Sounds like a well thought out build. The components you/your builder have spec'd out look to be well matched. I think you will be very pleased w/ the results.

Not sure if you/your builder has spec'd the cam material, but I STRONGLY suggest you consider using a billet, and not a cast core. In spite of Comp's claims otherwise, the cast billets have not held up nearly as well as the billet cores. You can also get your cam w/ a pressed on iron distributor gear so you don't have to replace your distributor gear.

Jim is right about the 540 -- it is basically a 496 but using either an aftermarket block (Dart, Merlin) or a Bow Tie block (GM) that allows a 4.50+ bore due to the siamesed cylinder walls. Externally they are dimensionally identical to their non siamesed bretheren. I run a 9.8" Mark IV Bow Tie (long out of production) and is externally identical to a standard passenger block 427/454. All part of the subterfuge....

And shaft rockers, albeit more expensive than stud mount rockers and girdle, can fit under factory stamped steel valve covers w/ VERY minor modifications. Ask me how I know.

Good luck,

Mark

 

Hi Jim

For sure I will look into those shaft rockers. Not only do I really prefer the stock look I would then be able to use my existing valve covers and have less hassle with my AC compressor. I am pretty sure the compression will be 10.8 and the only real question left is on the rotating assembly. I had asked him some questions about internal balancing and alum flywheels.

I can tell he really does not like alum flywheels because of some heat/warpage issues he has had with them on street motors and he is waiting back to hear on the internal balance issue. The issue being is whether or not the added expense for internal balancing will also bring about a lighter rotating assembly. If not then there is not enough benefit to justify the added expense. Now if the internal balance is lighter I will be more inclined to go with the aluminum flywheel and just accept the fact that he does not like them.

The main reason being is I figure that I do not need the extra initial momentum nor do I worry about loosing rpm's when shifting but the overall reduction in weight is part of the next plan on the agenda for my car. I already have the weight penalties imposed by the scattershield and a Vintage AC that are both non-negotiable. However I am going to put the car on a simple diet as time goes by and the steel versus aluminum flywheel difference has got to be significant start. Plus I do prefer a quick rev and used to use one with no problem.

If all goes as planned I will have my motor for Christmas and will start on the install right after the 1st.

I Hope to be able to post some rwhp charts soon afterwards.

Thanks again

Doug

PS Hi Mark

Just saw your post and the cam is to be steel as well as the rocker arms (He seems to be a steel minded person). You along with Jim and Gary have really helped a lot and have shared some great information. During the next couple of weeks I will be putting some 3.5' side pipes together like you suggested.

 

Good point on the cam....Mark remembered that one. For sure go with the pressed on cast iron dist gear....no need to mess with polymer whiz bang stuff.

Internal balance is no big deal these days..just order the right crank. Most of them balance easily with 6.385 rods and decent pistons. I didn't need any mallory metal in mine at all.

I like the ATI balancer. Good stuff.

Curious what the LSA on that cam will be?

Mark..what do you think of that cam with a 10.8 compression ratio? With A/C it will run nice...but I'm thinking heat etc and borderline detonation on pump gas in the real world. He does have 4.11's, but he also has O/D. It will be OK, but will need some good dist curve tuning to keep it out of trouble I would think.

Mark has been running an aluminum flywheel in his car for years. I have a lightened 22lb steel one in mine. But you have a lot more gear than we have too. I don't think the weight issue will hurt anything really one way or the other for normal stuff.


JIM

 

The LSA is 110 and I am pretty sure on that compression ratio. He did say that the only reason that I would get away with that number was because of the aluminum heads. I know he wanted the MSD over the mallory Unilite that I now run because of the ease of adjusting the curve. (besides the rev limiter)

BTW what is a "Thorington bearing"

Doug

 

Cam I think is OK at that CR. Doug, one of the advantages of a solid roller is it carriers rpm very well after peak HP. I’ll SWAG and say you’ll peak your HP somewhere in the 5800 – 6000 range. I certainly wouldn’t go any smaller.

I don’t think you’d see a significant difference one way or the other w/ an aluminum flywheel. These big arm engines don’t need the same inertia that a small buzz bomb engine requires. I have a little more “catchability” when I blow the tires away, and marginally more engine breaking w/ the aluminum flywheel. The difference in both is minor.

A Torrington bearing was originally a brand name of a needle bearing, but has been genericized to mean a particular style of needle bearing. I believe Torrington is now part of Timken.

Any ETA on build?

Mark

 

Hi Mark

I talked to the builder about shaft rockers versus realistic costs. He mentioned a name that sounded like "Jedsel" and said that the last time he checked they were around $800 or so. He had mentioned them once before and that he liked the technology they incorporated but that they were pricey. However realistically the big box valve covers are not going to be cheap and I know stock unpainted stock ones are somewhere around $300

The ones I am using now are chromed and I would be happy to use them again even though I prefer the painted ones like yours. There is a distinct added benefit for me if I am able to run stock covers because of my vintage AC compressor that is interfered with by the big Brodix covers and will require a little ingenuity. When I talked to the builder he said he was not sure that the "jedsels" would fit inside the stock valve covers but I told him that I knew someone who knew how to make them work together

So the real cost difference is nil at the figures I am guessing at. With the purchasing cost of new valve covers like the ones from Brodix that will hold a girdle plus the $350 price for steel rockers I am rapidly closing the gap on the overall difference. Add to it bracket mods and costs along with new belts for the ac unit plus the hassle involved, it is rapidly approaching to be a difference of under $100. To me that is a no brainer and if it works out that way I am indebted to you once again.

Interesting note on steel billet from Compcams. The camshafts that they make are mostly from a stock that they call tempered steel and not steel billet. The difference is only $16 more for steel billet but if you do not ask for it you will not get it. My builder was really surprised to hear that and passed along a thanks to you and the forum. He had been under the impression that their cams were all steel billet cams.

The word on the projected ETA for the motor will be Christmas and there would be very few things that would be able to make me any happier than a good solid performing motor for Christmas. However I am realistic and am aware of Harvey's Law that simply stated said that Murphy was an optimist. Things could be delayed for a number of reasons and if the time necessary to do it right is not taken the first time there will be another opportunity to do so right around the corner.

He has mentioned that he is well aware of how much my car means to me and that he will do his end well. At the same time he has cautioned me that with the light weight along with high HP and torque it will be a handful. He does not seem to consider my old lightly modified L72 or my highly modified 96 Impala stroker any type of what he calls "necessary experience" to handle something in the 5 to 1 weight/ power ratio.

We will just have to wait and see but meanwhile I am enjoying and anticipating the grin factor.

Thanks

Doug

 

Hey..I just saw this post on another Forum...looks like he almost built your motor!!


The Torrington bearing he was mentioning is probably on the timing chain set. Many people use them to cut wear on the block right behind the cam gear. But I don't like any more little needles in my motor than I need. I always drill an oiling hole directly into the #1 main galley in the block right behind cam gear. The gear presses back on it, so no oil pressure loss and you get pressurized oiling to cam gear. Blocks always stay perfect with that simple mod.

Just for reference, I use a simple Cloyes 3 position steel timing chain set.....the $30 kind. Never had an issue...comes with a GM part number on cam gear. They drive my roller cams with huge spring pressure and RPM and never a hickup yet.

What are you doing for oil pan and oil pump?

Anyway, thought you would like seeing these dyno results.

JIM

The best pull so far:
659.7 hp peak at 6,200 rpm
601.01 average horsepower from 4,500 rpm to 6,500 rpm
592.8 tq peak at 4,800 rpm
575.53 average torque from 4,500 rpm to 6,500 rpm

The engine is only barely falling off at 6,500 rpm it was 658.2 horsepower, the next pulls will go to 6,800 rpm.

The basic engine specs:
'73 454 two bolt studded truck block
Eagle 4.25" crank and rods with L19 bolts
SRP pistons, 10.76:1 actual compression ratio
Xceldyne belt drive
Comp XR solid roller 248/254 duration .675/.680 net lift after lash 110 center
Schubeck Roller-X lifters .903"
T&D 1.8:1 shaft rockers
Brodix BB2 heads 305 cc ported, 2.25" x 1.88" valves
Manley NexTek valve springs
Edelbrock Victor Jr. port matched
Carter 172 mechanical fuel pump
Tapered carb spacer to adapt 1050 Dominator to 4150 pattern intake.
Mallory HEI with MSD guts

This engine has been apart for months while I waited for the Schubeck Roller-X lifters, I had previously gone through a couple of sets of Comp solid rollers. I caught the first set of Comps when they started breaking up, I was just a little slow catching the second set - so the engine had to be refreshened to clean out all the roller lifter debris.

The engine dyno tuning has included two camshaft and three intake manifold tests. The testing started with a Chet Herbert 6K camshaft that was very close to the Comp cam, with a bit more exhaust side bias, and a vintage Edelbrock C454 intake manifold. That cam and intake were down about 30 points almost across the board. Next up was an RPM Air Gap with a tapered 4500 adapter spacer, which only slight improved over the C454. Then with the Victor Jr. it really started picking up everywhere. The Comp cam brought it to the current results, and moved the peak hp and torque rpms down 300 rpm vs. the Chet cam.

It will be another month before I get the car reassembled, and I'm looking forward to quicker e.t's and faster mph since I have more tq and hp across the board vs. what got me the e.t./mph listed in my signature.

Thomas
__________________
"Bomber" '67 El Camino eternal project/driveway art
'65 El Camino Street Beast 496, 1/8th mile 6.934 e.t. @ 101.84 mph, 1/4 mile???? probably ~ 10.8x @ ~ 126

 

I run a 9.8" Mark IV Bow Tie (long out of production) and is externally identical to a standard passenger block 427/454. All part of the subterfuge....

Good luck,

Mark[/QUOTE]

Let me just add this here, The Mark IV Bow-Tie is still in production, I'm not sure where you're info is coming from. The "original" Bow-Ties had the head bolts into the water jackets. These were the very first ones.

I'll list the part number's for the "new" "Sportsman" if it'll help anyone:

The 25534362 is the "short-deck" 2 piece rear main and comes with the 4.494" bores.

The 25534363 is the identical block except it has the 1 piece rear main. (We do not use these)

The 25534367 is the "tall-deck" 2 piece rear main and 4.494" bore.

The 25534364 is the "tall-deck" 1 piece rear seal and 4.494" bore.

The 25534368 is the "tall-deck" 1 piece rear seal but a 4.560" bore (finished-honed from G.M.) and it's "powder-coated".
ALL are CNC machined!

Now take note here: these "Sportsman" blocks all come with "stock" main caps, the "steel" cap option comes on the Bow-Tie "Race" blocks.

I know this all to be fact, I have 5 (short-deck) units on the engine stands, I have 20+ add'l on the shelf, and I know as of today they're not available until January 2007. This is from the local dealer. This is also why I must keep about 25/30 kickin' around.

Now back to this unit:

We've done numerous types of these in the past and are in the process of doing some 3 or 4 "stock-appearing" as I speak. To stay within a certain budget, Comp's "Pro-Magnum" rollers fit under the "bone-stock" short factory valve covers with a single thick gasket, it is a close fit but if you "work" the (exhaust) pushrod length's they go. Worst case scenario is a double-thick V/C gasket. Most units I do for the 100% "factory-appearing" restos must have the correct thickness single gaskets. The issue is the exhaust "poly-locks" not the rockers themselves.

(Important) Be very, very careful with ANY shaft rockers!!!! Most people that aren't extremely familiar with these assume they are merely a "bolt on and go deal". This couldn't be further from the actual truth.

Fact is you must establish the stand height's FIRST, this has nothing to do with the pushrod lengths, simply put, it merely sets the "contact pattern" on the valve tips, then you proceed to "position" all the adjusters in the rockers at a very specific position, this "maintains" the correct "oil metering" system, and last you order the pushrods to "connect" the lifters and rockers. (There are shims that are supplied with most "shaft" rocker assemblies to set these dimensions, this isn't as easy as it first appears at least to the lesser experienced! AND we know of more issues with respect to the ALL the BB's pertaining to the way they're mounted!)

That cam choice appears to leave some question in my own mind with respect to the compression ratio, not 100% sure, and will probably not change your "seat-of-the-pants" feeling, where it really counts!
Thanks Gary in N.Y.

(Add) I came back to add this here about the fuel system, I actually had 2 requests about the fuel line size with these BB's, this week. I would pass along the same feedback I gave them. These units really need a 1/2" line from the supply inside the tank/cell to the front!

P.S. With respect to the cam choice, ALL these units get the cams ordered by the specific "lobe-numbers", we very rarely use "catalog-cams" any more. "Specifics" to the individual units AND the "specifics" to the car dictate the cam numbers. There's no other more accurate way, "pump" all the numbers into the software, and order the best lobes! And as was stated above I believe by Jim, when you order the cam specify "Steel blank/cast gear". you'll be good to go! Personally I have many units out with the "cast blank/cast gear" combo and don't have a single issue. BUT, spring pressures are more critical with the cast pieces.

 

Hi Jim

I have not yet given the oil pump any personal consideration but it has been my plan to run a L88 pan. Once again my headers come into play and rule out big and wide pans.

I took a look at the specs on that "other" motor and they are similar with the nod going in his direction for probably 25-30HP more. At least that is how I see it. I like those lifters he is using but they have to go with my builders mandate of all comp cams parts for warranty purposes. He says some folks pay him thousands for 5-10 more HP in race applications but he is figuring 600-625 HP and 550 or so torque for me with virtually no maintenance and with a warranty. Those last two items are something the expensive race motors do not have although they are more powerful by a considerable margin.

Other than the intake I am inline with his recommendations and he understands my position on not making room and spending the money for the numbers like you and Mark are getting. I might go your route in 2 more years or so and after I harness what I will be getting now. As far as harness goes I am hoping for locators and a traction bar to work and a 12 inch organic clutch. The clutch disc has a 500 rwhp limit so we will just have to wait and see. I have never run a traction bar on my car and in the past the locators and controlled wheelspin (w/fat tires) got the job done. Now with todays rubber and going to the other end of available DR's instead of Mark's sticky MT's I plan to have some wheel spin just keep breakage down to a traction issue and not parts. I do not want to compete with John Z for a photo shootout of twisted shaft parts.

The racetrack situation around me is not good IMO because they are all 1/8 tracks and the nearest 1/4 is 3 1/2 hour drive away. The street scene is really bad with no organized legal events AND THEY SEIZE AND AUCTION OFF CARS CAUGHT STREET RACING.

Their used to be a 1/8 tack nearby for "run what you brung grudge racing" with no trailers allowed but it got closed down due to urban sprawl. The local BMW club does rent a road race track a couple hours away two weekends a year and they do accept other cars at their discretion. I know there are some 911's and a couple of Z06's in their group. It is a not a "race event" but a chance to let it all hang out in a safe jail free environment (and not loose your car). To me that sounds like real fun and worth the expense. To me the parking lot autocross events are spectator only and then only once in awhile.

Weekend 1/4 drag racing is expensive around here. The local dyno owner told me that even with him owning a truck and trailer it still costs him 1500 for the weekend. At 6000 a month that is not what I consider wise for me. However there are weekly muscle car gatherings around here that are kinda fun and I do know a couple of nice lonely roads for exercising driving skills (other than a high deer population that is a problem around here)

Doug

 

I didn't realize GM had brought back the Mark IV Bow Tie block. When I bough mine in the '89 or 90 time frame, GM stopped making the Mark IV Bow Tie. They came out later w/ the Gen 5 and shortly thereafter the Gen 6 version. It was a couple of years before aftermarket cast iron Mark IV blocks were available. For a few years, it was virtually impossible to get the Mark IV Bow Tie block. I'm surprised they came back w/ the Mark IV architecture.

The shaft deal required shims to get correct geometry (a rather time consuming, but not difficult propostion) as well as a significant amount of grinding the heads to gain sufficient pushrod clearance. Jesel instructions were easy to follow.

Mark

 

Edited to tone down my initial response

According to the GM Performance Parts catalog, these are not Mark IV pieces:



Note carefully the notation about requiring Gen V-VI front cover, as well as oil pans. These sportsman blocks are NOT Mark IV blocks, nor are they visually identical to the original Mark IV castings. I thought it strange I had *never* heard about the return of the Mark IV Bow Tie.


Mark

 

Hi Mark

IMHO these posts are for the benefit of all. Some may very well have knowledge that another does not and most of us would be less than truthful if we did not confess to receiving most of what we know from someone else.

Now I have the advantage of knowing for sure that all of you know more than I do on things pertaining to motors and corvettes. So consequently I have nothing to loose and everything to gain by any here whose words are proven. However so do each of you have the same opportunity to gain knowledge from each other.


Doug

PS. In my "occupation" pride is exposed for what it really is.... something that hinders you from learning from someone else and moving forward.

 

Doug, well said. My response, admittedly over the top, is a reaction to an accumulation of many questionable and often incorrect posts across several forums from Gary.

I'll edit it to be more civilized.

Mark

 

Read the part numbers in the post!!!!!

In the picture YOU posted count the timing cover bolts, I believe there's 10, not 6 there, even with my "bad" eyes!!

The blocks can be ordered with either rear seal! Wake up guy's?

The head bolt pattern on ALL the part numbers I gave you is for the MK-IV heads. Thanks, Gary in N.Y.

(Add) I ran out of time previously, if you are building the platform on the "old" MK-IV, the block to use, with the 9.800" deck, is the 25534362. This accepts all the MK-IV components with only one exception. This is the oil filter adapter. When G.M. upgraded to the "priority-main" system they omitted the older style filter adapter. Every other component, the "standard" 2 pc. rear seal, the MK-IV pan, the MK-IV timing cover, and the MK-IV heads, is all conventional! We do over 100 of these builds per year based on this particular block. I just placed another order this week and was told not available until (possibly) mid-January 2007. Price will remain about $2000.00. This is the "cast" main cap unit.

P.S. I have about 30 of these kickin' around here (2 pc. rear mains)! They are listed in the 2006 "Performance Parts" catalog as:Bow-Tie Sportsman blocks and Bow-Tie Race blocks! They use ALL MK-IV components except you have a 1 pc. rear main seal option. It's simple. You must simply know what part number to order. Years ago there was less options but todays blocks (above) are 100% compatible with ALL early parts.

 

Hi Mark

Well I was pleased to hear that the internal balanced assembly is considerable less reciprocating weight and the additional cost is only $250. (It is still forged steel) To me that sounds like good cost/performance so I am going to go with that and will also run a aluminum flywheel even though my builder is not keen on them.

The Jesels also sound great and my builder seems too have a certain amount of reverence for them. They too fall into the good cost/performance club if I can run my stock valve covers. However first I need to check with Brodix and confirm that they will work together and then from you on the clearance issues. I figure the baffle/breather must need some work and was wondering about your solution for that or any other concerns with using them together?

Thanks

Doug

 

To make the factory stamped steel valve covers fit w/ Jesel shaft rockers, I slightly elongated the 5 V/C bolt holes so as to position the covers "up" towards the intake side of the engine. This is required because the back of the rockers nudge the back of the valve covers (on the intake side). Then I use 2 gaskets, a thick cork gasket on top and a rubber/steel GM gasket on the bottom.

I don't know if the valve cover mounting surface height vs. stud boss of the Brodix heads are different than AFR. This could require more or less gasket height accordingly.

Its been years since I trimmed the oil baffle -- originally for clearance w/ Comp SS Hi-Tech rockers. I didn't remove it, only trimmed what was necessary for clearance. It did not require additional trimming to work w/ the Jesels.

BTW I'm running the Jesel Competition series. These are a little more expensive than the Sportsman series. As long as the stand & rocker body heights are the same between the 2 series (and I have no reason to think they would be different), valve cover clearance should be equal.

Regarding the aluminum flywheel, I did not notice a big difference from the steel flywheel. I'm glad I changed, but the difference was small. I'm sure you know already, but make sure you run a good harmonic balancer. Ask Jim what can happen if you go w/ a cheap damper. We now both run ATI Super Dampers.

Take care,

Mark

 

Hi

This question is for those such as Jim and Mark whom have made changes to their body and suspensions to accommodate higher overall engine heights. Now I believe your hearts desire is towards drag racing but IF you were to go road racing do you feel that your height adjustments to body and suspension would overall hinder or help your handling.

I am wondering about taking the extra time to do the fuel line right and then I might just as well go ahead and make the mods to go with the high single plane intake. Also if you have any opinions as to whether the short shaft 12 bolt Toms rear ends are good or bad for road racing. I know for high rpm launches with traction they are pretty good. I have heard that the traction bar is not good at all for handling but then wheel hop is a real big cause of expensive damage. I also know that I have to decide just what I prefer the car to be best at but you guys have already gone to the infinite degree of an ultimate power/weight ratio with a midyear and there is no substitute for experience.

Sorry for asking so much but as much as I would like my car on the road asap I would rather do it once right. (If that is realistically possible)

Thanks

Doug

 

I haven’t raised my body nor is my engine higher than an L88. I haven’t made any suspension mods to alter body or ride height. I run Bilstein shocks and a big front anti-roll bar. I also run the VBP offset upper A-arms. My back spring is a shortened 500 lb spring to compliment the offset control arms. No rear anti-roll bar as I have sufficient throttle induced oversteer. An understeering setup is much safer w/ big power.

I run 3” half shafts w/ 1350 u-joints and don’t see how that would affect road course handling one way or the other. My rear end is a Tom’s 3.08 unit upgraded w/ 30 spline inner and outer axles, not the 12-bolt. Jim is running the big 3.5” half shafts w/ 1480 u-joints, so he can talk more specifics on that system. The only downside I can see to the big 1480 setup is increased mass and a loss in travel. Again Jim can talk more about how much travel is lost w/ the 1480 setup. Of course Jim is also running a unique Dana 60 differential.

A center stabilizing bar is not really a traction bar in the conventional sense. It acts as a torque arm to stabilize the differential and keep it from rotating. I’m running a South Side Machine bar and the only downside to road racing I can see is the loss in ground clearance. Otherwise I can’t see it adversely affecting handling in any way. The heim jointed bars don’t hang as low as the SSM list bar.

Mark

 

I'm the goofy one that does weird stuff....Mark is more sane....at least slightly!!

My body was at stock height as well as engine for a long time. I was using a Team G single plane a Dominator. When I became determined to put a Super Tall Super Victor on it...I had to come up with something. Modifying the hood was one thing.....but then the body lift idea came along. I had body off frame anyway, so adding 1" spacers wasn't a big deal. It got me just enough room to stuff a Super Victor and a modified air cleaner under a stock 427 hood.

My suspension is nothing fancy. Until just recently I had VB 550 lb springs in the front, stock arms and stuff with poly bushings. I have a stock trailing arms right now with poly. I have some offsets in garage to install this winter.I have a steel Daytona spring with an extra added leaf, plus I do use a swaybar on the rear. I think it helps control launches somewhat.

But I don't do any serious cornering. I cruise...and go fast in a straight line.

Anytime you raise weight in the car..it wouldn't help handling...but I think even Guldstrand built a diff set up to raise diff higher. His reasoning was to correct halfshaft angles when car was lowered.

I guess it all depends on how serious you are about handling. I don't run sticky cornering type tires....so my supension is already much better than my tires...they are the limiting factor.

The Tom's 12 bolts would do fine cornering I'm sure. You want the good outer axles etc.


JIM

 

Hi Guys

Well Mark I guess I am not done learning about the dangers of assuming. Hope you did not take offense over me thinking that you too had done some mods to gain height in the motor bay.

I like the rear setups that both you and Jim have put together but for now I am going to have to get by with less then you guys have. However I did order the drag kit from dragvette.com that essentially is new rods to take the angle out of the half shafts. He claims a 1.45 at 60' with no other traction mods than tires and was real nice to talk to. That and I have run suspension locator plates in the past and will do so again. Who knows how it will all fit and come together with the TKO 600. Kinda cold this time of year to spend to much time on my back.

Also I did go with the internal balanced rotating assembly mainly because of the lightened reciprocating weight. Of course then switching to an alum flywheel was a natural. I choose a QFT 950 over the Holley HP because of a few issues with the last Holley's quality control. However I had to use their new Q series rather than the P model because I need to run a solenoid for my vintage air when it runs at idle. To bad about that but they will build to the specs of the motor and make it without any provisions for spark advance. Also I will take advantage of the super low base plate manufactures you mentioned and get as tall as air cleaner as possible. I had thought about those top piece filters but they are really ugly and if I can get a 4 inch in there or even 3 1/2 it will be better than stock

However I really wanted to wish you and the others a very happy holiday season and for the following year to be your best ever. You have immeasurably helped to construct what should be a real good running combination that should be completed by the 1st of the year.

Thanks again

Doug