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Author Topic:   Stroker (and other) questions...
futurattraction
Journeyman

Posts: 93
From: Iowa City, IA
Registered: Oct 2001

posted 10-21-2001 01:06 AM     Click Here to See the Profile for futurattraction   Click Here to Email futurattraction     Edit/Delete Message   Reply w/Quote
Hi,
Iíve been watching your board for several days now and have decided to jump in with some questions pertaining to various aspects of engine building on which Iíd appreciate getting feedback.

Iíve got a 351C in my 1979 Fairmont Futura which is currently built toward the ďstreetĒ side of street/strip, but Iím hoping to take it to the strip on occasion next year. The engine is built more toward torque than rpm. Toward that end Iíve installed a set of Australian 302C small port, small chamber heads. For what itís worth, Iím running a Comp Magnum 280 hydraulic, MSD ignition, bolt-down FRPP roller rockers, Weiand X-celerator intake, 750 (3310) Holley, 1-3/4Ē swap headers, C6 with 10Ē (advertised 3K) converter, and 3.70 gears. The car, with me in it, should weight around 3200. Front/rear weight percentages are 56/44. Following are my questionsÖ

1) I, like many others who have posted, am considering building a stroker at some point in the future, so am trying to do some research. Iím leaning toward the Scat 3.85 stroke crank. If I go with this piece, would 6.03Ē Aussie connecting rods (with polished/peened beams and ARP bolts) and custom pistons make for a reliable bottom end if I were to keep the engine under, say, 6K? The rods would make for a decent (not great) rod/stroke ratio 1.56+ and would be less expensive than aftermarket rods; the short compression height pistons for this setup would decrease weight, and I believe my reworked heads would support the cubes. While Iím in the viscinity of connecting rods, it appears that Scat offers both 2.311 and 2.1 journal sizes for this crank. I know if stock cranks are stroked for use with SBC rods that the rods have to be narrowed. Can anyone tell me whether Scat cranks with the 2.1 journal are designed to accept stock width SBC rods. It would make sense that they are, but I donít know. Also, are the 2.75Ē main cranks actually designed to be a true ďdrop-inĒ in a production 351C block or are they designed for the 351W and/or SVO block crowd and need additional components like a spacer ring at the snout for the damper, special main thrust bearing, etc.? Just trying to avoid surprises.

2) What kind of rpm and/or spring pressure will the bolt-down type roller rockers support? I know with the 5/16Ē pedestal bolt that there are obviously limitations as to what they can endure, but donít recall seeing any specs. When my goals were mostly aimed toward street use, this wasnít a particular issue in my mind, but now that Iím more seriously contemplating running it at the strip, reliability becomes more of an issue to me.

3) Since Iím not envisioning either my stock stroke C thatís in the car currently, or any subsequent engine seeing lots of revs, Iím thinking very seriously of putting a hydraulic roller in at some point in time. I donít believe that their extra weight should be a major factor in regard to valve float since my revs wonít be that high. More to the point, my question is this: Given my plans for the HR cam, what should I do to address the C oiling system? Iíve got the supplemental oil line that runs from the port up by the fuel pump to the rear sending port. Is something like the Moroso restricter kit good or bad? As Iím sure everybody is aware there are all sorts of opinions out there about what to do or not do to address the oiling issue.

4) For those of you who race, given the bit of information I provided about my car at the beginning, does anybody want to offer any guesses about what kind of ET I should be able to pull out of this combination? I will probably run at tracks that are around 600-800 ft sea level. Also, I have raced in the past, but not for years, so Iím not a rank amateur. I realize the 3.70s arenít conducive to the ultimate times, but theyíre at least a start. Iíve got a set of ET Streets, 28x11.5, that will be what I start with.

Thanks for any thoughts or opinions anyone cares to share.
Scott

------------------
79 Fairmont Futura, 351C, C6, 9-inch, plus...

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n2oMike
Gearhead

Posts: 1367
From: Spencer, WV
Registered: Jan 2001

posted 10-21-2001 01:51 AM     Click Here to See the Profile for n2oMike   Click Here to Email n2oMike     Edit/Delete Message   Reply w/Quote
You may want to think about some port work on the heads and intake.

The Weiand Accelerator for the 2V heads has extremely large ports outlets. They are quite a bit larger than the intake port openings on your heads. There is a severe mismatch there.

I recently finished porting two sets of Aussie heads, along with an Offy Port-o-Sonic and a Weiand Accelerator. Both are single plane intakes for the 351C.

I like the Weiand for an intake that will be used with heads that have the intake ports opened up, but it's just too large for stock heads. The Offy would be a better choice here. BOTH need considerable plenum work.

Porting the intakes...

Before starting, I cut port extentions to weld into the plenums at the four corners to help lengthen the center runners. A local machine shop installed them for me... then it was time to grind.

I bolted one inch spacers to both intakes and began hogging out the plenum, blending the sides down into ports with a 90 degree die grinder. The end ports were blended the most. They were hogged all the way to the top of the intake... to where the spacer bolts on, and blended smoothly a couple or inches or so into the port. The Offy was welded on the outside to allow maximum blending of the plenum. This was unnecessary on the Weiand.

The runners of the Weiand are huge all the way through, and were untouched. (Yes, it IS the 2V version #7516 I believe) The Offy needed its runners ground out, but I was unable to reach all the way into the center of the outboard runners. The Weiand turned out the best. It's quite purty.

I have no flowbench, but the heads seemed to benifit from some serious unshrouding of the combustion chamber. The exhaust valve is totally surrounded by chamber wall, and got a LOT of work. The intake port was unshrouded as well, and seemed to benefit from widening the floor of the port shortly before the turn into the combustion chamber. The port just looked "funny" before that was done.

There is a LOT of grinding to be done to a set of these heads. I would like to know someone who could test them on a flowbench, and if I find someone, I'll post the numbers.

These were a pain in the a$$ to port... a LOT different than the 289-302 heads I'm used to grinding on. Anyone else grind on a set of these? What did you think about them?

Later, and Good Luck!

------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367

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kid vishus
Gearhead

Posts: 3894
From: middle of NC
Registered: Oct 2000

posted 10-21-2001 02:01 AM     Click Here to See the Profile for kid vishus   Click Here to Email kid vishus     Edit/Delete Message   Reply w/Quote
Look at that!! Another Iowa guy!!
Welcome to M&M Scott.

First thing that grabbed my attention was the c6. A c4 is lighter, shifts better and is around 3-4 tenths faster than a c6.

Second thing was the possibility of a stroker with those small 2v heads. A big inch motor likes a lot of airflow and those heads arent capable of it without a ton of work.

And last thing, even in my street cars, I run solid cams to assure that the bottom end gets enuff oil. I have broke too many motors due to all the oil getting pumped to the top and starving the rod bearings.

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n2oMike
Gearhead

Posts: 1367
From: Spencer, WV
Registered: Jan 2001

posted 10-21-2001 02:21 AM     Click Here to See the Profile for n2oMike   Click Here to Email n2oMike     Edit/Delete Message   Reply w/Quote
As for your real questions... I got a little sidetracked.

The oil line is a good thing. I second the advice for a solid cam and oil restrictors to the top end. You'll also want a larger oil pan.

For good reliability, the heads will need machined for real screw-in studs and guideplates. I wouldn't trust that conversion kit for serious duty.

The hydraulic roller is limited to around 6000 rpm. A good solid works similarly with moderate durations. It's also less expensive. Ask around for advice on which ones to use.

A 750 vacuum sounds a bit small, but will be alright with the initial combo of a 3.7 rear gear and MT ET-Streets.

Grinding on the heads and intake will help... as long as it's done right.

I don't know much about the cranks....

Good Luck!

------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367

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Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 10-21-2001 10:31 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Welcome to M&M Scott.

------------------
Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

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futurattraction
Journeyman

Posts: 93
From: Iowa City, IA
Registered: Oct 2001

posted 10-21-2001 11:44 PM     Click Here to See the Profile for futurattraction   Click Here to Email futurattraction     Edit/Delete Message   Reply w/Quote
n2oMike, kid, and alex, thanks for your welcomeÖ

n2oMike: Thanks for your comments about the Aussie head prep and intake porting. Because I knew my post was going to be long I didnít elaborate on what's already been done to them. Because I didnít trust myself to do this, I sent them to a shop to have them reworked. This included getting both sides of them ported and polished. The intake port actually matches up to the X-celerator intake, so the mismatch you warned me about doesnít exist, but I do appreciate your heads-up. The chambers were also opened up to unshroud the valves and polished. I also had oversized valves installed 2.07?/1.71. Chamber volumes run in the 62-63 cc range. Iím sort of kicking myself now for not getting them converted to adjustable rockers when I had the chance, but oh well. I also kind of wish Iíd gone ahead and gotten them flowed after getting the other work done, but as I mentioned in my first post, I was really building them for street use, so didnít see the need (other than out of curiosity). The shop that did the work said theyíve done other Aussie heads pretty similar to these and they flowed around 240 and 170 @ 28Ē. Iíve seen other figures that showed higher rates than that, but they theoretically ought to be somewhere in that general range. Also, since this is in a fox chassis, Iíve got the double sump pan. It holds seven quarts with a rear sump pickup and some baffling.

kid: I was thinking Iíd read in one of the many strings I read through over the past few days that youíd said something that made me wonder if you werenít from the Iowa. Iím glad youíre as close as you are. Thatís an easy drive to track you down if youíd ever be of the mind to get together.  How much does a C4 weight in comparison to a C6? It seems like it would sort of a win-win to have less weight to pack around and less power lossÖ Now that you know a bit more about my heads, do you think theyíd come closer to working on my hypothetical stroker? I guess for the time being Iíll continue to ponder my camshaft choice. Iím guessing that the car will still see considerably more street time than track time.

Thanks again for your responses. Hopefully I can still get some more good pointers or comments regarding my other questions. Scott

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kid vishus
Gearhead

Posts: 3894
From: middle of NC
Registered: Oct 2000

posted 10-22-2001 10:49 PM     Click Here to See the Profile for kid vishus   Click Here to Email kid vishus     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by futurattraction:
Ö Now that you know a bit more about my heads, do you think theyíd come closer to working on my hypothetical stroker

My opinion,

No.

A motor that size will like flow more in the 300 cfm range. Even my little (357 ci) motor likes the bigger heads better. I had a 12.5-1 ported 2v headed motor in my car with a roller cam, it ran 10.40's. Same trans, convertor, gear, headers, carb, but a 11.5-1 4v headed motor with a solid cam, and it runs 10 teens.

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