318 Poly question
#2977166
10/22/21 10:32 AM
10/22/21 10:32 AM
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6PakBee
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Anyone know off hand what the piston height is on a stock 318 poly? Thinking about what it would take to build a zero deck motor for quench.
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
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Re: 318 Poly question
[Re: 6PakBee]
#2977314
10/22/21 04:28 PM
10/22/21 04:28 PM
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HotRodDave
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Zero deck is easy, about .035 ought to do that but quench? Even max milling the head will give no meaningful quench pad, you would have to weld em up and mill them flat again. Another option would be to use an end mill and machine some flat areas in there and get custom pistons with a matching raised area... I love what quench does for an engine but even I wouldn't bother with it for the gain you would get on that engine.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: 318 Poly question
[Re: HotRodDave]
#2977324
10/22/21 05:15 PM
10/22/21 05:15 PM
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6PakBee
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Okay, so trying to get quench is a stupid idea. No problem, I'll move on. Thanks for the frank comments, saves me continuing to pursue something that is questionable with this design.
Unfortunately it's been 50 years since I was inside a poly and I can't remember anything about it other than if you miss a gear and you see the tach going past 6500, you will bend a lot of pushrods.
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
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Re: 318 Poly question
[Re: 6PakBee]
#2977331
10/22/21 05:47 PM
10/22/21 05:47 PM
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Sniper
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Okay, so trying to get quench is a stupid idea. I believe it's the Marines that say if it works it ain't stupid. Not a stupid idea you have, might be tricky to implement and the gains may not make it worthwhile, but if you did it and it worked as you hope it's not stupid. Expensive, that is another story there.
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Re: 318 Poly question
[Re: Cab_Burge]
#2977451
10/23/21 01:21 AM
10/23/21 01:21 AM
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6PakBee
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It would be interesting to see how the poly heads flow compared to an LA or Magnum. I would think that would be the major difference between the engine families. And just looking at the heads, one would think, and I know this is an assumption, that the poly heads would flow better.
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
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Re: 318 Poly question
[Re: 6PakBee]
#2977460
10/23/21 03:20 AM
10/23/21 03:20 AM
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Guitar Jones
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Paddle faster! I hear banjo music!
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I've seen flow numbers for the poly heads in the past and even ported versions. Unimpressive to say the least but not horrible. You can use the LA stroker cranks in them and you might be able to bore some blocks .100 over. Unless you just want to do something different they probably aren't worth the effort.
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'92 D250 Club Cab CTD, 47RH conversion, pump tweaks, injectors, rear disc and hydroboost conversion. '74 W200 Crew Cab 360, NV4500, D44, D60 and NP205 divorced transfer case. Rear disc and hydroboost conversion. 2019 1500 Long Horn Crew Cab 4WD, 5.7 Hemi.
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Re: 318 Poly question
[Re: Sniper]
#2977511
10/23/21 09:41 AM
10/23/21 09:41 AM
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Joined: Nov 2020
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Gtxxjon
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Nothing wrong with Poly questions. Semi-hemi engines don’t squench like wedgie engines. Stroking is the easiest way to ‘up Poly compression’ methinks! Folks have been spoilt with LA engines for over 50 years! But the lowly 318 Poly can be made to work... The old trick was to overbore to 4 inch and turn down a 360 crank. But now we have high compression 402 kits for the serious Poly Folks. 400 horses not beyond a stout Poly build. We are moving on to a 500 horse Poly build now, with a blower... Dare I say it? Chevrolet intakes and headers from the LS range...
Last edited by Gtxxjon; 10/23/21 09:44 AM.
Carpe diem, quam minimum credula postero, thanx Horace!
There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...
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Re: 318 Poly question
[Re: Gtxxjon]
#2977512
10/23/21 09:43 AM
10/23/21 09:43 AM
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Nothing wrong with Poly questions.
Semi-hemi engines don’t squench like wedgie engines. Stroking is the easiest way to ‘up Poly compression’ methinks!
Folks have been spoilt with LA engines for over 50 years!
But the lowly 318 Poly can be made to work...
The old trick was to overbore to 4 inch and turn down a 360 crank.
But now we have high compression 402 kits for the serious Poly Folks.
400 horses not beyond a stout Poly build.
We are moving on to a 500 horse Poly build now, with a blower... Read the link I posted, 551 hp no blower needed.
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Re: 318 Poly question
[Re: Sniper]
#2977515
10/23/21 09:45 AM
10/23/21 09:45 AM
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Gtxxjon
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Read it many times and those parts are way too exotic for ‘shade tree’ mechanics like me. I have contacted these folks for help and advice, but no luck. Biggest problem was a trick roller camshaft, they are rarer then Unicorn tusks... Compcams have made them for the selected few, the rest of us have only flat tappets. Biggest we have found is a 'Custom ground' Schneider with a 0.525. This stuff is so rare you have to 'GO IN PERSON' and BEG!!! Its a long way from London Town to the West Coast... So it’s an ‘old school’ blower for us now to find another 100 horses...
Last edited by Gtxxjon; 10/23/21 11:09 AM.
Carpe diem, quam minimum credula postero, thanx Horace!
There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...
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Re: 318 Poly question
[Re: Gtxxjon]
#2977521
10/23/21 10:01 AM
10/23/21 10:01 AM
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Gtxxjon
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By a strange coincidence the fat intake flange method of port raising was done to my race engine in the 80’s. Back before aluminium heads were available for 440 engines it was the only way forward. The Ovalport intake was developed by Mother Mopar in the 60’s too. I have here a set of Big block heads with that same design for a Nascar development engine. Ovalport IN, D-port OUT... All that is Old is NEW again...
Last edited by Gtxxjon; 10/23/21 10:21 AM.
Carpe diem, quam minimum credula postero, thanx Horace!
There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...
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Re: 318 Poly question
[Re: Gtxxjon]
#2977525
10/23/21 10:18 AM
10/23/21 10:18 AM
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Gtxxjon
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My Rob Loring 452ci engine had the 'raised ports back in the 80's.
5/8 inch flanges and the ports raised by 1/2 inch with directional runners.
Engine made 550 hp and ran in the nines with a street Dart.
Very trick stuff indeed for the ERA!
Last edited by Gtxxjon; 10/23/21 10:20 AM.
Carpe diem, quam minimum credula postero, thanx Horace!
There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...
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Re: 318 Poly question
[Re: Gtxxjon]
#2977532
10/23/21 10:40 AM
10/23/21 10:40 AM
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Gtxxjon
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The wonderful Gary Pavlovich has been the Poly Guru, for as long as I have known! He supplied all the knowledge and the parts for our 402ci Poly stroker build. Work underway for the new Schneider camshaft and better valve seals. The biggest Poly flat tappet ever made @ 0.525'' with old school Crane dual valve springs... Gary's custom made valves at 2.02'' and 1.60'' with 11/32'' stems. Sure look much more exotic than a LA head lol...
Last edited by Gtxxjon; 10/23/21 11:05 AM.
Carpe diem, quam minimum credula postero, thanx Horace!
There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...
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Re: 318 Poly question
[Re: Gtxxjon]
#2977533
10/23/21 10:48 AM
10/23/21 10:48 AM
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Joined: Nov 2020
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Gtxxjon
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Facebook and ''62 to 65'' sites for Poly POWER! Some crazy OLD folks take POLY very seriously indeed... Me I'm just a DYNO-SNORE ps. the 2 bolt POLY caps were a little suspect so the last job I did before my retirement was a 340 cap conversion! (just in case we hit the 500hp) lol...
Last edited by Gtxxjon; 10/23/21 11:03 AM.
Carpe diem, quam minimum credula postero, thanx Horace!
There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...
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Re: 318 Poly question
[Re: Gtxxjon]
#2977576
10/23/21 01:22 PM
10/23/21 01:22 PM
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6PakBee
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I sure appreciate all the replies. I think I'm going to add this to the already bulging project list simply because you just don't see many polys any more. It's the original engine in a '65 Belvedere II I have and I think I'll keep it that way. Thanks again.
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
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