near coasting) conditions, it can buck from time to time up to 2000 rpm. Over time you get used to it and alter your driving style to either just clutch in when coasting or upshift to put more load on the engine (reduce engine vacuum). Its not uncommon for me to be in 6th gear in town at 45 mph.
Carbs have a huge disadvantage running large overlap camshaft. The air that escapes during the overlap will be an air/fuel mixture, so fuel economy will suffer. With OBD2 fuel injection, you can delay the injector spray to happen after the exhaust valve closes, so only air is lost during the overlap event - so you can run an overlap camshaft w/o as much of a fuel economy hit.
Will- Not sure how to answer the question. Both CamQuest and DD show a curve. CamQuest gives a curve but the graph isn't specifically marked, they show peak hp and torque, as well as average for both. DD's curve seems to start at 2K for all simulations. I have some screens I'll post up later.
Guru- CamQuest gives cam events seat-to-seat. DD let's you enter cam events at .50
[This message has been edited by Taijiguy (edited 08-25-2014).]
All those tools give you is the WOT power band, for drivability, you want to know how the cam will behave at power levels south of 50 hp.
Overlap at .050" is the best indication as to how choppy the idle is and what kind of part throttle manners it will likely have. If you can find copies of the camshaft cards for the cams you are looking at you can compare the overlaps between them at .050". The lower the overlap, the less chop the idle will have, but it will drive better. The more overlap it has, the more it will chop at idle and its drivability will suffer.
Overlap at .050 makes it quite easy for the exhaust gas to be pulled back into the combustion chamber during the intake stroke when manifold vacuum exceeds the scavenging effect of the exhaust. At low levels, this is a good thing as it acts like an EGR, but at higher levels it causes low rpm, near closed throttle "bucking". The lower the overlap, the better its low RPM response will be and the better street manners it will have.
With OBD2 fuel injection you can make several adjustments to improve the drivability of large overlap camshafts, but options with a carb are very limited.
For what it's worth, I remember reading some literature about the various factory cast Chevy V8 blocks where it stated that factory 4 bolt main blocks had a weakness. The main webbing area (the area of the block that supports the crankshaft main bearings) is very thin in the area where the outer main bearing cap bolts (those only used in 4 bolt main blocks) install into. The literature said testing had proved that factory 4 bolt main blocks were actually weaker than 2 bolt main blocks because of the holes drilled into this thin webbing area of the casting. It was said that a factory 2 bolt main block that had ARP main studs installed actually proved to be able to handle more power than a factory 4 bolt main block. That having been said, a splayed 4 bolt main setup is much stronger (but no factory blocks were ever offered in a 4 bolt splayed configuration, that is a conversion that requires a 2 bolt main block and custom machine work).
Concerning the L31 vortec heads, they flow pretty well right out of the box. If you are going to do any porting work to them whatsoever, I recommend you focus your attention on the exhaust side and not worry so much about the intake ports. I have an article showing stock flow port numbers for the Vortec heads, and they are as follows:
As you can see, these heads (with stock ports) don't make much use of valve lift much above 0.500", at least stock.
But as was mentioned earlier in this thread, if you don't know what you are doing and you try to do your own porting work, you can easily make the ports flow worse than they do stock. There are a couple of books available that explain basic porting work you can pick up and read that will give you an idea of what needs to be removed & where in the port without screwing them up. I would highly recommend you get such a book and read it before you attempt to do any of your own porting work IF you don't have experience with where to remove the material from.
Concerning the factory vortec lifters, if you are going to use an aftermarket cam, I would definitely contact the company who makes it and get their advice on what lifters to use. Cams with radical profiles (that require stiffer than stock valve spring rates) tend to require a hydraulic lifter with a higher internal preload spring than what the factory lifters come equipped with.
-ryan
------------------ OVERKILL IS UNDERRATED Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com
[This message has been edited by Darth Fiero (edited 08-25-2014).]
Overlap fills the torque curve. Even as the powerband is moved around, an engine with a constant ratio of head flow to cylinder displacement will like a more or less constant overlap (measured in degree-inches, not just degrees), with the RPM of the powerband determined more by duration, while the shape and peakiness of the curve is influenced by overlap... too little overlap and the curve is flat, missing out on a lot of peak power; too much overlap and the curve is peaky, missing out on a lot of low RPM torque and area under the curve.
Higher flow heads on a given cylinder size like less overlap for the same powerband shape.
This is in addition to the drivability problems that Guru mentioned.
Overall, stay conservative with the camming OR have option A, B, C, etc. and be ready to spend the money in a methodical way to find a cam you like.
quote
Originally posted by Darth Fiero: But as was mentioned earlier in this thread, if you don't know what you are doing and you try to do your own porting work, you can easily make the ports flow worse than they do stock. There are a couple of books available that explain basic porting work you can pick up and read that will give you an idea of what needs to be removed & where in the port without screwing them up.
Vortec heads are particularly finnicky and should just be left alone... they're already the best bang for the buck iron heads on the market; accept that and move on.
Also, for his power an RPM range a 2 bolt block is fine.
Concerning the factory vortec lifters, if you are going to use an aftermarket cam, I would definitely contact the company who makes it and get their advice on what lifters to use. Cams with radical profiles (that require stiffer than stock valve spring rates) tend to require a hydraulic lifter with a higher internal preload spring than what the factory lifters come equipped with.
-ryan
LS7 lifters have been popular drop in's for quite a while. the F-body crowd loves them.
I don't think the lifters will be an issue, the beehive springs I ordered don't have that much higher of a compression rate than stock, and at this point, I'm not planning to use higher ratio rockers. Although I've been reading some interesting info on mixing 1.6 on the intake and 1.5 on the exhaust. I doubt there's enough difference to make it worthwhile for this street motor. Frankly, I'm probably obsessing a little as it is. It will be a street motor that will get driven a couple thousand miles a year at most anyway. I'll probably never get to enjoy thefull potential of the motor until I replace the transaxle anyway, and even then I'm going to be concerned that it just won't stand up.
I had that flow data, I've been using it on my simulations, but it's good to have confirmation of the numbers I had.
One thing I haven't quite been able to figure out, is CamQuest seems to always show higher hp and torque than DD, even though they both get the same data. And it kinda looks like CamQuest is based on DD.
[This message has been edited by Taijiguy (edited 08-25-2014).]
Frankly, all this fretting over the cam, I have everything else already determined, I'm just going to call Howard's, Crane, and Comp and get their suggestions. Then I'm going to find the closest grind from Howard's and go with that.
Originally posted by Taijiguy: Frankly, I'm probably obsessing a little as it is. It will be a street motor that will get driven a couple thousand miles a year at most anyway.
Then stick with a conservative cam that makes it easy to drive and doesn't make you hate sitting at stoplights.
Then stick with a conservative cam that makes it easy to drive and doesn't make you hate sitting at stoplights.
Why? If I'm only gonna drive it a couple thousand miles year, I want the thing to have a grunt n grin factor that a conservative cam probably won't give me!
