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306 Engine build

2985 Views 63 Replies 14 Participants Last post by  JMGlasgow
I'm in the process of building a stock block, crank, and rods 306 street engine for my 93 GT

Here is what I have done so far:
-Fully machined block and balanced rotating assembly with Trick Flow (Wiseco) +2cc pistons. The rods have been resized. Block has been decked .005". I figure it will have approx 10:1 compression. I assembled the bottom end and measured all the bearing clearances with a micrometer and bore gauge. I also used Speed Pro plasma moly 1.5mm file fit rings and 3mm standard tension oil rings.

-ARP main bolts, rod bolts, and head bolts. I believe the rocker studs are ARP

-Jones Cam Designs camshaft and drop in hydraulic roller lifters installed and degreed to his spec.
Receipt Font Paper Paper product Number


-Summit 9-way adjustable roller timing chain set.

-Mid 90's TFS TW170 62cc heads. They have been surfaced .005" to get the slight warp out, ported, new valves and viton installed. 9333pt1 head gaskets

-Power Bond SFI 50oz harmonic balancer

-Explorer intake with EGR. I'm planning on sending the upper and lower to Tmoss to have his shop work his magic.

-Comp Cams Ultra Pro Magnum 1.6 ratio 7/16 stud roller rockers (ordered), and then I can get the pushrods measured once they arrive.

-Standard flow and pressure Melling oil pump with ARP oil pump driveshaft

-JBA Cat4ward headers, BBK Xpipe with cats and Borla catback exhaust

-Canton stock appearance drag race 5qt oil pan.

I have a Moates QH with Binary Editor for when this engine is ready to be tuned.

I'm stuck on which injectors, MAF and throttle body I should get. I know I want the Pro-M 75mm Bullet MAF, and was thinking 36lb Holley injectors or Deka 60's. I was also looking at either the 70mm SVE throttle body and EGR plate, or BBK 70mm. I like Accufab, but I don't want a polished TB. I would also like to keep the stock air filter housing and duct for simplicity and stock appearance.

Are there any suggestions you all have? Is there anyone here that could write a base tune once I decide which injectors, MAF, and TB? Should I get the MAF with matching injectors? Would that make a tune easier?

This engine will remain naturally aspirated and I'm contemplating a 125hp NOS 05115 dry kit.

So what do you all think?
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I looked up some CFM figures for 70mm accufab TB, 75mm MAF, and a ported Explorer intake as well as did a calculation for maximum CFM of a 306cid engine assuming 100% VE (I know in reality it would be around .8 to .85) as a absolute best case scenario.

So a 306 engine at 100% VE will flow 548CFM at 6200 rpm.

Accufab 70mm TB flows 787CFM
Pro-M 75mm Maf flows 964CFM from what I can find.
And an Explorer intake at best flows 210CFM at each runner?

So, seeing all that. A 75mm MAF and 70mm Tab will flow far more than the engine will at 6200rpm.

What would the main benefit of a 75mm TB and 80mm MAF be?
In a properly tuned engine a slightly larger TB has no downside and some upside.
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None. The cobra/explorer intake has a factory 68mm-70mm T-body inlet. And this engine with this set up with roller cam and everything combined will peak horsepower around 5800 rpm.
So, seeing all that. A 75mm MAF and 70mm Tab will flow far more than the engine will at 6200rpm.
What would the main benefit of a 75mm TB and 80mm MAF be?
It'll accelerate faster, no downside, other than the myths that are perpetuated on here.
In a properly tuned engine a slightly larger TB has no downside and some upside.
I used a 75 on a 9.0:1 347, with a 90mm Mass Air, because I could split it.

Worked great.
I looked up some CFM figures for 70mm accufab TB, 75mm MAF, and a ported Explorer intake as well as did a calculation for maximum CFM of a 306cid engine assuming 100% VE (I know in reality it would be around .8 to .85) as a absolute best case scenario.

So a 306 engine at 100% VE will flow 548CFM at 6200 rpm.

Accufab 70mm TB flows 787CFM
Pro-M 75mm Maf flows 964CFM from what I can find.
And an Explorer intake at best flows 210CFM at each runner?

So, seeing all that. A 75mm MAF and 70mm Tab will flow far more than the engine will at 6200rpm.

What would the main benefit of a 75mm TB and 80mm MAF be?
you're really putting a lot of effort into a relatively mild build lol. Keep the questions coming lots of good information here
This isn't a maximum effort build, street manners and reliability are important. But I do want it to run as good as it can with my chosen parts. It hasn't been cheap
This isn't a maximum effort build, street manners and reliability are important. But I do want it to run as good as it can with my chosen parts. It hasn't been cheap
If that summit timing set included a no name chain, those are junk. Canton pans are the king of oil leaks
I don't remember exactly the name on the chain but it started with an R. It was stamped on every link.

Who's 5 quart pan would you recommend?
70mm Accufabs flow very well. I would use a 75mm ProM Bullet with 24's. Should run fine until you find a tuner. The stock air box will be fine and you don't have to deal with the Anderson Power Pipe that always seems to be in the way when you want to do something, gets hot as hell, and rattles when the plastic ring keeps falling out.
If that summit timing set included a no name chain, those are junk. Canton pans are the king of oil leaks
2138 for the win. and a stock replacement spectra oil pan.
The timing set I bought is Summit part# SUM-G6620R-9. It has a Rolon chain.
The timing set I bought is Summit part# SUM-G6620R-9. It has a Rolon chain.
Made in India chain, they get sloppy quick
Which one from Comp cams with a 9 way crank gear fits a roller 302? What would you recommend?
I don't remember exactly the name on the chain but it started with an R. It was stamped on every link.

Who's 5 quart pan would you recommend?
What's wrong with the stock one?

if all you're looking for is a fun car to bomb around andhave fun in you don't really need special oil pan or bigger mass air meter, and throttle body, whatever you can find cheap will work.

FMS makes decent timing chain sets, or used to anyway.
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Which one from Comp cams with a 9 way crank gear fits a roller 302? What would you recommend?
Why Comp?

Use Rollmaster and be done.
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The no name chains which comp uses on the cheaper sets are complete trash before you even start the engine. You want the german iwis-jwis chain. I don't know if comp is selling anything with the German chain. Comp is not manufacturing any of these sets, just buying and reboxing them.
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cloyes makes a good budget chain
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I ended up buying the Rollmaster CS3060 for '84 and later HO EFI 302 engine with a IWIS pro series chain. I thought it over and don't want to chance it with the Summit chain set. And you're right, going cheap on the valvetrain isn't a good idea.

What is the brass shim for? And do I need it if I'm using the stock cam retainer? Right now the camshaft end play is .005".

I'm still on the fence with the Canton stock design and capacity oil pan. I've read both good and bad reviews with that pan. If anything I'll check the fit and if it doesn't seem good then I'll get the Spectra stock replacement part. I have 3 OEM pans and they are all bent at the rear drain plug and from the engine being set down on the pan, and dented from being banged around during removal and storage. These came with other engines I've picked up.

Another question. How much pitting is acceptable at the water ports on a timing cover?

I would also like recommendations for pushrods brands
Always get the bigger TB. No downsides, idle surges or delayed response like some fear will happen with mild motors.

Back in 2010ish when I switched from a 75mm TB to a 90 with the same 76mm meter it helped greatly with upper rpm power. Able to move shift point up 3-400 rpm and bet it picked up 10-15hp from 6000+.

Good luck
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Debating next doing an 8.2 deck 3 1/4 stroke 347 or just going for a stump puller 430+ ci. Wondering if a 90mm would be enough for an 8500ish rpm 347????. A 430 I would definitely do a 4 barrel TB no question.

My Wilson TB on my 302 had the greatest whistle at idle and part throttle. VERY loud to boot! Educated 5.0 guys know what I mean. I would actually miss that with a 4barrel deal.
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