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workable compression heights for a stroker 2003 John Foottit

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workable compression heights for a stroker April 13 2003 at 12:15 PM John Foottit   (Login CrazyHorseEB)
from IP address 206.207.159.23
I'm trying to build a 408C for my 1970 mustang fastback, and was looking at possible combos to keep the CR in check, I was wondering if I'd run into problems with this combo:
 
4" stroke 4340 scat crank with 2.1" rod journal (small block chevy)
6" 4340 Childs and Albert Trackmaster connecting rods for a SBC with .927 pin ends
Wiseco 4.030" bore 1.125" comp height flat top pistons (have to cut new valve reliefs?)
 
this is going into a 4 bolt 351 cleveland with 4 barrel quench heads and from my number crunching yields a piston height.075" below deck and would yield a 10.6 compression ratio based on a 8.8 cc head gasket, and 62 cc heads.
 
I'm wondering if anyone cold advise on whether having the piston that far down in the bore would cause problems with heating issues, and also if it would cause me to loose the quench benifits. I plan to fit the motor with a fairly good size mechanical roller cam, and a single plane with a 750-900 cfm holley, and am fitting a richmond 6 speed behind it in the car. I intend to use the car for occasional street driving, some 1/4 mile, but mostly open track road corse enjoyment.
 
Please advise, and help me with anything I might be overlooking, as this is my first cleveland buildup...
 
John Foottit
1970 Boss 302 clone
1970 Bronco SEFI 5.0, dana 60's, etc
1993 F250 Turbo tow rig
Vallejo, CA
 
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Ben Sinclair 
(Login duplox)
Moderators
12.243.130.105
no more quenchie April 13 2003, 12:55 PM 
 
yeah, .075 plus a gasket is wayyy too much. .075 including the gasket is too much. get your block decked so you have .06 maximum total piston to quench area clearance. so if you have a .04 head gasket, deck your block so the piston is .02 in the hole at most. the closer the better, i'd zero deck it if you can handle the compression. wiseco makes a reverse dome piston, 22cc. If they offer it in the CH you want, that'd be the way to go. zero deck your block, .04 gasket, quench heads, reverse dome... that'd be one hot street machine.
 
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RWalton 
(no login)
65.73.75.217
Re: April 13 2003, 1:30 PM 
 
Ben,can you get .075" off of a block.I know some you can but not without port matching.
 
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Ben Sinclair 
(Login duplox)
Moderators
12.243.130.105
your intake will have to be milled.. April 13 2003, 5:55 PM 
 
yeah, thats a bit much. maybe if you get it milled like .040 you could run a .023 thick gasket, that'll get you .058 clearance... not bad. Or get the heads O-Ringed and run it without a gasket, get your block milled .015. tune the carb on the rich side and you'll be okay.
 
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Brian S
(no login)
152.163.189.132
A few red flags April 13 2003, 6:28 PM 
 
There's been a lot of discussion about 408Cs in the past. It wouldn't hurt to go back through the old posts. It's a big step for a first timer.
 
The scat cranks are for 351W applications. When they advertize 351C, they mean a 351W aftermarket block with 351C main journal diameters. 
 
The crank should still work if you use a spacer for the timing chain gear. The harmonic balancer is another consideration because the crank is also 3/4" shorter.
 
A 4" stroke in a Cleveland has some side effects because the deck height is very short. You end up with a rod/stroke ratio that has a lot more side load on the already too thin cylinders. 
 
The piston is so short that the oil ring passes though the wrist pin. The rings are thin and stacked very close together. All this makes the piston is less stable and has a tendency to burn oil.
 
Verify the journal width of the 2.1" crank. Make sure it is the same as the Chevy rods because aside from some aftermarket cross breeding, Ford rods are narrower. 
 
Also check the 1.125" CH Wiseco piston. I don't have that height listed for a Cleveland piston in my catalog. 1.23 & 1.43" only. Maybe they're new or you were talking about a custom made set.
 
Don't try using a Chevy piston with new valve reliefs cut unless you are using small valves and a very mild cam.
 
A piston to head clearance over .060" will sacrifice any quench benefits. I'd recommend a 393 stroker as a much better street/strip application.
 
Looking at the rest of your plans has me wondering if you're another one of those dreamers? or do you really have the funds to finish this project.
 
 
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John Foottit 
(Login CrazyHorseEB)
206.207.159.23
Re: A few red flags April 13 2003, 10:19 PM 
 
the piston I was looking at was for a chevy 350 with a 6" rod...I may wind up having to keep it down to 393, but even there looks like CR trouble with the quench heads... What type power could I reasonably expect out of a 393? I want nice numbers, but much more important to me is to have an engine with good longevity, which, thanks to this site now has me rethinking the solid roller cam, I've never had problems with them before, but they have always been in race motors that were torn down after 2 or 3 events (572 donovans with 14-71's and enderle bird catchers...) As for funds to finish the rest of the project, I've been slowly collecting parts and building over the years (bought the car at 16 in 96)most of it is sitting on shelves in the garage right now, as the car gets painted in a month or so, then I can start to put it all back together... 
 
John Foottit
1970 Boss 302 clone
1970 Bronco SEFI 5.0, dana 60's, etc
1993 F250 Turbo tow rig
Vallejo, CA
 
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Brian S
(no login)
64.12.96.202
Expectations April 14 2003, 2:07 AM 
 
It's a matter of money and intended use. What is a nice number?
 
Parts combination guides.
 
Cleveland pistons have a valve relief that goes beyond the piston edge. Chevy pistons may not have enough material in this area.
 
Solid cam/rollers are expensive and require a lot more maintenence. Not many street grinds are available.
Consider a hydraulic roller instead.
 
Go back a few pages for a lot more 393 & 408 info. 
Also read my deck height topic.
 
Add up your costs and post them here so readers can advise more info. 
 
 
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Clive NZ
(no login)
203.97.2.243
Could you show your calculations for static C.R. as........... April 14 2003, 6:23 AM 
 
I have just seen a guy spend over $40,000 on a stroker 460 thats out to 512. Before they put it back in for the third time they worked out that the engine calculations had all been done on the stock stroke figures. Measure twice and cut once!!
 
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futurattraction 
(no login)
128.255.165.160
CR April 14 2003, 9:01 AM 
 
I'm gathering parts for a 393. I'll be running 6" H-beams SBC rods with a Scat cast steel crank. With around a 64cc chamber volume (mine are Aussies), you're going to be looking at around a 14cc reverse dome piston to keep the compression down in the low 10:1 range. That's with a 0 deck height. I calculated it all out awhile back, so I'm going from memory, but I know the above is pretty close. As was pointed out, SBC pistons aren't going to have the valve reliefs in the proper location. With C's having the notch clear out to the edge of the piston, ring placement is typically farther down on the piston than would be with a chebby-sourced piston. I'd opt for true C-designed pistons to avoid the headaches/hassle of dealing with the mismatched parts. It ain't worth it, in my opinion, to jury rig parts to work, just because they're cheaper up front. Also, compression height for a 393 with 6" rods should be around 1.27-1.28, with a nominal crank CL-to-deck dimension of 9.206. This will help keep the wrist pin out of the oil ring groove and provide a bit more stability for the piston.
 
Hope this helps!
Scott
 
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Brian S
(no login)
152.163.189.132
Oil ring location April 14 2003, 4:22 PM 
 
The valve notch definately works against you when a short piston is needed. I would be very surprised if 1.27-1.28" CH was enough to keep the oil ring away from the wrist pin.

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