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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.
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
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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.
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.
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.
Quote:
Originally Posted by Damon
Given the fairly high compression ratio and extra cubes I wouldn't be too afraid of the biggest cam in your selection.
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.
Quote:
Originally Posted by Damon
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.
Plan would be to use something like the LT4 spring retainer, though I need to look for the part # and make first.
Quote:
Originally Posted by Damon
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.
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.
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.
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.
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.
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.
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.
Quote:
Originally Posted by 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.
Sounds good if I can get away with that copression.
Quote:
Originally Posted by Rolling Thunder
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.
Was thinking of reusing the COMP Cams 981-16 I have on my current LO3, they have around 20k miles.
Quote:
Originally Posted by Rolling Thunder
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.
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.
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.
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.
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.
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.
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.
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.
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
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
Another big decision I need to take. Rockauto has e-mailed me that marshall engines is willing to send me a set of 083 to replace the 193 heads, but I dont whant to waste peoples $, so I have not decidet yet.
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?
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"?
, Marshall engine's technician claims they are acceptable replacement for 083.
