Hey group have a big block that is over cammed over headed and under compressioned. if wolfplace aka mike is reading maybe he will remember. you were very helpful.

well as it turned out it seems i have a bad bearing somewhere so engine is coming apart. not good news but maybe i can fix mix matched parts some

i have a 496 and what is believed to be between 8.5 and 9.5 flat top pistons GEN VI block

comp xr 294 roller. 242/248@.050.

topline 320 rectangular port heads.

single plane pro products or rpm air gap intake(i have both) and a 870 avenger carb.

headers 2" primarys to 3" x-pipe to spin tech mufflers

full msd ignition

what i am planning on doing is having the block cleaned up and crank checked and turned and everything else involved in getting this thing together cleaned up and back together. i was going to re-cam but for $250 more i can go ahead and put special order srp's with domes that will bump the compression up to 10 to 10.5 depending on the true size of the chamber on the heads(builder has seen some toplines with 124 cc chamber instead of 119). if i have engine builder advance the presenet cam do you guys believe my engine will have the low end grunt i want? if anybody has desk top dyno and would not mind running numbers i will give you my first born :D , second born too, if you want ;)

i am tired of this dark side nightmare and i might as well fix while it is apart. i am really wanting a stump pulling car that wont fall flat on its face above 5000 grand though. this car is a street car with the possibility of taking to the track but for no other reason than to see what i have. i would appreciate any and all comments...good bad or indifferent. thanks to all who respond. tommy

I think you will get all the grunt you need from the 496 itself.. You may kill off alot with the big heads, I've never owned a 496, and I'm not a mechanic either (thats for sure..), but thats what I get from just reading other posts and looking at yours.
I also have 320cc heads (on a 454 +.030), on the dyno monday, the builder was said they made good torque for such a large head. So a big rectangle certainly won't be the be all and end all, but the consensus here seems to be you get grunt from ovals, but the I would say that a well put together rectangle combo, in a long stroke motor like that, will make good grunt.
I am in the middle of a cam swap, and although my cam is pretty radical, I don't drive the car alot, about 2k miles a summer. If you are thinking more use than that, you _might_ (just my .02) consider a less radical grind, like the AR rollers, or give Lunati-Harold a call and see what he has to say, or maybe (?) throw out the idea of a decent size hydraulic roller, they pull fine to about 6k, I'd think they would work fine in a 496. again.. just my .02. I think the right solid roller is just as reliable as a regular solid or hydraulic or hydraulic roller, but there is some question as to whether the XR-series of cams is gentle enough.
OK.. I thought something was up, I didn't remember an XR294 in the catalog, and there isn't one. the 242/248 is the XR280, which should be fine size wise, but there seems to be some disagreement as to whether the XR lobe series is truly gentle enough for long term street use. I don't know if anyone knows for sure.

I think i need to write a disclaimer about anything I say into my sig..
graemlins/clonk.gif

Matt

Marv. thanks for the post. i will be real interested to see what your motor does on monday. do you have oval or rectangular heads?

as far as the cam it is a hydraulic roller and it is a 294 but for a gen vi block(under the gen v and gen vi cams) it is NOT a retro fit. i thought i may have put that in the post but maybe not. I had this discussion on a previous post that is why i capped GEN VI block. :D

the funny thing is, is that the brief time the motor was up and running the cam is quite streetable. it idles great at 800 and is much more tame than my xe 284 in the 383(camaro) my main concern was that when got into the motor it did not really pull until 4000 rpm. up to that point i think my 383 had more pull. but at 4 grand it was a rocket. this is my previous post and the assumption made my people much more in the know than me

the car is also a 4 speed car with 3:42 posi rear

http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=4;t=019155

this might give all a little more back ground.
thanks tommy

Oops sorry about that, I read XR294 roller and went looking the comp cams catalog in the mechanical roller section.
Its over cammed for your compression a bit, but I don't know if its totally overcammed for a street/strip 496. The seat duration isn't insane for a 496, and the .050 #'s look "healthy." Too bad you couldn't get more run time with it. You may want to go for the pistons instead, I think that would make a good premium pump gas 496.
My heads are rectangles too. I don't know, thats just what I think. I imagine you might like that cam in a 10:1 496. Cam swaps are easier than piston swaps, and I assume you'd be running it on 92 octane even w/o the piston swap right?

Matt

thats the deal. motor is coming apart due to bearing failure/unaccepable clearances(bearing material in lifter valley when i changed to air gap mandifold, all on brand new motor). at least now i know why my oil pressure was low ;) so now is the time to change out pistons. i have flat top srp's now and AM going to swith to a dome piston that i hope gets me 10.5.

the heads are aluminum and i run premium in my cars anyway.

Matt what cam are you running and have you run the numbers on your combo? tommy

Tommy,
If those are truly flattops & the head is 119cc's you need to change the pistons.
You have very close to 8.4 & that is assuming a deck of .005 which is unlikely unless someone set it.
If the deck is the usual .020 down you are at 8.2 & if the head chambers are on the large size which I would suspect with the pros like 122cc's you are around 8.0-8.1
Couple that with a port that is on the large size for a 5500-6000 rpm engine & with the Team G, it is just not going to be a killer on the bottom.
Get the compression up to at least 9.5 preferably 10.0-10.5 & put on the Air Gap & you will have a different engine ;)

Or leave the pistons & put a blower on it :D

67, compression would have had a bunch to do with it. At 10:1, that thing should pull oak stumps, even with rect port heads. Choose the AirGAP.

Find out EXACTLY what you have before you buy anything!

mike, yeah my engine builder says the same thing. to bad i cant get a blower for 500.00/price of pistons. like i said i am hoping for 10.5 compression. builder says heads sometimes measure 120-125 cc chamber so milling of heads might also be in order.

i will go with the same cam, air gap, heaads and keep fingers crossed. thanks for the response. hopefull in a month or so i will report back that the dark side is good, not evil.

Brian i pretty much know what i have with the exception of pistons. i do know they are flat tops. i do know i will be putting a domed piston in(unfortunately it is not an off the shelf piston). i do know that the block will be align bored/honed, decked to zero if not(i doubt it is now)vatted, cleaned in order to put new bearings in. crank polished and or ground if needed. rods will be resized if need and new rod bearings installed. pretty much a clean up and fix what last engine builder could not do right(there is a lesson in here to someone who is purchasing an engine...my recommendation, buy locally, especially if you think you know a lot and really dont :confused: )i do know that if heads need to be milled they will. i do know i want 10.5 compression 10 minimum, no exceptions. other than that i dont know squat. :D

i being a very new at this am at the mercy of you knowlegdable people and a local engine builder i feel comfortable with. once i have engine to him and sit with him and get the specifics i will relay to you guys. but as it stands i will keep and use all the parts i have with the exception of pistons and go from there. thanks all and i look forward to updating you in a month or so.

look for future garage sale...new flat top stroker pistons and single plane intake(or maybe i could build another boat anchor ;) ) tommy

oops, sorry

Tommy,
Who told you you can't use a shelf piston???
SRP has pistons for both the 6.385 & 6.135 rod unless you are boring it to a goofy size.

yeah but i think it is not a true 496, it is only .030 over and from what i understand the domed pistons start at .060. i have heard this numberous times. what do you have there? do you have a part number mike?

maybe my understanding of off the shelf is different. could it just be a special order?

GOOFY would certainly be in order :D

thanks tommy

What they said. You are bleeding compression off with that cam to boot. I would keep the cam if it looks good and get some compression. You will find it to be a different motor graemlins/thumbsup.gif . Don't forget to check valve to piston clearance real well when putting it together. I thought the Lemans was a chevelle :D .

I thought the Lemans was a chevelle :D . [/QB]Hey Live wondering why you capped Lemans and not chevelle. ;) i originally was going to get a 67 velle but fell in love with the lemans' headlights. so i just started puttin velle parts on it. more than anything i guess it is an a body, with chevy motor even the 12 bolt is out of a 70 el camino. i think there is more chevelle in this car than some chevelle's :D


thats the goal. when the builder is checking cc of heads he will also check clearance of piston to valves. at this point in the build and unbuild and rebuild i am just going to leave that to the builder. i have learned all the lessons on this motor i care to learn. graemlins/clonk.gif graemlins/clonk.gif graemlins/clonk.gif

like i have told friends i have had a good run of luck with both cars and law of averages was bound to catch up, but it certainly has not deterred. thanks tommy

Ah, don't let these guys fool you, under the duress of interrogation they would almost all agree the GTO/Tempest has a more 'handsome' body style!

Yup, its all about cylinder pressure. You give a rat, any rat, enough cylinder pressure, and you'll get low end, even with large ports and a hefty cam.

Froidian slip. Or lousy spelling grammar. Take your choice graemlins/beers.gif .

[QUOTE]Originally posted by 67lemanster:
yeah but i think it is not a true 496, it is only .030 over and from what i understand the domed pistons start at .060. i have heard this numberous times. what do you have there? do you have a part number mike?

maybe my understanding of off the shelf is different. could it just be a special order?

GOOFY would certainly be in order :D

thanks tommy [/QUOTE=
=

These are the old SRP numbers, I believe they have been changed but will interchange with the newer numbers.
6.135 rod 17cc dome, 1.520 CH
139523 - .030
139524 - .060
139525 - .070
139526 - .100

6.385 rod 18cc dome, 1.270 CH
142990, 991, 992 & 993 are .030 .060, 070, & .100 respectively.
All are 10.2 approx at zero deck with a 118 cc head.
You need to mill to about 115cc or approx .020 thou for 10.5
This is for the 496 & will vary a little with the larger bores.

What's wrong with sticking a set of worked over large oval closed chambered heads on her and using .022" shim headgaskets??

Should be up around 10.13 to 1 CR., then, depending on the valve notch cc range if the closed chambered heads are right at 104 cc's due to unshrouding for big valves..

-------(4.31"b x 4.25" s, + .025" down, +4 cc v/n, 104 cc heads and .022" h/g's...)---------

I bet it would be a monster even with the big cam due to port velocity.... And it should drop the torque peak down rpm-wise some, I would think???

pdq67

i wouldnt count on anything until you get that motor apart.

What makes you think that its a std/std deal, it might already have been cut once.

I think the topline heads, for what you want, are too big. You want torque, 320cc are large.

If you already have 781's use them, if not, find a set of #215 heads, and find pistons for closed chamber heads that work with them.
Set up right, and theey will work great, and wont be RPM limited. One certain racer, with a 468" turns 67-6800rpms through the traps.

I would NOT suggest using a roller in anything but a limited street/Track car. Too much maintainence for your typical street ride.

Tommy,
I don't know why people are trying to talk you out of the heads you already have.
They will make more torque than you can use in a 10-10-5 compression 489/496 with the cam you have.
You will need to cut them about .042-.049 thou to get to 10.5 with your new pistons if we call them 122cc's now assuming zero deck.
Your hyd roller is not to big for a 4.250 stroke rat.
I have built & dynoed basically the same deal except with 315cc AFR heads & it had 500+ft lbs from 2900. Peak torque was at 45-4600 & peak power was at 5800 & about 620.
Same engine with a 254/260 solid roller had almost identical torque at the same rpm & 670HP at 6300 again with 500+ft lbs from 2900 up
This was with a Vic Jr & an 850.
This was with a true 9.8 compression.
Rectangular port heads will make power on 500 inch engines.
Your engine with the EDE Air Gap & some compression is going to make torque period.

Maybe they would trade even up for my aluminum heads for there steel ones ;) .

Mike i appreciate your help as well as everybodsy elses help and opinions. i will take the piston info with me to buillder

I AM KEEPING HEADS. cant just throw new ones on. MONEY tight, i have a good foundation as people have mentioned. if i can put pistons in and get compression up motor will work. i have read to many post here that are proof. Matt just went to the dyno with a 460 similiar heads(rectangular w/320 runners) and cam and had very, very respectable numbers. a quote from his post-- the general jist of things was about 555-565hp @ 6000(depending on which dyno test, I didn't stick around for the final pulls) hp, and 500-550 ft-lbs of torque from 2500-6000.

throw in my longer stroke and i should have respectable numbers also.

did i make a bad purchase with heads. probably(but hey the are aluminum and look cool, that will make it go faster huh :D , but i am now stuck with what i got. good thing not married i would probably be really stuck having to explain this whole ordeal tongue.gif

Brian i dont have a set of heads laying around, well i do but they are small blocks.

so with that being said on to other news. motor will be out tonight and at machine shop/engine builder tomorrow. more will be revealed then. thanks all who posted i do value all opinions as well as really appreciate all responses. thanks tommy

Is there an ET goal in mind with this motor? Inquiring minds want to know ;) :D

No. Just exercising my right to be a kid(the toy i never had). However talked to a buddy of mine yesterday who works at the local harely shop and he said the owners are going to let him race there bike. so if he goes i will go to track and see for giggles. i guess low 12's high 11's. does that sound reasonable? mostly a street car, if not all street car with maybe a little attitude ;) .

if i new more people in the dallas area who go out to the drags i would be a lot more receptive to it.

however i just enjoy being in the garage and not out on the street, kinda that peace finding deal in the garage. :mad:


Chris any thoughts? tommy

Tommy,low 12's/high 11's should be very,very easy,and that will be with traction problems..what do you plan on running for a trans/convertor (if an auto) and gear?

Originally posted by 67lemanster:
No. Just exercising my right to be a kid(the toy i never had).
Chris any thoughts? tommy Tommy, ABSOLUTELY, I love excersing that right!
Oh, and Tommy, yeah, I'm not Chris, but buddy, my car runs low12's MAYBE high 11's if I can launch it hard enough. Heck man, you'll me MUCH faster than that. I set the engine up to me at max dynamic compression. I figured around 8.3-8.4:1. Well, a bit of head dusting, decking, stabbing the cam in advanced, etc, and now it calculates to 8.6:1 dynamic. Max for pump gas, and I might have an issue with 92 octane. BUT, BIG BUT, that's how even a large port little 427 makes some grunt down low - CYLINDER PRESSURE.

One thing I did learn, if you think the heads are a bit on the big side, keeping the cam advanced helps the intake charge velocity.

Oh, and I use 325CC old GM alums on mine. Your heads are better. Not saying much, my 074s pretty much suck. Yet the car makes enough oomph to hit the end of the track at 118+. With a roller and a different carb setup ( I use a tripower), I have no doubt I could get the car into the 120+ range.

With the wrong heads. :confused: Not to brag, but 118 from a pure street car is a decent amopunt of powr. easy to drive too. That UltraDyne cam is a bit 'lumpy' at idle though!

Yeah, you just need some cylinder pressure man. SRPs are NICE pieces too. Light. In my case, hyper slugs would have required weight added to the crank to balance. they had to take a little weight off the crank to balance with the SRPs.

4 speed m 20 car with 3:42 posi rear now. i have 275/40/17's now and will keep these.

to be honest traction issues is kinda what i want. like i said i am a big big kid. just having fun.


i am kinda torn between rear gearing to low 3's or high 2's or going with the new tremec. i really want a better final drive ratio. tired of turning 3000 at 70. i want it like my camaro with the 200 4r.

You will have serious traction issues :D
I have them at 35-40 MPH in my car,and thats with 2.73's

You got a pic of those 17s on a Lemans. I gotta see it!

Yeah, I use 3.31s and a Richie 5 speed, 3.04 1st. With the little short stroke, I could sue more 1st gear, although I'll pulling the 1/2 shift before the 60' mark already. Best 60 is onloy a 2.05 sicne I havent giving it a big rpm clutch drop yet. 2.05 60' let is go maybe 12.25. 1.85 60' should be doable and net out an 11.85 or so.

Based on power, the car should run 11.60, but stick cars ain't no 'footbrake' car. Harder to launch.

Hey 'kid' here's some fun. Get your rear suspension dialied in ( using an airbag and sway bar) so that when you light them up, the car tracks straight as an arrow.

It's fun to pass folks, going straight as an arrow, SMOKIN" the hides as you grab a gear.

Let's them know where the Rat is AT! tongue.gif

OK Kids , don't do this at home.

6.385 rod 18cc dome, 1.270 CH
142990, 991, 992 & 993 are .030 .060, 070, & .100 respectively.
All are 10.2 approx at zero deck with a 118 cc head.
You need to mill to about 115cc or approx .020 thou for 10.5
This is for the 496 & will vary a little with the larger bores. [/QB][/QUOTE]

Mike will i need to have any work done to the manifold with taking off that much. assuming 122 cc chamber to 115cc chamber that is 7 cc's times the .007 per cc rule you stated above = .050?

Serious traction issues? like my daddy used to say "if you are going to be a bear, be a grizzly".

Hey buddy go to my pics and the lemans is in there. it is black with cragar ss. kinda old school meets new.

Buddy thats what i am talking about smoking the hides. i've got the hotchkits boxxed loweres with adjustable uppers and sway bar. once the tires warmed the car really gripped with the old 383 graemlins/sad.gif thats why i wanted the stroked rat. tommy

I was under the impression you didnt have the heads yet.

In which case, if you're goals are to run low 12's high 11's, then you definetly dont need a solid roller cam, and you dont need/dont want 2" primary tube headers.

Start by letting me know what you already have and what's on the shopping list.

Brian is right on..a solid flat tappet or hydraulic would be all that is required,and 1 3/4" headers would be ideal also.My car has run a high 12 with a mild 454 and 2.73 gears in street trim..So,a 496 should be easy low 12's/high 11's in a mild state of tune with mild gear (no more than 3.42's/3.55's) and having traction problems..if not it would be a crime graemlins/sad.gif ;) :D

Brian i will try to be quick about this. i had a 496 built gen vi block. i had the comp cam and the topline heads. after break in i notice that the motor did not pull until 4000 so i put an airgap in place of the single plane. with intake off i found bearing material in lifter valley :mad: . then talking to Mike we got on the subject of motor not being 9.5 comp. like my builder said but more like 8 to 1 comp. so motor has to come out and do a rebuild on bottom end. so while in there my goal is to use the parts i have but put new pistons in the bump up comprssion. this is going to cost enough and i dont want to go on another buying spree. that is why i am trying to replace just what is needed.

the motor has been up and running. but do to incorrect bearing clearance i guess from the guy who built the short block or a goofy crank...its a scat and i have heard they are hit or miss on quality control, the motor must come apart to correct. so with that said i am doing the best to make a bad sitution good and it seems the easiest most cost effective way is to put new pistons in.

hope that clears some of this up. tommy

roller block might as well keep the roller hydraulic cam thats in it.

I havent had any problems with the Scat stuff we got into the shop over here.

The first rule of thumb in engine building, is Check every peice that you install to the Nth degree.
Thats it, WJ would send you a crank, but you still dont know its good until you check it!

What it sounds like to me is that you want to build it up the same, but with more compression then before, and thats it.

I was thinking solid roller when i saw XE roller, no idea that it was a hydro you are refering to.

Good luck with the build up, and of course, ask questions on anything you're wondering about.

Originally posted by 67lemanster:
with intake off i found bearing material in lifter valley :mad: ugh, deja va. Mine was in the oil lifter element. Saved a "spectacular" breakdown as the shop owner said as we tore the pan off and took it down.

While not a fan of hydrualic anything for a performance motor, your Comp294 seems a very correct fit to the engine and driveline. Coming off the line with a M20 and only 3.42s, you shouldn't want/need much more. It'll be a new animal once it's redone paying particular attention to cylinder pressure and proper clearances throughout. Consider it 'blueprinted' when its done. Sounds like the crank needs a refinish and slightly over bearings used. Balance the thing to flippin' 1-2 grams if he'll do it without charing an arm and a leg. Recommend you put that cam in at least +4 if you have the piston/intake valve clearance to do so.

BUT BE CAREFUL, smokin' them hides so easily will bring 7 grand up quick!

Tommy,
For info, from 12+ years of using them Scat's quality control is excellent, but as Brian said always check everything as anyone can make a mistake & stuff happens ;)

You know, measure once,,,cut twice or somethin like that graemlins/clonk.gif

Let everyone know how it works out.

BTW,,,, 2 grams ain't what I consider balanced in my shop graemlins/sad.gif

Hehehe, you're a good man Mike! OK 1/2 gram! Admittedly, I can't tell you what mine is. Likely 1-1.5 grms.

Originally posted by 427L88:
Hehehe, you're a good man Mike! Thanks,,,,it's just no one has figured out what for yet :(

Your all good men and i appreciate your patience with me. you have been very informative. and i look forward to getting this pig up and running.

The motor was pulled this afternoon and all accessories stripped off. i went a head and left both heads and all valve train intack for checking piston to valve clearance.

I was planning on having cam advanced 4 degress per mikes suggestions on my last post. i will request a balance of less than 1 gram. i feel confident with this builder and look forward to speaking with him tomorrow when i drop off engine. hopefully i will be up in running in a month or so. thanks for all your help guys. until my next problem. tommy

67lemanster;

Is this the same engine that had low oil pressure because the builder left out a couple oil gallery plugs and a check ball by the oil filter? You had posted about the low oil pressure before the gold color in the lifter valley? If so are you changing builders or were these items mutually overlooked?