1g rods with 2g crank PLEASE help

[black97spyder]

Okay so about 3 months ago when i was in the middle of buying parts for my engine rebuild I came across a unused set of forged Wiesco 8:1 and scat H beam rods for $450 online.... The guy said that they were for a 7 bolt, standard bore and ready for install!! So i made a road trip and went and inspected them and they looked great! Jus minute surface rust patches Here and there on the rods so i bought them.... First off, they ended up being .020 overbore so i Thought no big deal, I'll just bore my block and go on with the install. So i bored my block and found out the guy I got them from Had 3 out of 4 rods turned around backwards. Once again dumb me Thought no big deal, so i turned them around so the bearing tangs were facing the correct way. Being that i Thought I had everything ready for my build to begin, I went ahead and put my ARP main studs in and dropped my crank in...... Now I started to put the pistons in, compressed the rings and stuck the first one in to find out that my rods are too wide for my 7 bolt block!!! .... So I found out once again the guy I bought them from deceived me yet again and they were 6 bolt rods Not 7 bolt rods

Situation is that i am now broke otherwise I would just buy a set of 7 bolt rods and sell the 6 bolt ones

Is there any problems that anyone can forsee me running into by simply swapping the rods to 7 bolt rods? Are the wrist pin sizes the same between 6 bolt and 7 bolts? I'm trying to solve this massive headache as easy and cost friendly as possible.. What options could I do to make the 6 bolt rods work with my 7 bolt crank??

ALL would be greatly appreciated! Thanks, Matt

 

[TurboAnything]

6-bolt rods use a 21mm piston pin and 7-bolts use a 22mm pin. But I have a solution for you This is something EVO guys do. Take the rods to a machine shop and have the big end narrowed to the width of a 7-bolt rod. You have to use 6-bolt bearings but otherwise it will work perfect.

 

[black97spyder]

I did the them to a machine shop already and that's what he suggested but the thing is the machine shop didn't know if he needed to take material off of one side of the rods because the way of the offset of my 7 bolt bearings. Or if he had to remove material from both sides evenly?

TurboAnything, will the 6 bolt bearings fit in my 7 bolt crankshaft journals? Or would that need to be made wider to accept the 6 bolt bearings? as well as the resizing of the rods?

 

[BogusSVO]

If you have the 6 bolt rods cut down to fit a 7 bolt crank, you will need to run the 7 bolt rod bearings.

There is a difference in the width of the rod bearings between the 6 bolt and 7 bolt.

Personally, I would say sell/trade the 6 bolt rods and pistons for a set of 7 bolt. I am guessing it will be about $40-50 a rod to have them cut down properly and have the rod champhers machined back into the rod.

There is appox. difference of .125 between the width of the bearings.

 

[black97spyder]

Yeah I found that the 6 bolt rods are 2.98mm bigger/wider than 7 bolt rods . I am not against any ideas! Though id like to use the setup I have because idk What problems I will run into with the wrist pins on the pistons if i tried to put 7 bolt rods in place of my current ones that are ready to bolt in minus the fitting problem on the crank? I haven't had time to see how big the wrist pin is, if It's a 22mm or 21mm so If I went to put the proper 7 bolt rods on the pistons I'm scared the wrist pins won't be the proper size and then I would have to do machine work on the wrist pins instead of the big end on the rods....

What do you guys think??

I am kind of stuck in a bad position now, as the only way I see this build coming together without buying new rods and pistons would be to do customs machine work on the parts I Already have. And Then possiblly running into more problems with a custom fitment

I've been trying to find someone with 7 bolt H beams that would be willing to trade me for my unused 6 bolt scat H beams??

 

[BogusSVO]

6 bolt rod has a 21mm wrist pin

7 bolt rod has a 22mm wrist pin

So hanging a 1g/6bolt piston on a 7 bolt rod will not work unless you have the bushings replaced in the small end if the 7 bolt rod.

It will cost you more in the long run in custom machine work to make the 6 bolt rods and pistons work with your 7 bolt block and crank.

 

[Diamond Star Werks]

6bolt rods would have to be narrowed 1mm on each side to be able to work on a 7bolt crank. The 6 bolt crank is 2mm wider at the rod journals. Effort is not worth it.
You'd be better off polishing and shot peening the 7 bolts

 

[black97spyder]

Thanks for all the input guys. I'm still kinda at a dead end and don't know which Way i need to go. Mainly because I'm broke after buying all the parts needed for my rebuild.

Has anyone else put 6 bolt rods in a 7 bolt? I'm trying to find the cheapest route to fix this problem. Machine shop isn't a problem because there is one 2 miles from my house.

 

[Diamond Star Werks]

Thanks for all the input guys. I'm still kinda at a dead end and don't know which Way i need to go. Mainly because I'm broke after buying all the parts needed for my rebuild.

Has anyone else put 6 bolt rods in a 7 bolt? I'm trying to find the cheapest route to fix this problem. Machine shop isn't a problem because there is one 2 miles from my house.

Cost and risk aren't worth it. You may just end up out of 450$ if they aren't narrowed and machined. Oh more if they damage your crank. Sell them and buy 7 bolts

 

[black97spyder]

Yeah i haven't throught about it that way. I don't want something to go wrong aftet ive spent all kinds of money... What's another $500-$1000 for peace of mind!!

I did want higher compression anyway!! I just don't have the funds to buy the proper things now ...

 

[clipto]

Can always run evo piston and rods.

 

[black97spyder]

Hmmm haven't Thought about that... What are that goods and bads about EVO pistons and rods?? I'm wanting to put a lot of power down (350-400whp) in the future with peace of mind in my DD.

What power level do they start to break and have probelms at?

 

[clipto]

They will be perfect for you. Probably little less compression ratio, but that just means safer to boost more. Probably like 8:0 due to head to block surface distance. Stock evos make 500hp so its not going to be a problem. Direct swap into 7 bolt motors. I have couple friends who run em they have no problems. You should be able find them cheap too, most evo guys upgrade for big hp.

 

[black97spyder]

That would be great!! I found a set of forged manley 10:1 or 10.5:1 pistons with eagle rods for $775... What problems if any would I have from having a lot higher compression? Would there still be plenty if valve clearance or would i have to have the valves sunk or something else?? I'd really like to run more compression and a little less boost because I have an automatic so the Car would be easier to drive on the street before the turbo kicks in due to the stock stall converter

 

[Diamond Star Werks]

Evo rods are the strongest 7 bolt rods. You won't have an issue with your power range. 2g rods can run 450 with arp bolts, evo rods can handle around 550. Polishing and shot peening will strengthen them even more. Your compression will be 8.3:1 I believe.
If you 775 to spend I'd suggest manley turbo tuff rods.

 

[BogusSVO]

The Manley 10.5:1 pistons are the high compression E85 pistons they have come out with.

 

[black97spyder]

I dont have that much, I only have around $200 but Im gonna ask to borrow money... And It's not just rods for 775 its manley pistons, H beam rods, rod bolts, wrist pins and rings.. Im guessing I have 6 bolt pistons as well so Im just going to try to sell the forged 6 bolt stuff I have.

What problems would i run into, if any, when running 9.5:1 or 10:1 compression?? That's what im looking at to get Now

Also What kind of fuel would i have to use with it being my DD and having that high of compression ratio?

 

[Riceburning101]

higher compression can lead to engine killing detonation

 

[Archer Fabrications]

Probably 94 oct or e85, I'm 9.2:1 and had no problems with 92 oct in seattle. But now I'm where 94 is available i use that.

Rice burning, not true. It's all in the tuning.

 

[slo2spool]

The cheapest solution would be for you to have the rods machined to fit. This is done by blanchard grinding the big end width down to the 7 bolt width. Your standard engine machine shop won't have a blanchard grinder but if there are any companies in your area that do precision grinding they will have one and shouldn't charge too much to grind the big ends for you. All you have to do is give them the size and tolerance, and take the pistons off of course.

 

[Diamond Star Werks]

Grinding? No.

 

[arrowhead]

Find a machine shop that cuts cranks they probably will have the proper equipment to do the work on your 6 bolt rod, use the 7 bolt bearings and be happy, it is not a difficult procedure, the machinist should know that it has to be cut pn both sides.

Dont make life so difficult for yourself.

They will be perfect for you. Probably little less compression ratio, but that just means safer to boost more. Probably like 8:0 due to head to block surface distance. Stock evos make 500hp so its not going to be a problem. Direct swap into 7 bolt motors. I have couple friends who run em they have no problems. You should be able find them cheap too, most evo guys upgrade for big hp.

The evo pistons sit about .007 lower than the dsm but the dish is a lot less, I have not done the math but it seems that compression would be up a tad not down.

 

[BogusSVO]

The cheapest solution would be for you to have the rods machined to fit. This is done by blanchard grinding the big end width down to the 7 bolt width. Your standard engine machine shop won't have a blanchard grinder but if there are any companies in your area that do precision grinding they will have one and shouldn't charge too much to grind the big ends for you. All you have to do is give them the size and tolerance, and take the pistons off of course.

I would have to say you are wrong, a typical automotive machine shop can cut them down, if they wanted to.

I know I could. On 2 different machines, on one machine 2 different ways.

I have done the procedure before, but it is not common to do.

The "Blanchard Machine" is found in machine shops, just a smaller version, one being a wet segment stone grinder, commonly used for surfacing heads and blocks
Another would be a flywheel grinder.

Grinding? No.

MJ, Sorry, grinding would work work with the proper set up, it would be slow going though.

 

[Diamond Star Werks]

MJ, Sorry, grinding would work work with the proper set up, it would be slow going though.

if you added material then grinded down to specs yes. The rods are wider not narrower.
Unless I'm missing something?

 

[black97spyder]

Well I got a small loan from my family so i can buy new pistons and rods and just sell my old ones. I know machining would work but this is going to be my DD so I want all the peace of mind I can get and want the rebuild done proper. I personally like to do things only once and don't want any other small problems popping up.

Urbansmoker, how did u get your 9.2 compression ratio? I was looking at Manley 9.5:1's or Manley 10:1's and was wondering if the true compression ratio would be the 9.5 or 10:1 with a head that has never been machined before or if it would be slightly lower than what they advertise?

All I I have for pump gas around Here is 91 octane, and can think about running E-85 in a few years but defenately no time soon.