getting nervous on rebuild

[marcr1]

An update on my 1600 dp rebuild to 1776.


                   The mechanic doing the rebuild has told me he does not need to machine the case in order to fit the new cylinders and pistons.  This goes against everything i have read and have been told by other mechanics who have done this.
                   He has told me he has gone all the way up to the  92mm pistons and not had to do any machining they are slip ins.     
                    This guy has come very highly recommended from other vw owners in the area and my own mechanic.
                     Am i missing something or is he forgetting something.   

[braidmeister]

Something there doesn't sound right. If your motor is a stock 1600 it used 85.5mm barrels/pistons. The 1776 should be using 90.5mm barrels and the case & heads DEFINATELY have to be machined for this. The only other slip-in options you have on a stock case is either 87mm to give you a 1641cc engine, or 88mm to give you a 1679cc engine. The 88mm slip ins are too thin & NOT RECOMMENDED!!!

Make sure you are not getting screwed - meaning that the mechanic (of which I don't know who it is, nor do I want to know) - is not going to just install 85.5 or 87mm barrels and keep your 90.5s for himself, thinking in his mind that schmucky schmucky you aren't going to know the difference. Not saying he would, but some people like to take advantage. I would ask him how he expects to build a 1776cc engine without machining your case. I would also ask him if he is going to re-use YOUR case, or swap it out for another one he has laying around, which may already be bored...and that brings up the question of heads being bored as well.

Don't be afraid to ask the engine builder questions. There is nothing rude about being crystal clear about how YOUR money is going to be spent & how YOUR engine is going to be built.

-Brady

[lovebus (jack)]

You can get 88mm slip ins but thats not the way to go as the walls of the cyls. are thiner. If I was you I would look for another mechanic or you tell him what you want, on second thought I would go to another mechanic. Who is this guy?

Your not missing anything, he is. Tell him your dog got sick and you don't have the money now, take your parts anfd run.

[marcr1]

Jack,

                 the guy is by me in the east brunswick area.   i spoke to my mechanic today who recommended this guy.
                  He agrees that for the 90.5's he needs to machine the case that is why he sent me to this guy he has the equipment  to do so and knows he has done it in the past. My mechanic has a ghia of his own and said this guy did the work for him.   
                    Tuesday is the next day he works,so i guess i will hit him over the head with the new cylinders so he can see the difference.

[njgt-1]

this might sound harsh but RUN! don't walk! get your parts out of there and find someone who knows the difference between "Machine in" and "Slip in". What hes saying is impossible and you are going to pay for something you won't be getting plus if hes screwing you on engine size I'd hate to see what else hes putting in this engine!

As the other guys have already said, 87mm & 88mm are the only size cylinders that will fit into a VW case without machine work or cutting the holes in the case bigger where the cylinders set. Your choices for a bigger displacement engine have to be made carefully, if you go with 88mm slip ins or 92mm machine ins the cylinder walls are very thin and after some time ( not much! ) will distort and you would experience something called "blow by" or the compression getting past the rings - not good! A set of 90.5s or a good set of 94s are close to the same thickness of a stock cylinder, way more sturdy than the others and will give your engine a normal lifespan. Consider all of this before you let this guy talk you into something thats not gonna last!  

Who is this guy

like Jack said, I'd like to know also. If you don't want to post that info here just send us a PM.

[VWPANZER1]

  I'm with Bob on this on!

  We have a long list (A Black One) of so-call great VW mechanics. Even club members have sworn to their expertise. However when we tear their rebuilt engines apart we find a horrendous mismatch of-and/or incorrect parts.

  Anyone (mechanic) that can read can rebuild a VW engine but it takes a lot of time, measuring and reassembling and almost always you have to get mail order parts to do right. This is where the quick-job mechanic fall short. They substitue used or something close and push them on some poor unsuspecting VW owner.
  Thats when he finds his engine falls short of a factory engine. Instead of getting 100,000 miles he's lucky to get 10,000, if that.

  Based on what you said ... I would run!


jt 

[Baha (Shawn)]

Here's the gospel of pistons & cylinders, from a mahle vendors ad. It's everything you need to know.

 
Mahle pistons and cylinder for VW Volkswagen have always been the engine builders choice when it comes to quality. They are also an OEM manufacture for Volkswagen. Mahle pistons are available in cast or forged with a graphite coating. Stock pistons were always cast but forged pistons are will endure higher temperatures with less distortion. If you drive your motor hard or at high rpm's for sustained periods (I know I do in my bus when freeway driving), forged pistons will endure more punishment.  When using big bore piston sets (88mm-94mm), machining to the engine case and heads are required. Although using slip in big bore pistons sets (87mm and 88mm) can be convenient, there is a downside. If you enlarge the piston size from 85.5mm to 87mm or 88mm and do not increase the outside diameter of the cylinder, you are boring the cylinder thinner to accommodate larger pistons. Now you have less cylinder material to dissipate heat and the strength of the cylinder has been compromised. Excessive heat will want to distort the barrel and raise the oil and head temperature. Your best bet when choosing larger pistons and cylinders is to bore the case and the heads larger. 90.5mm cylinders are the thickest and will run cooler than 92's. 94mm cylinders are thicker than 92's but require 8mm head studs. 90.5's are usually for the guy who wants more power but and still run cooler. 94's are for the guy who just wants the make most horsepower and stomp everyone else. Stock 1600cc motors have a 69mm crankshaft. 69mm and 74mm cranks require stock stroke pistons and cylinders. 78mm-90mm cranks require stroker pistons. 76mm cranks can use either stock stroke pistons or strokers. If you use stroker pistons with a 76mm crank and stock cc heads, you can not get the compression ratio higher than about 7:1 due to the large amounts of deck height of pistons and cylinder. If you want the compression ratio higher with a 76 crank, you must use stock stroke pistons and a barrel shim to achieve desired deck height. Calculating compression ratios is only one of the key components if you want you motor to live. It is always a good idea to have your engine parts balanced , tap your engine case for full flow, so you can run an oil filter system, and keep you compression ratios conservative for pump gas. Keeping the oil clean and cool will keep it alive.