Sign in to follow this  
Followers 0
BlizzND

How high can you twist a Cleveland ?May 14 2003 Bob Jackson

1 post in this topic

How high can you twist a Cleveland ?May 14 2003 at 5:51 PM    Bob Jackson  (Login 8848jackson)
from IP address 152.163.253.4
First a little info about my motor. 
1970 351 Cleveland Block, stock crank, manley rods, TRW pistons(10.5-1), Manley extreme valves, & springs. 4v quench heads with Ford racing adjustable rockers. Edlebrock torker intake, Holley HP Performer carb. MSD Ignition, Blaster coil, Mallory distributor, hooker custom headers.
This is a drag racing motor in a 1950 lb altered. I launch at 4400 and shift at 6400. Problem is I use a 33 inch slick that only allows my c-4 to get the car into the 5300 rpm range at the finish line. The current gear is a 4.56 Richmond.The car runs 10.86 @ 120 mph with this setup. The motor sounds way too strong for this slow et & mph.
I am buying a larger gear either 4.86 or 5.14 to get the rpm higher into the torque range. QUESTION: What is the minimum high rpm this motor should turn without coming apart, and what is the rpm that I should not hit. I'm thinking 6500 to 7000 is OK, but 7000-7500 is nervous time. Also any idea what rpm it will turn with the 4.86 & 5.14 gear.

Thanks, this forum really helps this novice get information I need to sort out with other experts.

Bob Jackson
 
   

Brian S
(no login)
64.12.96.202    
Guessing game    May 14 2003, 6:36 PM 

Isn't it always? Your RPM numbers are pretty close to what I would be running with a stock type rod, crank and TRWs.

Long rods, aftermarket H beams or lighter pistons/pins would let you spin higher.

33s are tall, I'd vote for the 5.14s. That should give you 6000 @ 120, 6500 @ 130. I like to leave a little room so I can play with a Nitrous set up, but if you never plan to use any, even 5.33 or more may be better.
6700 @ 130, 7000 @ 135.

It depends how high your top speed changes.


Bob
(Login machoneman)
Member
12.250.29.237    
I'd say.....    May 14 2003, 7:01 PM 

your rpm (actually, at 1,100' mark or so) or at shift point into high gear should be at least 6,700-6,800 and climb to 7,000-7,100 at the line. Keep in mind that the total time or duration that the engine is at or near 7K is minimal even if your 1-2 shift is at or near 7K. 

Most racers overgear their cars and turn too much rpm in last part of track. You have a bad case of undergearing it. This is especially critical in a "C" due to int. port size greatly minimizing low end torque compared to other engine types of the same displacement. 

btw, what the heck are you doing with a Edel. torker on this engine combo in a lighweight altered? A trade for a good single plane hi-riser intake should help. 

Best NHRA Cleveland altered and econorail combinations in the past (mid-70's to early 90's) ran approx. 8,000-8,800+ rpms. Problem is many $$ needed to approach these rpm limits on a reliable basis.
 

kid vishus
(no login)
165.247.137.204    
Don't worry.....    May 14 2003, 9:15 PM 

That motor will take 8000 rpm if the clearances are correct before you ever have any problems. My motor has stock rods, and I shift it at 7500. When running qrtr mile, I cross thru the lights at 7400 while running high 9's. The weak link is the stock rods, and you already replaced them. If the camshaft makes power at 7500, turn it up there.

Basically, if I had your motor, I would set the rev limiter around 8500 and stick a 5.30 something gear in it. Mine is set at 8000 now, and it has seen it more than a few times.
 

Bob
(Login machoneman)
Member
12.250.29.237    
Hey Kid V!    May 14 2003, 9:42 PM 

He said he's leery of 7.5k rpm! 

Seriously, I forgot to ask about your cam. What does the cam card say about max h.p. & max torque and at what rpms? No sense winding her up beyond rpm range. 

Kid V. is right. Rods in 351C and Boss 302's very suspect after 7,000-7,500 rpm. Believe me I know after punching out too many good blocks with stock rods. Hey, new, bare 351C 4-bolts and Boss 302 4-bolts were just under $200.00 back then. 

You seem to have most of the parts to make this combo a real screamer w/o blowing it up. I would have also stated 7,500 - 8,000 had you not mentioned the above. Cam & springs though must be able to reach these rpms. 

Assuming no street driving (kinda' tough in an altered!): 
Intake - needs a single plane at these levels.
Block - would hard-bloc it to strengthen walls. 
Valve Stud Girdle - mandatory with springs needed at this rpm level. 
Tit. retainers - cheap at $90 a set and does wonders to spring life & attainment of rpm level. 

If your bracket racing though, I'd keep rpms to 7-7.5 max for a full season of low maintenance. Still, would pull valve springs regularly to check tension since heavy valves and hi-rpms will kill them, then lead to a dropped valve.
 
kid vishus
(no login)
165.247.137.254    
Re: Hey Kid V!    May 15 2003, 12:37 PM 

With the cam he has, I would shift it at 7000, and set the rev limiter to 8000.

Animal Jim told me the stock rods are generally good to 8000 if they are prepped correctly. I have never had a rod failure that wasn't directly related to a rod bearing failure. I run heavy pistons and pins, and yet the rods seem to take it quite well. My current pistons and pins are just as heavy as my old TRW's I used to run, and I spun them to 7500 also with no problems.
 
 Roger (Fordwiser)
(no login)
207.179.193.54    
Re: How high can you twist a Cleveland ?    May 14 2003, 10:44 PM 

Are those Manley rods aluminum? Everyone has a different idea how long aluminum rods will last, and if they'll last longer if you're easier on them. One thing is for sure, the heavier the piston is, the harder it is on the rod(probably even worse on aluminum) those TRWs are no lightweights. I think I would take it easy on the rpms, should be able to go more then you are though.
Roger
 
Brian S
(no login)
64.12.96.202    
Aluminum rods    May 14 2003, 11:30 PM 

I had a similar opinion about the TRWs, I don't think they bother to list weights. I think the technology is from the 70s, and there are lighter piston/pins available now.

Personally, 7200 is about all I would push it if it were mine, unless someone offered me a money back guarantee.

If I had a well prepped 302C rod with a KB short piston 489g, and pin 103g I'd go 7500. 8000+ with an H beam.

I'm wondering about aluminum rod durability. I've read newer alloys are good enough for 30-40,000 miles. Custom lengths are usually less expensive than custom steel rods.

Chris
(no login)
219.88.3.168    
Ran a similar combo    May 15 2003, 6:15 AM 

some years back, venolia 5.7" c#@v 2.100 rods and trw 12:1 pistons and stroked 4MA crank. Installed the old oil restictor plugs in the cam galleries...no other oiling mods apart from HV oil pump ofcourse. Used to turn it to 8200rpm with no problems, just remember to allow alittle extra deck clearance to allow for rod stretch but in saying that, I don't think it was much at these revs. High tens in a 3100 lb car. If your cams making power up there I doubt if you'll have any problems.....
 
   
Bob Jackson
(Login 8848jackson)
64.12.96.202    
Cleveland Motor Info    May 15 2003, 7:46 AM 

More info: Intake is a Edlebrock Victor Jr. not the Torker.
Cam Card AS Follows: Crane Solid Lifter # F-246/3294-2-8
Degrees Duration @ .050
Int: 246
Ext. 256
Degrees Advertized @ .050
Int. 282
Ext. 292
Degree Lobe Separation: 108
Gross Lift
Int. .570
Exh. .590
Basic RPM as advertised by Crane: 3800-7000, 11.0-12.5 compression, auto trans w/3500= converter

Compression: Each Cylinder went to 160lbs.
TRW 10.5-1 Pistons 
4V Quench Head 1970
Adjustable Ford Racing Rockers lashed @ .026
Timing Set @ 42 Degrees ( 3800 rpm)

Holley 750 HP, 77 Fronts, 85 rear ( We are changing to 80/88 as plugs look lean. 

* Have bought the 5.14 gear, now need an estimate of 
rpms at the finish line in 1/4. Still have time to drop to 4.86 gear. 
* Again this car is running 119-120 @ 10.86-10.90 at only 5300-5500 rpms in the quarter. I think getting it up into the 6500-7000 range should take off .3 to .5 tenths of the et.

Keep The info coming, gear change is set for Tuesday night.

Thanks,

Bob Jackson
 
Bob
(Login machoneman)
Member
12.250.29.237    
Good!    May 15 2003, 8:59 AM 

Victor Jr. is a good choice. Since cam runs out of steam at 7,000, no need to wind it higher. Still, should shoot for 7,000-7,100 right before the line to be sure your at max. hp. 

Agree that change should pick-up e.t. by .3 to .45. Motor would respond much better to 12:1 to 13:1 comp. ratio, but....then requires race gas. Wouldn't do this unless higher lift, duration cam is also in the plan for next season. 

Have you experimented with carb spacers? 1" min. would help, likely 2" would help more unless you have to fool with a new scoop. Would change rear jetting to 87-88's first, check plugs, only then step up primaries (good DP'er rule of thumb is 10 steps higher in the back). 

Brian
(no login)
24.157.102.174    
Why 10 steps higher in the back at wide open throttle?    May 15 2003, 9:08 AM 

If the power valves are plugged, 750HP has front and rear, why not square the carb if you are always at wide open throttle?
 

Bob
(Login machoneman)
Member
12.250.29.237    
10 steps for carbs with PV still installed!!!!    May 15 2003, 9:21 AM 

I should have added this. With blocked PV, all bets are off on 10 step rule. With carb leaving the line at w.o.t. AND (emphasis) blocked PV, DP's should start at square or near square jetting and go from there. Often, rear jetting may need a few steps higher after experimentation. 

While on the top of blocked PV's, I've never been a fan of doing this unless:

-it's a very light car @ less than 2,500 lbs
-it's a very (emphasis) powerful engine.
-it's a dual quad set-up with a tunnel ram/sheetmetal intake. 
-all of the above combined. 

I know, I know....many here run blocked PV's but...rather than debate same....let me see if I can post a good article here (if I can find it again! LOL) on the why's and wherefores of blocked PV's. 

 
    
michael
(no login)
154.5.219.37    
victor for a 351c?    May 18 2003, 3:51 PM 

when did that come out?
where can i get one?
 
     
michael
(no login)
154.5.219.37    
victor    May 18 2003, 3:54 PM 

http://www.edelbrock.com/automotive/man_ford_351c.html

which one can be made to work with 4v heads?
 

Brian
(no login)
24.157.102.174    
I run the same cam as you    May 15 2003, 9:00 AM 

Hi Bob, I'm bracket racing a 70 mustang with the same cam. I'm running 11.90's through full dual exhaust shifting at 6200 and going through the traps at 6600 in a 3300lb car with myself in it. My stall is an 8" 4700 and I launch off the two step at 4000. I have removed my exhaust(75lbs) and put 3" torque pipes on the headers. Crane also advised me to shift at 6500 with my set up. Have you tried different shift points?
Have you dynoed this engine? If so,I would love a copy of the dyno sheet. I also run a 750HP,I plugged both power valves and run 81 square with a 2" 4 hole spacer. It was a bit rich with the full exhaust but should be just about right with it removed.
 

Brian
(no login)
24.157.102.174    
Forgot to mention    May 15 2003, 9:01 AM 

I have run this motor to 6700 rpm regularly in third gear with stock rods that have ARP bolts, polished and shot peened rods. Never a problem.
 
       
Bob
(Login machoneman)
Member
12.250.29.237    
See below: Richmond Gear.com gear ratio calculator    May 15 2003, 9:08 AM 

http://www.richmondgear.com/112901.html

Can plug in your variables and calculate finish line rpm. Be aware though that with slicks (non-radial), tire "growth" at finish line will affect overall diameter quite a bit unlike radials or street tires. Another (here I go again!) rule-of-thumb is a minimun 3% growth. Another way to "size" finish line tire diameter size is to pump about 25-30 lbs. of air in a a slick (off the car!) and then measure tire diameter at the center of the slick's tread (not edge). This should be close to the real size under load at the line.
 

Bob
(Login machoneman)
Member
12.250.29.237    
btw: when visiting the Richmond site, click on.....    May 15 2003, 9:41 AM 

the gear calulator "box" in the lower right of the Richmond page I mentioned in my earlier post. It will provide other formulas for figuring out gear selection @ known rpm, speed, power, etc.
 
     Edit Message   Delete Message   Lock Thread   Respond to this message   
Bob
(Login machoneman)
Member
12.250.29.237    
Here's another "gear calculator" site: Jack Chrisman's    May 15 2003, 9:53 AM 

http://www.chrismans.com/Calculators.html

btw, Jack was the running mate to Dyno Don Nicholson with the factory Mercury flip-top SOHC 427 Ford funny cars. Jack's GT-1 was the first blown nitro roadster Mercury Comet funny car (chopped top) to break the 7 second barrier in........... 1967!

Share this post


Link to post
Share on other sites
Sign in to follow this  
Followers 0