steveelsbury

I had an engine built for me last year, and have hurt a piston thru detonation. The engine builder gave me no build sheet. I am in the UK, and the builder is in the states. When I asked him for the info, he asked me to send him the broken piston, so he has clearly kept no records either!

OK, so I went to the JE site and downloaded their PDF spec sheet, but my piston isn't listed, and I can find no email address for JE.

The engine builder said the pistons are SRP, which I understand are the JE, cheaper, off-the-shelf pistons, so I'm surprised they're not listed.

What I need is a 400 series 23 degree flat top at 4.155 bore, 3.48 stroke, 6 inch rod, 1.125 comp height (pin height) 76cc

I'm not expecting anyone to say 'hey, I have one to sell you', but it's really frustrating trying to find performance parts in the UK for an American motor, and I've learnt on this forum the more info I provide up front, the better the replies!

So what are my questions?

1. Well, I've hurt one piston out of 8 (busted lands), but sadly have a scored bore (fingernail just catches) - How big of a skim bore can I get away with and keep the same size piston. Don't want buy 8 if I can buy juist 1!

2. Does anyone have an email address for JE? I tried calling them, and got put thru to someones voicemail.

TIA
Steve

danno85

Do you have 6" rods or 6.125"??

Look at their catalog again. I think what you need is near the bottom of
page 4 under the 400 series pistons. Part number 181933 matches the
bore size and compression height you listed but is for a 6.125 long rod.
They also show one for a 6" rod, but is 1.250 comp height.

Dan

427Hotrod

First off...here's the numbers I have.... JE (714) 898-9763.
Website= http://jepistons.com

and

SRP (714) 373-5530 http://srp.com


The SRP line of pistons are produced on the high $$ equipment that JE and GM put together to make the 502 pistons for the crate motors. High volume equipment makes them less expensive. They are a high quality piston that is made of a slightly different alloy that allows tighter bore clearances than regular forged race type pistons.

It kind of goes like this...Wiseco owns JE who owns SRP. SRP is the high volume line of pistons that can be sold cheaper because everyone uses the same thing. JE makes serious race pistons at a relatively high volume for the most popular combos and a some custom stuff. Wiseco makes very serious race pistons and really cater to the custom stuff crowd.

It's interesting that one got damaged. They are a very tough piston. I have them in my 540 and recently had it apart for inspection and HP upgrades and found them to still look like new after two years of running.

You really need to look into that detonation source. It must have been severe.

Luckily, SRP typically specs tight bore clearances. So if the engine was built relatively tight, you can hone that hole and still be OK.


You might check Flatlanderracing.com. They sell lots of this stuff and might be able to help. Ask for Phil.

Good luck,

JIM

SloRvette

Are you sure you've got all your measurements right? Do you know what your actual deck height is? Those numbers you posted don't really jive with what's "normal".

WashingtonRacer

Did you destroy any of the rings?? or are there any "bruse marks on parts of the land or where it busted? "darkened spots in the metal."?

CFI-EFI

I could look around at work to see if I can find a "straggler". But IF your dimensions are correct, I won't find one. Something listed is wrong. Your specs leave a whopping, 0.160 deck clearence. With a 76 cc head, this would make a 6.00:1 compression ratio, or so. Please confirm the specs and give me the ring widths you need. Good luck, and...

RACE ON!!!
1984 Crossfire
Member NHRA

steveelsbury

Danno85 - the rods are 6 inch for sure. Regarding the catalogue, you have made the same mistake I did (just realised) - by looking in the JE Automotive catalogue instead of the SRP one. However, my combo isn't listed in the SRP cat either.

427Hotrod - thanks, but I've rung JE several times, and get put through to some dude's voicemail. I leave messages but he never gets back to me. Regarding the detonation source, I think my problem is simply that it was a hot day and I was running 38 degrees total advance. I'll be backing off to 34 degree max. The big end bearings are all shot, so I'm guessing all the pots were detonating, but luckily only 1 piston failed. I'll check out FlatlanderRacing - thanks.

SloRvette - measured everything twice, but I don't know my deck height, and my engine builder clearly never even kept a build sheet for himself, let alone sent me one, because he can't/won't answer that question.

WashingtonRacer - No ring damage and no bruise on the piston, although there is the classic blow-by burn on the top edge. The damaged land area is shiny clean - just cracked and with a piece of metal missing. Rings are very tight, but not locked.

CFI-EFI - Haven't CCd the heads yet - I was making an assumption based on the engine builder having told me the motor is at 9.69:1, then looking up similar speced pistons in the JE catalogue, and read off the cc that generated a close CR - I know, I know, amateur hour, right?

So the general assumption is that my pistons spec isn't quite right, yet the compression on the good pots of around 200 would indicate it's highly unlikey the compression ratio is that far out. The engine builder assures me he can get a piston in the right spec, and although I'd rather not be dependant on him for various reasons, it's about the only source I have right now. He also believed that cylinder score could simply be scotch-brited out - although I'm a little uncomfortable about that!

If my previous experience with getting parts from the US is anything to go by, my car will be off the road for at least the next six months :-(

Steve

SloRvette

Steve, have you physically measured the stroke ? Check a piston's travel in the bore. Those numbers would work out perfect for a 3.75" stroke. If those numbers are right they took a big cut off the deck.

Also, personally I'd back the timing down to 26 to 28 degrees total if you're running pump gas. I'd rather be a couple degrees retarded to have it on the safe side. Keep an eye on your plugs for speckling, brown/black or aluminum specks.

CFI-EFI

I'm afraid something is seriously wrong, here. As SloRvette said, that compression distance is correct for a 3.75" stroke, coupled with a 4.155" bore, makes a 406. You couldn't get a 9.69:1 compression ratio with a steel plate (0 ccs) welded to the top of the block, with a 1.125 compression height, 6.00" rods, and a 3.48" stroke. That combination of parts puts the piston 0.160" down the hole at TDC. And that is with the 9.025", blueprint, crank centerline to deck dimension.
A 4.155" bore, 1.125" compression height, flat top, SRP piston, carries SRP part number 138700. This piston is flat with two valve reliefs, totalling +5ccs. I don't have any in stock. If you buy one, only, piston, be prepared to re balance, or at least, match the new piston weight with the others. Good luck, and...

RACE ON!!!
1984 Cossfire
Member NHRA

[EDIT] typos


[Modified by CFI-EFI, 7:31 PM 6/19/2003]

steveelsbury

SloRvette - yep, deffo 3.48" stoke. Timing comment makes sense, as I'd like to actually put some miles on the motor before I hurt her again!

CFI-EFI - pulled the block today and am arranging for a hone and crank grid, so I'll get them to check the crank centreline to deck height. I told the guy at the engineering shop my problems, and he says he sees this kind of thing all the time when people in the UK buy an engine from the States (i.e. not getting what you actually ordered) :-( Thanks for the piston part number - I'll see if I can get to talk to a human at SRP and actually order one! Now I've found a good engineering shop, getting the rotating assembly balanced shouldn't be a problem.

Thanks for all the help guys

Steve

Edited to add this: CONFUSION! JE say there's no such part number as 138700 and there has never been an off the shelf piston in the spec I quoted. Tomorrow I'll put a piston back in and measure the stroke with my vernier. Eyeballed it with a ruler just now, and crank centreline to outside of big end bearing looks greater then 1.74 (half 3.48). Trouble is, by eye it looks greater then 1.825 (half of 3.75) as well! Assuming it is a 3.75 stroke, that would make it a 407 - how much would it have to have been decked to return it to a 377? Oh well, I'll be able to do my own build sheet when this nightmare is over!

PS Rod length is measured from wrist-pin centre point to big end centrepoint, right?


[Modified by steveelsbury, 7:10 PM 6/25/2003]

danno85

Correct.

CFI-EFI

I believe I may have mis-typed. I was, and am, going by memory. The number, probably should be a 138100. Sorry. They should have found it as easily as I did, if you're giving us both the same specs.
As with the connecting rod, the journals must be measured, "center to center". A 350 block takes a crank with a 2.45" main journal. A 400 block takes a crank with a 2.65" main. If you have a 4.155 bore, your block has to take the 2.65" main. The rod journals are 2.10" for either.
Most of us call that a 406, but there is no point arguing about "rounding". The deck cannot be "adjusted" to work with a 3.48"-3.50" stroke crank to make a 406 into a 377. I'm afraid you will need the proper pistons.

Good luck, and...

RACE ON!!!
1984 Crossfire
Member NHRA


[Modified by CFI-EFI, 7:45 PM 6/25/2003]

steveelsbury

This just goes from bad to worst! Took the block to a local specialist to have the cylinders honed and the crank ground. A day or so later he calls me back:

"You brought in a 400 block to us"? - "Yep" - "Well, it's actually a 350 block that's been bored out to 4.1645, and has a 350 crank with a 20 thou grid already on it - also, ALL the main crank bearings need replacing and there's no way this amount of damage comes from detonating one cylinder"

"Oh" say I, realising just how badly I've been ripped off.

"I'd guess this engine was just lying in a shop and shipped to you as a new build, or if it was built, then it was built dirty"

So, my advice to any UK owners looking for a new engine is do NOT buy from a US builder. I'm sure many are fine, but if you get one that isn't, what are you going to do?

So the massively strong and upgradeable 400 I paid for is actually an old 350 that's been reamed out within an inch of it's life!

Randy at O'Donohue Racing - get ready for some legal action my friend, because I cannot let you get away with this. Now the reason you always conveniently forgot to send me an invoice becomes clear - fortunately, I have every email you ever sent me - including ones which describe the block as the Bowtie 400, never fitted in a production car, and the crank as being new and the heads as being new 220s not second hand 200s, and the cam as being suitable for a blower motor when everyone else says isn't.


Break, break...

Anyway, back to my original pistons question: The rebore dude says my block measures 7.69 inches from deck to the edge of the crank journal - i.e. not to centre. The stroke is 3.48,. the pin height 1.125 and the gap from piston head to deck approx 40 thou at TDC....do THESE numbers make sense for a 377?

Steve

Fed up, depressed and desparate to have a running car again even if I have to put a Honda engine in it.

SloRvette

Those numbers work out Steve. They cut around .120" off the original deck height.

I didn't think it was possible to bore a 350 that far. The 400's are siamesed between the cylinder bores to allow the larger bore.

Are the connecting rods what they're supposed to be ?

Is the crank forged steel at least ?

I'm sorry to hear this. I hate hearing stories like this.

WashingtonRacer

with cylinder walls that thin I would swear you could be able to see the pistons moving up and down from outside the block. That is so messed up. I had the same kind issue with the engine that came with my vett.. the seller told me 420hp professionally built block, all records and yada yada yada, the build sheet looked impressive, however when tearing it down, I found almost all of it to not be true. But who could I blame, it's was months after I got it, who's to say I didn't swap out the parts my self. secondly can't go after the builder, as I am not the original buyer. Oh well. I have 2 much nicer engines in my garage now. But I learned quick not to even think of ever buying an assembled engine from ANYONE!!.. only buy bare components.

CFI-EFI

Do some more checking. It really may not be as bad as it first looks. The Bowtie blocks come ready for the 2.45 main journal crank, NOT the 2.65" journal 400 crank. Look on the side of the block for the Bowtie Chevy logo. Only, the Bowtie blocks have that logo. It could actually be a Bowtie block. If in doubt, have the cylinder walls sonic tested for thickness. Most production 350 blocks will be super thin at that bore. The Bowtie blocks have siamesed cylinder bores, like the 400 engine, regardless of the finish bore. The main bearing saddles tell you it's not a 400 block. The bowtie block will safely accept a 4.200" bore. The centerline of the crank to deck dimension, is nominally 9.025". The 350 main saddle measures 2.6406/2.6415. Half of that (2.640 / 2) is 1.32". Plus your measured 7.69, equals, 9.01" crank centerline to deck. That only represents a .015" decking, short of the blueprint dimension. So far, nothing looks totally awful. Lets stack the numbers from the other perspective. The crank throw is 3.48 / 2, or 1.74". plus .040 deck clearence, and a piston deck height of 1.125", adds up to (1.74"+.040"+1.125") = 2.905. Add a 6.00" rod to that and you are at 8.905. We're off by 0.105". How accurate are some of these measurments? Is the bearing bore to deck dimention, accurate? Are you sure of the piston deck height? The rod? Could it be a 3.50" stroke instead of 3.48. I cannot comment on the care and quality of the rebuild, but you MAY have not been screwed as badly as you first thought. Good luck, and...

RACE ON!!!