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Making a Clevo really REV!

30K views 162 replies 30 participants last post by  XDman 
#1 ·
Just finished putting together a fairly hot 351C, balanced, flat tops, good heads, redline manifold, 750SQ DP, etc etc, and am about to start building another engine piece by piece.

Since i'm going to be bulding it slowly over the next year, I really want to build something that is going to rev like crazy, yet still make plenty of power through the mid-range.

The main thing I want to find out is how to make the bottom ends safe and strong for up to around 7500rpm.

What are the main things to do to a clevo bottom end to help them cope with this kinda revs?

I've already started knive-edging and rubbing back the crank, and will have it balanced well, i've also bought a main-cap girdle to help the bottom end.

Almongst other things I plan on doing to the engine, what will keep the bottom end strong for up to 8000rpm rev bursts?

Thanks
 
#2 ·
What rods are you running? I've had my 351 rods to 8500rpm but honestly I wouldn't do it on a regular basis.

I've been told by various cleveland builders that:

a 351 rod will do 7000rpm safely when prep'd,
a 302 rod will do 7500rpm safely when prep'd.

Just make sure it's all balanced properly, down to the gram. Otherwise it'll go bang. Yes, measure the machinists work as some are pretty rough, even though it looks good.

Brenden
 
#3 ·
Oil restrictors and a solid cam would be mandatory. The oil restrictors (which fit into the mains) restrict oil flow to the top end of the engine and keep it down the bottom where it is needed most.
 
#6 ·
Brenx: I have both 351 and 302 rods. I am going to use the 302 rods for better rod geometery, increased TDC time, easier revability, etc, etc.

I will be balancing most of the engine myself to make sure everything is spot on.

Racer: I will definetly be running a solid, and I was looking at changing the oiling system, so as to not require restrictors in the bottom end, as RevHeadRon said, mainly with revised oil pump, different pressures, big sump and deburred top end/block.

Supa R00: I realize it must be balanced extremely well, but what I'm trying to find out is all the other aspects of keeping it together well.

Anyone used or looked into using or know about main cap girdles?

Std, 4MA, 4MAB?

4 bolt caps? either std or redrilled?

tunnel boring, deck heights, etc a must?

Thanks everyone. :)
 
#8 ·
de-stroke?

me non comprahende. understand no.

Naa, I'd like to stick with as much cubes as I could. considered a 377 or so stroker, but it kinda went against my original plan of strength and revability.

wouldn't using a 302 crank make it a 302? is is that what you are calling a destroked 351. otherwise know as a 302.
 
#10 ·
Some Pro Stock drag Clevelands used to de-stroke them, but they were also revving to almost 10,000rpm.
8000rpm is really a practical limit for a road going engine, with your limit of 7500rpm being more sensible.
You will also need a decent explosion proof harmonic balancer and a steel flywheel, I would also use 4 bolt mains and have it tunnel bored.
Any of the cranks will do, some say the 4MAB's are the best, but in reality there is not much difference between them.
6" rods are mandatory.
A bulletproof oil pump drive.
The others have already mentioned most of the other stuff.

Rick.
 
#11 ·
DON'T bore too much they can split bores. But thats somewhat corrected these days with tighter clearanced pistons. Don't close clearances up on mains either at high rpm they have trouble feeding enough oil in there...
 
#12 ·
I wasn't keen on destroking just to gain a coupla hundred, maybe a thousand comfortable rpms.

I'd prefer to stick to my limits as Soxx has pointed out, and maintain a strong 351.

Good Balancer-check-romac 8500rpm rated
Steel Flywheel-check
4-Bolt Mains-no, but are they really neccessary? have considered though.
Tunnel bored-definetly
I've got a 4MAB so I'll run it at probably 10/10
6" Rods-most probably
Bulletproof Oil Pump Drive-check

I hear you ebxr8240, not boring with keep it stronger. is .030" too much?
I'd love to get hold of a std bore black block, but reality is they are getting hard to come by.

Will be injected so a rev limit of say 6000 to 6500rpm on the street and 7500rpm strip should keep it all happy :)

Then bolt the bottle back on >)
 
#14 ·
qwikcorty - Tunnel boring may not be neccasary, however it does make certain that the tunnels are true. I would do it.

ebxr8240 is right, Clevos are thin walled, try and bore only 0.020" if possible.

4 bolt mains may also not be neccasary as they actually add only a little strength to the bottom end as the 2 bolt caps are huge anyway. 4 bolts do however help stop the caps 'walking'. You can probably get away without it.

Rick.
 
#15 ·
You could use a stud girdle which would add considerable strength to your bottom end without deflating your bank balance.They are only around $300 and are a cheaper alternative to 4 bolt mains. Obviously not as tough as 4 bolt mains but it should handle those revs that you are affter.

If you do go to 4 bolt mains setup you will have to register the caps properly, locate & drill the holes in the block & then align bore & align hone the crank bearing saddles. By the time you do all of these things the cost would be substantial.
 
#16 ·
I went for a nitrided offset ground 4mab crank that was using 6 inch chevy rods. Solid cam that run up to 7500.

Was good for up to about the revs your looking for , the only concern is the crank when you offset grind it with real big revs. But if you build it right then 7500 on the strip isnt so bad.

Was advised not to thrash the tits off it everyday though.
 
#17 ·
Soxx: Yes I think I will tunnel bore. Nothing like knowing in the back of your mind that it is one less thing that could be wrong.

I8AHSV: Stud Girdle will also be a must I think. Looked into the aftermarket 4-bolt mains that require tapping a thread into the block. Although after machining, everything should be honky doory, I have heard from more than one source that it can infact weaken the main cap area and cause cracking, leading to boom!

bdave351: The 4MAB I have started polishing is std/std and i will have it hardened once balancing/finishing is done, may have to go to 10/10.

I have decided that I too will be running 6" rods (or 302C possibly), but with the shorter deck height pistons that are readily available now at a reasonable price. The only problem being, finding pistons that are low comp.

But as you say, not flogging the crapper out of it all the time will hopefully keep it together a bit longer.

Slowly coming together now, just keep playing. thinking about alloy heads now too. ahh more power = more $$
 
#18 ·
""I have decided that I too will be running 6" rods (or 302C possibly), but with the shorter deck height pistons that are readily available now at a reasonable price. The only problem being, finding pistons that are low comp.""

why do u want low compression? a engine making power around 7000rpms is going to need a big cam that inturn needs lots of compression.

im using a acl race kit, which includes the 302rod low pin pistons.
 
#19 ·
If you are going to run those sort of revs tunnel bore is mandatory. This is to make sure that the bearings are going to have a correct crush & you want risk spinning the bearing(s). This is because high crank loads can cause the main bearing caps to stretch vertically cousing the bore to be no longer round

Due to continual heating and cooling cycles block can suffer some warpage which can couse some misalignment of the main bearing bores. This process occurs slowly over time and crank & main bearings compansate for this with the gradual wear. If you install a reground or a new crank this misalignment could cause a crankshaft to bind & it will destroy your new motor.

As for the 4 bolt main coversion cousing cracking of the mains as far as i know this is only a problem on late model Windsors & not on Clevos. Anyways a properly setup stud girdle should be more then enough to stop the caps from walking. I would only sugest to buy new aftermarket front and rear caps if you are planing to run those sort of revs for prolonged periods (eg like they do in boat racing). Otherwise it's all good.

Also you should consider using some reputable afftermarket rods like Eagle. By the time you shot peen & polish your rods, Buy bolts, crack test them & balance them & resize them u will find that price wise you are not that far away from some aftermarket rods. That is if the budget alows.

As for the Alloy clevo heads recently, I've been in a customers XW 378ci clevo with Air Flow Dynamic heads (mild porting & cleaning + 3 angle valve job) running a nice solid cam 10.5 comp..etc and all I can say to anyone that can afford them is go for them. The car went nuts like a pisspot on a payday. Once again if the budget alows go for them.
 
#20 ·
qwikcorty: I kind of worded that improper :p I plan on using the same engine, next build, but with around 8:1 comp/ratio.

Have looked into the ACL race series kits, which are good for the dollars spent, yet are only a cheap copy of good pistons.

I have used the kit you speak of in a mild/hot 351 and the results are excellent, especially since it was built on a reasonable budget.

But the piston crown is not up to any kind of misuse, or modification. :(

I8AHSV: I am aware of what tunnel boring is. thanks.

The aftermarket 4-bolt mains you speak of, have you tried them? If so, what were your experiences? Were they the kind that you use with a 2-bolt block, then drill and tap?

Rods, that is why i said prob 302C rods. There is no question that aftermarket rods such can be a lot stronger/durable than stock 302 pieces. and yes after comparing, there isn't much difference.

Alloy Heads, I just gotta keep saving.
 
#22 ·
4 bolt steel caps are a MUST in any serious clevo making serious power or you will end up with caps walking and inturn putting uneven pressure on the bearings. Secondly block choice will healp you also. Try getting you hands on a PILLOW block. Pretty much any clevo block can be made into 4 bolt

Thirdly use a ressin to fill you block to the top of the core plugs(level) . at this point it will be kist level with the front holes of the block where your water pump sits.

Also stroke it!!!! Use a chev sized rod( NOT A CHEV ROD) but an eagle 6.0 rod. If you want you can use a 5.7 but you will find that it puts alot of side load on your bores.
With it being strokes you have also made the big eand bearing diameter small :).

You heads and cam will need to be the correct size if you actually want to make POWER at these revs as apposed to just reving it to these revs.
 
#24 · (Edited)
Maniac:

Pillow Block, NASCAR Block, Interceptor Block, what ever. I would love to be able to afford one of these to be the base of my engine.

I know there has been discussions about grout/resin/whatever in the base of the block. Does it really help that much? Is it worth it sacrificing cooling performance? Does it affect cooling at all? I wouldn't of thought much.

Stroke it? By stroking it, I'm gunna loose alot of my revability. The piston has to travel further from BDC to TDC to do the same thing. Piston speed increases, and then so does piston/bore wear, etc. The ability to rev easily will be hampered.

Have looked at stroking, seems to be the biggest gain from this is mid-range torque. but a stroked engine doing 7500+rpm just doesn't seem a real long lived project.

Also stroking to get a smaller big end diameter would have been one of the last things I would of contimplated. strength down.

But I do agree with using the 6" rods. Eagle and the such. Good items. :)

EDIT: Soxx, you made your post as I was typing. agree with your comments re: clevelands stroke.
 
#25 · (Edited)
My ute ran a pillow block picked it up for 200 dollars of Murray Occoner. If you think stroking is a bad idea then you are so far of the mark its not funny. How can more cubes be a bad thing? If you have cylinder heads to support the extra cubes then your crazy for not doing it. My ute ran 8000 rpm all th time on the strip and on the street. Your rev range isnt determined so much from cube its from cylinder head size and cam.

You loose any cooling ability from resin filling the block..ALL my street clevos are done.

Obviously big bore small stroke is better but when you are restricted to bore sizes then you have no chioce to stroke..

I mean seriously you guys arent talking about 10000 rpm 331 cube motors here in cars that weigh in @ 1500 pounds you talking about 7500- 8000 rpm street car. My ute ran 9.85 @ 135 mph 3700 pound 383 cubes 8000 rpm..............

I used a Oliver 6.125 rods and a callies crank after i bent the 4mab crank.

JE pistons, yates heads.
 
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