thomas1976

I need some experts advise, I will have a 91-92 camaro/firebird remanufactured L98 longblock from Marshall Engines to play with, plan is to get a solid 270rwhp@4500-5000rpm TBI engine to replace the original LO3.

From reading around, the L98 longblock with some pocket porting to the 083 heads, screw in studs and a better cam should be up to the task. If they are not then I’ll wait and seave for some AFR or Trick flow.

This are the cams I was looking at : XR252HR, XR258HR, 264HR-12
http://www.compcams.com/Cam_Specs/Ca...?csid=184&sb=2
http://www.compcams.com/Cam_Specs/Ca...?csid=193&sb=2
http://www.compcams.com/Cam_Specs/Ca...?csid=212&sb=2
With these rockers ? http://www.compperformancegroupstore...e=SBCNEWRocker


Im using this to calculate 10.156 CR. http://www.kb-silvolite.com/calc.php?action=comp
I have not recived the engine yet so the walues are estimated.
64cc heads, piston (dish) 7cc, gasket 0.015 with 4.1 bore, cilinder bore 4.03, deck 0.025, stroke 3.48, rod 5.7.

Wich DCR would be better ?

Fueling and tunig should be no problem, though the easier to tune the better.

Thanks, Thomas

Damon

The minute you go away from the swirl port heads, "peanut" cam and add almost 50 more cubic inches it's going to need to be tuned, no matter how "mild" you might think you're building it.

Given the fairly high compression ratio and extra cubes I wouldn't be too afraid of the biggest cam in your selection. Be careful of the lift with that cam, though. .480" is dicey with factory heads that have no machine work to open up the retainer-to-guide clearance.

Aftermarket heads would be nice if you've got the scratch. But if budget is a prime consideration I think you can hit your goal with factory castings.

thomas1976

With, fueling and tunin not being a problem, I meant I know how to take care of it. I dont know why my signature dosent show up.
This is my actual set up, it is as fast as a 91 5.7L Z28 with full exhaust.
lo3, LT1 cam, 46mm bore performer tbi intake manifold, turbocity's 46mm TB, cold air intake, RBob's EBL flash, ACD#EP241 TPI fuel pump, turbocity's VRFPR 16-23psi, 3.5"aluminium driveshaft, Eaton LSD, GM 3.23, mac headers #TF8692, hoocker #16823 cat back, catco 3" cat, 3 wire heated oxigen sensor, Bilsteins, ebmiller88's 1LE front brakes.

Could not get as low as 9.7 stock CR using the information I found on tgo. Can it be that the calculators are on the high side? Aniway good information, high compression needs bigger cam.

Plan would be to use something like the LT4 spring retainer, though I need to look for the part # and make first.

It will depend how much it will take to set the 083 up, once all summed together. Thing is I havent come across any dyno # using 083 and read that there not good, not that bad, so I dont really know.

Rolling Thunder

Few things ide like to mention. Compression is your friend. At a little over 10 static i wouldn't expect you would have a problem with detonation even with cast iron heads and a tame cam. Adding the cam will kill it down some but i wouldn't put in a big cam with the idea in mind of trying to cut back on the compression because as is i think you will be just fine. Personally i think the second cam you have listed 258hr would be my choice. Its a fairly tame cam but a strong street performer that would have a good bump in performance while maintaining good mileage and street ability. Coincidentally they even claim in the application box that its recomended for TBI motors with characteristics matching what you want. Although you can always go to comp cams website and get the free engine simulator program and doing some testing of your own with different cams. I suspect when you try the different cams youll see youll like the performance of the 258hr over the others.

Second at .480 lift i wouldn't be too worried about valve clearance issues im pretty sure you would be just fine. Though there's no harm in checking and really no reason not to. I definitely would recommend more than lt4 retainers for any cam you should get new valve springs and for higher performance cams its not recommended to just get a new factory set you should get the set thats matched to your cam. Usually cam kits of that sort come with retainers anyways.

Lastly as far as the 081s are concerned as far as factory heads there not bad. With alittle work there actually fairly decent. That being said there are a lot of better aftermarket choices you could use even on a budget. Vortec heads for example can be picked up for about 500 new which would outperform the 081s. To take it even further bowtie vortecs for about 700 would be even better. The 081s though probably take you to to your goal just fine.

Damon

The thin shim head gasket and flattop is what's putting you a little over 10:1. With a slightly thicker gasket like a GMPP .028" head gaskets you would be down around 9.8:1. But that also opens up the quench a little, so probably wouldn't be of much benefit in the end. Except that shim-type gaskets can be a little more touchy getting them to seal up if things aren't perfectly flat.

thomas1976

Id did spend some time reading around and the quench seems to be important, besides the remanufactured block and heads should have been resurfaced, well'see.

Sounds good if I can get away with that copression.

Was thinking of reusing the COMP Cams 981-16 I have on my current LO3, they have around 20k miles.

The 350 L98 longblock should have the 083. Im aware of the potential of Vortec's, but if I add iron heads, intake manifold, egr connection, mods to the heads and shipping for all that a pair of AFR or Trickflow would be more interesting. Probably even perform better. I skip the Vortec's.

thomas1976

The long block is here, they put 193 heads on it , Marshall engine's technician claims they are acceptable replacement for 083.

Now which heads would be best?
http://www.summitracing.com/parts/TFS-30400006/
The + : factory look, 62cc, price
the - : springs will probably need to be replaced, not sure if they are available with the two center 72° intake bolts.

http://www.summitracing.com/parts/AFR-0919/
+: CNC, good reputation
-: price, 65cc (though I think they can be ordered milled for 64 63 62cc)

Damon

Sky is the limit if you're going with aftermarket heads. AFRs cost more becuase they're worth it- probably the best out-of-the-box heads you can buy today. Not that there's anything wrong with Trick Flows or any other name-brand performance head. Consider your budget and your goals.

Kingtal0n

Hi Damon! long time!

Build power based on what the heads can flow. If you can cram 400hp worth of air with little/no pressure drop then pick an intake that supports the same thing, pick a cam that supports the same thing, and give it fuel to match the expected airflow.

Apply this to any engine to get maximum performance, since the head is where maximum performance starts. Utilize the equation:

CID X maxRPM / 3456 = CFM * .069 = expected Lb/Min airflow
To get a rough idea of what VE will be at what RPM so you can select the right camshaft for instance:

350 X 6000 / 3456 = 600~rough * .069 = 42lb/min or about 420brake horsepower (using 400WHP heads as an example)
So now that you expect 400~ horsepower @ 6000RPM you can also expect about 90-100% VE since thats what it will take. Now you know that you need 90-100%VE @ 6000RPM so you need a camshaft that supports a duration capable of fulfilling that need.

See where this is going?

thomas1976

Nice formula. By max hp at 5000rpm thats 500CFM and 350 brake hp. Do you have a formula for the duration?

thomas1976

Im tring to gather some specs on this remanufactured Marshall engines.

cilinder head casting: remanufactured 193

bore size: 4.060
1piece main seal rollerblock casting 14093638, how well will it support 350fwhp?

pistons: silvolite 1470, 13cc dish, 1.54" compression hight (stock 1.56")
I thought 90-92 L98 had 7cc dish.

Thats all I have for now. I cant belive they dont even know what specs the engine and parts have they use. Im disappointed.

Damon

Will it work? Yes. Is it like stock? No. 60 over block with swirl port heads and dished pistons tells me they cobbled something together from what was laying around the joint.

thomas1976

So it would be a ok base, to upgrade pistons, cam and heads for a little performance.

Damon

Probably. Quality of the parts that are in it is one thing. Quality of the machining and assembly is a different issue and there's really know way to know that from a spec sheet.

I wouldn't even swap pistons, give you're trying to do a budget daily driver. Even with the dished slugs it'll be a bit over 9:1 compression with 64cc heads. If you really want to change them then flattops would get you up close to 10:1.

thomas1976

Yes, pistons will mostly depend on how much the deck hight was milled. If it was milled 0.020 then those pistons could be ok.

Waithing on the engine stand to start disassembly.

Would the 350 block + 193 with 3 angle valve job, 9.6 CR, pocket porting, comp cam 8-500-8, tune, full exhaust, fueling ... make 270rwhp @ 4-5000rpm ?

The compcams cam quest download, estimates 306hp@4000 and 470 ftlb@2000, fwhp probably, to me is seems a little low for 270rwhp.

Damon

Not sure. Not saying no, but not saying it would be an easy number to hit.

Check over on the TBI board. There's a couple guys who have wrung some really impressive power out of various TBI combos. For sure, the magic is almost always in the specific combo and the tune that gets the most out of it.

Stuff like 305-powered conversion vans that run low 14s. Stuff that a lot of care and attention was paid to in order to get results many might consider impossible.

thomas1976

Yea I know the TBI board kinda by heart, but do not have magical powers.

Kingtal0n

As to camshaft selection-

you mention the word daily driver. to me, a daily driver has a reliable valve train. Not the strongest spring, not the biggest cam. Your best bet for a 6,000RPM limitation is nothing larger than 230 @ .050 with a roller profile this duration should give lasting VE beyond 6k, with your DD you are not so worried about the high VE at peak RPM, you should be using a taller gear(numerically lower) and an overdrive transmission with a nice factory closed loop operating O2 sensor... all of this adds up to a mid-range fuel efficient engine capable of producing hot strong combustion with good brake specific numbers in the mid-range, not a peak ve motor for racing.

use the highest lift you can get while still maintaining a low/medium stiffness spring to preserve valvetrain components. If the engine is ever to be forced inducted err on the side of less overlap (112-114-116). If you decide to use a 110overlap or shorter expect poorer fuel efficiency.

it seems you selected the 258H which is certainly a good match for this description, actually its smaller than I expected most people err on the big side good job, that will be a very fuel efficient engine if everything rotates smoothly

thomas1976

Nice info, thanks.

By playin with the comp camquest6, I used the stock flow numbers of the 193 and 083 I found on tgo and get the exat same ratings.
8-408-8 370hp@5000 and 484ftlb@2000 average 107 hp 168 ftlb (appers to have a little more to offer from lower rpm's)
8-500-8 367hp@5000 480ftlb@3000 av. 105 hp 166 ftlb

The camquest6 preprogrammed low performance head's show around 300hp@4000 and 470ftlb@2000 av.72hp and 131ftlb.

With AFR 180 flow numbers and valves.
8-408-8 377hp@5000 490ftlb@2000 av. 109hp 171ftlb
8-500-8 381hp@5000 483ftlb@3000 av. 108hp 170ftlb

Even by pocket porting the 193 I doubt they will flow like the 083 on the intake. The 083 exhaust will probably not impress either after a little grinding, but thats what the full exhaust is there for, isent it?

stock 193 int. - exh.
0.100 70.4 - 55.7
0.200 100.2 - 115.6
0.300 145.7 - 125.8
0.400 164.7 - 138.9
0.500 178.9 - 146.8

stock 083 int. - exh.
0.100 53.9 - 41.6
0.200 111.2 - 95.2
0.300 157.3 - 112.4
0.400 182.0 - 116.6
0.500 192.3 - 116.9

Damon

Flow numbers alone don't tell the whole story, as you can imagine. That being said, no, the 083 heads aren't going to be "holy cow!" better than the swirlies for what you are doing. My experience says they are bolt-on better, despite the fact that it looks like you're just trading some exhaust flow for some intake flow. Just my experience.

Before you drop coin on a set of aftermarket heads you should carefully consider if they are worth the price. Yes, you will make considerably more power with aftermarket heads, but is it worth it for the cash outlay? Only your can answer that.

For what you said your goals were, I don't think they are absolutely necessary, but you're on the borderline. Some modest work to the stock castings could probably get you where you want to go for less money.

I mean, seriously, do you need a set of AFRs to have a "fun daily driver"?

thomas1976

Finally on the stand.

thomas1976

Heads off.
Piston to deck:
#1 .044, #3 .045, #5 .045, #7 .053
#2 .048, #4 .051, #6 .046, #8 .055

If anyone ever considers buy'n a remanufactured engine from Marshall Engines, this will give an inside view. https://www.thirdgen.org/forums/clas...ufactured.html

thomas1976

The block is ready to go to the machine shop for decking.

Not sure if its worth keeping the remanufactured internals. Im wondering how well .020 undersize crankshaft, 13cc dish cast pistons and remanufactured Rod's (not shure if Rod bolts are new) will hold with 10.5 CR.

Found this behind a freez plug, https://www.thirdgen.org/forums/cool...reez-plug.html

Kingtal0n

Damon has a point, your mild power goals are achievable with a set of random iron heads, no need for the afr name brand route...
but I understand if you are trying to get the best of what you can get. But from this perspective, you are installing golden heads on a 4-cylinder in disguise... to truly take advantage of those heads with the camshaft you've got and the rpm limitations you expect... I see forced induction in your future very soon...

The good thing is you HAVE them now. I mean if this engine gets trashed, you can usually just stick the awsome heads on another engine. and maybe at that point you will have different goals... So its not a waste its just misappropriation of funds, temporarily, in a broke ***' point of view.

heads are power production POTENTIAL

Kingtal0n

the CR doesnt matter. what matters is how you USE it. If your octane requirement is not met for the ignition timing / temperature setting / environment in which you intend to light off fuel and air together (combustion chamber) then you will have combustion issues... which will eat away at components involved in combustion (everything from the deck surface, head sealing surfaces, hot spots, bearings, rings etc...) and lead to failure of something

good tuning and good diagnosis will keep the mistakes away. watch your timing in peak VE areas (peak torque) this is usually the lowest-ignition timing advance spot that everyone misses.

um.. your taking off the factory rocker arms right? that should be rhetorical

You know your are essentially creating a very torque truck monster, taking advantage of the cubic inches down low... i assume you are running a very tall gear and overdrive to take advantage of this fuel economy potential! with that compression ratio its going to be sick and very strong and snappy even with heavy components. the rotating mass will only add to the truck torque, but if you put some lightweight components in there it will make a VERY snappy tire chirping machine, which i hope is automatic for fun.

thomas1976

I will use full roller rockers and LT4 timing chain.
Probably going to pick one of these 4 options, I honestly dont know wich would be the most powerful @1000-5000rpm.

1. Use the reman. 193 casting heads, with srew in studs new valves, comp cam springs, LT4 style retainers, some DIY pocket porting and around 9.6 CR with the comp cam 8-500-8.

2. Use the reman. 193 casting heads, with srew in studs new valves, comp cam springs, some DIY pocket porting and around 9.6 CR with the GM LT4 cam #12551142 gmpartsdirect, Duration @ .006 - 282/277, Duration @ .050 - 203/210, Lift w/1.5 rocker -.446/.449, LSA 115*.

3. Find a set of 083 casting heads do the same mods, with either the mentioned LT4 or the 8-500-8 cam.

4.Use TFS 175, 56cc combustion chamber heads, comp cam springs, around 10.5 CR with the 8-500-8 cam. They'r combustion chamber design appears to make them the best choice of the 4.

(Note that buy'n used 083 and remanufacturing will cost me the same if not more then the TFS 175 with com cam springs shipped to my Door)

Belive me, in case of excessive tire spin I would be glad to put the original 2.73 geared G80 back in the rear end, the low rpm was cool, courrently have 3.23 Eaton in it.

I have a rather heawy foot, thats why im not sure about the rotating assembly and cast pistons. How long would a remanufactured stock rotating assembly survive pushing such a heawy car with 270rwhp up the mountains? supposing its tuned ok.

86LG4Bird

iTrader: (1)

As long as any engine would, as long as it's assembled correctly.

thomas1976

Working my way to plan 4. with TFS 175, 56cc combustion chamber heads, around 10.5 CR with 12dish pistons, comp cam springs with the 8-500-8 cam.
Any reasons not to use the TFS 175 on a max5000rpm 350, let me know.

After milling the deck, the piston to deck mesures of the cylinders had too big differences with the remanufactured rotating assembly. I ended up with a new Scat rotating assembly and hypereutetic KB 12cc (dish) pistons from cnc.motorsports.com

Just started the pre-assembly, a little slow due to limitted time.

Kingtal0n

keep chipping at it!
use screw in rocker studs only! ( i remember something about press in TFS...)

that compression is going to make you a very peaky strong mid-range torque, you probably wont have a full 36* of timing there, more like 30-32* but a dyno will tell you! Going uphill? less timing for safety please!

thomas1976

CR 10.5 - 56cc 175cc/67cc 1.95"/1.5" valves http://www.summitracing.com/parts/TFS-30300005/
I would use comp-cam 26981-16 valve springs, 2 TGO members ended up with valve spring failure.

CR 10 - 60cc 165cc/60cc 2.02"/1.6" valves http://www.summitracing.com/parts/EDL-CR 60859/
General bad feedback about cheap valves and springs.

CR 9.8 - 62cc 170cc/69cc 2.02"/1.6" valves http://www.summitracing.com/parts/SUM-162108/
Not many feedbacks, CR is low for aluminium heads. Valve springs would be replaced with compcams.

These are the only direct replacement smog legal aluminium heads, smaller then the AFR 180, I could find.

I have not ordered the heads yet, but it looks like 10.5 CR is about correct for aluminium heads. Working the SA table is pretty quick with the EBL flash I have.

360ci roller block
8-500-8 cam http://www.summitracing.com/parts/CCA-08-500-8/
tfs 175, 10.5 CR
Appears to be similar to a GMPP ZZ4 engine.

I was wondering, Dynamic Effective CR.
http://www.kb-silvolite.com/calc.php?action=comp
http://www.compcams.com/Cam_Specs/Ca...?csid=193&sb=2

thomas1976

Hmm, I need to figure out DCR

https://www.thirdgen.org/forums/tech...-dcr-help.html

thomas1976

I think Im getting an idea of what you are saying, 10:1 up CR = wild and around 9.8:1 = resonable/safe. (Comp cams thech also suggests 62cc heads).

I tried this DCR calculator, if I did it correct the 62cc heads would be good.
http://www.projectpontiac.com/ppsite...=112&advance=0

ci 360.42, static CR 9.85:1 and Dynamic Compression Ratio 8.1:1

bore=4.06, stroke=3.48, combustion chamber=62, deck hight=0.003, gasket=0.041, piston dish=12, piston ring height=0.3, piston to bore clearance=0.0028, Rod lengt=5.7, cam intake duration=258 (seat to seat), lsa=112 (lobe centerline), advance=0

thomas1976

Here the Summitracing 170 cylinderheads https://www.thirdgen.org/forums/tech...ads-clean.html


Final assembly, finally!

My Dura-bond Cam bearings oil hole location: #1 @1 and 5 o clock, #2,3,4 @3 and #5@1-2 http://www.dura-bondbearing.com/TechSupport.aspx

It took two sets of piston rings to get the KB pistons 0.032 in gaps perfect well it was my first time. http://www.kb-silvolite.com/assets/kb_installation.pdf

I used the yellow standard pressure spring in the M55HV oil pump. http://www.youtube.com/watch?v=tOiHd...eature=related http://www.youtube.com/watch?v=7IpJl...eature=channel

Now its time to clean up the cylinder heads.

InfernalVortex

iTrader: (4)

Definitely trash the 193 heads. Those things are just as bad as the 187 heads your 305 originally had.

thomas1976

Yea, did not whant to use them either, so I ended up with summitracing's 170 heads. https://www.thirdgen.org/forums/tech...ads-clean.html