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#1
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68 WT Build
’68 GTO with a numbers matching WT 400, 16 heads. Three speed Dearborn Trans, 3:55 axle,
Previous owner rebuilt the engine in 2001. Bored .030 over. Engine was operated for about 500 miles before it was pulled and stored. When I bought the car earlier this year I pulled the heads and oil pan. Found surface rust in the crankcase, scored bores, heavy carbon on the piston tops. I took it to a local well known machine shop (recommended by other Pontiac owners) for a teardown and inspection and they reported the following: The Bad Excessive wear on the rod bearings and crankshaft. (rod ends reportably to tight) Excessive wear on the cam bearings All cylinder bores scored Deck surface rough Valve guide inserts worn The Good Passed Mag inspection Line bore was good Machine work they recommend Bore .040 with Torque Plates Machine crankshaft to .020 New Bronze valve guides Light deck and head resurfacing Resize factory rods Balancing What I Want At least 325-350 flywheel HP and to operate on 91 octane with 10% ethanol. I’ve done some reading on similar engine builds and I think the following will work for me. Q-Jet Factory Intake Ram Air exhaust manifolds. Upgrade the camshaft to Melling SPC7 or Lunati Voodoo 10510702 New lifters, oil pump, pushrods, timing gears. From Spotts Performance KB pistons 17cc dish (KB346-040) with recommended rings 670 head kit . Seeing how I need to clean up the deck, would zero deck clearance be beneficial? Machine shop says they can keep the compression to about 9.5 with the combination of the dished pistons and the right type of head gasket. A stroker kit is tempting but due to budgetary concerns I’ll be using the original crank and rods. Engine had about 115k on it when it was rebuilt the first time so I’m thinking the original rods will be sufficient for the power levels I’m looking for. Thanks in advance for any advice.
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express 2024 Cadillac LYRIQ Last edited by OG68; 07-16-2019 at 12:20 PM. |
#2
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What is a 670 head kit?
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#3
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670kit - 670 (and most 67-70 iron heads) performance head combo
* Crower #68404 springs, Comp Cams #740 and #611 10 degree chromemoly retainers and locks and Ferrea stainless valves (2.11/1.77). Springs will install at 1.600 w/approx pressure of 110 lbs. to allow up to .600 lift for hyd, hyd roller or flat tappet cam usage.
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express 2024 Cadillac LYRIQ |
#4
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I would not use stock rods
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2008KRE Q16 Winner 2014 atco raceway doorslammer winner 86 grand am tube car 8.95 @152 455 eheads solid flat tappet cam Hoffman Racing building and racing Pontiacs for 35 years |
#5
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I would not use KB Hypers. Get Icon forged dished pistons. Also agree with above.
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http://www.machdevelopment.com/album...775/527566.htm |
#6
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If that's the numbers matching engine to your GTO, I think I would upgrade the rods to a forged rod too. Would be pretty cheap insurance in the end. Having said that, if you decide to go with the cast rods and pay to have them resized, I would at a minimum have ARP bolts installed in them. They would probably be fine in a relatively stock build that won't see 6,000 rpm. I think I would just use that Melling SPC7 cam. That should hit your horsepower goal and be very easy on parts while making it run like a GTO should.
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#7
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Agreed
I've had several bad experiences with resized rods. Never again.
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“Nothing in the world can take the place of persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan Press On! has solved and always will solve the problems of the human race.” ― Calvin Coolidge |
#8
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Crankshaft.
Quote:
__________________
“Nothing in the world can take the place of persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan Press On! has solved and always will solve the problems of the human race.” ― Calvin Coolidge |
#9
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Thanks for the advice and the heads up regarding the KB pistons. After doing some more reading and parts checking it appears that ICON IC891-040 pistons and Eagle 6.625 H rods are my best bet but it does take a bite out of my budget.
Some of my reading involved decking of the block and from what I understand it can get somewhat complicated. Some advocate deck the block first then buy pistons and rod, others deck the block to match the pistons and rods. Arrrgh... I understand that proper decking will help achieve my goals towards a more efficient low compression engine (targeting 9.0-9.25). Am I overthinking this thing?
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express 2024 Cadillac LYRIQ |
#10
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If you are limited on budget, the stock rods are fine, just get some ARP bolts for them as suggested. Also, I've assembled a number of 400's, just did one that was a 69 with the 62 casting heads and go with flat top pistons as you're putting a cam in it anyway. You can run this no problem on 91 octane all day long with the right cam. Something similar to XR276 and stock exhaust, intake and carb will be fine with adjustment and it'll wake that motor up.
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#11
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Some people don't like the heavier TRW L2262 pistons but at around $300-$350 a set they are hard to beat for a forged piston in a street application. However, they are not dished. If you want 9:1 compression, they won't work for you with the 16 heads. I do know that on a #'s matching engine, especially a stick shift block, I would build it to last. It is rare to find the matching engine in a factory stick GTO this day and age.
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#12
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Thanks to Tom S in Long Beach I got a great deal on a set of new RPM I beam rods. I also picked up a Melling SPC 7 cam for a great price at O'Reilly's. I'm about ready to meet with the machinist and get started with the engine build. I think the ICON 14cc dished pistons will work out but will leave it up to him to pick the right ones after the block machining is done.
My next set of questions deal with the #16 heads; After inspection, the machinist thinks they'll be fine with just new bronze guides and a light cut. I'd like to replace the valve springs with Crowers 68404. I've also been thinking of installing 1.65 steel rockers to add a little top end to the 068 cam. The valves are new (18 years old) stock length PAW valves and do not need refacing. . I'm aware that new pushrods are needed and may need a little head clearancing. I'm running Ram Air manifolds. Any comments good or bad with this?
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express 2024 Cadillac LYRIQ |
#13
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Quote:
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http://www.machdevelopment.com/album...775/527566.htm |
#14
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"...ICON IC891-040 pistons and Eagle 6.625 H rods are my best bet but it does take a bite out of my budget..."
IF budget is a major concern, there are a few ways to build, a little cheaper. (1) Pistons: Go with the SP L2262F40 pistons. If you want dish pistons, a good machine shop can cut a dish in those pistons. Total price of pistons & machine work should be less than the Icon pistons. Lots of guys have posted here about dishing the SP forged pistons. https://www.ebay.com/itm/Speed-Pro-T...sAAOxyB0VRuHEA (2) Many have posted that they have run 10:1 CR on pump gas, with no problems, by using a cam with big adv duration, & keeping the ignition advance reasonable. That will save you the price of dishing the pistons. A couple of big duration cams might be a Melling SPC-3 & a Summit 2802. (3) Go with factory 1.5 rockers, a Summit cam & cheap Jegs lifters(USA made). https://www.summitracing.com/parts/sum-2801 https://www.jegs.com/i/JEGS/555/20702/10002/-1 (4) If you go with an 068 clone or Summit 2801, you won't need the high priced Crower springs. https://www.ebay.com/itm/Pontiac-V8-...AAAOSwmrlU0mJ9 https://www.jegs.com/i/COMP-Cams/249/988-16/10002/-1 https://www.ebay.com/p/192751619?iid...8aAo_cEALw_wcB (5) Use the cheap FP 8518PT head gaskets. https://www.summitracing.com/parts/f...EaArArEALw_wcB There is always a rod debate. I had good luck with cast rods, to 6000 in 400's & 5500 in 455's. But, cast rods are now more than 30 years older than when I used 'em. And, I've read that resized rods/ARP bolts now cost over $200. New RPM H-beam rods are $400. So, better, lighter rods are less than $200 higher. May not help OP. But might help somebody. Last edited by ponyakr; 09-27-2019 at 03:17 PM. |
#15
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"...picked up a Melling SPC 7 cam...thinking of installing 1.65 steel rockers...I'd like to replace the valve springs with Crowers 68404..."
As mentioned, with the SPC-7 cam, even with 1.65 rockers, you don't need those high priced Crower springs. https://www.ebay.com/itm/Pontiac-V8-...AAAOSwmrlU0mJ9 https://www.ebay.com/p/192751619?iid...gaAuY_EALw_wcB |
#16
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The engine is now being built. Went with the Melling 068 clone cam, forged RPM I beam rods, and ICON 14cc dished pistons. The heads will have 7/16" studs installed with new stamped 1.5 rockers, Teflon seals and new springs from Spotts Performance.
After cleaning the engine the builder brought my attention to a couple spots he found on the block and one of the cylinder heads. Apparently there was a small gouge on the edge of the cylinder that had been repaired. He thinks it was done at the factory. There was also some small fractures around a coolant hole in one of the heads. Builder was slightly concerned since one of the fractures was close to the fire ring of the gasket. He's confident he can make the necessary repairs and save the head.
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express 2024 Cadillac LYRIQ |
#17
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Good luck with the build. I’m following the progress!
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GOD does business with people that mean business! |
#18
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Good deal on not using those 50 year old rods. A friend just vented his newly rebuilt 455 at about 4500 with stock rods.
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#19
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Is this build done? If so how did it turn out.
Greg |
#20
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Quote:
I used one on a 69" Trans Am RAIII and it made 380HP on the engine dyno Engine was 10:1 CR
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Carburetor building & modification services Servicing the Pontiac community over 25 years |
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