Budget stroker build parts questions

[MoFo]

I am planning a budget stroker and need help with parts decisions.

I have 2 running RENIX 4.0 engines and a 99 4.0 with a spun rod bearing. This stroker will be replacing a 4.0 in a 1987 XJ.

I am planning to use a RENIX block because:

• No ECU or harness changes required
• Knock sensor
• Stronger block; is this true?

From the 99 engine, I plan to use

• Intake and TB
• Camshaft
• PS pump and bracket
• Crank bearing girdle; will this fit the RENIX?

I already have a head and set of injectors from a 1995 4.0.

I am having trouble finding a 4.2 crankshaft. The supply seems to be much leaner than it was when I first looked at this a year ago. I understand I need a crank from a serpentine-equipped 4.2.
Can someone recommend a source for an affordable crank?
What vehicles, model and year, came with the right crankshaft? I may need to buy a junkyard engine to find one.

TIA

 

[Talyn]

I would skip trying to find a reground or used crankshaft. Instead I would go with a Scat 4.2L crankshaft. Should be around $350

 

[redrider2911]

From the 99 engine, I plan to use

• Intake and TB
• Camshaft
• PS pump and bracket
• Crank bearing girdle; will this fit the RENIX?

I already have a head and set of injectors from a 1995 4.0.

TIA

You will need a 91-94 fuel rail and TB. For the life of me I cant remember why you need the fuel rail besides that it still has the regulator on the rail itself and not in the tank. but The TB pre 95 still uses the MAP sensor on the firewall. You will have to dremel out the renix TPS to bolt to the 94 TB. As well as modify the end of the butterfly shaft.

 

[MoFo]

I forgot to include that I have the right fuel rail and fuel line with the regulator and return line. I also have a '94 TB already.

Does anybody know if the 99 girdle will fit the RENIX lower end?

Is the Scat crank a new aftermarket crankshaft?

 

[bigdaddyjlove]

The girdle will fit, but you will have to space it to clear the crank.

I used 2 1/4" washers per stud.

 

[Talyn]

Is the Scat crank a new aftermarket crankshaft?

I think its been out for like a year or so.

 

[Mesh]

I like your mix of parts it's close to what I have. The RENIX block is a little stronger because of the higher nickel content.

 

[MoFo]

For a budget stroker, which length rods and what pistons would you recommend?

I would rather not deck the block and would like to run regular gas:cheers:.

 

[Talyn]

Short 4.2L rod with 4.0L stock replacement piston.

 

[old_man]

I would rather not deck the block and would like to run regular gas:cheers:.

Decking the block which adjusts the quench height is the way you end up running regular gas with the higher compression ratio.

 

[old_man]

If you are buying pistons, you might as well run the H802cp pistons since they will run you about the same amount.

 

[kastein]

Minor correction, 95 and down fuel rails are the ones with the regulator on them, 96 and up have the regulator in the tank.

Carry on :thumbup:

 

[MoFo]

I have been doing a lot of searching and reading both here and strokers.com. I am having touble with the relationships between deck height, quench, SCR and DCR. Is there some reference you can point me to that explains these relationships and detonation?

 

[Talyn]

Static Compression is the compression ration of just the piston, cylinder, head gasket, combustion chamber. Most compression ratios you see listed are this.
Dynamic compression is the static with the cam taken into consideration. What your actual engine will see during running.
Quench is the distance between the black part on the head and the flat part on the piston. Tighter is usually better, but you can't go 0 because of growth of parts when heated and piston rock. Usually 0deck clearance with a .043" gasket is what you should go for. Or if you want to leave room for more decking if necessary leave the piston in the hole a bit. Reduce your quench and your compression will go up. However better quench reduced detonation, which can negate the effects of higher compression. I can't tell you what SCR you can run on what fuel.

 

[MoFo]

old_man - Why would the H802cp piston be a better choice over the 677CP? It looks like the H802cp has a smaller dish and would boost the CR 0.3 higher than the 677CP. If I understand the game right, the goal is to get the quench as low as possible (0 deck), then dish the piston or increase the chamber volume to limit the CR. Is this correct?

I am looking at the Keith Black 944 pistons, because of the 21cc dish. This should keep the CR down at 0 deck. Here are the dish sizes for the pistons I have looked at so far:

H802cp 15.8cc
SP 677CP 17.5cc
KB944 21.0cc

What piston and con rod combination is everyone else running and why?

 

[Talyn]

The KB 944s aren't exactly budget, but are a good choice. They are used with the 4.0L rods.

 

[Dr. Dyno]

old_man - Why would the H802cp piston be a better choice over the 677CP? It looks like the H802cp has a smaller dish and would boost the CR 0.3 higher than the 677CP. If I understand the game right, the goal is to get the quench as low as possible (0 deck), then dish the piston or increase the chamber volume to limit the CR. Is this correct?

I am looking at the Keith Black 944 pistons, because of the 21cc dish. This should keep the CR down at 0 deck. Here are the dish sizes for the pistons I have looked at so far:

H802cp 15.8cc
SP 677CP 17.5cc
KB944 21.0cc

What piston and con rod combination is everyone else running and why?

The H802CP piston has a 1.592" compression height which is 0.007" more than that of the 677CP (1.585"), and will therefore yield a 0.007" lower deck clearance and quench height. The resulting SCR would be 0.3:1 higher 'cause of the smaller dish volume and lower deck clearance. Both of these pistons are used with 4.2 rods.
The Keith Black IC944 pistons (21.6cc dish) have a compression height of 1.353" and must be used with the longer 4.0 rods. The advantage of using this piston/rod combination is that you can shave 0.020" from the block deck and still have an acceptable SCR (~9.6:1) but with a lower quench (0.051" with a 0.043" head gasket).

 

[Talyn]

Keith Black IC944 pistons (21.6cc dish)

Its actually 21.73cc. Not that that would make a whole lot of difference.

 

[gradon]

I'm using the h825cp30s in my build(same as h802cps). I had the block decked .028", have .011-.013" deck clearance and the HG is .051". My SCR is 10:1, DCR 8.56:1, and have to use 93 octane to minimize pinging(which is mainly where comp builds in the 2.5k-3k range and the obd2 is still hugging 14.7:1 before O/L). I would try to get the dcr to 8.0-8.4:1, zero deck the block and have the HG compressed thickness to be the quench(.043-.051"), and then you shouldn't have to worry about pinging.

 

[MoFo]

Thanks for the help. Has anybody put together a list of all the available pistons (for both the 4.0 or 4.2 rods) that includes compresson height and dish volume. It would help if this was all in one place.