Spare engine to mess with

Mrmerlin · 05-08-2001, 06:39 PM

Hi All I wanted to know if anyone has experience with rebuilding IE boring out the block and possibly grinding the crankshaft on a 86 951 motor, I have one that the #2 bearing went south on and all of the motor is filled with lil bits of bearing material, the #2 bore has some gooves cut into it and the crank looks like it might just need to be polished on the #2 rod journal.
So would it be worth it to have the block ground out to say the 2.7 litre dimension, if the crank has to be ground should I replace instead of grinding on it, I know it will need a new set of pistons and i am thinking it might be a good idea to replace all the rods as well, I know #2 rod is toast, also the cam housing has all the lifters kinda stuck in place as the fine metal bits have bound the tappets into there bores, I pretty much have a complete motor but i am wondering if it would be worth to sink the bux into it for say a track car, I also have a 87 turbo body that is hit on the front the frame rails are toast and I was wondering if I might find a turbo body that needs a motor or better yet a 944 Na that i could put all of the stuff i have onto it for a track car...any Ideas ?......Stan

geoffbaltz · geoffbaltz's Garage

May be good for a 2.7 stroker kit. I have heard that doing that makes one hell of a motor for a track car.

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Geoff Baltz
'86 944 Turbo

porschepatron · 05-08-2001, 08:19 PM

Hey Stan I have heard about the 951 cylinders being silica impregnated or coated or something like this, and if you were to bore the block would I was told it be quite costly for the machine shop the re-treat the block. This is all just hear say so correct me if Im wrong. I would love to know this because I will be rebuilding my 86 951 motor this summer when I return from Europe in mid June. I was considering the machine work but if its outrageously expensive Ill just stay standard .

951carter · 05-09-2001, 02:43 PM

the block can be bored. you can sleeve it or bore it. it does take a special process but it is not too complicated. you just have to polish the silica back up.you can even get the factory pistons oversize. you can also turn the crank if it is not too bad and get the correct size bearing. when you do get it back together you should put on an accusump. we sell a bolt-on kit if you are interested.where are you located? if you are near virginia i can take care of it for you.

porschepatron · 05-09-2001, 05:46 PM

951Carter I appreciate the info, but what is an accusump? I may be interested, and yes Im in VA on the coast. I ll have to get back to you because I am leaving on Friday. THANKS!

Mrmerlin · 05-11-2001, 06:59 PM

Hi 951 can you give me more info on the engine bore process on a 86 951 what kind of cylinder coating is required, what is, and how does an accusump work, and also is it a good idea to grind on a turbo crank, as it has heat treating on it from the factory............Thanks........Stan

951carter · 05-11-2001, 07:40 PM

an accusump with an electric solenoid wired correctly creates oil pressure as soon as you turn the key. this eliminates dry starts and keeps constant oil pressure. what happens to the #2 rod bearing on 944 engines is that when it is subjected to cornering forces the oil sloshes to the side of the pan and causes the oil pickup to go dry. without oil being sucked up by the pickup there is no oil going to the bearings. porsche did update the oil pan baffle to help this problem,but i have seen many with the updated baffle do the same thing.the accusump adresses the problem by keeping oil pressure under any condition. the process of boring the cylinders is done by using a special boring process. you bore it to a set amount and then go the rest of the way with a special polishing stone and compound. what this does is expose the silica in the aluminum so that you do not have aluminum against aluminum. you get aluminum against silica. being that i am in Virginia where reynolds metals is i know a few engineers from reynolds that actually worked on the development on the 944 engines composite. just a few years ago they melted a 944 engine that they had as a sample!! due to their contract with porsche they could not sell or give it away! i tried real hard to get it, believe me!it is fine to turn/polish the 951 crank. it can also be cross-drilled and knife edged too if you like!! i am not sure but i believe that huntley racing advertises it on their website if you want to check it out.

Mrmerlin · 05-13-2001, 04:57 AM

Hi 951 Hey do you know about how much a new set of oversized pistons and rods would cost as well as how much the boring and crank polishing should go for , also how much is an accusump?..Thanks ..........Stan

Dave951M · 05-13-2001, 06:18 AM

Is there an advantage of going with a dry sump instead of an accusump? I would think that the dry sump would be immune to cornering g's. Also, the 928 guys have a problem with the 2/6? rod journal that was solved by redrilling the oil passages. Since the 944 block is very similar to the 928 in many aspects, is this not possible to do on the 944? What is the max overbore for the 2.5? If you are going to go to the extent of boring, don't stop there. Align bore the crank, balance and blueprint at the very least. In short, approach it as if it was to be a 24hr race motor. Safety wires are also a good idea. I have built only Fords and Fiats, but I believe that the concepts are still valid.

Dave951M

Mrmerlin · 05-14-2001, 05:21 PM

[QUOTE]Originally posted by Stan Kolen:
Hi All has anyone done any extensive engine work and had to buy new pistons and rods for a 951 ,IE regarding costs and engine enlarging say to a 2.7 lite dimension any thoughts would be appreciated..Stan

951carter · 05-14-2001, 09:14 PM

off the top of my head, mahle pistons $750
i would have the rods magnefluxed as you probably wont need to replace them. if so i would suggest some lightweight billet rods. turning the crank is not very expensive, depends on how bad it is. the bearings are only $100. our accusump kit is $750. the boring is $75 @ hole. it depends on how you want to go about getting a 2.7/2.8. you can bore and sleeve it or you can get a 3.0 crank and rods to stroke. either way you are looking at about $3k in parts. there are advantages to dry sump over accusump but it is very costly. yes you can drill the oil passages but i would still put on an accusump personally. as far as the bore i have heard of people building as big as 3.3 litres along with stroking. the possibilities are only limited by ones budget.

marksportcts · marksportcts's Garage

Here it Vancouver, it is going to cost me $275Can to have my block honed. I took my motor apart last night. It is an '86 N/A with a Callaway TurboSystem kit at 7PSI. I heard it knock before and thought it wasn't going to be any danger. WAS I WRONG. Piston #1 ok. #2 has 3 cracks. #3 has 2 cracks. #4 has 2 cracks and some of the lower skirt broken off. All the cracks were between the the rings. Thank god I've got 951 pistons and rods ready to go in. I'll post pics soon.

[This message has been edited by marksportcts (edited 05-15-2001).]

Mrmerlin · 05-18-2001, 07:41 AM

[QUOTE]Originally posted by marksportcts:
Hey Mark did you have the 944na pistons in when the motor blew?
If so then the compression ratio was higher than the 951, i would think that putting in lower compression 951 pistons will let your motor live longer as well as the fact that the 951 pistons are probably stronger...Stan

pst · 05-22-2001, 11:05 AM

Strange....a while back I posted that I was working on a 3.3L engine but only got criticed on the crank work and sleeving the cylinders. I am going to use 400 CID Chevy pistons, 924 rods and a welded/offset ground crank. As I mentioned on the post, up until reciently it was common practice to do this on 928's. Now they make a new crank forging. However, I am on a budget and will go the weld/grind route.
The 2.5L block can be safely sleeved to 4.125" but you cannot use the factory pistons with sleeves. They are either iron plated or chrome plated (depending on the manufacture). The easiest is to use an existing piston or to go to a piston maker and get custom pistons made.

951carter · 05-22-2001, 03:00 PM

you were not criticized by me :^) i do not know anything about the chevy pistons, admittedly, but i imagine that they are pretty heavy. i would probably look to JE for pistons. keep us posted.