Jump to content
Catman

90mm- is this cylinder bore size in the danger zone

34 posts / 3584 viewsLast Reply

Recommended Posts

I have been piston shopping.Everything I'm finding is somewhere around 90mm CP - Maxsil - Wiesco- and Irelands for example.I have a set of CP 10.5 to 1's on order from Vac ( as of 4:30 today ).Just wondering what the thoughts are.all of the tech guys were to busy to return my call at CP when I was ordering them.They say by default 90mm unless otherwise stated.

Mourab at VAC say thats what everyone wants.My machine shop says allitle close to the limit.

Catman

Share this post


Link to post
Share on other sites

Both my tii engines were bored 2nd oversize.

Mahle's in the 72tii engine

pics12102010018.jpg

Kolbenschmidt's in the 73tii engine

IMG_1211.jpg

Depending on the checkout by a machine shop, I may go with 90mm for the 72 engine going in the 69. I too have been looking at replacement pistons.

Jim

Share this post


Link to post
Share on other sites
Guest gliding_serpent

I went through this recently after some bad cylinder #1 and mild #3 scoring. All I could find we're 90mm also. At the end of the day 89.5 2nd oversize did not cut it, so it made my decision easier.

Some people scooped up Oem pistons at smaller oversized at the end of the last production run (89.25 and 89.5). Some will part them if you ask nicely. Expect to pay a premium. Remember you can always go custom forged for about 600$. Unless you have a numbers matching car you plan to sell for top dollar, they may be good options.

Step one: Go to your machinist with block in hand and find out what size you will need. Save metal whenever possible because once gone, it is not coming back. Sleeving is an option, but you need to overbore even more than 90mm to do that, so avoid it (I will only do it after I get to 91+mm)

I am no expert, but someone with far more 2002 experience than I said 91mm is about as far as they would recommend going for a street car. The extra heat and compression ratio changes become too much after that without serious mods.

In summary, confirm the exact overbore you need with a reputable machinist. Search for pistons that size or as close as possible. If you can, save 90mm for the next overbore, not this one. If you need to go above 91mm, think hard about a new block, or sleeving and returning to 89 mm. You can overbore a good sleeve down the road.

Good luck.

Share this post


Link to post
Share on other sites

90mm is "4th overbore." Should be fine. that is what I just ran for 3-years in my race engine with no problems. I am going to 90.5 mm on my current engine build. People have gone up to 92mm with the M10 block, but to do that the block should really be sonic-checked to ensure adequate wall thickness and no core shift.

Fred '74tii & '69GT3

Share this post


Link to post
Share on other sites

Thanks you guys- These pistons are $850 a set and marked down at Vac performance for 695.00. The are giong to knock off another 75.00 Cause Im getting a Shrick 292 and springs along with head and main studs - rod bolts and coated bearings. This is my dream pile of parts. My machine shop is first class Scotts in Fayetteville Ga.Only a hand full can afford to own the machines to grind cranks. Check them out online. They are a nice group too.Every one who has m10 pistons are 90 mm. no one has Mahle anything. Ireland has theirs made- They look like CP I havent asked but they are the only player besdes JE and Maxsill and I have heard some horror stories about Maxsil's stuf.I just neede to hear from some one who has gone to 90mm size and lived to tell about itMy block has never been open. I show it on another post I think 88.67 A10 very tiny ridge.I lost oil pressure.On teardown I found the relief valve stuck at the top of the tube.

Still havent fond out if this caused it.VAC will rebuild with new guts and 1 nut type gear. Catman

Share this post


Link to post
Share on other sites

What cylinder head are you using? Will the new 90mm pistons work with your head? Note my pictures. 121 head has different piston dome shape than the E12 head. If I go with new pistons, I'll need them to work with 121 type head.

Share this post


Link to post
Share on other sites
They say by default 90mm unless otherwise stated.

Mourab at VAC say thats what everyone wants. My machine shop says a little close to the limit.

I'm not sure it's fair to label 90mm as a 'default'... but it IS a common size for a performance piston. Data point: In my experience 90mm is safe, and nobody I know who runs that size has had issues related to that bore size.-KB

Share this post


Link to post
Share on other sites

I just built an engine for the touring using these exact pistons. I've be running 90MM in race engines for over 10 years.....

Bob

Share this post


Link to post
Share on other sites

In the order form Carrillo asks for head casting numbers and a picture if you can provide -I did E 12.What cam your going to use so they can do valve relief at the same time - Rod length center to center ( 135 ). These are truley full custom made.Carrillo -what a deal -695.00 even better.3 week turn around at this time not 5-6 as normal. They must need to sell some pistons.I also got the Shrick 284 instead of the 292. Because of the low end torque opposed to high end revs . According to them anyway.I am inlisting all of the tech service help I can. I am not trying to reinvent the wheel just make I roll really nice.Pics of my internals for your viewing pleasure-- lol

PS - Also Eibach dual matching valve springs - I now have Eibachs on 2 cars suspension and an engine - that is way cool. Like ive said these are dream parts to me. I know there is an infinate amount of money you could spend but for a nice street fighter. I think I will have a nice one.

Catman

post-8235-13667668090511_thumb.jpg

post-8235-13667668091657_thumb.jpg

Share this post


Link to post
Share on other sites

Thanks Bob that seals it I am no longer going to lose sleep over this .The stuff has been ordered and I cant wait to get it. Maybe I could run with you guys for allittle while If you cut me some slack -----

Catman

Share this post


Link to post
Share on other sites

Default is what Carrillo says their 90mm size is on the form if you order 1, unless you change the dia. you will get one 90mm.

As you can see I went with some new ones at this price and being CP's it was an easy chioce no hard feelings I hope.I am also trying to finish my 1965 Coronet 500 BB 440 Pro Touring. Ive had it 10 years and decided to upgrade its engine from a 383 man. to a 440 six pack auto / street fighter. My 02'died in the process. so I had that engine almost assembled on the stand - fabing a stainless Triangulated 4 link rear almost done -when I stopped to rescue my little girl.

I have big boy American Iron and my Baby German Soligen Steel.Oh and a few others .I am addicted - card carrying- car crazy. Ill be 60 this summer and I cant think of a better way to celabrate then blasting around in my owncars built by me.With some of you guys help of course.

Catman

Share this post


Link to post
Share on other sites

Chassis dyno ? RWH? Or the block house ?Good luck do you have some numbers you are shooting for based on old fashioned seat of the pants stuf or is it some algorythm science fiction calculator stuf.

I was in Offshoreracining in Miami.Aluminum fabricator at a hot shot Catamaran race shop.When they dyno'd their motors the ground shook.Real exciting.Its all exciting to me.Shoot Ide love to be able to dyno my motor.There ought to be a bunch of dyno shops up there in nascar land.Let me know what happens . I checked out your web site .Are you the old guy'. Old guys rule! Thats what my tee shirt says anyway.

Catman ( Now you know why the Catman - Offshore power boat racing with Cats' - 4 / 750 hp engines 650 gallons of Cam2 and lots of $$$$$$ )

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.