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So I'm building a street car. Are there actual advantages to the mahle piston over speed pro in my application. I already have the thinner cometic gaskets and the block will be decked.
Trying not to spend money where I don't have to.
On a side note can I use 4.125 bore head gaskets on a .30 over bore block?
Which Speed Pro pistons and which Mahle pistons ? The stock replacement ones or performance versions ? I think the Mahle performance pistons are much more modern designs compared to the Speed Pro performance ones.
Which Speed Pro pistons and which Mahle pistons ? The stock replacement ones or performance versions ? I think the Mahle performance pistons are much more modern designs compared to the Speed Pro performance ones.
Speedpro 2321f 5.8 cc dish
mahle pistons were the 10cc dish ones don't know the part numbers but think there is only one for Oldsmobile.
While not knowing details on the Mahle model # I have had both in my hands & engines and the first analogy that strikes me is comparing a Checker airport limo to an F1 car. The Speed Pros have been a dependable (when proper clearance observed) cornerstone of Olds builds for a long time but there are some newer style & tech pistons now commonly available that far surpass the athleticism of the SP. Lower static weight & according reciprocating mass, quicker rpm response, modern ring package are advantages of Mahle, etc. Where do things end up with a short skirt design 50-100k miles down the road? I don’t know.
Not to discourage using the SP but if you don’t already have them & the money is anywhere near similar I would go with a more modern piston. Just my opinion, good luck with your build regardless of what you end up using, with a block looking that pretty how can you miss?!?
Looks like the Mahle pistons have an oddball pin size that requires honing the rod to fit. .984 compared to the stock .980 Also the compression height is taller 1.625 compared to 1.612 for the Speed Pro.
Mahle is also oddball bore sizes so if you block is a true .030 oversize then you will have to use the Speed Pros. Mahle is only available in 4.065 4.100 and 4.125 Your bore should be 4.087
I was the driving force in getting Mahle to make this piston. Let me explain the logic here.
4.065 bore is good for the 400E that may have been bored .030 already as well as a 350 with very little wear. The 4.100 was again for the 400E as well as the 350 that was already .030 over and/or one that had excessive wear from std.
The 4.155 is for all three, the 350, 400E as well as the 425 as they all share the same comp distance. Note, you make pistons to available ring sizes. That’s a huge factor in deciding how big to make the piston.
The reason for the .984 pin is twofold. One it’s more readily available and cheaper because it’s the std pin for Mopars, it’s by no means an oddball size. Two it would allow anyone to hone their rods for proper fit in the event the small ends have been compromised in some way. Remember most are using 50+ year old rods.
In addition the 10cc valve reliefs work well in giving reasonable comp ratios in all three engines with their std heads. Pius the taller comp distance may nullify the need for more expensive thinner shim or multi layer gaskets in order to achieve the desired squish.
And finally, Mahle used their latest, and proven skirt design on this piston. They do a tremendous amount of OEM stuff so again it’s a proven design.
My Hope is that someday people who don’t have all the facts don’t post until they do. Sorry but all that does is muddy the water.
Hope this helps.
Last edited by cutlassefi; April 23rd, 2020 at 08:30 AM.
My Hope is that someday people who don’t have all the facts don’t post until they do. Sorry but all that does is muddy the water.
Hope this helps.
Really dont want to get in a "pissing" contest but . . . . .what facts did I not have ????? For the average person looking for replacement pistons, the facts were as I stated them. They are right out of the Mahle catalog.
It looks like the original poster has a +30 block already so unless he is willing to have it redone he will not be using the Mahle pistons. The pins are most certainly an "oddball" size IF you are referring to the stock Oldsmobile size.
When I looked at the dimensions I pretty much figured the reasons they were using those sizes but for the average guy building an engine it is not obvious.
Really dont want to get in a "pissing" contest but . . . . .what facts did I not have ????? For the average person looking for replacement pistons, the facts were as I stated them. They are right out of the Mahle catalog.
It looks like the original poster has a +30 block already so unless he is willing to have it redone he will not be using the Mahle pistons. The pins are most certainly an "oddball" size IF you are referring to the stock Oldsmobile size.
When I looked at the dimensions I pretty much figured the reasons they were using those sizes but for the average guy building an engine it is not obvious.
The block is not bored yet so I have options. The builder sent me the speedpro pistons as his suggestion but I'm sure he is not aware of the mahle pistons. I'm trying to decide if it really matters in a non racing application either way but sounds like in general the mahle is a better piston.
I dont also get why you wouldnt just buy 4.125" bore SBC400 pistons, then you just automatically buy 6.000" long aftermarket chevrolet rods. All you need to do is cut the journals down and either open the crank or then mill a a little from big-end width of those rods. With 4.125" bore, almost all 350 blocks are applicable, almost all rod-journal sizes on crank goes with those rods. You get good piston + good rods, now you just settle for heavy questionable rods with modern piston.
Killing conversations about products you try to push is really squishy businessmodel.
Last edited by Inline; April 23rd, 2020 at 09:22 AM.
When I looked at the dimensions I pretty much figured the reasons they were using those sizes but for the average guy building an engine it is not obvious.
Then why didn’t you say that? You’re educated, just say what you know.
And I would think a .980 pin would be an oddball to the Mopar guys then?😉
I dont also get why you wouldnt just buy 4.125" bore SBC400 pistons, then you just automatically buy 6.000" long aftermarket chevrolet rods. All you need to do is cut the journals down and either open the crank or then mill a a little from big-end width of those rods. With 4.125" bore, almost all 350 blocks are applicable, almost all rod-journal sizes on crank goes with those rods. You get good piston + good rods, now you just settle for heavy questionable rods with modern piston.
Killing conversations about products you try to push is really squishy businessmodel.
I didn’t kill any conversation about the product, I simply set the record straight.
And why would he want to go thru all that trouble to use the Chevy piston? In the past most guys went through that trouble in order to use a better piston and consequently the rod. But now with a lighter, more modern piston available you've automatically made the rod and Crank stronger so to speak because of the lighter reciprocating weight.
Also when you use the Chevy rod, because it’s offset unlike an Oldsmobile, you sometimes have to mill the top of the rod or the underside of the piston so they don’t interfere with the pin boss. Another step he wouldn’t have to do if you used a better aftermarket piston, best of both worlds there in my opinion.
Hope this helps.
I remember that there was talk about offset on Chevrolet rods. I remember googling out those rods, and found out from few sources that SCAT makes "true-center" SBC rods ( traditional "SBC" having off-set off .035", while LS1 is true-center). Turns out they really werent "true-center" rods, but had about an .015" offset, but that worked fine.
Also Oldsmobile rod-journal, stock is 2.125" from my notes, while Chevrolet rods i used have rod-journal size of 2.100.
Looking from my notes, announced deck-height of small-block Oldsmobile is 9.330". I remember wrong- i used 6.200" long rods - With 6.200" long Chevrolet rods, and Pistons with 1.425" compression distance, you end up ( with stock stroke) to 9.3175" height. Thats almost spot-on to Olds deck-height, only additional machining expense therefore being milling the big-end of rods smaller, when we figure that in both cases you need to bore the block 4.125" - if thats what weve settled for- plus the rod-journal size is so near that machinery wont likely take any extra for cutting to it like they did boring the block for so big over-size, atleast here.
In my opinion that is really cheap way to get also better rods- aftermarket rods are cheap for SBC. And as added plus, there are off-the self oversizes for 4.125" bore 1.425" compression distance pistons- havent seen any mentions you have oversizes available from Mahle unless special-ordered. On the other side, Mahle has thinner rings - those have 1/16 - 1/16 - 3/16 rings. Lets assume both pistons costs the same- you get new rods added to your build with just the costs of the rods and milling the big-end narrower- in my opinion, thats really worth the money.
Slightly off-topic, as point of curiosity, from my notes, i weighted these with kitchen-scale: including piston, all rings, bearings, possible spiro-lock and piston-pin, per cylinder, stock "complex" weighted 1675 grams. New one weighted 1317 grams ( which of course depents on the new parts you decide to use). Multiply that with eight, and you just lost 2864 grams from reciprocating weight of your engine.
Last edited by Inline; April 25th, 2020 at 10:38 PM.
Actually yes. Here's my reasoning.
I remember that there was talk about offset on Chevrolet rods. I remember googling out those rods, and found out from few sources that SCAT makes "true-center" SBC rods ( traditional "SBC" having off-set off .035", while LS1 is true-center). Turns out they really werent "true-center" rods, but had about an .015" offset, but that worked fine.
Also Oldsmobile rod-journal, stock is 2.125" from my notes, while Chevrolet rods i used have rod-journal size of 2.100. Standard SBC rods have a .050-.060 offset not .035 or even .015. And most of the Scat LS rods aren't truly centered. in most cases they just took a Std. SBC rod and and milled off one side of the small end so it doesn't interfere with the pin boss on some pistons. The only one I believe that's truly centered is their 6.100 H beam.
Looking from my notes, announced deck-height of small-block Oldsmobile is 9.330". I remember wrong- i used 6.200" long rods - With 6.200" long Chevrolet rods, and Pistons with 1.425" compression distance, you end up ( with stock stroke) to 9.3175" height. Thats almost spot-on to Olds deck-height, only additional machining expense therefore being milling the big-end of rods smaller, when we figure that in both cases you need to bore the block 4.125" - if thats what we've settled for- plus the rod-journal size is so near that machinery wont likely take any extra for cutting to it like they did boring the block for so big over-size, at least here. FYI - I did this exact build over 10 years ago. It worked out ok but a longer rod will typically raise the power peak of any engine, all else being equal. Do you really want to do that on a SBO street build? I don't.
And with the advent of new modern pistons available I'd go another route today. Plus both Scat and Molnar will be releasing new SBO rods shortly, lighter and stronger than the stockers.
In my opinion that is really cheap way to get also better rods- aftermarket rods are cheap for SBC. And as added plus, there are off-the self oversizes for 4.125" bore 1.425" compression distance pistons- haven't seen any mentions you have oversizes available from Mahle unless special-ordered. They're listed, twice. But let me list them a third time, 4.065, 4.100, 4.155, all off the shelf. On the other side, Mahle has thinner rings - those have 1/16 - 1/16 - 3/16 rings. Lets assume both pistons costs the same- you get new rods added to your build with just the costs of the rods and milling the big-end narrower- in my opinion, thats really worth the money.
Slightly off-topic, as point of curiosity, from my notes, i weighed these with kitchen-scale: including piston, all rings, bearings, possible spiro-lock and piston-pin, per cylinder, stock "complex" weighted 1675 grams. New one weighted 1317 grams ( which of course depents on the new parts you decide to use). Multiply that with eight, and you just lost 2864 grams from reciprocating weight of your engine. There is no doubt lighter rods and pistons can be beneficial but your depth of knowledge falls a bit short here. Let me explain balancing. The balance "bobweight" takes two sets of bearings, two big ends of the rods as well as the reciprocating weight of just ONE cyl not two, so your calculations are grossly incorrect, sorry.
Hope this helps for all.
Last edited by cutlassefi; April 26th, 2020 at 06:42 AM.
Wow. Aftermarket rods for SBO? Thats some great news! Really great news. Makes one to wonder when they are going to be released?
If geared accordingly- what does it harm to have power peak higher? With the miles "hobby-cars" are mostly driven, wear wouldnt hardly become problem ever. Not sure why everyone fear to spin the engine little higher.
When i mentioned weight- i didnt mean it too technically, it was just an "fyi". I have no idea what the correct Word in English would then be when not speaking technically correct, other than "reciprocating mass". Hopefully this doesnt make too much confusion, but thanks anyways for pointing this out.
I didnt say all SCAT-rods are "true-center" ones, but with some searching found ones that were almost.
Last edited by Inline; April 26th, 2020 at 07:02 AM.
Had to google a bit, hence another post, since i didnt have all the info on my notes.
For 6.200 Chevrolet rods, 1.425" compression distance, flat-top pistons with 4-5cc valve reliefs, SRP/ JE has pistons sizes accordingly ( starting from Oldsmobile 350 stock-bore and upwards) : , 4.060", 4.125", 4.130", 4.145", 4.155", 4.165" ( not commenting how far its WISE to go, just listing sizes as i sayed), and to choose from forged 2618 or forged 4032-pistons. This gives a VAST BIGGER selection of pistons available to fit every need on SBO ( minus 403 before someone points that out). Dont even care to look all the pistons through which ring-sets they use, just noticed different pistons had different ring-sets.
And those were only sizes which SRP/ JE-pistons offer. Add other manufacturers, and you have boatloads more choices.
Last edited by Inline; April 26th, 2020 at 08:20 AM.
April 22nd, 2020, 02:17 PM
