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Mr Polson

Pistons - 351 crank, 302 rods

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My 351 will be using the above mentioned parts.

 

Pretty sure this means I need special pistons that have the gudeon pin lower (I think)?

 

Am I right, and if so where's a good place to get them?

 

Also are they available in flat top and dished? I'm not sure on what heads I'll have yet so don't know if I'll need to lower the comp or not.

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Common 351 combinations

351 with 5.77" rods piston 1.678 pin height (stock)

 

351 with 6"(302 length rods) rods with 1.456 pin height piston. I am building a 14:1 engine for speedway with this combo using chev rods.

 

351 with chev 6.125" rod 1.331 pin height. This piston is also used in 393 strokers with 6" piston.

 

351 with chev 6.2" piston with 1.256 pin height. Ls1 have these pistons. Make a good screamer 8000 rpm engine these.

 

Can get all these pistons in dish flat or dome. Speedshops , rocket, performace wholesale, vpw can get them, summit racing or jegs in america are good too

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Hey Chris,

 

I to am using this same combo the issues you will have as I didn't presumably you only want a mild street cruise engine, is compression ratio using 302 64cc close chamber heads will be way to high even if you dont deck the block and run dish pistons ( the biggest available) there is not enough crown to spin the piston down due to the high pin hight your cr would be about 12.9 to much for pump and cruise, I now have a set of 351 2v open chamber heads with 4v valves fitted, running it decked with slightly dished piston say 8cc gives me around 10.9 excellent for mild cam and 98 juice

 

So all in all its probs best to do a little research on the 302 head but thats just my seeing.

 

I have a mate that spent a reasonable amount of money on a set of 302 heads for his 351 and it went pretty well, he put a stock set of 351 2v on it with v4 valves went off its head.

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I think you have your wires a litte crossed mate. By my maths a 302 head closed chamber head (around 58cc) 4.1 hole gasket with .04 crush with flat top .03 over pistons with only intake valve relief of 3cc zero decked comes to 12.1 which is fine if you running decent cam and alloy heads. Leave the piston .01 below the deck brings it down to 11.19 which doable with iron head.

 

351 2v closed chamber was around 64cc and open chamber 4v varied from 68 to 76cc from memory.

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Yeah seems as if I got screwed up with holden heads, there 64cc my bad.. , but the formula is still much the same I don't think Chris is intending in running alloy heads so comp is to high really alloys wouldn't be a issue but in terms of a slap on ok performance thing without doing valve cuts etc the 351 2v open chamber would be best option as 4v would be over kill for his application and give no down low..

 

My only opinions is going on what I gathered from what chris has said regarding his set up..

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Precisions are where i last bought my 302 long rod combo pistons from but was a long time ago. they were a hypotechtic piston (not sure on spelling).

 

not really a combo i like personally as the valve relief is quite close to the top ring.

 

good luck with the build

 

cheers Carl

 

Edit....my pistons were flat tops but cant remember the releif cc off top of my head.

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Thanks for the replies guys!

 

Regarding my setup/combo I'm pretty much wanting a mild street/cruise engine, something better than a stock 351 but not too wild.

 

I plan on just sticking with cast iron heads, I may be on to a set of 351 OC heads thatve had 4V valves fitted, but port size is still 2V.

 

Ideally would like to be able to run on 95 rather than 98, not due to cost but due to availability in the more remote parts of Tassie.

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Good stuff chris my opinion is only from what I gathered you have said your using im the past, got my 351oc heads with 4v valves tonight, slightly work will be good set of heads,

 

For you thats all you need for a nice set up with 95 octane juice, just chuck a bottle of octane boster behind the seat if you can get premium,

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Yeah I think I wrote an entire plan for the motor once, but it would've been ages ago and I don't even know if it would've been on this forum or not!

 

You didn't go buy yours from Deloraine did you? That's where the set I found are.

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Oh no your joking I work in deloraine man there my mates lukes heads he asked me about them if I wanted them a week ago and I said ill get them so got em tonight, after he put them on gumtree he said he forgot to ask,

 

Now I feel like a dog man,

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Yeah sorry man I feel dog, wish I new, if i see a set in my travels will pick them up for you if there good,

 

Yeah my alloy head plans have changed slightly decided to do the work to cast one as I have access to a mate in launceston that does port work on the side for a small amount will have a good set of heads for the power im chasing, if I can maybe in two years or so might get alloys when finances get better from health being down, but atm just going to go good street engine for now,

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Regarding my setup/combo I'm pretty much wanting a mild street/cruise engine, something better than a stock 351 but not too wild.

 

I plan on just sticking with cast iron heads, I may be on to a set of 351 OC heads thatve had 4V valves fitted, but port size is still 2V.

 

 

GTHO III only ran 14.4 down the dragstrip. Build it to them specs. :D

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High output had solid cam. I like the sound of solid cammed motors. And wouldn't mind a bit of adjustment on the lash every now and again.

 

 

Cheers - Steve

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Point is, 14 1/2 second quarter mile times are nothing these days, you could build a daily drive engine that shits on a 'stock' XY GT.

Clean up the 2V heads, roller cam and rockers, balance everything. Will spin to 5 grand all day everyday.

(....and, yes, the Hoey had a mechanical cam and lifters.)

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I've just had my motor built using 302 rods, 351 crank, precision pistons, 2V closed chamber heads with 4V outlets. It was professionally built, he said it is 10.5:1 compression. He used Hypatec piss-tins, (6.025 rod) - Part No: PFO351C680203H

It hasn't been started yet so no dyno figures available but i'm guessing between 400 & 450HP. It has a 750cfm Holley, Redline 'Street Torker' single plane manifold running into the heads and 4 into 1 extractors on the outlet which run into a twin 2" system.

The cam is a Crow Cam Part No. 61249.

G'box is a full manual C10 with stg 3 shift kit and 3000rpm TCE converter. 

Diff gears are 3.5:1 L.S.D.

Information so far is this basic street combo is good for low 13 sec quarters in full street trim in an XD.

This is a pretty common, tried and tested combo that most guys use with the set-up you're looking at.

It will look slow compared to a drag car but fun enough for the street.

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i had a 351 built using 4mab crank 02 rods short skirt racing piston a stage 3 competition cam 460 valves in open chamber heads ,not throtted,it ran a 780 holley extractors ,t5 box 345lsd in an EA the most it did on the dyno ,was 290rwhp,and this thing went like shit off a shovel,lol 450 asking a little to much imo!

YOU  will find the compresson with close chamber heads is more like 13to 1, and itl ping like a bitch ,i have a mate with the same combo as you ,its fucked and pings everywhere

 

 

 

this build combo is called a 383 stroker!

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i had a 351 built using 4mab crank 02 rods short skirt racing piston a stage 3 competition cam 460 valves in open chamber heads ,not throtted,it ran a 780 holley extractors ,t5 box 345lsd in an EA the most it did on the dyno ,was 290rwhp,and this thing went like shit off a shovel,lol 450 asking a little to much imo!

YOU  will find the compresson with close chamber heads is more like 13to 1, and itl ping like a bitch ,i have a mate with the same combo as you ,its fucked and pings everywhere

 

 

 

this build combo is called a 383 stroker!

Definitely not expecting 450hp, i'm hoping for close to 400fwhp, if it falls short of that, so be it, it's only a street car. You think 400fwhp is a bit ambitious? I wouldn't have a clue, haven't really thought that much into it. What HP would an XD have to be putting out to get a flat 13 secs with 3.5's? I'm guessing you'd know more than me about that sort of thing, i like making cars look nice, when it comes to making them go nice, i pay someone else. lol.

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it really depends on  lot of things,id say 290rwhp isnt impossible ,i mean the gtho,p3 that did the 1,4 run back in its day only had 300hp and cracked 14,1,

 

you are going to run into detonation problems bc the old skool closed chamber heads cause it ,

 

with super led fuels we could get away with higher comps as we had led to lube the valves,or run av gas ,but the fuel today is shit as 98 hi octane burns slower ,and dumbs down the out put of the motor and it also causes a longer burn ratio for fuel to air

95  with octane booster is much better ,but the octane isnt in it

LPG  today is a mix of many diff gases and still doesnt give the octane it used to yurs ago ,

either way unless you have a plane ,to get av gas its gunna ping

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