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Old 10-11-2003, 04:26 PM
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Question PMD OHC6 Sprint Build Up

Howdy,

I am daring to be different and need some advice regarding a build up I have going for a 67 Pontiac Tempest Sprint-running on the street on pump gas. I need to determine what the maximum duration and lift should be on a cam I wish to have reground-running on 91 octane fuel-my days of mixing fuel are over. The bottom end will consist of a 69 250ci block bored .060 over, new Crower Sportsman rods, NOS TRW Powerforged pistons, a NOS Weber aluminum flywheel, and gapless rings. I am also considering having 20 pounds liberated from the crank to bring the reciprocating mass down to around 53 lbs. On the top end, SS Chevy valves cut down to size 1.60" and 1.92", hardened seats in either a 9 to 1 or 10.5 to 1 compression head (the later looks like detonation problems may occur) with new followers and lifters. Intake is a stock 4bbl set up and carb and exhaust is handled with long tube headers. I am not really concerned with vacuum at idle, nor higher idle characteristics. Would 280-290 duration with .495 maximum lift work or is this asking too much? Any insight or guidance would be outstanding.

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Old 10-11-2003, 09:27 PM
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Cool unique motor! I honestly have no experience with Pontiac Overhead Cam 6's but here is a bulletin board where someone might be able to answer your questions...

http://pub83.ezboard.com/bsohcsix

Good luck and keep us in informed.
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Old 10-11-2003, 09:32 PM
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Good site from 6567GTO
my neighbor has a 63 tempest rag top with a trans axle needs lots of work. FYI if any one is looking.
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Last edited by 1BAD80; 10-11-2003 at 09:38 PM.
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Old 10-11-2003, 09:33 PM
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Arrow

An old friend used to run a OHC 6 in his '67 Tempest and it was built to the hilt. He still has it but doesn't drive it as often, he built it in the early '70's and used to kick the butts of many a V8 car. You can put big valves in it and if I recall correctly (and I do) the Chevy 250 and 292 cranks will drop in and they are fully counterweighted (the PMD 6 isn't). He ran a 292 crank for the extra inches. Because it was built so many years ago and the cam designs have changed so much this would be a good one to have the cam company (which ever you decide to use) set you up with a profile designed for your application. They will have a lot better profile than was available then, and unless someone on the board is running one it's unlikely that any numbers that may be thrown out will work well. The requirements of the six (especially with it's rpm capability) are different than the average V8. That's what the cam companies have the tech support for,use it.
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Old 10-11-2003, 09:39 PM
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I don't know a darn thing about the Over head cam Pontiac but I thought I would congratulate you on the project. I had a 71? two door, plane jane Tempest, with three on the tree and that OHC "sprint"? six. It was bone stock with lots of miles and ran pretty darn good and sounded like a Jaguar. This was about 78 or 79. I really hadn't though about that car until I read your post. Hope U see your progect through! Try the Pontiac sites. As a matter of fact, I remember seeing them at the local drag races, ocassionally. They did pretty good! I'm sure folks will remember hotrodding them and will respond to your post. Keep at it.
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Old 10-12-2003, 07:19 AM
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Nath777, I haven't seen one of those engines since high school, and a friend had a 67 Firebird with a Sprint 6 and that thing would run with my 326 LeMans. Check out the Performance Years website and you can get alot of info on your engine there and advice on buildups.
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Old 10-12-2003, 12:08 PM
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Howdy Once Again. The Ezboad site is pretty cool, and I am fairly active on it. I figured, someone in this forum may have hopped one of these little demons years ago and might be able to shed some light on it. I visited Mike Kirby in Covina, CA (of lump porting fame on the 292) who was the first to do a 292 crank swap, even showed me the crank. The problem with this set up is the inheritly bad rod to stroke ratio, something like 1.53=built in rev limiter. It is a hell of a lot of work to get it all to fit together, so I'll opt to use the stock cast iron 250 rotating assembly that has the 12 counterweights-the 230 had only 4. If anyone has spare parts laying around that they need to get rid of to make space for their ongoing projects or know of anyone that does, please feel free to drop me a line at nathe777@aol.com. Desperately trying to track down anyone who actively campaigned an OHC6 setup back in the day to see what they have to say about getting it dialed in. I would really dig getting some kill stickers come springtime. And yes, in stock form, the little beast will wind to 7,000 grand before hitting valve float. I have successfully broke two equalizer (z bars) from dumping the clutch consistantly at 3,400rpm-come to think of it, damn near all my cars have experienced a similar fate. Thank God for nickle rod!
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Old 12-05-2006, 05:06 PM
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Help with this motor

How are things going with your build? I am just starting into a build of a stock version of a sprint motor/ Do you have any spare parts?

Mike
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Old 12-05-2006, 07:14 PM
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A guy in my HS auto shop class had a 69 Firebird with a 250 Sprint engine in it. All I remember was him rebuilding it with forged pistons and some other assorted hot rod parts and backing it up with an M21 Muncie and a set of 4.10's in the 12 bolt out back. That thing would run. He did one thing that I thought was very cool. He had 3 different valve cover/camshaft assemblies and would switch them out from time to time. One time you heard the car it sounded stock and the next time it sounded radical. I thought that was extremely cool. Good luck on your project. Don't let anyone talk you out of it!

Barry
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Old 12-05-2006, 10:45 PM
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Webrodder had a build up on an OHC. This is the first installment. http://www.webrodder.com/article.php...&SID=60&CID=15 They have 9 installments with more to come IIRC. May help you.
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Old 12-06-2006, 05:27 PM
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Thanks

I will check with them...
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Old 01-31-2007, 10:32 AM
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Cammer Update

Here is the quick lowdown. I am over in Korea and picked up another *****ing 67 Sprint, but get this, it is a legit 4 speed, no PS, no PB, bucket Le Mans just before my departure. I did manage to get the aforemention engine fired up and unwillingly mothballed it to preserve all the effort expended. Here are the stats. 66 4bbl head with SS valves decked now .030" mated to a 68 250 block bored .060" over and zero decked, plenty of porting, a reworked intake manifold coupled with a Primatech header, a one off grind ~ 231 degree intake / 236 degree exhaust duration at .050", .496" total lift, Fisher harmonic damper, Crower 5.7" Sportsman rods, a set of coated custom Ross pistons that weigh in at 468 grams.....alas, I was only able to break in the cam and listen to hundreds of angry hornets grumbling through the open headers. It does sound mean and I look forward to breaking in the Tim Moore built rear end along with truly seating the rings in the not too distant future. The 4 speed has got to go, so I'll opt to drop a Kessler Tremac 5 speed in. Running 26.1 MT Street Drag radials on the 15" x 7" Ralley IIs that need to be smoked for the edification of Car Craft readers. The high compression is nourished on 110 leaded octane diet that can be leaned down a tad over 100 by cutting it with some pump super unleaded. Really not too concerned about the overall appearance. I preserved the superficial surface rust with Eastwood Rust Encapsulator, yet kept some pantina to go for the rat rod look. Entirely new wiring harness, suspension...I can proudly say I did damn near most of it myself, aside from machining. Polishing stainless steel trim is time consuming but well worth the results. Anyhow, enough ramblings for now. A few more months till a maiden voyage occurs and the time capsule of yester year (youth) returns.
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Old 03-23-2007, 05:42 PM
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Your not alone

25 years ago a wrecked 69 big block chevelle and a 67 firebird body were combined. It has been a great little rocket but a more recent search of the cars history shows it to be a 4 barrel sprint. Recently I found a few ohc6 engines to return this car to it's original form. I'd like to improve it along the lines of what your doing. I have a few questions maybe you can help with. It is a 4 speed car and it looks like the bellhousing was unique. BOP pattern with the starter relocated. Is that true? What are the limitations of the bottom end and how much can the deck be cut? Keep us posted and thanks for the insight

potts
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